Optical waveguide, optical waveguide module, and method of fabricating optical waveguide

The present invention relates to miniaturization of optical components, and more particularly to an optical waveguide that can change the direction of an optical waveguide with a minute size, an optical waveguide module, and a method of converting the optical waveguide direction.

At present, the operating speed of electric circuits is approaching the operating speed of optical transmission circuits. However, further increasing the operating speed of the electric circuit has a higher principle barrier than improving the operating speed of the optical transmission circuit. This is because the time constant due to the capacitance attached to the electric circuit increases at high speed operation. Therefore, in order to partially supplement the high-speed operation of the electric circuit with an optical transmission line, research and development for fusing the electric circuit and the optical circuit are being actively carried out.

Specifically, a VCSEL (Vertical Resonator Type Surface Emitting Laser) is mounted on an electric circuit board, and the optical signal emitted from the VCSEL (Vertical Cavity Surface Emission Laser) is incident on an optical fiber or an optical waveguide and propagated, and then PD (PD) mounted on an electric substrate. A photodiode) receives light and transmits a signal. A method of embedding the optical fiber or the optical wave guide in the electric circuit board itself or a method of using the optical fiber or the optical wave guide as a substitute for the current electric cord between a plurality of electric circuit boards is being studied. Further, as optical fibers and optical waveguides used for the above-mentioned applications, for example, organic waveguide sheets (typical waveguide sheets include polyimide waveguide sheets) and optical fiber sheets have been proposed. There is.

The VCSEL is a surface-issued laser, and the emission direction of the laser light is perpendicular to the mounted electric circuit board. If the laser mounting direction is perpendicular to the electric circuit board, the laser light emission direction will be parallel to the electric circuit board, but such laser mounting has the advantage of high-density multiplex mounting of the VCSEL. It ruins and is not normally used.

In addition, since the optical waveguide and optical fiber embedded in the electric circuit board transmit light in the direction parallel to the electric circuit board, the laser light emitted from the VCSEL is coupled to these optical waveguide and optical fiber. Requires a 90 degree optical waveguide direction conversion.

As such a method of converting the optical waveguide direction of 90 degrees, a method of polishing the end face of the optical fiber or the waveguide to 45 degrees and applying metal vapor deposition or the like to the polished surface to make a mirror, and performing a conversion of 90 degrees. A method of performing conversion with a mirror having an angle of 45 degrees is being studied.

In addition, although the application area is different from the necessity of conversion in the 90-degree optical waveguide direction as described above, for example, in FTTH, an optical fiber is wired in the user's house, but in general optical fiber, mechanical characteristics and optical characteristics Because it is not possible to bend the optical fiber within a few centimeters, it is necessary to secure a space to gently bend the optical fiber at the corner of the room or at the hole where the optical fiber is taken from outdoors to indoors. And indoor landscapes are to be spoiled. On the other hand, in recent years, optical fibers that can be bent mechanically and optically even if the minimum bending radius is 15 mm have been developed.

Further, as an application for converting the optical waveguide direction in an ultra-compact manner, a method of thinning a desired portion of an optical fiber to a very fine diameter and bending it has been proposed and commercialized. In this method, the optical fiber diameter of the thinned part is about several μm to 10 μm, and even if the optical fiber is bent with a bending radius of 1 mm, the bending strain due to the bending is 1% or less, which is mechanically sufficient. It becomes possible to bend. Optically, the structure does not confine light only by the fiber of this thin part, but the combination of this thin optical fiber part and the environment outside it, that is, air, makes the core an optical fiber and the clad an environment (air). ), And it functions as a waveguide with an ultra-high equivalent refractive index difference of several tens of percent, and it is possible to bend even with a small bending radius without loss of light.<patcit num="1"><text>PatNo.US2003 / 0165291A1</text></patcit><patcit num="2"><text>PatNo.5138676</text></patcit><patcit num="3"><text>Japanese Unexamined Patent Publication No. 2000-329950</text></patcit><nplcit num="1"><text>Oki et al. "Development of 60bps Class Parallel Optical Interconnect Module (ParaBIT-1F)" 2000 IEICE Technical Report EMD2000-7</text></nplcit><nplcit num="2"><text>Shimizu, et al. "Optical I / O Built-in System LSI Module (3) Optical Coupling System Design" 2003 IEICE Electronics Society Conference C-3-125</text></nplcit><nplcit num="3"><text>Sasaki, et al. "Development of board-mounted connector for system LSI module with built-in optical I / O" 2003 IEICE Electronics Society Conference C-3-127</text></nplcit>

