Two-way optical communication module

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention is a bidirectional optical communication module that enables bidirectional communication by a single optical communication path element and an optical signal, more specifically, home communication, communication between electronic devices, and LAN (Local Area Network). ), Etc. are related to the bidirectional optical communication module.

【0002】

[Conventional technology]

With the development of the information-oriented society, network technology using an optical communication path element having an optical communication path through which an optical signal is passed is drawing attention. An optical communication path element having an optical communication path through which an optical signal is passed is, for example, an optical fiber or a plastic optical fiber. In particular, in recent years, with the reduction in loss and widening of the bandwidth of plastic optical fibers (hereinafter referred to as POF), the application of POF extends to home communication and communication between electronic devices. The POF has a large diameter of about 1 mm. Therefore, the POF can be easily combined with the optical communication module. Further, by using the POF, it is possible to obtain an optical communication link that allows easy insertion and removal of the optical fiber and the optical communication module.

【0003】

Conventionally, a full-duplex system using two optical fibers has been the mainstream in an optical communication link that uses an optical fiber as a transmission medium to transmit and receive signal light of the same wavelength. However, when two optical fibers are used, there are problems that it is difficult to miniaturize the optical communication module and that the cost of the optical fiber increases as the transmission distance increases. Therefore, although the number of optical fibers used is one, a bidirectional optical communication module capable of performing full-duplex optical communication has been proposed.

【0004】

In the above-mentioned bidirectional optical communication module, transmission and reception are performed by one optical fiber, that is, the same optical fiber. Therefore, it is important to prevent interference between the light transmitted to the communication partner (transmitted light) and the light received from the communication partner (received light).

【0005】

The above interference mainly occurs in the four cases described below.

【0006】

(1) When the transmitted light is reflected by the end face of the optical fiber when the transmitted light is incident on the optical fiber. (Hereafter, this reflection is referred to as near-end reflection.) (2) When the received light received by the communication partner is emitted from the inside of the optical fiber, and the emitted light is reflected by the end face of the optical fiber. (Hereafter, this reflection is referred to as far-end reflection.) (3) When unnecessary light reflection occurs in the bidirectional optical communication module of the communication partner (this reflection is hereinafter referred to as the partner module reflection). (4) When internally scattered light is generated in the bidirectional optical communication module. (The internally scattered light generated in this bidirectional optical communication module is hereinafter referred to as internal diffused light.) Of the above four cases, scattering in the bidirectional optical communication module is particularly difficult to predict. Therefore, it was difficult to reliably reduce the interference caused by the ambient light in (4).

【0007】

When an optical fiber, for example, POF, is used for communication between electronic devices, communication is performed over a relatively short distance of about 1 m. In the case of such communication, the light emitted from the optical fiber may hurt the human eye. Therefore, in the case of communication as described above, safety for the human eye (eye safety) must be considered. In consideration of eye safety, the amount of transmitted light (the amount of light emitted from the optical fiber) must be set low in the case of communication as described above.

【0008】

By the way, a semiconductor laser is generally used as the light source of the optical communication module. The points to be noted when using a semiconductor laser as the light source of the optical communication module are described below.

【0009】

FIG. 18 shows the relationship between the drive current of the semiconductor laser and the optical output in the region where the optical output is not saturated. In the region where the optical output is not saturated, the relationship between the drive current and the optical output can be approximated by the polygonal lines of the two straight lines. The graph of FIG. 18 is a graph in which the optical output is on the vertical axis and the drive current is on the horizontal axis. Comparing the two straight lines, the slopes of the straight lines are both positive, but the magnitudes of the slopes are different. According to FIG. 18, when the optical output is on the vertical axis and the drive current is on the horizontal axis, the two show a linear relationship starting from the origin. However, the slope of the straight line becomes large after a certain value. In FIG. 18, the region from the origin until the inclination changes is indicated by B, and the region after the inclination changes significantly is indicated by A. In addition, the straight line in the area A is extended, and the point where it intersects the horizontal axis is indicated as Ith. This Ith is a threshold current. The region described as A in FIG. 18 can be roughly expressed as the laser oscillation region, and the region described as B can be roughly expressed as the spontaneous emission region.

【0010】

When a pulse is input by taking a current larger than the value of Ith as the bias current, the optical output becomes large even at "0" of the pulse signal. Therefore, the extinction ratio becomes high. On the contrary, if a current smaller than Ith is taken as the bias current, the pulse width decreases (change in duty ratio) due to the oscillation delay. Therefore, normally, the bias current is set near Ith. When the bias current is set near Ith, there is naturally emitted light even if the pulse signal is "0", so the extinction ratio is determined from the ratio of the naturally emitted light to the light output when the pulse signal is "1". For example, in the case of a semiconductor laser with spontaneous emission light of 0.3 mW, it is necessary to set the maximum output (output when the pulse signal is "1") to 3 mW or more in order to set the extinction ratio to 10 or more. Thus, attention should be paid to changes in the duty ratio and extinction ratio.

【0011】

When using optical fibers for communication between electronic devices, safety (eye safety) must be taken into consideration. In consideration of eye safety, the amount of transmitted light must be set low. When a semiconductor laser is used as a light source, there is a method of reducing the output of the semiconductor laser as a method for setting the amount of transmitted light low. However, if the output of the semiconductor laser is reduced, it becomes difficult to satisfy the extinction ratio described in the above precautions. Further, if the bias current is lowered, the duty ratio changes, which causes a problem in communication. Therefore, if an attempt is made to set the transmitted light amount low by reducing the output of the semiconductor laser, problems of the extinction ratio and the duty ratio occur, and a satisfactory result cannot be obtained.

【0012】

When a semiconductor laser is used as a light source, another method for setting the amount of transmitted light to be low is to reduce the coupling efficiency (transmission efficiency) between the light emitted from the semiconductor laser and the optical fiber.

【0013】

There are two methods shown in (a) and (b) below for reducing the transmission efficiency. (A) A method of reducing the amount of light by using a filter or polarizing element with low light transmittance. (B) A lens called a transmitting lens is used to collect the light emitted from the light emitting element and combine the light with the optical fiber. A method of cutting light rays with a large emission angle by reducing the lens diameter of the transmitting lens.

【0014】

When the method (a) above is used, in the case of interference occurrence, the interference due to the reflection of the other module in (3) increases. Therefore, it is difficult to apply the method (a) to full-duplex communication with a single optical fiber. In addition, the method (a) has a problem that the number of parts increases. Therefore, the method (a) is generally used for full-duplex communication with a single optical fiber.

【0015】

However, in the method (a), the amount of light that does not actually contribute to transmission (light cut by the transmitting lens) increases. Therefore, in the case of interference occurrence, there is a problem that interference due to internal disturbance light in (4) tends to increase. In particular, in order to perform full-duplex communication with a single optical fiber, it is necessary to efficiently couple the received light emitted from the optical fiber to the light receiving element. However, when the reception efficiency is increased, at the same time, the light due to near-end reflection and internal diffused light is efficiently received, and there is a problem that interference is further increased.

【0016】

As conventional optical communication modules, there are optical communication modules disclosed in JP-A-11-237535 and JP-A-2001-116961. Hereinafter, these optical communication modules will be described.

【0017】

The optical communication module described in Japanese Patent Application Laid-Open No. 11-237535 will be described with reference to FIG. In this optical communication module, the angle of the transmitted light 108 is adjusted so that the reflected light 117 of the transmitted light 108 does not enter the light receiving element 105 which is the light receiving surface. The light emitting element 104 emits light, and at least a part thereof is transmitted as transmission light 108. The transmitting lens 106 collects the light emitted by the light emitting element 104 into the transmitted light 108. After condensing, the transmitted light 108 is reflected by the rising mirror 110 to convert the optical path. After the optical path conversion, the transmitted light 108 is incident on the optical fiber 102. The received light 109 emitted from the optical fiber 102 is coupled to the light receiving element 105 located at a position facing the optical fiber 102. In this optical communication module, the reflected light 117 emitted from the transmitting lens 106 and reflected by the optical fiber 102 irradiates a portion other than the light receiving surface of the light receiving element 105. That is, the transmitted light 108 is incident on the optical fiber 102 from a direction different from the direction in which the received light 109 is emitted from the optical fiber 102. By incident the transmitted light 108 in this way, the reflected light 117 irradiates a portion other than the light receiving surface of the light receiving element 105. As a result, interference due to near-end reflection can be prevented.

【0018】

The optical communication module described in Japanese Patent Application Laid-Open No. 2001-116961 will be described with reference to FIG. In this optical communication module, a light-shielding plate 207 is used. The transmitted light 208, which is at least a part of the light emitted by the light emitting element 204, is first focused on the transmitting lens 206 and then coupled to the optical fiber 202. On the other hand, the received light 209 emitted from the optical fiber 202 is focused by the receiving lens 224 and then coupled to the light receiving element 205. A light-shielding plate 207 made of metal or the like exists between the transmitting unit and the receiving unit. When the transmitted light 208 is coupled to the optical fiber 202, a part of the transmitted light 208 is reflected by the optical fiber 202. The shading plate 207 prevents the reflected light from binding to the light receiving element 205.

【0019】

[Problems to be Solved by the Invention]

However, when the reflected light 117 is prevented from being incident on the light receiving element 105 by the method disclosed in JP-A-11-237535 shown in FIG. 19, the transmitted light 108 is greatly tilted with respect to the optical axis of the optical fiber 102. There is a need. When the transmitted light 108 is greatly tilted with respect to the optical axis of the optical fiber 102, the numerical aperture (NA) of the transmitted light 108 when coupled to the optical fiber 102 becomes large. Further, the transmitted light 108 biased in one direction is incident on the optical fiber 102. That is, the transmitted light 108 is excited only in the high-order mode without the low-order mode.

