Optical switch and method of manufacturing the same

[0001] [Technical field to which the invention belongs] The present invention relates to an optical switch used for switching an optical path in an optical communication facility. [0002] [Conventional technology] An example of an optical switch based on the prior art is disclosed in Japanese Patent Application Laid-Open No. 2002-174784 (Patent Document 1). In this optical switch, a polymer optical waveguide film is used as a medium for carrying light. The base material of the polymer optical waveguide film is a polyimide film, and linear parts called cores, which have a slightly higher refractive index than the surroundings (clad part), are two-dimensionally embedded and arranged in a grid pattern. It is a thing. A notch groove is formed at the intersection of the cores. This optical switch is a holding plate provided with through holes corresponding to the intersections of the cores of a polymer optical waveguide film having cut grooves so that the intersections of the cores are exposed from the through holes. It is configured by sandwiching and arranging drive members on both sides or one side of the intersection of the cores. [0003] In this optical switch, when the notch groove is closed, light passes through this portion. This state is called a "transparent state". On the other hand, when the notch groove is pushed from the back side by the driving member, the notch groove opens, so that an air layer is formed between the cores facing each other across the notch groove. If the refractive index of the core and the clad portion and the intersection angle between the cores are properly designed in advance, when the notch groove is opened and an air layer of sufficient thickness is formed in the notch groove, the light to pass will pass. It will be totally reflected. That is, switching of the optical path can be realized. This state is called "reflection state". [0004] As shown in FIG. 8 of Patent Document 1, a plurality of cores on the input side and a plurality of cores on the output side are provided, and a notch groove is formed at each of the intersections of these cores to form an input port and an output port. For each core on the input side, one of the notch grooves intersecting with the core is set to the reflection state, and the other is set to the transmission state so that there is a one-to-one correspondence. This will direct the light to the desired output port. [0005] In the optical switch disclosed in Patent Document 1, the notch groove is formed by using a sharp blade or a blade such as a dicer. Alternatively, cleavage is generated while these blades are being inserted. [0006] [Patent Document 1] Japanese Unexamined Patent Publication No. 2002-174784 [0007] [Problems to be Solved by the Invention] When a notch groove is formed with the act of inserting a knife, chips are generated. In addition, the side surface of the blade rubs against the machined surface. As a result, unevenness is formed on the side surface of the notch groove, which is the machined surface. This means that the reflecting surface in the reflecting state has irregularities. If the reflecting surface is uneven, the reflection loss becomes large. Further, even when the cut groove is closed to make the cut groove transparent, the presence of unevenness on the side surface of the cut groove causes a portion having a minute gap in which air is interposed inside the cut groove. Since a part of the light is reflected in the part having such a minute gap, a part of the light also advances to the port on the reflecting side even though it is in a transmitted state, which causes crosstalk. .. [0008] On the other hand, when the notch groove is formed while rotating the blade using a dicer, the machined surface becomes a smooth surface to some extent because it is polished by the rotation of the blade, but since it is a complete cutting process, the material is used. It will be partially scraped off, and usually the cut margin will be about 15 μm wide. With this, it is possible to obtain a reflection state, but it is almost impossible to obtain a sufficiently good transmission state. [0009] Therefore, an object of the present invention is to provide an optical switch having reduced reflection loss due to a processed surface in a reflection state, transmission loss in a transmission state, and crosstalk, and a method for manufacturing the same. [0010] [Means for solving problems] In order to achieve the above object, the optical switch based on the present invention includes a film basically made of a polymer, a holding plate having a through hole for switching, and a driving means. Here, the film has an optical waveguide extending linearly inside the film and a notch groove provided so as to cross a switching portion in the middle of the optical waveguide. Further, the film is held by the holding plate so that the switching portion is exposed from the switching through hole. Further, the driving means is for selecting the path of light by approaching and separating the gaps of the notch grooves. The notch groove is formed by first forming a starting groove on the surface of the film and pressing the switching portion with a pressure member from the back side of the starting groove while holding the film by the holding plate to cleave. It was formed by producing