<p>First, in the above-mentioned method of polishing the end face of the optical fiber or waveguide to 45 degrees, metal vapor deposition on the polished surface to make a mirror, and converting 90 degrees, the optical fiber or waveguide is systematically set to 45 degrees. Polishing work is not easy, and further processes such as metal deposition require large-scale manufacturing equipment. It is necessary to mount the 45-degree surface without twisting directly above or below the circuit board at the time of mounting, but such mounting is not easy. In addition, in this method, after conversion from the core of the optical fiber or the core of the waveguide in the 90-degree direction, the light is guided through a medium that does not have a waveguide structure, so that the beam diameter is widened and good coupling is obtained. Is difficult.</p><p> In addition, in the method of performing conversion with a mirror with an angle of 45 degrees, a minute mirror is required for miniaturization, and the light beam propagates in space to the alignment with this minute mirror and the mirror part. In order to suppress the beam spread due to this, lens parts and the like must be added, the number of parts increases, and it is not easy to align them.</p><p> Furthermore, in a system with spatial propagation, the end face of light emitted from the waveguide or optical fiber to the space requires a large amount of reflection attenuation, so anti-reflection coating or diagonal polishing is required, but anti-reflection coating is a large-scale device. In diagonal polishing, the radiation direction of the light beam deviates from the optical axis in the waveguide or in the optical fiber, so that the alignment with the 45-degree mirror may be more difficult.</p><p> Next, even if the minimum bending radius is 15 mm, an optical fiber that can be bent mechanically and optically is effective outdoors, but it is better that the allowable bending radius is small indoors or in a narrow space. It cannot be used when you want to make it smaller than the bending radius of 15 mm.</p><p> In the method of thinning the desired portion of the optical fiber to a very fine diameter and bending it, the outer diameter is about several μm, which is a very small diameter, so that there is a problem that the optical fiber is broken during handling. Further, in this method, the reduction of light loss at the bent portion is basically that the external environment acts as a clad and is sensitive to changes in the external environment. That is, if moisture dew condensation occurs in this minute diameter portion due to environmental humidity or temperature fluctuation, light confinement in the minute bending portion due to the pseudo ultra-high Δ does not work.</p><p> In order to maintain the function of confining light in the minute bent portion, it is necessary to perform airtight sealing of this minute diameter portion in a state of being exposed to a gas such as air. That is, it is necessary to arrange a minute diameter portion in the cavity for airtight sealing, but this is not easy. Further, even if the micro-diameter portion is small, the structural portion that airtightly seals and protects the micro-diameter portion must have a structure that is much larger than that of the micro-diameter portion.</p><p> Moreover, organic waveguide sheets and optical fiber sheets have been proposed as the above-mentioned optical fibers and optical waveguides. First, the optical loss of the organic waveguide sheet at the current technical level is very high at about 0.2 dB / cm. It is large, and the optical power is lost by 3 dB, that is, less than half, even if it is transmitted 15 cm in length. Considering the case of transmitting an optical signal from an optical fusion substrate to a back plane and another optical electric fusion substrate, it is considered that the optical signal transmits a distance of about several tens of cm to 1 m. In this case, the connector part Ignoring the connection loss of the above, the maximum optical loss of about 20 dB will be generated only by the transmission loss of the waveguide. After all, when optical transmission is performed using an organic waveguide at the current technical level, it is limited to short-distance transmission. Further, the characteristics of the organic waveguide are liable to fluctuate depending on the temperature, and the long-term reliability in a high temperature and high humidity state such as an electric circuit is lower than that of an optical fiber.</p><p> On the other hand, the optical fiber sheet is obtained by wiring a plurality of optical fibers between two flexible plastic films, and the characteristics are determined by the optical fibers. The transmission loss of the optical fiber is about 0.2 dB / km, which is much smaller than that of the quartz optical fiber, which is 0.2 dB / cm, which is 0.2 dB / cm in the organic waveguide. The transmission loss is negligible at a distance of several meters at the maximum, such as transmission in optical fiber. In the case of plastic optical fiber, there is an increase in transmission loss of several dB to several tens of dB / km, but even with a loss of 500 dB / km, for example, it is about 0.5 dB / m, which is about 1/40 of that of an organic waveguide. The transmission loss is still small at a distance of several meters at the maximum, and there is no problem in practical use.</p><p> However, in this optical fiber sheet, since light is wired to a desired location in a plurality of optical fibers, the wired optical fibers intersect, and optical loss occurs depending on the degree of the intersection. In order to avoid the light loss due to this intersection, it is conceivable to devise the wiring shape or put a cushioning material in the intersection, but such a measure deteriorates the yield and leads to further cost increase. Further, the wiring on the sheet has a problem that the bending radius cannot be reduced due to the optical and mechanical strength of the optical fiber.</p><p> In general, quartz-based optical fibers have a concern of increased optical loss and mechanical destruction when the bending radius is 15 mm or less, so it is necessary to wire with a radius larger than that, and it is difficult to make the optical fiber sheet smaller. The shape is also limited. Regarding the mechanical strength of an optical fiber sheet using a quartz optical fiber, for example, Japanese Patent Application Laid-Open No. 2000-329950 proposes to use a carbon-coated fiber in which the surface of the optical fiber is coated with carbon. The carbon-coated optical fiber has a black surface, and even if the fiber is coated and colored, there is a problem that the difference in color cannot be discriminated.</p><p> Further, when an optical fiber sheet is embedded in an electric circuit board to produce an optical electric fusion board, the optical fiber causes microbend loss due to the unevenness of the surface of the electric circuit board. This can be easily understood as a situation in which small irregularities hit the side surfaces of the optical fiber to generate lateral pressure, and fine bending is continuously generated in the longitudinal direction of the optical fiber. Such microbend loss may also occur when the temperature of the optical fiber sheet alone is lowered. This is caused by the flexible plastic film forming the sheet shrinking at a low temperature, the optical fiber shrinking small because it is glass, and the optical fiber undulating finely due to the difference in shrinkage length.</p><p> The present invention has been made to solve the above-mentioned problems. The purpose is an optical waveguide that has a small number of parts, does not require alignment, converts the waveguide direction of light in a very small part, is insensitive to external environmental fluctuations, and does not require a special protection mechanism such as airtight sealing. , An optical waveguide module and a method of converting the optical waveguide direction.</p>