【0020】

When the numerical aperture (NA) is large as described above, the influence of mode dispersion in the optical fiber 102 becomes large. Therefore, there are problems that the transmission band is narrowed and the transmission loss in the optical fiber 102 is large.

【0021】

Further, when the transmitted light 108 biased in one direction is coupled to the optical fiber 102, there are the following problems. When the optical fiber 102 is short, the transmitted light 108 is emitted from the optical fiber 102 before it becomes a steady state, so that the emitted light has almost no low-order mode. As a result, the light emitted from the optical fiber 102 is biased. Further, the distribution of the emitted light is a ring-shaped distribution in which the amount of emitted light from the central portion of the optical fiber 102 is small. Such light bias and light distribution cause a problem of affecting the reception efficiency of the other module.

【0022】

When the angle of incidence of the transmitted light 108 on the optical fiber 102 is reduced, the following problems occur. The light kicked by the transmitting lens 106, in other words, the light passing through the outer peripheral portion of the transmitting lens 106, irradiates and reflects the optical fiber 102 and the optical fiber plug. There is a problem that the reflected light tends to cause internal diffused light.

【0023】

In the method of separating the transmitting unit and the receiving unit using the light-shielding plate 107 shown in FIG. 20, disclosed in Japanese Patent Application Laid-Open No. 2001-116961, the thickness of the light-shielding plate 107 cannot be used in the region of the optical fiber 102. .. Therefore, there arises a problem that the reception efficiency becomes low. Another problem is that the number of parts increases and the cost increases. Further, the light kicked by the transmitting lens 106, that is, the light passing through the outer peripheral portion of the transmitting lens 106, irradiates and reflects the optical fiber 102 and the optical fiber plug. There is a problem that the reflected light tends to cause internal diffused light.

【0024】

In particular, in an optical communication module using POF, it is necessary to reduce the transmitted light coupled to the optical fiber 102 by reducing the diameter of the transmitting lens 106 due to the above-mentioned eye safety problem and the extinction ratio. When the transmitted light is reduced in such a way, more light passes through the outer peripheral portion of the transmitting lens 106. As a result, in the conventional bidirectional optical communication module, there is a problem that the light passing through the outer peripheral portion of the transmitting lens 106 becomes stray light and causes internal diffused light. The stray light referred to here is the light emitted from the light emitting element that is not coupled to the optical fiber by the transmitting lens 106.

【0025】

As a method for reducing stray light, Japanese Patent Application Laid-Open No. 61-122614 discloses a method of attaching a light-shielding object to a collimator lens used in an optical isolator. That is, by inserting a light-shielding object between the semiconductor laser and the collimator lens, the stray light generated in the lens is reduced. Furthermore, it prevents the stray light from returning to the semiconductor laser so that the semiconductor laser can be driven stably.

【0026】

However, the above method prevents the light emitted by itself from returning to its original state, and cannot prevent interference with the light receiving element as in the bidirectional optical communication module. Further, the stray light in the lens is reduced, and the stray light in the optical communication module and the scattered light in the optical fiber plug or the like cannot be prevented. Further, the light emitting point of the semiconductor laser is minute, and in the above method, it is sufficient to prevent the return light to the minute light emitting point. However, in the bidirectional optical communication module, it is more difficult to reduce the internal disturbance light because it is necessary to separate the received light. Furthermore, it is necessary to clearly separate the internally diffused light and the transmitted light. In addition, when inserting a light-shielding object, it is necessary to pay attention to the insertion accuracy of the light-shielding object, management of the light-shielding object, adhesion of the light-shielding object, deterioration due to aging of the light-shielding object, and the like. Therefore, more cost is required, and the performance of the bidirectional optical communication module is also a problem.

【0027】

The present invention has been made in view of these problems, and an object of the present invention is to enable bidirectional communication by an optical communication path element such as a single optical fiber, and to separate transmitted light and stray light. The purpose is to provide a bidirectional optical communication module that reduces crosstalk and has high reception efficiency.

【0028】

[Means for solving problems]

In order to solve the above-mentioned problems, the bidirectional optical communication module of the present invention uses one optical communication path element having an optical communication path through which an optical signal is passed, and uses one optical communication path element from the light emitting element to the one end surface of the optical communication path element. An optical signal is transmitted by injecting light into the optical communication path, and the light receiving element receives an optical signal by receiving the received light emitted from the optical communication path on the same one end surface of the optical communication path element. Then, in the bidirectional optical communication module that communicates bidirectionally with the partner station, the first transmission light to be transmitted among the light emitted from the light emitting element is incident, and the first transmission emitted from the incident light is incident. The first transmission light control unit that controls the first transmission light so that the light is incident on the optical communication path at the end face of the optical communication path element, and the light emitted from the light emitting element are not transmission targets. The second transmitted light is incident so that at least a part of the second transmitted light is not incident on the end face of the optical communication path and the optical communication path element on which the first transmitted light is incident. It is characterized by having a second transmission light control unit that controls the light.

【0029】

According to the above configuration, it is possible to clearly separate the light emitted by the light emitting element into the first transmission light which is the transmission target and the second transmission light which is not the transmission target. The clarity of the separation is effective when a small-diameter lens is used for the first transmission light control unit in order to reduce the transmission efficiency as one of the means for satisfying the conditions required for eye safety. Become. That is, even if stray light, which is the second transmission light, is generated by using a lens having a small diameter, the stray light can be controlled by the present invention. As a result, a bidirectional optical communication module satisfying the conditions for eye safety can be obtained even if the output of the light emitting element is kept sufficiently high and the extinction ratio is made sufficiently large.

【0030】

Further, according to the above configuration, at least a part of the second transmitted light does not irradiate the end face of the optical communication path element and the optical communication path. That is, the end face of the optical communication path element and the optical communication path are prevented from being irradiated with at least a part of the second transmitted light. Therefore, it is reduced that at least a part of the second transmitted light is reflected by the end face of the optical communication path element or the optical communication path. When such reflected light is reduced, it is possible to suppress the incident of such reflected light on the light receiving element, so that interference between the second transmitted light and the received light can be effectively suppressed. The above-mentioned interference means, for example, that the above-mentioned reflected light enters the light receiving element and interferes with the original received light.

【0031】

Further, the bidirectional optical communication module of the present invention is characterized in that, in addition to the above configuration, a second transmission light control unit is continuously formed on the outer periphery of the first transmission light control unit.

【0032】

According to the above configuration, by forming the second transmitted light control unit continuously on the outer periphery of the first transmitted light control unit, the first transmitted light control unit controls the light passing through the outer periphery without being focused. can do. That is, in addition to the effect of the above configuration, it is possible to control all the light emitted by the light emitting element with a simple configuration.

【0033】

Further, in the bidirectional optical communication module of the present invention, in addition to the above configuration, a shielding member that absorbs the irradiated light is arranged at a position where at least a part of the light that has passed through the second transmission light control unit is irradiated. It is characterized by doing.

【0034】

According to the above configuration, the shielding member absorbs at least a part of the light that has passed through the second transmission light control unit. As a result, the stray light that is scattered a plurality of times and coupled to the light receiving element in the bidirectional optical communication module is reduced. As a result, in addition to the effect of the above configuration, interference due to internal disturbance light can be further reduced.

【0035】

Further, in the bidirectional optical communication module of the present invention, in addition to the above configuration, a shielding member that reflects the irradiated light is arranged at a position where at least a part of the light that has passed through the second transmission light control unit is irradiated. It is characterized by doing.

【0036】

According to the above configuration, the shielding member reflects at least a part of the light that has passed through the second transmission light control unit. As a result, the stray light that is scattered a plurality of times and coupled to the light receiving element in the bidirectional optical communication module is reduced. As a result, in addition to the effect of the above configuration, interference due to internal disturbance light can be further reduced.

【0037】

Further, the bidirectional optical communication module of the present invention is characterized in that, in addition to the above configuration, the second transmission light control unit is composed of a prism, a lens, a material that reflects light, or a light absorber.

【0038】

According to the above configuration, the second transmission light control unit is composed of a prism, a lens, a material that reflects light, or a light absorber. The prism or lens refracts light that does not contribute to transmission. This refraction clarifies the separation between transmitted light and stray light. In addition, when a material that reflects light is used, the separation between transmitted light and stray light is clarified by reflecting light. Further, when a light absorber is used, the stray light can be absorbed and the absolute amount of the stray light can be reduced. As a result, in addition to the effect of the above configuration, interference due to internal disturbance light can be further reduced. In addition, the angle of the prism can be adjusted easily, and the curvature of the lens can be easily adjusted. Therefore, the separation of transmitted light and stray light can be easily optimized. Further, the designer of the bidirectional optical communication module can adopt the optimum one suitable for each bidirectional optical communication module for the second transmission optical control unit.

【0039】

Further, the bidirectional optical communication module of the present invention is characterized in that, in addition to the above configuration, the first transmission light control unit and the second transmission light control unit are integrally formed of the same material.

【0040】

According to the above configuration, since the first transmission light control unit and the second transmission light control unit are integrally formed of the same material, the number of parts can be reduced. As a result, in addition to the effect of the above configuration, it is possible to obtain an inexpensive and compact bidirectional optical communication module with less deterioration over time. Further, by preventing such an increase in the number of parts, the manufacturing process can be simplified.

【0041】

Further, the bidirectional optical communication module of the present invention has a first surface and a second surface which is a back surface of the first surface in addition to the above configuration, and the first surface reflects received light and the surface thereof. The received light control unit that collects the reflected received light on the light receiving element and reflects the light that irradiates the second surface to prevent the light that irradiates the second surface from irradiating the light receiving element. It is characterized by being prepared.