it. [0011] BEST MODE FOR CARRYING OUT THE INVENTION (Embodiment 1) (Constitution) The optical switch according to the first embodiment based on the present invention will be described with reference to FIGS. 1 to 3. As shown in FIGS. 1 and 2, this optical switch includes a polymer optical waveguide film 2 which is basically a film made of a polymer, and a holding plate 3 which sandwiches and holds the polymer optical waveguide film 2. A core 1 (core 1a, 1b) passes through the inside of the polymer optical waveguide film 2 as an optical waveguide. A notch groove 6 is provided so as to cross the core intersection 7 where the core 1a and the core 1b intersect. The core intersection 7 is a switching point of the light path. [0012] A cross-sectional view is shown in FIG. In the state of FIG. 2, the notch groove 6 is closed. That is, it is in a transparent state. The holding plate 3 has a through hole 31 for switching. The holding plate 3 holds the polymer optical waveguide film 2 so that the core intersection 7 and the notch groove 6 provided therein are exposed from the through hole 31. At the location where the notch groove 6 is located, the pressurizing member 4 is arranged so that the polymer optical waveguide film 2 can be pushed up from below. The pressurizing member 4 can be displaced up and down by a driving means (not shown). FIG. 3 shows a state in which the pressurizing member 4 is raised by the driving means. In this state, the notch groove 6 is opened by being pushed up from below by the pressurizing member 4. That is, it is in a reflective state. [0013] The driving means is for selecting the path of light by approaching and separating the gaps of the notch grooves in this way. [0014] As shown in FIG. 4, the notch groove 6 is formed from the back side of the starting point groove 5 in a state where the starting point groove 5 is first formed on the surface of the polymer optical waveguide film 2 and the polymer optical waveguide film 2 is held by the pressing plate 3. It is formed by causing a cleave by pressing the switching portion with the pressure member 4. [0015] (Method of forming a notch groove) The method of forming the notch groove 6 will be described in more detail. As shown in FIGS. 4 and 5, the polymer optical waveguide film 2 is sandwiched and held by the holding plate 3 in a state where a shallow starting point groove 5 is formed in advance at a place where the notch groove 6 is to be formed on the surface. .. At this point, the notch groove 6 has not yet been formed. In this state, the pressurizing member 4 is pushed up by using a driving means (not shown). Then, the stress is concentrated on the starting point groove 5. Moreover, since the portion of the starting groove 5 is the most fragile portion, the crack grows from the starting groove 5 as a starting point. That is, cleave occurs. In this way, the notch groove 6 is formed as shown in FIG. [0016] As described above, the method for manufacturing an optical switch based on the present invention includes a step of causing a cleave by pressing. The process of causing a cleave by pressing is also called "cleave process". [0017] (Preferable conditions for starting groove) A shallow groove is sufficient for the starting groove 5. It is desirable that the origin groove 5 is above the center of the core 1 farther than half the length of the mode field diameter of the beam propagating in the core 1. That is, it is preferable that the distance between the bottom and the center of the core 1 at the deepest portion of the starting groove 5 is larger than half the length of the mode field diameter. This is because the starting groove 5 is made by cutting with a cutting tool or the like in the same manner as the conventional method of forming the cutting groove, so if the starting groove 5 is too close to the core 1, a large amount of light is reflected by the starting groove 5. This is because the problem is the same as in the past. [0018] The starting groove 5 is preferably formed with a width as narrow as possible. It is considered that the width of the upper end of the groove 5 is particularly large at the deepest position of the starting groove 5, but the width at this position is preferably 1 μm or less. This is because if the width of the upper end of the groove at the position where the starting groove 5 is deepest is too wide, it is uncertain from which position in the width direction the cleave proceeds, and as a result, unevenness is generated on the machined surface. [0019] In addition, in figures such as FIGS. 2 and 5 in which the starting groove 5 appears, the starting groove 5 is exaggerated and displayed in a large size for convenience of explanation. [0020] (Preferable conditions for cleaving) It is preferable to perform the cleaving by repeatedly raising and lowering the polymer optical waveguide film 2 to repeatedly fatigue the polymer optical waveguide film 2, rather than performing the cleaving by simply raising the pressure member 4 once. By doing so, it is possible to accelerate the progress of the cleave while shortening the time during which the excessive stress acts. [0021] [0021] If the force is suddenly pushed up with a large amount of displacement from the state where no cracks have occurred, the force acting at that time does not contribute to the progress of the cleave (progression of cracks), but