<p> The inventor has conducted extensive research to solve the conventional problems. As a result, it was found that when the desired part of the optical waveguide is heated to a predetermined temperature, the part of the optical waveguide is in a state where the processing strain is released, and when bending is performed with a predetermined bending radius in that state, the optical waveguide is bent without distortion. did. The present invention has been made based on the above-mentioned research results, and the first aspect of the optical waveguide of the present invention is an optical waveguide having a core and a clad, in which a desired portion is heated to release processing strain. Move to the state. Then, the optical waveguide that has shifted to the machining strain open state is bent in a curved shape with a predetermined bending radius to shift to the machining strain state.</p><p> A second aspect of the optical waveguide of the present invention is an optical waveguide in which the portion of the optical waveguide to be used is heated to a temperature within the range of the bending point or more and the softening point or less to shift to a processing strain state.</p><p> A third aspect of the optical waveguide of the present invention is an optical waveguide which is an optical fiber having an outer diameter of 50 μm or more and μm or less. The material of the optical fiber includes quartz, all plastic, and plastic clad.</p><p> A fourth aspect of the optical waveguide of the present invention is an optical waveguide in which the outer diameter of the optical waveguide used is 10 times or more the mode field diameter.</p><p> A fifth aspect of the optical waveguide of the present invention is an optical waveguide in which the bending radius of the optical waveguide used is 5.0 mm or less.</p><p> A sixth aspect of the optical waveguide of the present invention is the equivalent refractive index difference Δ between the core and the clad of the optical waveguide to be used.₁Is in the range of 0.8% or more and 3.5% or less, preferably Δ₁Is an optical waveguide in the range of 1.0% or more and 3.0% or less. The equivalent refractive index difference refers to the difference in refractive index between the maximum refractive index of the core portion and the refractive index of the effectively clad portion. Further, the refractive index profile of the optical fiber is not particularly limited, such as a single peak type profile and a W type profile.</p><p> In the first aspect of the optical waveguide module of the present invention, any one of the above-mentioned optical waveguides is composed of a plurality of optical waveguides, the optical waveguides are arranged in an array, and at least a part of the optical waveguides is a positioning mechanism. It is an optical waveguide module fixed to a member provided with.</p><p> A second aspect of the optical waveguide module of the present invention is an equivalent refractive index difference Δ between a core and a cladding at at least one end of any one of the optical waveguides described above.₂This module reduces the mismatch of the equivalent refractive index difference Δ and the mismatch of the mode field diameter by fusing and connecting optical waveguides with a value of 0.2% or more and heating that part.</p><p> A third aspect of the optical waveguide module of the present invention is an optical waveguide module in which any one of the above-mentioned optical waveguides is fixed in a state of being wired on one sheet.</p><p> A fourth aspect of the optical waveguide module of the present invention is an optical waveguide module in which any one of the above-mentioned optical waveguides is fixed in a state of being wired between at least two sheets.</p><p> A fifth aspect of the optical waveguide module of the present invention is an optical waveguide module in which a plurality of optical waveguides are used and are fixed in a wired state.</p><p> A sixth aspect of the optical waveguide module of the present invention is an optical waveguide module in which the material of the sheet used is a flexible material. The materials include polyimide, polyethylene terephthalate, low density or high density polyethylene, polypropylene, polyester, nylon 6, nylon 66, ethylene-tetrafluorethylene copolymer, poly4-methylpentene, polyvinylidene chloride, plasticized. Films such as polyvinyl chloride, polyether ester copolymers, ethylene-vinyl acetate copolymers, and flexible polyurethanes are used.</p><p> The first aspect of the method for producing an optical waveguide of the present invention is to heat a desired portion of the optical waveguide and shift the portion to a processing strain release state. Then, it is a method of making the optical waveguide which shifts to a machining strain state by bending the said part of the optical waveguide which has shifted to a machining strain state to a predetermined bending radius. By using an optical fiber as the optical waveguide used here and using the material as an all-plastic or plastic clad, it is possible to bend the optical waveguide into small pieces without bending loss. Moreover, the work at a high temperature as in the case of a quartz-based optical fiber becomes unnecessary.</p>