【0042】

According to the above configuration, the received light control unit has a first surface and a second surface which is the back surface of the first surface. Further, the first surface reflects the received light and collects the reflected received light on the light receiving element. Further, the second surface reflects the light irradiating the second surface to prevent the light irradiating the second surface from irradiating the light receiving element. As a result, in addition to the effect of the above configuration, it is possible to reflect light other than the received light coming from the opposite side of the first surface which is the receiving surface and reduce the combination of the light other than the received light with the light receiving element. it can. That is, by providing one received light control unit, both the function of the first surface for receiving the received light and the function of the second surface for reflecting the light irradiating the second surface are controlled by the received light. The club plays. As a result, it is possible to more easily reduce the interference generated by combining light other than the received light with the light receiving element.

【0043】

Further, the bidirectional optical communication module of the present invention is characterized in that, in addition to the above configuration, a light shielding unit that blocks light reflected by the end surface of the optical communication path element is provided on the second surface of the received light control unit. There is.

【0044】

According to the above configuration, a light shielding unit is provided on the second surface of the received light control unit. Therefore, it is possible to block the light reflected by the optical communication path element, for example, the light reflected by the first transmission light by the optical communication path element, and prevent the light from being coupled to the light receiving element. Therefore, in addition to the effect of the above configuration, interference due to near-end reflection can be reduced more effectively.

【0045】

Further, in the bidirectional optical communication module of the present invention, in addition to the above configuration, the portion where the received light control unit is formed, the first transmission light control unit, and the second transmission light control unit are integrally made of the same material. It is characterized by forming.

【0046】

According to the above configuration, since the portion where the received light control unit is formed, the first transmitted light control unit, and the second transmitted light control unit are integrally formed of the same material, the number of parts can be reduced. As a result, in addition to the effect of the above configuration, it is possible to obtain an inexpensive and compact bidirectional optical communication module with less deterioration over time. Further, by preventing such an increase in the number of parts, the manufacturing process can be simplified.

【0047】

Further, in the bidirectional optical communication module of the present invention, in addition to the above configuration, a prism is installed between the first transmission optical control unit and the optical communication path element, and the first transmission light is transmitted from the outer peripheral direction of the optical communication path. It is characterized in that the prism refracts the first transmitted light so that the light is incident.

【0048】

According to the above configuration, the prism refracts the first transmitted light so that the first transmitted light is coupled to the optical communication path. The refraction regulates the optical path of the first transmitted light. That is, the first transmitted light can be controlled so that the first transmitted light passes through a place extremely close to the received light control unit. Further, the first transmitted light is incident on the optical communication path from the outer peripheral direction of the optical communication path. In other words, "from the outer peripheral direction" means that, assuming a surface facing the end face that is incident at the time of transmission, it is from outside the region of the facing surface. For example, considering the case where an optical fiber is used as an optical communication path element, the first transmitted light is incident on the optical fiber from the outer peripheral direction of the optical fiber (optical communication path of the optical fiber). As a result, in addition to the effect of the above configuration, the transmission area can be reduced and the reception area can be increased accordingly.

【0049】

Further, in the bidirectional optical communication module of the present invention, in addition to the above configuration, the shape of the end face of the optical communication path element is inclined with respect to the optical axis, and the side where the cross section of the optical communication path element becomes blunt due to the inclination is It is characterized in that the optical communication path element is fixed so that the first transmitted light is incident on the optical communication path element.

【0050】

According to the above configuration, the shape of the end face of the optical communication path element is inclined with respect to the optical axis, and the first transmitted light is incident on the optical communication path element on the side where the cross section of the optical communication path element becomes blunt due to the inclination. The optical communication path element is fixed so as to be on the side of the line. When the light is inclined and fixed in this way, the direction of the light reflected at the far end at the end face of the optical communication path element changes. As a result, in addition to the above configuration, interference due to far-end reflection can be further reduced.

【0051】

Further, the bidirectional optical communication module of the present invention is characterized in that, in addition to the above configuration, the shape of the end surface of the optical communication path element is spherical.

【0052】

According to the above configuration, the shape of the end face of the optical communication path element is spherical. With such a spherical surface, the direction of light reflected at the far end at the end face of the optical communication path element changes. As a result, in addition to the effect of the above configuration, interference due to far-end reflection can be reduced. Further, when the cross section of the optical communication path element is inclined, the side where the optical communication path element is fixed is taken into consideration. However, if the shape of the end face of the optical communication path element is spherical, there is an advantage that it is not necessary to consider the side on which the optical communication path element is fixed.

【0053】

Further, in the bidirectional optical communication module of the present invention, in addition to the above configuration, the first transmission optical control unit is characterized by including a plurality of lenses.

【0054】

According to the above configuration, the first transmission light control unit includes a plurality of lenses. Normally, the first transmission light control unit includes one lens. However, the first transmission light control unit may include a plurality of lenses. For example, the transmission light control unit may include a first transmission lens and a second transmission lens. As a result, in addition to the effect of the above configuration, the ability of the lens to collect light can be increased, and the types of light emitting elements that can be used can be increased. For example, when the transmission light control unit includes a first transmission lens and a second transmission lens, a light emitting diode (LED) having a wider emission angle and a larger light emitting part area than a semiconductor laser can be used as a light emitting element. it can.

【0055】

Further, the bidirectional optical communication module of the present invention is characterized in that, in addition to the above configuration, a receiving lens that collects received light is installed between the received light control unit and the light receiving element.

【0056】

According to the above configuration, a receiving lens that collects the received light is installed between the received light control unit and the light receiving element. As a result, in addition to the effect of the above configuration, the receiving lens can further collect the received light collected by the receiving light control unit, and the receiving efficiency can be improved.

【0057】

BEST MODE FOR CARRYING OUT THE INVENTION

[Embodiment 1] An embodiment of the present invention will be described below with reference to FIGS. 1 to 15.

【0058】

The present invention is not limited to the following embodiments, and various modifications can be made within the scope of the present invention.

【0059】

FIG. 1 shows the configuration of a bidirectional optical communication link. The bidirectional optical communication link 3 includes an optical fiber 2 for bidirectionally transmitting modulated light suitable for transmission based on a data signal to be transmitted. Further, the bidirectional optical communication link 3 is provided with one bidirectional optical communication module 1 at both ends of the optical fiber 2. The optical fiber 2 is one of the optical communication path elements having an optical communication path through which an optical signal is passed.

【0060】

FIG. 2 shows a bidirectional optical communication module according to an embodiment of the present invention. An optical fiber 2 which is an optical communication path element is connected to the bidirectional optical communication module 1. An optical fiber plug 26 is used to bond and fix the tip of the optical fiber 2 to the bidirectional optical communication module 1. That is, the optical fiber plug 26 constitutes at least a part of the end face of the optical communication path element. By inserting the tip of the optical fiber 2 into the recess of the receptacle 27 which is a part of the bidirectional optical communication module 1, the optical fiber 2 and the bidirectional optical communication module 1 are optically coupled.

【0061】

The bidirectional optical communication module 1 includes a light emitting element 4, a light receiving element 5, a transmitting lens 6 which is a first transmitting light control unit, a reflection mirror 7 which is a receiving light control unit, an optical member 10, and a prism 11. , Submount 12, stem 13, monitor photodiode 14, transmitter cover 15, light-shielding section 16, electrode 21, divergence section 25, and receptacle 27.

【0062】

A light receiving element 5, an optical member 10, an electrode 21, a submount 12, and a monitor photodiode 14 are aligned and arranged on the stem 13. The stem 13 is electrically connected to a circuit (not shown).

【0063】

Further, the transmitting lens 6, the diverging unit 25 which is the second transmitting light control unit, the electrode 21, and the reflecting mirror 7 which is the receiving light control unit are present on the optical member 10. In addition, a reflection mirror 7 is installed next to the optical fiber plug 26 so that the received light emitted from the optical fiber 2 can be received. Further, a space is prepared above the reflection mirror 7 for transmitting the first transmitted light 8, which is the light to be transmitted among the light emitted by the light emitting element 4. Further, the reflection mirror 7 has a role of shielding light traveling from the light emitting element 4 side toward the light receiving element 5.

【0064】

Further, the optical axis of the optical fiber 2 and the center line of the emitted light of the light emitting element 4 are parallel. The optical axis of the transmitting lens 6 coincides with the center line of the emitted light of the light emitting element 4. That is, the optical axis of the optical fiber 2, the center line of the emitted light of the light emitting element 4, and the optical axis of the transmitting lens 6 are parallel. By arranging the light emitting element 4, the light receiving element 5, and the optical member 10 on one stem 13 in parallel with the optical axis of the optical fiber 2, the bidirectional optical communication module 1 can be easily assembled. effective.

【0065】

In the present embodiment, as described above, the light emitting element 4, the light receiving element 5, and the optical member 10 are arranged parallel to the optical axis of the optical fiber 2, respectively. However, the arrangement may not be parallel. For example, in order to stabilize the oscillation of the light emitting element 4, the optical axis of the light emitting element 4 is tilted with respect to the optical axis of the optical fiber 2, so that the light emitted from the light emitting element 4 is reflected by the optical fiber 2 and is reflected again by the optical fiber 2. It is also possible to prevent it from returning to 4.

【0066】

The light emitting element 4 is arranged on the submount 12. The light emitting element 4 generates transmission light which is modulated light based on a data signal. The light generated by the light emitting element 4 radiates radially according to the radiation angle of the light emitting element 4. After that, the transmitted light 6 converts the emitted light into an arbitrary numerical aperture and condenses it. The focused light passes through the optical member 10 as the first transmitted light 8. After that, the first transmitted light 8 passes through the prism 11 and is coupled to the optical fiber 2.

【0067】

The submount 12 is made of a material having excellent heat dissipation characteristics such as silicon carbide (SiC). The light receiving element 5 receives the received light 9 from the optical fiber 2. The transmitting lens 6 collects the light emitted by the light emitting element 4 and couples the first transmitted light 8 to the optical fiber 2. The divergence unit 25 diverges a part of the light (second transmission light) emitted from the light emitting element 4 to reduce interference due to internal diffused light and near-end reflection. The optical member 10 has a prism 11 having an inclination with respect to the optical axis of the optical fiber 2. The prism 11 exists on the surface from which the first transmitted light 8 is emitted and refracts the first transmitted light 8. After receiving the refraction, the first transmitted light 8 is incident on the optical fiber 2.