the pressure member 4 and the polymer optical waveguide. Excessive stress acts on the contact points with the film 2 and the contact points between the inner peripheral edge of the through hole 31 of the holding plate 3 and the polymer optical waveguide film 2, and the polymer optical waveguide film 2 is plastically deformed. In some cases. From the viewpoint of preventing such a problem from occurring, the depth of the notch groove 6 reaches a desired value by repeatedly raising and lowering with a small amount of displacement at first and gradually increasing the amount of displacement to push up. It is desirable to do up to. [0022] (Depth of cut groove) FIG. 6 shows a cross-sectional view of the notch groove 6 generated as a result of this cleaving process. In this figure, the shape of the machined surface when viewed from the side is shown. The core 1 exposes its cross section inside the notch groove 6. The bottom 8 has a curved shape like an arc, but when the pressurizing member 4 pushes up the polymer optical waveguide film 2 by the same displacement as the depth at the deepest position of the bottom 8, the bottom 8 becomes It becomes almost linear. When the pressurizing member 4 is pushed up further, the crack further develops and the depth of the notch groove 6 increases. Therefore, the depth of the notch groove 6 is determined by the maximum amount of displacement pushed up during cleaving. After that, if it is not pushed up by a displacement amount exceeding the depth of the notch groove 6, no further cleaving will occur, and the push-up operation performed during normal use as an optical switch is more than the depth of the notch groove 6. If it is performed with a small displacement amount, it is possible to avoid the occurrence of undesired creep and the progress of cracks. [0023] (Action / effect) In the present embodiment, since the notch groove 6 is formed by causing a cleave without the entry of a cutting tool or the like, the machined surface is smooth without unevenness due to scratching. .. Therefore, the reflection loss in the reflection state can be reduced. Further, since the cut groove 6 is formed by causing a cleave, there is no cut margin inside the cut groove 6. Therefore, it is possible to reduce the transmission loss in the transmission state. [0024] Further, by setting the displacement amount during normal use to be equal to or less than the depth of the notch groove 6, it is possible to prevent further cracks from growing during use, and it is possible to obtain a highly reliable optical switch. [0025] Further, by performing an annealing treatment on the polymer optical waveguide film 2 after the cleaving process, the strain generated during the cleaving process can be eliminated, and the loss due to birefringence caused by the strain can be reduced. [0026] (Embodiment 2) (Production method) A method for manufacturing an optical switch according to a second embodiment based on the present invention will be described with reference to FIGS. 7 and 8. In the method of manufacturing this optical switch, as shown in FIGS. 8A and 8B, a pressure member 4f having a flat tip like a flat-blade screwdriver is used. The pressurizing member 4f comes into contact with the polymer optical waveguide film 2 at the contact points 9a and 9b, and the contact points 9a and 9b are on the line of the starting groove 5 when viewed in a plane, as shown in FIG. And make sure that the position is such that the core intersection 7 is sandwiched between them. Here, an example of using a flat pressure member 4f like a flat-blade screwdriver was shown, but the pressure member is a polymer optical waveguide film 2 at two points sandwiching the core intersection 7 on the line of the starting groove 5. Any other shape may be used as long as it has a shape capable of contacting the. [0027] Using the above-mentioned pressurizing member 4f, a pushing operation as described in the first embodiment is performed to generate a cleave as shown in FIG. 8A to form a notch groove 6. The method for manufacturing an optical switch according to the second embodiment based on the present invention includes such a step. [0028] The preferable conditions for the starting groove and the preferable conditions for pushing up are the same as those described in the first embodiment. [0029] (Action / effect) In this embodiment, since the pressurizing member 4f is in contact with the polymer optical waveguide film 2 at the two contact points 9a and 9b, the cleave is first not directly above the core 1 but directly above the contact points 9a and 9b. Occurs in. From these points, cracks grow due to cleave, and the cracks that grow from the left and right are connected to each other just above the core intersection 7. In this way, the notch groove 6 extending in a desired range is obtained. [0030] Here, problems in cleaving will be described. Also in the first embodiment (see FIGS. 4 to 6), at the position where the pressurizing member 4 is in contact with the polymer optical waveguide film 2, a large stress is first generated by being pressed, and the moment when a crack develops. The crack grows to a certain depth that is released at once. At this time, if there is a rattling in the shape of the bottom of the starting groove 5, a crack grows at a stretch from that portion while the directionality is unstable, and as a