<p> With the optical waveguide of the present invention, it is possible to bend a desired portion with a desired radius and change the optical waveguide direction to a predetermined angle while reducing the connection loss due to fusion splicing. Further, they can be used to reduce the size of the optical waveguide module.</p>

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. (Embodiment 1)

FIG. 1 is a diagram illustrating an outline of a first aspect of the optical waveguide of the present invention. That is, the optical waveguide is bent by a predetermined radius in a state where the desired portion of the optical waveguide is heated to a high temperature (above the bending shop or above and below the softening point) by arc discharge. Since the bent portion of this optical waveguide is bent at a high temperature and then brought to a normal temperature environment after being bent, there is no distortion due to bending. That is, it is processed so that the bent state becomes the initial state. When the optical waveguide is deformed from the processed state after processing, distortion occurs and breaks, but by setting the processed state to the bent state, distortion does not occur and the optical waveguide does not break. However, when this bent portion is returned to a straight line, distortion occurs and breakage occurs. After all, by selecting whether the initial strain release state is a linear state or a bending state, it is possible to avoid fracture due to strain when creating a desired shape. Since it is an object of the present invention to convert the optical waveguide direction in a minute space, breakage is avoided by processing the state for conversion so as to be the initial strain release state. When performing this processing, the method of heating the desired part of the optical waveguide may be any means such as heating by arc discharge, heating by a burner, heating by a furnace, etc. The purpose is to bend the optical waveguide at the same time to reduce processing strain. It is to process while opening. (Embodiment 2)