【0068】

The received light 9 emitted from the optical fiber 2 is reflected by the first surface of the reflection mirror 7 (received light control unit). The reflection mirror 7 has a curvature. The curvature of the reflection mirror 7 may be set so that the reflection mirror 7 collects the received light 9 and the collected light is coupled to the light receiving element 5. In the present embodiment, the curvature of the reflection mirror 7 is R = 2.2 mm.

【0069】

Further, the reflection mirror 7 which is a received light control unit is a thin film that reflects light. That is, the thin film (reflection mirror 7) is thinner than the light-shielding plate 207 of FIG. When the reflection mirror 7 which is the received light control unit is configured by such a thin film, the loss due to the thickness of the thin film can be significantly reduced.

【0070】

The surfaces (inner surfaces) of the stem 13, the transmitter cover 15, and the receptacle 27 are preferably a color having a high light absorption rate such as black, which can reduce excess scattered light.

【0071】

As shown in FIG. 2, when the first transmitted light 8 and the received light 9 are spatially separated within the aperture of the optical fiber 2, the received light 9 is emitted from the position where the first transmitted light 8 is incident. There is something. However, the received light 9 emitted from such a position does not couple to the light receiving element 5. Considering the received light 9 emitted from the position where the first transmitted light 8 is incident, the portion of the cross-sectional area perpendicular to the optical axis of the optical fiber used by the first transmitted light 8 to be incident on the optical fiber 2. Should be small. Further, in order to reduce the portion used by the first transmitted light 8 for incident on the optical fiber 2, it is preferable that the position where the first transmitted light 8 is incident is near the outer peripheral portion of the optical fiber 2. When the portion used by the first transmitted light 8 for incident on the optical fiber 2 is reduced as described above, the received light 9 emitted from the position where the first transmitted light 8 is incident decreases. That is, the received light 9 that does not couple to the light receiving element 5 is reduced. As a result, the received light 9 can be efficiently coupled to the light receiving element 5.

【0072】

Further, a part of the reflection mirror 7 which is a reception light control unit is provided with a light shielding unit 16 on a surface opposite to a surface for receiving the reception light 9. The surface that receives the received light referred to here is the first surface of the received light control unit. The surface opposite to the surface that receives the received light is the second surface of the received light control unit.

【0073】

The light-shielding portion 16 is arranged so as to be in contact with or close to the optical fiber 2. The role of the light-shielding unit 16 is to block the light reflected by the end face of the optical fiber 2 which is an optical communication path element, and prevent the light reflected by the end face of the optical fiber 2 from being coupled to the light-receiving element 5. By such shading, interference due to near-end reflection can be prevented.

【0074】

Here, the light-shielding portion 16 is a part of the reflection mirror 7. That is, the portion of the second surface of the reflection mirror 7 that is close to the optical fiber 2 is referred to as a light-shielding portion 16. Further, unlike this, a light-shielding portion 16 can be provided as a member separate from the reflection mirror 7. That is, a light-shielding portion 16 which is a separate member can be provided on a portion of the second surface of the reflection mirror 7 that is close to the optical fiber 2. Further, the light-shielding portion 16 which is a separate member may be made of the same material as the reflection mirror 7, for example. Further, for the light-shielding portion 16 which is a separate member, for example, a material suitable for the light-shielding portion 16 may be selected rather than the material of the reflection mirror 7.

【0075】

When the transmitted and received light is spatially separated by using one optical fiber 2, as shown in FIG. 3, if the transmission area in which the first transmitted light 8 is coupled to the optical fiber 2 is made small, the receiving area becomes large. As the reception area increases, the available received light 9 increases. As a result, an efficient bidirectional optical communication module 1 can be obtained.

【0076】

In order to obtain the efficient bidirectional optical communication module 1 as described above, it is important how to separate the first transmitted light 8 and the received light 9 with less light loss. In the method using the light-shielding plate 207 as shown in FIG. 20, the loss becomes large due to the thickness of the light-shielding plate 207 and the spatial separation of the transmission / reception area. That is, the thicker the light-shielding plate 207 of FIG. 20, the more the received light 209 blocked by the light-shielding plate 207, and the less the received light 209 coupled to the light-receiving element 205. Further, the shading plate 207 of FIG. 20 forms a transmission area and a reception area shown in FIG. Therefore, the received light 209 emitted from the transmission region does not couple to the light receiving element 205. However, in the method shown in the present embodiment, the transmitted / received light is separated by the thin-film reflective mirror 7. Therefore, the loss due to the thickness of the thin film can be made substantially zero.

【0077】

In the present embodiment, the prism 11 refracts the first transmitted light 8, and the first transmitted light 8 passes through a place extremely close to the reflection mirror 7. Further, the first transmitted light 8 is incident on the optical fiber 2 from the outer peripheral direction of the optical fiber 2 (the outer peripheral direction of the optical communication path). As a result, the transmission area can be reduced. As the transmission area becomes smaller, the reception area naturally expands. As the reception area expands, the available received light 9 increases. As a result, an efficient bidirectional optical communication module 1 can be obtained.

【0078】

Next, the reduction of internal disturbance light will be described with reference to the figures shown in FIGS. 4 to 8. When using an optical fiber for communication between electronic devices, set the amount of transmitted light low in consideration of safety (eye safety). However, if the output of the semiconductor laser is reduced, the extinction ratio and the duty ratio cannot be satisfied. Therefore, it is necessary to cut a part of the light by the transmitting lens 6. As shown in FIG. 4A, the transmitting lens 6 collects a part of the light emitted by the light emitting element 4 to obtain the first transmitted light 8. On the other hand, of the light emitted by the light emitting element 4, the light passing through the outer periphery of the transmitting lens 6 (second transmitted light) is cut as stray light 18.

【0079】

The light cut by the transmitting lens 6 (passing through the outer periphery of the transmitting lens 6) becomes stray light 18 and scatters in the bidirectional optical communication module 1. In the case of the structure of FIG. 4 (a), a part of the stray light 18 irradiates the optical fiber 2 or the optical fiber plug 26. FIG. 4 (b) is a diagram showing a state when the configuration of FIG. 4 (a) is viewed from the direction of arrow A. In Fig. 4 (b), there is a shaded area. The shaded portion 32 shows a portion of the stray light 18 irradiating the optical fiber 2 or the optical fiber plug 26. Further, the stray light 18 irradiated to the shaded portion 32 is reflected in the direction of the reflection mirror 7. Therefore, it is difficult to separate it from the received light 9. Further, the stray light 18 is likely to be coupled to the light receiving element, which causes interference due to internal diffused light.

【0080】

In order to control the stray light, in the present embodiment, as shown in FIG. 5A, a divergence portion 25 is formed around the transmitting lens 6. Further, FIG. 5 (b) is a diagram showing a state when the configuration of FIG. 5 (a) is viewed from the direction of arrow B. The divergence unit 25, which is the second transmission light control unit, changes the direction of the stray light 18 when the second transmission light 33 is incident. The second transmitted light 33 is the light before the diverging unit 25 sets the second transmitted light 33 as the stray light 18. So to speak, it is the light that is before the stray light 18 and is heading toward the divergence part 25. Further, the stray light 18 is diverged so as not to irradiate the optical fiber 2 having an optical communication path located above the transmission lens 6 and the optical fiber plug 26 corresponding to the end face of the optical communication path element drawn on FIG. 4 or FIG. Part 25 turns the stray light 18. As a result, interference of internal diffused light caused by stray light 18 is significantly reduced.

【0081】

In order to prevent interference due to internal disturbance light, it is better to prevent the stray light located below the transmission lens 6 in FIG. 4 or 5 from irradiating the member of the bidirectional optical communication module 1, the optical fiber 2, and the like. preferable. A reflection mirror 7 as a received light control unit can be used to suppress interference caused by stray light located below the transmitting lens 6.

【0082】

Next, the divergence unit 25 will be described. The divergence portion 25 is located on the outer peripheral portion of the transmitting lens 6. The divergence unit 25 is for clarifying the separation between the first transmitted light 8 and the stray light 18 and controlling the stray light 18. In particular, the divergent portion 25 is arranged so that the light passing through the outer peripheral portion of the transmitting lens 6 becomes the stray light 18 and the stray light 18 does not irradiate the optical fiber 2 or the optical fiber plug 26. By arranging the divergence unit 25 in this way, the received light 9 and the stray light 18 can be easily separated.

【0083】

FIG. 6, FIG. 7 and FIG. 8 show an example of the divergence section 25. FIGS. 6, 7 and 8 show an example in which the divergence unit 25 (second transmission light control unit) is continuously formed on the outer periphery of the transmission lens 6 (first transmission light control unit).

【0084】

As shown in FIGS. 6A and 6B, the divergence unit 25, which is the second transmission light control unit, can have a prism shape continuously formed on the outer periphery of the transmission lens 6. FIG. 6A is a cross-sectional view showing the configuration of a prism-shaped divergent portion. FIG. 6 (b) is a plan view showing a view of FIG. 6 (a) from the direction of arrow C. Further, the divergence portion 25 in FIG. 6 shows a shape in which a cylinder is hollowed out in a conical shape and a transmission lens 6 is arranged in the hollowed out central portion as an example of a prism shape.