FIG. 2 is a diagram showing an outline of aspects 3 and 5 of the optical waveguide of the present invention. In this aspect, the optical waveguide direction is changed in a minute space, but the size that can be practically used is defined by the physical size of the optical waveguide to be used. In this aspect, the outer diameter a of the optical waveguide is 50 μm or more. The bending radius R is 5.0 mm or less. That is, it is physically impossible to bend the bending radius R at 50 μm with respect to the optical waveguide having an outer diameter a of 50 μm. In addition, since it is not easy to handle an optical waveguide having an outer diameter a of less than 50 μm, an optical waveguide having a minimum outer diameter of 50 μm is specified to ensure ease of handling, and the optical waveguide used as a bending radius is used. The structure is such that bending is physically realized by making it 10 times the minimum outer diameter. Further, since the optical waveguide having an outer diameter a of 125 μm has an outer diameter compatible with a typical optical waveguide generally used at present, the scope of application of the present invention can be greatly expanded by using this outer diameter. Can be unfolded. Further, by setting the bending radius R to 5.0 mm or less, the advantage of adopting the method of the present invention is utilized. That is, when the bending radius R exceeds 5.0 mm, when a small-diameter optical fiber is used, fracture strain may not be reached depending on the bending radius, and the strain release processing of the present invention may not be required. If the diameter is 5.0 mm or less, the strain release processing of the present invention is required even for an optical waveguide having a minimum outer diameter a of 50 μm, which is not difficult to handle. In this embodiment, an optical fiber having an outer diameter a of 80 μm is bent at 90 degrees with a bending radius R of 1 mm. (Embodiment 3)

FIG. 3 is a diagram illustrating an outline of a sixth aspect of the optical waveguide of the present invention. In the optical waveguide direction in a minute space according to the second embodiment, emphasis was placed on a method of avoiding mechanical breakage, but in this embodiment, optical waveguide in a minute space while maintaining good optical characteristics. It makes it possible to change the direction. Equivalent index of refraction difference between core and clad of optical waveguide Δ₁Is in the range of 0.8% or more and 3.5% or less, preferably Δ₁Is within the range of 1.0% or more and 3.0% or less. That is, in a commonly used optical waveguide, the equivalent refractive index difference Δ between the core and the cladding.₁Is usually around 0.3%. However, the equivalent refractive index difference Δ of around 0.3%₁When the optical waveguide is bent with a bending radius R of 5.0 mm or less, the light confined in the core is no longer confined and radiates to the clad, resulting in a drastic increase in light loss at the bend. However, the equivalent index of refraction difference Δ₁Is in the range of 0.8% or more and 3.5% or less, preferably Δ₁Even if the bending radius R is 0.5 mm within the range of 1.0% or more and 3.0% or less, the light loss at the bent portion can be suppressed to 0.5 dB or less. High equivalent refractive index difference Δ that exceeds 3.5%₁If it is set to, the bending loss can be made smaller even if the bending radius is 0.5 mm or less, but in this case, in order to maintain the single mode operation, it is necessary to make the mode field diameter extremely small, and it is necessary to make the mode field diameter extremely small. Equivalent refractive index difference Δ₁Should be within the range of 1.5% or more and 3.5% or less. In this embodiment, the equivalent refractive index difference Δ is used to bend 90 degrees with the outer diameter a being 80 μm and the bending radius R being 1 mm.₁An optical fiber with a value of 2.5% is used. The wavelength used is 1.3 μm. (Embodiment 4)

FIG. 4 is a diagram illustrating an outline of a first aspect of the optical waveguide module of the present invention. The optical waveguide module of this aspect is an array of the optical waveguides of the present invention, and can collectively convert a large number of channels in the optical waveguide direction. Further, since the input / output portion of the module of the present invention is an optical waveguide having characteristics compatible with those of a general optical waveguide, it is possible to connect to an external device with good characteristics. In this embodiment, the outer diameter a is 80 μm and the equivalent refractive index difference Δ₁Fixes 2.5% optical fiber to a member with a positioning mechanism. In addition, a 90-degree optical waveguide direction conversion is performed from the input to the output, and both the input and output surfaces are polished at an angle of 4 degrees with respect to the 90-degree surface. The number is 12 in a horizontal straight line at intervals of 125 μm. (Embodiment 5)

FIG. 5 is a diagram illustrating an outline of a second aspect of the optical waveguide module of the present invention. In the optical waveguide module of this embodiment, the equivalent refractive index difference between the core and the cladding is Δ.₁Is in the range of 0.8% or more and 3.5% or less, preferably Δ₁Is in the range of 1.0% or more and 3.0% or less, and the equivalent refractive index difference between the core and the cladding of the first optical waveguide Δ₂It is fused and connected to a second optical waveguide having a value of 0.2% or more, and the fusional connection portion is heated to reduce the mismatch of the equivalent refractive index difference Δ between the core and the clad and the mismatch of the mode field diameter, and the optical wave An optical waveguide module that heats and bends a desired portion of a waveguide.

That is, since the optical waveguide module according to the second aspect uses an optical waveguide having a high equivalent refractive index difference, the equivalent refractive index of the core or clad is different from the equivalent refractive index of the core or clad of a general optical waveguide. Further, since the equivalent refractive index difference Δ is also different, there is a difference between the mode field diameter of the general optical waveguide and the mode field diameter of the optical waveguide used for the optical waveguide direction conversion unit of the present invention. When objects having different refractive indexes are brought into contact with each other and an optical signal is passed through that portion, light is reflected at the boundary portion of the refractive index. This is a phenomenon that must be avoided in optical communication. Generally, 50 dB or more is required as this reflection attenuation amount.

Further, when those having different mode field diameters are connected to each other, a connection loss occurs due to the diameter difference at the connecting portion. The mode field diameter of a general optical waveguide varies depending on the wavelength used, but is about 10 μm, and the mode field diameter of the optical waveguide used for the optical waveguide direction conversion unit of the present invention is about 3 μm. If connected as it is with this diameter difference, the connection loss will be 5 dB or more. Further, in order to facilitate the connection with an external device or a laser, it is effective to connect a general optical fiber and the external device, and then connect to the optical waveguide direction conversion unit of the present invention. Therefore, in the second aspect, in order to reduce these reflections and connection losses, the equivalent refractive index difference between the core and the cladding is Δ.₁Is in the range of 0.8% or more and 3.5% or less, preferably in the range of 1.0% or more and 3.0% or less, and the equivalent refractive index difference between the core and the clad Δ₂Reflection is reduced by fusion-connecting a second optical waveguide having a value of 0.2% or more and heating the fusion-bonded portion to reduce the mismatch of the equivalent refractive index difference Δ between the core and the cladding and the mismatch of the mode field diameter. The amount of attenuation is increased to suppress connection loss. By this method, the amount of reflection attenuation was 50 dB or more, and the connection loss was about 0.2 dB.

In this embodiment, the outer diameter a is 80 μm, the bending radius R is 1 mm, and the bending is 90 degrees, but the equivalent refractive index difference Δ₁Using an optical fiber with a single mode of optical waveguide mode depending on the wavelength used at 2.5%, the outer diameter a is 80 μm on one side, and the equivalent refractive index difference Δ₂At 0.35%, a fusion connection is made with an optical fiber whose optical waveguide mode according to the wavelength used is a single mode, and the fusion connection portion is heated with a gas burner to eliminate a mismatch in the equivalent refractive index difference Δ and a mismatch in the mode field diameter. Decreased. The wavelength used is 1.3 μm. According to the measurement results, the amount of reflection attenuation was 50 dB or more, and the connection loss was 0.2 dB. (Embodiment 6)