【0085】

FIG. 7A is a cross-sectional view showing the configuration of the lens-shaped divergence unit 25 (second transmission light control unit). FIG. 7 (b) is a plan view showing a view of FIG. 6 (a) from the direction of arrow D. As shown in FIGS. 7 (a) and 7 (b), the divergent portion 25 can have a lens shape continuously formed on the outer circumference. As an example of the lens shape, the divergence portion 25 in FIG. 7 shows a shape in which a cylinder is hollowed out in a hemispherical shape and the transmitting lens 6 is arranged in the hollowed out central portion. These diverging portions 25 refract the light emitted from the light emitting element 4 that passes through the outer peripheral portion of the transmitting lens 6 in the outer peripheral direction. This refraction prevents the stray light 18 from irradiating the optical fiber 2 and the optical fiber plug 26.

【0086】

The diverging portion 25 facilitates the separation of the first transmitted light 8 and the stray light 18 by refraction. Further, depending on the arrangement of the light emitting element 4 and the optical fiber 2, the angle of the prism and the curvature of the lens can be changed so that the optical fiber 2 and the optical fiber plug 26 are not irradiated with the stray light 18. That is, the angle of the prism and the curvature of the lens can be arbitrarily selected and easily optimized.

【0087】

Further, FIGS. 8 (a) and 8 (b) show a divergence unit 25 (second transmission light control unit) that blocks the outer periphery of the transmission lens 6. FIG. 8A is a cross-sectional view showing the configuration of the divergence portion 25 that shields the outer periphery from light. FIG. 8 (b) is a plan view showing a view of FIG. 8 (a) from the direction of arrow E.

【0088】

The divergence unit 25 (second transmission light control unit) that blocks the outer periphery of the transmission lens 6 as described above absorbs or reflects the light that passes through the outer periphery of the transmission lens 6. Such absorption or reflection of light prevents the stray light 18 from illuminating the fiber optic 2 and the fiber optic plug 26. The divergence portion 25 shown in FIG. 8 is perpendicular to the optical axis of the light emitting element 4. However, the divergent portion 25 does not have to be perpendicular to the optical axis of the light emitting element 4. For example, the divergent portion 25 in FIG. 8 may have an inclined shape or a curved surface shape. As the light-shielding material of the divergence portion 25 shown in FIG. 8, a material that reflects light or a light absorber is used. The material that reflects light, that is, the material having high light reflectance is, for example, a metal having high reflectance such as aluminum or gold, or a material similar to that used for the reflection mirror 7. The light absorber is, for example, a paint having a high light absorption rate.

【0089】

By providing the divergence unit 25 which is the second transmission light control unit as described above, the divergence unit 25 can control the stray light 18 even if a small-diameter lens is used for the first transmission light control unit. As a result, when a semiconductor laser is used as the light emitting element, a bidirectional optical communication module that satisfies the conditions for eye safety can be obtained even if the output of the semiconductor laser is kept sufficiently high and the extinction ratio is made sufficiently large. ..

【0090】

Further, FIG. 9 shows the bidirectional optical communication module 1 in which the shielding unit 30 is present. FIG. 9 shows an example in which a shielding unit 30 (shielding member) that absorbs or reflects the irradiated light is arranged at a position where at least a part of the light that has passed through the diverging unit 25 (second transmission light control unit) is irradiated. is there.

【0091】

The shielding portion 30 is installed at a position where the first transmitted light 8 does not pass and a position where the light (stray light 18) that has passed through the diverging portion 25 irradiates. Further, the shielding portion 30 has a light absorbing layer (shielding member) 31 having a high light absorption rate. When the light absorbing layer is irradiated with the stray light 18, the light absorbing layer absorbs the stray light 18. As a result, the stray light 18 that is reflected or scattered a plurality of times and is coupled to the light receiving element 5 in the bidirectional optical communication module 1 is reduced. Therefore, the shielding portion 30 and the light absorbing layer 31 surely reduce the interference due to the ambient light. As the light absorption layer 31, a material coated with a paint having a high light absorption rate or a material having a high light absorption rate can be used. Further, a material having high reflectance may be arranged instead of the light absorbing layer 31 to reflect the stray light 18 in a direction not coupled to the light receiving element 5.

【0092】

The reflection mirror 7 reflects the stray light 18 as shown in FIG. More specifically, the second surface of the reflection mirror 7 (received light control unit) reflects the stray light 18. That is, the reflection mirror 7 prevents the stray light 18 from coupling to the light receiving element 5, and also serves as a shielding portion.

【0093】

As described above, by arranging the divergence portion 25 around the transmission lens 6, the first transmission light 8 and the stray light 18 can be easily separated. Further, it is possible to easily prevent the stray light 18 from coupling to the light receiving element 5 and causing interference due to the ambient light. Further, by arranging the shielding portion 30, it is possible to more reliably prevent interference due to internal diffused light.

【0094】

Further, the transmission lens 6 (first transmission light control unit) and the divergence unit 25 (second transmission light control unit) can be integrally formed of the same material. Further, the transmitting lens 6 (first transmitted light control unit), the diverging unit 25 (second transmitted light control unit), and the shielding unit 30 can be integrally formed with the optical member 10. By such integral formation, the number of parts can be reduced, and an inexpensive and compact bidirectional optical communication module 1 can be obtained.

【0095】

In addition, injection molding of resin was used for manufacturing the optical member 10 in this embodiment. Further, the inside of the optical member 10 in the present embodiment has a structure filled with resin. However, it is also possible to have a structure in which a part of the optical member 10 has a cavity.

【0096】

Further, the shielding portion 30 or the light absorbing layer 31 may be formed on the surface of the prism 11 on the optical member 10 except for the region through which the first transmitted light 8 passes. That is, of the surface of the prism 11, the region through which the first transmitted light 8 passes is left as the prism 11, and the shielding portion 30 or the light absorption layer 31 is formed on the surface of the prism 11 which is a portion other than the passing region. May be good. The portion other than the region through which the first transmitted light 8 passes can be rephrased as the portion of the light emitted by the light emitting element 4 through which the light that is not transmitted to the communication partner (counterpart station) passes. Further, when the shielding portion formed on the surface of the prism 11 is made of a material having high reflectance, the shielding portion 30 can be formed at the same time as the reflection mirror 7. Therefore, forming the shielding portion 30 on the surface of the prism 11 with a material having high reflectance simplifies the manufacturing process. Therefore, there is an advantage in terms of manufacturing cost.

【0097】

Next, the principle of preventing near-end reflection and stray light will be described with reference to FIG. The first transmitted light 8 is refracted by the prism 11 of the optical member 10. After that, the first transmitted light 8 is incident on the optical fiber 2 from the outer peripheral portion of the optical fiber 2. At the time of the incident, the reflected light 17 is generated. The reflected light 17 travels toward the center of the optical fiber 2.

【0098】

The light-shielding portion 16 is provided at the tip of the prism 11 of the optical member 10 as a part of the reflection mirror 7. Further, the light-shielding portion 16 is arranged so as to be in contact with the optical fiber 2 or at a position separated from the optical fiber 2 by several tens to several hundreds of μm. Further, the light-shielding portion 16 is provided on the surface of the reflection mirror 7 opposite to the side on which the received light 9 is incident (the second surface of the received light control unit). Since the light-shielding portion 16 is in such a position, the reflected light 17 is reflected by the light-shielding portion 16. As a result, the reflected light 17 does not enter in the direction of the light receiving element 5.

【0099】

Further, a part of the light emitted from the light emitting element 4 (second transmitted light 33) passes through the diverging portion 25 without being incident on the transmitting lens 6 and becomes stray light 18. As described above, the divergence portion 25 is installed so that the stray light 18 does not irradiate the optical fiber 2 and the optical fiber plug 26. That is, the diverging portion 25 changes the direction of the stray light 18 so that the stray light 18 advances to the outside from the outer circumference of the optical fiber 2, and the stray light 18 is moved from the optical fiber 2 side (left side in FIG. 10) to the first surface side of the reflection mirror 7. Prevents the incident. As a result, the stray light 18 is prevented from being coupled to the light receiving element 5.

【0100】

Further, the reflection mirror 7 prevents the stray light 18 from entering the inside of the reflection mirror 7 (first surface side) from the opposite side of the optical fiber 2 side (right side in FIG. 10), that is, from the light emitting element 4 side. The prevention is due to the fact that the reflection mirror 7 is installed so as to completely cover the light receiving element 5. Further, this is because the stray light 18 irradiates the surface opposite to the surface on which the light receiving element 5 is arranged in the reflection mirror. The "surface opposite to the surface on which the light receiving element 5 is arranged in the reflection mirror" is the second surface of the received light control unit.

【0101】

Further, with the above configuration, even if the position shift of the light emitting element 4 occurs due to the assembly tolerance of the light emitting element 4, unexpected stray light 18 does not enter the light receiving element 5. If the assembly tolerance of the light emitting element 4 is set to high accuracy, the assembly cost becomes high. However, according to the configuration of the present embodiment, the reflection mirror 7 can prevent unexpected stray light 18 from being incident on the light receiving element 5, so that the assembly tolerance of the light emitting element 4 can be increased accordingly. As a result, the assembly cost can be reduced. The assembly tolerance of the light emitting element 4 is generally about several tens of μm.

【0102】

Further, the reflected light 17 also becomes stray light and scatters in the bidirectional optical communication module 1. However, for the same reason as the stray light 18, it does not couple to the light receiving element 5. The same reason is that the reflected light 17 irradiates the second surface of the reflection mirror, which is the received light control unit, that is, the surface opposite to the surface on which the light receiving element 5 is arranged. That is, the reflection mirror 7 has a function of coupling the received light 9 to the light receiving element 5 and also has a function of optically separating the reflected light 17 and the stray light 18 from the light receiving element 5.

【0103】

The reflection mirror 7 can be formed by forming a thin film on the optical member 10. For example, a thin film such as aluminum is formed on the optical member 10 by a thin film deposition method or the like. Since the reflection mirror 7 optically separates the light receiving element 5, the arrangement of the light emitting element 4 can be determined without worrying about the influence of the stray light 18. Since the arrangement of the light emitting element 4 can be determined in this way, the effect of increasing the degree of freedom in designing the bidirectional optical communication module 1 and the effect of facilitating the assembly adjustment of the bidirectional optical communication module 1 are obtained.