FIG. 6 is also a diagram illustrating an outline of a second aspect of the optical waveguide module of the present invention. In the optical waveguide module of this embodiment, the equivalent refractive index difference between the core and the cladding is Δ.₁The equivalent refractive index difference between the core and the cladding is Δ at both ends of the first optical waveguide in which is within the range of 0.8% or more and 3.5% or less, preferably 1.0% or more and 3.0% or less.₂It is fused and connected to a second optical waveguide having a value of 0.2% or more, and the fusional connection portion is heated to reduce the mismatch of the equivalent refractive index difference Δ between the core and the clad and the mismatch of the mode field diameter, and the optical wave guide is used. An optical waveguide module that heats and bends a desired portion of a waveguide. In the fifth embodiment, an optical waveguide compatible with the characteristics of a general optical waveguide is fused and connected to only one side of the optical waveguide direction conversion unit, and the connection portion is heated to cause a mismatch and mode of the equivalent refractive index difference Δ. Although the mismatch of field diameters has been reduced, in the sixth embodiment, optical waveguides compatible with the characteristics of general optical waveguides are fused and connected to both sides of the optical waveguide direction conversion section, and the connection section is heated to have an equivalent refractive index. Reduce the mismatch of the difference Δ and the mismatch of the mode field diameter. As a result, both sides of the optical waveguide direction conversion unit can be easily connected to an external device.

In this embodiment, the outer diameter a is 80 μm, the bending radius R is 1 mm, and the bend is 90 degrees, but the equivalent refractive index difference Δ₁2.5%, using an optical fiber in which the optical waveguide mode according to the wavelength used is a single mode, the outer diameter a is 80 μm on both sides, and the equivalent refractive index difference Δ₂Is 0.35%, and the optical fiber whose optical waveguide mode is single mode depending on the wavelength used is fused and connected, and the fusional connection part is heated with a gas burner to eliminate the mismatch of the equivalent refractive index difference Δ and the mismatch of the mode field diameter. Reduced. The wavelength used is 1.3 μm. According to the measurement results, the amount of reflection attenuation was 50 dB or more, and the connection loss was about 0.4 dB. (Embodiment 7)

FIG. 7 is a diagram showing an outline of aspects 4 to 6 of the optical waveguide module of the present invention. According to the present invention, when the optical waveguide module is manufactured, the equivalent refractive index difference between the core and the clad of the optical waveguide built in the sheet Δ₁Was set within the range of 0.8% or more and 3.5% or less. In this embodiment, an optical fiber having a general outer diameter of 125 μm in the outer diameter of the glass portion and 250 μm in the outer diameter of the coating is used, but the equivalent refractive index difference between the core and the clad is Δ.₁Is 2.5%, which is the equivalent index difference of a general single-mode optical fiber Δ₁Very large equivalent refractive index difference Δ, which is different from about 0.3%₁The optical waveguide of is used.

Equivalent refractive index difference Δ of such a general single-mode optical fiber₁Large equivalent index of refraction difference Δ₁When the optical waveguide module is manufactured using the optical fiber having the above, even if the optical waveguide module is wavy or bent, the loss due to the swell or bending is reduced. Specifically, an optical waveguide module using a general optical fiber was sandwiched between two sheets of sandpaper and pressed, and a loss fluctuation test was conducted in that state by a temperature cycle of -40 ° C to + 80 ° C. The result was a very bad result with a maximum loss of about 20 dB at a low temperature of -40 ° C, whereas the equivalent refractive index difference Δ₁In the optical waveguide module under exactly the same conditions except that is 2.5%, the result of the same test shows that the maximum loss fluctuation value due to the temperature cycle of -40 ° C to + 80 ° C is about 0.1 dB. , Almost no loss fluctuation appears.

Equivalent index of refraction difference Δ₁Even if the value was lowered to 1.5%, the loss fluctuation in the above test was still about 0.1 dB. However, the equivalent refractive index difference Δ₁Then, the loss fluctuation gradually increases, and the equivalent refractive index difference Δ₁When was 1%, the maximum loss fluctuation in the test was about 0.5 dB. Although there is no practical problem even at 0.5 dB, the optical waveguide module of the present invention is used in connection with the optical waveguide direction conversion element of the previous invention, and has good optical transmission characteristics and connection characteristics. Therefore, in consideration of the connectivity with the optical waveguide direction conversion element of the previous invention, the equivalent refractive index difference Δ used in the optical waveguide direction conversion element of the previous invention₁It is stipulated that the minimum value of 1.5% or more.

Also, the equivalent refractive index difference Δ₁The larger the value, the smaller the loss fluctuation, but the equivalent refractive index difference Δ₁If is made too large, the mode field diameter in the optical fiber becomes small, and high-precision position accuracy at the time of connection is required, and in consideration of the connectivity with the optical waveguide direction conversion element of the previous invention. Δ₁Was 3.5% or less.

In order to make it mechanically small, the outer diameter a of the glass part should be made smaller, but if the outer diameter is made too small, the light trapped in the core escapes because the clad is too thin. Causes transmission loss. Therefore, by setting the clad diameter, that is, the outer diameter of the optical fiber, to at least 10 times or more the mode field diameter, it is possible to suppress this transmission loss.

In addition, by making it thinner, it becomes weaker in the loss fluctuation test due to the temperature cycle of -40 ° C to + 80 ° C as performed in this embodiment, but the equivalent refractive index difference Δ₁However, it was confirmed that the maximum loss fluctuation was about 0.1 dB in the fiber with the mode field diameter of 5 μm, where the outer diameter a of the optical fiber was 50 μm at 1.5% or more, and very good characteristics were maintained. (Embodiment 8)

FIG. 8 is a conceptual diagram in which the optical waveguide module of the present invention is applied to square wiring in a house. As described above, in the wiring of the optical waveguide at the corner of the room in the house, it was conventionally necessary to secure a minimum bending radius of several cm of the optical waveguide. However, by using the optical waveguide module of the present invention, the module can be used. Square wiring is possible with a size of 1 cm or less. Note that b in FIG. 8 shows that it is possible to bend at 90 degrees. (Embodiment 9)

FIG. 9 is a diagram showing an outline of applying the optical waveguide module of the present invention to an electric optical circuit fusion substrate. The electric-optical fusion board has a structure in which an optical waveguide module is sandwiched between two electric circuit boards, and the optical waveguide of the present invention is located at the end of a 90-degree optical waveguide direction conversion section of the optical waveguide module to the surface of the electric circuit board. A waveguide module is installed.

With the optical waveguide of the present invention, the optical waveguide direction can be changed to a predetermined angle by bending a desired portion with a desired radius while reducing the connection loss due to fusion splicing. Furthermore, the optical waveguide module can be miniaturized by using them, and has high industrial utility value.

<figref num="1">FIG. 1 is a schematic view of bending an optical waveguide using an arc discharge.</figref><figref num="2">FIG. 2 is a schematic view of aspects 3 and 5 of the optical waveguide of the present invention.</figref><figref num="3">FIG. 3 is a schematic view of aspect 6 of the optical waveguide of the present invention.</figref><figref num="4">FIG. 4 is a schematic view of an optical waveguide module in which an arrayed optical waveguide is fixed to a member.</figref><figref num="5">FIG. 5 is a schematic view of aspect 2 of the optical waveguide module of the present invention.</figref><figref num="6">FIG. 6 is a schematic view of aspect 2 of the optical waveguide module of the present invention.</figref><figref num="7">FIG. 7 is a schematic view of the optical fiber sheet.</figref><figref num="8">FIG. 8 is a schematic view of the optical waveguide direction conversion module applied to the square wiring in the house.</figref><figref num="9">FIG. 9 is a schematic view of an optical waveguide direction conversion module applied to an electro-optical circuit fusion substrate.</figref>

Code description

1 Optical fiber 2 Arc discharge 3 Electrode 4 Desired part 5 Positioning mechanism 6 Member 7 Fusion splicing part 8 Sheet 9 Window 10 Optical waveguide module 11 Optical optical circuit fusion board