【0104】

Next, the principle of preventing reflection of the mating module will be described with reference to FIG. In the bidirectional optical communication module 1 of the present embodiment, the following two lights are the factors that cause the mating module reflection. When the following two lights are coupled to the optical fiber 2 again, interference due to reflection from the mating module occurs. (1) Element reflected light 19 reflected on the surface of the light receiving element 5. (2) Prism reflected light 20 in which a part of the received light 9 emitted from the optical fiber 2 is reflected by the optical member 10 (mainly the prism 11).

【0105】

First, measures for the element reflected light 19 will be described. The light receiving surface of the light receiving element 5 is coated with an antireflection coating to prevent reflection of the received light 9 and improve the light receiving efficiency. The antireflection coat is, for example, a thin film of silicon nitride. However, not all of the received light 9 is incident on the light receiving surface. A part of the received light 9 is incident on a surface other than the light receiving surface and reflected, which causes reflection of the mating module. Therefore, an antireflection film is formed on a portion other than the light receiving surface. In this way, by forming the antireflection film on the portion other than the light receiving surface, the reflection of the mating module is surely suppressed. The antireflection film is made of a material having a high light absorption rate and a low reflectance in the wavelength region to be used. For example, a black colored resist or the like.

【0106】

Next, measures for the prism reflected light 20 will be described. By optimizing the tilt angle of the prism 11, the prism reflected light 20 can be prevented from being coupled even if the prism reflected light 20 is incident on the optical fiber 2. That is, the inclination angle of the prism 11 may be optimized so that the prism reflected light 20 is incident on the optical fiber 2 at an angle larger than the numerical aperture of the optical fiber 2. For that purpose, the inclination angle of the prism 11 with respect to the optical axis of the optical fiber 2 may be set to about NA of the optical fiber 2 or more. For example, when the optical fiber 2 having NA0.3 is used, the inclination angle of the prism 11 may be 10 ° or more, preferably 17 ° or more. The inclination angle of the prism 11 is the angle formed by the axis perpendicular to the optical axis of the optical fiber 2 and the prism 11 in FIG. However, when the inclination angle of the prism 11 is increased, the incident angle of the first transmitted light 8 on the optical fiber 2 is also increased. As a result, the coupling loss of the first transmitted light 8 may be reduced, or the excitation may be performed only in the higher-order mode. Therefore, it is necessary to set the optimum prism tilt angle in consideration of the above items.

【0107】

Further, the countermeasure for the prism reflected light 20 may be a countermeasure as shown in FIG. That is, the portion through which the first transmitted light 8 passes (indicated by A in the figure) does not form the prism 11, and the portion through which the first transmitted light 8 does not pass (indicated by B in the figure) is a prism having a large inclination angle. It is a measure to form 11. In this case, the prism reflected light 20 reflected at the portion where the prism 11 is not formed becomes the mating module reflection. However, it is possible to reduce the reflection of the mating module by sufficiently reducing the area of the portion where the prism is not formed. Alternatively, a measure may be taken in which the inclination angle of the prism 11 in the portion through which the first transmitted light 8 passes is reduced and the inclination angle of the prism 11 in the portion through which the first transmitted light 8 does not pass is increased. That is, the inclination angle of the prism may be set in two stages. Further, a measure may be taken in which an anti-reflection coating (AR (anti-reflection) coating) is applied to the surface of the optical member 10 irradiated by the received light 9 to reduce the reflectance.

【0108】

Next, the far-end reflection of the optical fiber 2 will be described. As shown in FIG. 2, when the end face of the optical fiber 2 is perpendicular to the optical axis (90 °), the difference in refractive index between the optical fiber 2 and air causes a far-end reflection of about 4%. The amount of far-end reflection is the absolute amount of far-end reflection, and the amount of reflected light on the far-end surface of the optical fiber 2 is expressed as a ratio (%) with respect to the amount of light emitted from the optical fiber 2.

【0109】

This far-end reflection can be reduced by devising the end face shape of the optical fiber 2 (the shape of the end face of the optical communication path element). For example, as shown in FIG. 13, there is a method of inclining the end face of the optical fiber 2 (optical communication path element) with respect to the optical axis. Further, as shown in FIG. 14, there is a method of making the end face of the optical fiber 2 (optical communication path element) spherical.

【0110】

Both of the above two methods change the direction of the light reflected at the far end on the end face of the optical fiber 2 so that the angle of the reflected light is equal to or greater than the numerical aperture of the optical fiber 2. This prevents the light reflected from the far end from propagating through the optical fiber 2.

【0111】

It should be noted that, for example, a plastic optical fiber (POF) is suitable for devising the shape of the cross section of the optical fiber (optical communication path element) in this way. In POF, as described above, it is easy to process the end face so as to be inclined and to process it into a spherical surface. For example, it can be processed by pressing the end face against a hot plate having an arbitrary shape and melting the end face.

【0112】

Next, the configuration of the bidirectional optical communication module 1 when the end face shape of the optical fiber 2 is changed as described above will be described.

【0113】

FIG. 13 shows a case where the optical fiber 2 having an inclined end face is coupled to the bidirectional optical communication module 1. In this case, the side on which the first transmitted light 8 of the optical fiber 2 is incident is fixed to the side where the cross section of the optical fiber 2 has an obtuse angle (the angle formed by the end surface of the optical fiber 2 and the outer side surface of the optical fiber 2 is an obtuse angle). It is coupled to the optical fiber communication module 1. With such an arrangement, the reflected light 17, which is the light reflected by the optical fiber 2 by the first transmitted light 8, is reflected toward the outer peripheral portion of the optical fiber 2. As a result, interference due to near-end reflection can be reliably reduced. Further, the received light 9 emitted from the optical fiber 2 is refracted toward the light receiving element side (lower side in FIG. 13) due to the inclination of the end face. Therefore, the refracted light travels in the direction of the reflection mirror 7, and the reception efficiency is further improved.

【0114】

By setting the end face inclination angle of the optical fiber 2 according to the numerical aperture (NA) of the optical fiber 2, far-end reflection can be reliably reduced. Specifically, the inclination angle is set so that the light reflected by the end face of the optical fiber 2 does not propagate through the optical fiber 2. Most of the reflected light has an angle of NA or more with respect to the optical axis of the optical fiber 2. Therefore, if the inclination angle is set to an angle larger than the NA of the optical fiber 2, the light reflected at the end face of the optical fiber 2 does not propagate through the optical fiber 2, and the far-end reflection can be surely reduced. However, if the tilt angle is too large, it becomes difficult for the first transmitted light 8 to be coupled to the optical fiber 2. Therefore, the inclination angle is determined so as not to prevent the first transmitted light 8 from being coupled to the optical fiber 2. When the inclination angle α of the optical fiber 2 of NA0.3 was set to 80 °, the far-end reflection was reduced to 0.4%. When α is 90 °, the far-end reflection is 4%.

【0115】

FIG. 14 shows a case where the optical fiber 2 having a spherical end face is coupled to the bidirectional optical communication module 1. When the end face of the optical fiber 2 is spherical, it is not necessary to determine the direction of the optical fiber 2 with respect to the bidirectional optical communication module 1 as in the case of tilting. Therefore, the optical fiber 2 can be easily inserted and removed without worrying about the direction. When the first transmitted light 8 is incident on the optical fiber 2 having a spherical end face from the vicinity of the outer peripheral portion, the reflected light 17 is reflected in the outer peripheral direction of the optical fiber 2 as in the case where the end face is inclined. As a result, interference due to near-end reflection can be reliably reduced. Further, a part of the received light 9 emitted from the optical fiber 2 is focused by the spherical end surface of the optical fiber 2 and then emitted. Therefore, the reception efficiency is improved.

【0116】

When the end face of the optical fiber 2 is an inclined surface or a spherical surface, the first transmitted light 8 incident on the optical fiber 2 is refracted by the shape of the end face. In order to increase the coupling efficiency of the first transmitted light 8 to the optical fiber 2, it is necessary to make the angle of the refracted first transmitted light 8 with respect to the optical axis of the optical fiber 2 smaller than that of the NA of the optical fiber 2. In order to meet the needs, it is preferable that the inclined surface of the prism 11 is an inclined surface in the direction opposite to the direction shown in FIGS. 13 and 14, as shown in FIG. As described above, by inclining or making the end face of the optical fiber 2 spherical, far-end reflection can be reduced and reception efficiency can be improved.

【0117】

Next, a method for preventing electrical / electromagnetic interference will be described. The stem 13 is connected to the ground electrode of the light receiving element 5. The submount 12 is formed by using an insulator such as silicon carbide (SiC). That is, the light emitting element 4 and the light receiving element 5 are electrically separated. Further, the reflection mirror 7 is also formed in the lower part of the optical member 10 (electrode 21). The electrode 21 electrically connects the stem 13 and the reflection mirror 7. That is, when viewed from the light emitting element 4, the reflecting mirror 7 and the stem 13 of the light receiving element 5 shield the light receiving element 5. This shield suppresses electromagnetic interference.

【0118】

The reflection mirror 7 is formed by depositing a material having high reflectance and conductivity. In this embodiment, aluminum is used for the reflection mirror 7. The reflectance of the reflection mirror 7 in this embodiment is about 90% (when the wavelength of light is 650 nm). As the material of the other reflection mirror 7, for example, a metal such as gold may be used. As shown in FIG. 2, the reflection mirror 7 is formed on the lower left side of the optical member 10. When the reflection mirror 7 is formed, the electrode 21 is also formed at the same time. As shown in FIG. 2, the reflection mirror 7 and the electrode 21 are installed on the entire lower surface of the optical member 10. Therefore, the reflection mirror 7 and the electrode 21 can be easily formed without patterning with a mask or the like.

【0119】

Further, the transmitter cover 15 covers the light emitting element 4 and the monitor photodiode 14. The transmitter cover 15 is adhered to the optical member 10 and the stem 13, and seals the light emitting element 4 from the outside air. The transmitter cover 15 is also electrically connected to the stem 13. With this connection, the transmitter cover 15 also has a role of electromagnetically sealing the light emitting element 4 from the outside.

【0120】

Further, a part of the optical member 10 is used as a part of the sealing member of the light emitting element 4 (corresponding to a normal cover glass). Such use contributes to a reduction in the number of parts, a reduction in the cost of parts, and a simplification of the manufacturing process.

【0121】

Next, each component of the bidirectional optical communication module 1 shown in FIG. 2 will be described. As the optical fiber 2, it is preferable to use a multimode optical fiber such as POF. The core of POF is made of highly light-transmitting plastic such as PMMA (polymethylmethacrylate) or polycarbonate. The POF clad is made of a plastic having a lower refractive index than the core described above. It is easy to increase the diameter of the core of such an optical fiber 2 from about 200 μm to about 1 mm as compared with a quartz optical fiber. Due to its ease, the POF can be easily coupled and adjusted with the bidirectional optical communication module 1. Further, POF can be used to obtain an inexpensive bidirectional optical communication link 3.

【0122】

As shown in the present embodiment, when the first transmitted light 8 and the received light 9 are spatially separated, it is preferable to use a POF with a core diameter of about 1 mm. Further, PCF (Polymer Clad Fiber) in which the core is made of quartz glass and the clad is made of polymer may be used instead of POF. Although PCF is more expensive than POF, it has the characteristics of low transmission loss and wide transmission band. Therefore, by using the PCF as a transmission medium, it is possible to obtain a bidirectional optical communication link 3 capable of long-distance communication and high-speed communication.

【0123】

As the light emitting element 4, a semiconductor laser or a light emitting diode (LED) is used. The wavelength of the light emitting element 4 is preferably a wavelength at which the transmission loss of the optical fiber 2 used is small. From the viewpoint of manufacturing cost, it is more preferable to select a wavelength at which the light emitting element 4 is cheaper from the above wavelengths. For example, when POF is used as the optical fiber 2, a semiconductor laser having a wavelength of 650 nm or the like can be used. Semiconductor lasers with a wavelength of 650 nm are inexpensive because they are effective for mass production such as DVDs.

【0124】

A monitor photodiode 14 is arranged at the rear of the light emitting element 4. The monitor photodiode 14 has a role of keeping the amount of light of the light emitting element 4 constant.

【0125】

As the light receiving element 5, a photodiode capable of converting the intensity of the received modulated light into an electric signal and having high sensitivity in the wavelength range of the light emitting element 4 is used. Such photodiodes are, for example, PIN photodiodes made of silicon, avalanche photodiodes, and the like.

【0126】

The optical member 10 is made of a plastic such as PMMA or polycarbonate and is manufactured by injection molding or the like. Then, a metal thin film having high reflectance such as aluminum or gold is formed on the side of the optical member 10 to be the reflection mirror 7 by a vapor deposition method or the like.

【0127】

The reflection mirror 7 is formed by vapor deposition from the lower left side of the optical member 10 of FIG. Therefore, the reflection mirror 7 can be easily formed without patterning with a mask or the like. The reflection mirror 7 has a curved surface and has a role of condensing the received light 9. Further, an electrode 21 is formed on the lower surface of the optical member 10 in contact with the stem 13.

【0128】

The electrode 21 is formed at the same time as the reflection mirror 7 by a vapor deposition method or the like. Further, the electrode 21 is connected to the reflection mirror 7 at least in part thereof.

【0129】

The optical member 10 includes a transmitting lens 6 that collects the first transmitted light 8 and couples it to the optical fiber 2, a diverging portion 25 for preventing interference due to stray light, and the optical fiber 2 that refracts the first transmitted light 8. A prism 11 is formed to be incident on the optical fiber. Further, although not shown, a positioning uneven portion used for positioning the light emitting element 4 and the light receiving element 5 is formed on the optical member 10. The optical member 10 is also used as a part of the sealing member of the light emitting element 4. In this way, since one optical member 10 has many functions, the number of constituent members can be significantly reduced, and the tolerance at the time of assembly can be reduced. Therefore, a low-cost and compact bidirectional optical communication module 1 can be obtained. It becomes possible to obtain.

【0130】

Further, the light emitting element 4, the light receiving element 5, and the optical member 10 can be arranged on one stem 13 in parallel with the optical axis of the optical fiber 2, respectively. As a result, a complicated assembly process becomes unnecessary, and the assembly process can be significantly reduced.

【0131】

As described above, by using the bidirectional optical communication module 1 shown in the present embodiment, interference due to near-end reflection, far-end reflection, mating module reflection, and internal diffused light can be prevented. Further, by using the bidirectional optical communication module 1 shown in the present embodiment, electrical / electromagnetic interference can be reduced. Therefore, by using the bidirectional optical communication module 1 of the present embodiment, full-duplex bidirectional optical communication by one optical fiber 2 becomes possible. In particular, by forming the divergent portion 25 around the transmitting lens 6, the first transmitted light 8 and the stray light 18 can be easily separated. As a result, interference due to internal disturbance light can be reliably reduced. Further, since one optical member 10 has many functions, it is possible to obtain a bidirectional optical communication module 1 which can be manufactured at low cost, in a small size, and easily.

【0132】

[Embodiment 2] Other embodiments of the present invention will be described with reference to FIG. For convenience of explanation, members having the same functions as the members shown in the drawings of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

【0133】

FIG. 16 shows a bidirectional optical communication module 1 using the first transmitting lens 22 and the second transmitting lens 23. FIG. 16 shows an example in which the first transmission light control unit includes a plurality of lenses. When the first transmitting lens 22 and the second transmitting lens 23 are used as shown in FIG. 16, a surface emitting type object such as a light emitting diode (LED) or a surface emitting laser can be used for the light emitting element 4. ..

【0134】

The light emitted from the light emitting element 4 is collected by the first transmitting lens 22 and passes through the optical member 10. Further, the light is collected by the second transmitting lens 23 and coupled to the optical fiber 2.

【0135】

When an LED is used as the light emitting element 4, an expensive drive circuit as in the case of using a semiconductor laser for the light emitting element 4 becomes unnecessary. Therefore, if an LED is used for the light emitting element 4, a low-cost bidirectional optical communication module 1 can be obtained.

【0136】

However, compared to semiconductor lasers, LEDs have a wider radiation angle and a larger light emitting area. Therefore, when an LED is used for the light emitting element 4, it is necessary to bring the light emitting element 4 and the transmitting lens 6 close to each other in order to combine the light with the transmitting lens with high efficiency. However, since the LED has a wide radiation angle and a large light emitting portion area, there is a problem that sufficient light collection cannot be performed when the light emitting portion is brought close to the transmitting lens 6.

【0137】

In the bidirectional optical communication module 1 shown in the present embodiment, the light emitting element 4 is LED by using a plurality of lenses, the first transmitting lens 22 and the second transmitting lens 23, as the first transmitting light control unit. Is also used, the first transmitted light 8 can be easily focused. Further, by using two transmitting lenses (first transmitting lens 22 and second transmitting lens 23) as described above, transmission efficiency can be improved.

【0138】

In the second embodiment, the prism 11 as shown in FIG. 11 or 12 in the first embodiment is not arranged. However, the received light 9 emitted from the second transmitting lens 23 diverges and is reflected by the second transmitting lens 23. Therefore, the second transmitting lens 23 can prevent the reflection of the other module.

【0139】

A divergence portion 25 is formed on the outer peripheral portion of the first transmission lens 22 as shown in the first embodiment. The divergence unit 25 separates the light into the stray light 18 and the first transmission light 8. Further, the divergence portion 25 prevents the stray light 18 from irradiating the optical fiber 2 or the optical fiber plug 26.

【0140】

Further, a divergence portion similar to that of the divergence portion 25 of the first embodiment may be formed around the second transmission lens 23 to prevent interference due to internal diffused light. For example, a divergent portion may be continuously formed on the outer circumference of the second transmitting lens 23. Further, the divergent portion may be made of, for example, a prism, a lens, or a material having a high light reflectance.

【0141】

As described above, by using the bidirectional optical communication module 1 shown in the second embodiment, an inexpensive LED can be used, and interference due to internal disturbance light can be reliably prevented.

【0142】

[Embodiment 3] Yet another embodiment of the present invention will be described with reference to FIG. However, the same member numbers are assigned to the members having the same functions as those described in the first and second embodiments, and the description thereof is omitted.

【0143】

FIG. 17 shows an example in which a receiving lens that collects the received light is installed between the reflection mirror 7 (received light control unit) and the light receiving element 5. In the present embodiment, the receiving light 9 focused by the reflection mirror 7 is further focused by the receiving lens 24 to further improve the receiving efficiency.

【0144】

The receiving lens 24 is integrally formed with the mold portion 29. The mold portion 29 seals the light receiving element 5 and the preamplifier 28 arranged in the vicinity thereof from the outside air. A transparent resin such as acrylic or polycarbonate is used as the material of the mold portion 29.

【0145】

By sealing the light receiving element 5 and the preamplifier 28 from the outside air, it is possible to prevent the performance from deteriorating due to deterioration over time. Further, when the receiving lens 24 is formed in the mold portion 29 as compared with the case where the receiving lens 24 is installed alone, the bidirectional optical communication module 1 becomes smaller.

【0146】

A divergence portion 25 is formed around the transmission lens 6. In this embodiment, a light-shielding film is used as the divergence portion 25. As the light-shielding film, for example, a film having a vapor-deposited mirror formed around the transmission lens 6 as a reflective film, a film coated with a material having a high light absorption rate, or the like can be used. Of course, as in the first or second embodiment, the diverging portion 25 may be composed of a prism or a lens continuously formed on the outer periphery of the transmitting lens 6.

【0147】

As described above, the bidirectional optical communication module 1 shown in the third embodiment has high reception efficiency, exhibits stable performance, and can surely prevent interference due to internal disturbance light.

【0148】

[Effect of the invention]

As described above, in the bidirectional optical communication module of the present invention, the first transmitted light to be transmitted among the light emitted from the light emitting element is incident, and the first transmitted light emitted from the incident light is the optical communication. The first transmitted light control unit that controls the first transmitted light and the second transmitted light that is not the transmission target of the light emitted from the light emitting element are incident so as to be incident on the optical communication path at the end face of the path element. The second transmission that controls the second transmission light so that at least a part of the second transmission light does not enter the end face of the optical communication path and the optical communication path element on which the first transmission light is incident. It is configured to be equipped with an optical control unit.

【0149】

Therefore, even if the output of the light emitting element is kept sufficiently high and the extinction ratio is made sufficiently large, the effect of obtaining a bidirectional optical communication module satisfying the conditions for eye safety is obtained. In addition, it has the effect of effectively suppressing interference between the second transmitted light and the received light.

【0150】

Further, in addition to the above configuration, the bidirectional optical communication module of the present invention has a configuration in which a second transmission light control unit is continuously formed on the outer periphery of the first transmission light control unit.

【0151】

Therefore, in addition to the effect of the above configuration, it is possible to control all the light emitted by the light emitting element with a simple configuration.

【0152】

Further, in the bidirectional optical communication module of the present invention, in addition to the above configuration, a shielding member that absorbs the irradiated light is arranged at a position where at least a part of the light that has passed through the second transmission light control unit is irradiated. It is a configuration to do.

【0153】

Therefore, in the bidirectional optical communication module, in addition to the effect of the above configuration, the stray light that scatters a plurality of times and is coupled to the light receiving element is reduced, and the interference due to the internal disturbance light can be further reduced. Play.

【0154】

Further, in the bidirectional optical communication module of the present invention, in addition to the above configuration, a shielding member that reflects the irradiated light is arranged at a position where at least a part of the light that has passed through the second transmission light control unit is irradiated. It is a configuration to do.

【0155】

Therefore, in addition to the effect of the above configuration, in the bidirectional optical communication module, the stray light that scatters a plurality of times and is coupled to the light receiving element is reduced, and the interference due to the internal disturbance light can be further reduced. Play.

【0156】

Further, the bidirectional optical communication module of the present invention has a configuration in which, in addition to the above configuration, the second transmission light control unit is composed of a prism, a lens, a material that reflects light, or a light absorber.

【0157】

Therefore, in addition to the effect of the above configuration, it is possible to further reduce the interference caused by the internal disturbance light.

【0158】

Further, in the bidirectional optical communication module of the present invention, in addition to the above configuration, the first transmission light control unit and the second transmission light control unit are integrally formed of the same material.

【0159】

Therefore, in addition to the effect of the above configuration, it is possible to obtain an inexpensive and compact bidirectional optical communication module with less deterioration over time.

【0160】

Further, the bidirectional optical communication module of the present invention has a first surface and a second surface which is a back surface of the first surface in addition to the above configuration, and the first surface reflects received light and the surface thereof. The received light control unit that collects the reflected received light on the light receiving element and reflects the light that irradiates the second surface on the second surface to prevent the light that irradiates the second surface from irradiating the light receiving element. It is a configuration that is prepared.

【0161】

Therefore, in addition to the effect of the above configuration, it is possible to more easily reduce the interference generated by the light other than the received light coupled to the light receiving element.

【0162】

Further, the bidirectional optical communication module of the present invention has a configuration in which, in addition to the above configuration, a light-shielding unit that blocks light reflected by the end surface of the optical communication path element is provided on the second surface of the received light control unit. is there.

【0163】

Therefore, in addition to the effect of the above configuration, it is possible to more effectively reduce the interference caused by the near-end reflection.

【0164】

Further, in the bidirectional optical communication module of the present invention, in addition to the above configuration, the portion where the received light control unit is formed, the first transmission light control unit, and the second transmission light control unit are integrally made of the same material. It is a composition to form.

【0165】

Therefore, in addition to the effect of the above configuration, it is possible to obtain an inexpensive and compact bidirectional optical communication module with less deterioration over time.

【0166】

Further, in the bidirectional optical communication module of the present invention, in addition to the above configuration, a prism is installed between the first transmission optical control unit and the optical communication path element, and the first transmission light is transmitted from the outer peripheral direction of the optical communication path. The prism refracts the first transmitted light so that the light is incident.

【0167】

Therefore, in addition to the effect of the above configuration, the transmission area can be reduced and the reception area can be increased accordingly.

【0168】

Further, in the bidirectional optical communication module of the present invention, in addition to the above configuration, the shape of the end face of the optical communication path element is inclined with respect to the optical axis, and the side where the cross section of the optical communication path element becomes blunt due to the inclination is The configuration is such that the optical communication path element is fixed so that the first transmitted light is incident on the optical communication path element.

【0169】

Therefore, in addition to the above configuration, it has the effect of further reducing interference due to far-end reflection.

【0170】

Further, in addition to the above configuration, the bidirectional optical communication module of the present invention has a configuration in which the shape of the end face of the optical communication path element is spherical.

【0171】

Therefore, in addition to the effect of the above configuration, the effect of reducing the interference due to the far-end reflection can be obtained.

【0172】

Further, in the bidirectional optical communication module of the present invention, in addition to the above configuration, the first transmission optical control unit includes a plurality of lenses.

【0173】

Therefore, in addition to the effect of the above configuration, it is possible to increase the focusing ability of the lens and increase the types of light emitting elements that can be used.

【0174】

Further, in addition to the above configuration, the bidirectional optical communication module of the present invention has a configuration in which a receiving lens that collects received light is installed between the received light control unit and the light receiving element.

【0175】

Therefore, in addition to the effect of the above configuration, the receiving lens can further collect the received light collected by the receiving light control unit, and the receiving efficiency can be improved.

[Simple explanation of drawings]

[Figure 1]

It is a top view which shows the structure of the bidirectional optical communication module of this invention.

[Figure 2]

It is sectional drawing which shows one Embodiment of the bidirectional optical communication module in this invention.

[Fig. 3]

It is a top view which shows the transmission area and the reception area of the bidirectional optical communication module in this invention.

[Fig. 4]

(a) is a plan view showing an optical path when the bidirectional optical communication module in the present invention has no divergence portion, and (b) is a plan view showing a state of (a) viewed from the direction of arrow A. ..

[Fig. 5]

(a) is a plan view showing an optical path of light passing through a divergent portion when the bidirectional optical communication module in the present invention has a divergent portion, and (b) is a plan view showing (b) from the direction of arrow B. It is a top view which shows the appearance.

[Fig. 6]

(a) is a cross-sectional view showing a configuration of a divergent portion of the bidirectional optical communication module in the present invention, and (b) is a plan view showing a state of (a) viewed from the direction of arrow C.

[Fig. 7]

(a) is a cross-sectional view showing another configuration of the divergent portion of the bidirectional optical communication module in the present invention, and (b) is a plan view showing a state of (a) viewed from the direction of arrow D. ..

[Fig. 8]

(a) is a cross-sectional view showing still another configuration of the divergent portion of the bidirectional optical communication module in the present invention, and (b) is a plan view showing a state of (a) viewed from the direction of arrow E. is there.

[Fig. 9]

It is a top view which shows the structure which includes the shielding member in the bidirectional optical communication module in this invention.

[Fig. 10]

It is a top view which shows the principle of interference prevention performed by the bidirectional optical communication module in this invention.

[Fig. 11]

It is a top view which shows the prevention principle of the mating module reflection of the bidirectional optical communication module in this invention.

[Fig. 12]

It is a top view which shows the structural example of another prism shape of the bidirectional optical communication module in this invention.

[Fig. 13]

It is a top view which shows the structure which inclined the end face of the optical fiber used for the bidirectional optical communication module in this invention.

[Fig. 14]

It is a top view which shows the structure which made the end face of the optical fiber used for the bidirectional optical communication module of this invention a spherical surface.

[Fig. 15]

It is a top view which shows the structural example of the bidirectional optical communication module in this invention in the shape of another prism.

[Fig. 16]

It is a top view which shows the structure which made two transmission lenses of the bidirectional optical communication module in this invention.

[Fig. 17]

It is a top view which shows the structure which installed the receiving lens of the bidirectional optical communication module in this invention.

[Fig. 18]

It is a graph which shows the relationship between the drive current of a semiconductor laser, and an optical output.

[Fig. 19]

It is a top view which shows one configuration example of the conventional bidirectional optical communication module.

[Fig. 20]

It is a top view which shows the other configuration example of the conventional bidirectional optical communication module.

[Explanation of symbols]

1 Bidirectional optical communication module 2 Optical fiber (optical communication path element) 3 Two-way optical communication link 4 light emitting element 5 Light receiving element 6 Transmission lens (1st transmission light control unit) 7 Reflection mirror (received light control unit) 8 1st transmission light 9 Received light 10 Optical members 11 prism 12 submount 13 stem 14 Monitor photodiode 15 Transmitter cover 16 Shading part 17 Reflected light 18 Stray light 19 element reflected light 20 Prism reflected light 21 electrodes 22 1st transmitting lens 23 2nd transmitting lens 24 Receiving lens 25 Divergence unit (2nd transmission light control unit) 26 Fiber optic plug 27 Receptacle 28 preamp 29 Mold part 30 Shielding part (shielding member) 31 Light absorption layer (shielding member) 32 shaded area 33 2nd transmission light