result, as shown in FIG. 9, it corresponds to directly above the contact point. Vertical streaks 10 may occur on the machined surface at the position where it is to be processed. When the contact point is directly below the core intersection 7, the streak 10 overlaps the exposed surface of the core 1 as shown in FIG. Since the streaks 10 have irregularities, the reflection loss increases when they overlap the exposed surface of the core 1. [0031] On the other hand, in the second embodiment, the contact points 9a and 9b (see FIG. 7) are not directly under the core intersection 7 but at a position away from the core intersection 7, so that even if they are in contact with each other as shown in FIG. Even if the streaks 10a and 10b occur just above the points 9a and 9b, they do not overlap the exposed surface of the core 1. Therefore, in the second embodiment, it is possible to prevent the reflection loss due to the streak generation phenomenon on the processed surface during the cleaving process. [0032] (Embodiment 3) (Production method) A method of manufacturing an optical switch according to a third embodiment based on the present invention will be described with reference to FIG. In this method of manufacturing an optical switch, a notch groove 6 is formed in the polymer optical waveguide film 2 by performing a cleaving process as described in the first or second embodiment. However, during the processing, the optical characteristics of the optical switch 100 composed of the polymer optical waveguide film 2 are monitored. To perform this work, as shown in FIG. 11, a light source 13 and an input fiber 11 are prepared as an input side to the optical switch 100, and a power meter 14 and an output fiber 12 are prepared as an output side from the optical switch 100. .. [0033] The holding plate 3 of the optical switch 100 is provided with a large number of through holes 31, each of which exposes the polymer optical waveguide film 2. Each of these exposed points includes a core intersection and serves as a switching point for the path of light. Here, an example is shown in which the monitor is performed for one desired switching point 20. Cleeve processing is performed on the switching portion 20 in order to form a notch groove. [0034] Prior to the cleaving process, first, the input fiber 11 and the output fiber 12 are arranged at the input point and the output point corresponding to the desired switching points 20, and the optical axes are aligned with each other. That is, the optical axis of the core 1c and the input fiber 11 is aligned on the input side, and the optical axis of the core 1d and the output fiber 12 is aligned on the output side. [0035] If a fiber array or the like is attached to the optical switch 100 side in advance, connect the corresponding input / output fiber terminals to the light source 13 and the power meter 14, respectively. [0036] When the optical axis alignment or connection is completed, pressing by the pressurizing member is started. In the initial state where the cleave has not yet occurred, the amount of light output from the core 1d is very small, but as the crack progresses, the amount of light output from the core 1d when the switching point 20 is in the reflective state increases. When the pressure member repeatedly pushes up, the position of the pressure member is adjusted in the direction parallel to the surface of the polymer optical waveguide film 2 so that the amount of light output from the core 1d is maximized for each push-up. To do. Even if the pressurizing member is pushed up, the pushing up is repeated until the amount of light output from the core 1d does not increase more than the previous pushing up. [0037] (Action / effect) If the cleaving process is performed without monitoring the optical characteristics, conditions such as the amount and number of times the pressurizing member is pushed up and the pushing time are set. In that case, the notch groove may end without being formed to a sufficient depth. On the contrary, it is possible that the notch groove is formed to a sufficient depth at an early stage, and after that point, only unnecessary stress is generated. [0038] On the other hand, in the present embodiment, since the optical characteristics are monitored, only the necessary and sufficient push-up operation can be appropriately performed. Therefore, a highly reliable optical switch can be obtained. [0039] (Embodiment 4) (Production method) A method for manufacturing an optical switch according to a fourth embodiment based on the present invention will be described with reference to FIGS. 12 and 13. In this method of manufacturing an optical switch, a switching point is formed from the surface on the opening side of the notch groove 6 with respect to the polymer optical waveguide film 2 in which the notch groove 6 is formed by cleaving in any of the first to third embodiments. Perform with the crushing process. Hereinafter, the crushing process will be described in detail. [0040] As shown in FIG. 12, the polymer optical waveguide film 2 is placed on a flat base 15, and the pressurizing member 16 is placed above the notch groove 6. Align the contact points between the core intersection 7 and the pressurizing member 16. The portion with the notch groove 6 is pressurized by the pressurizing member 16 from the surface on the open side of the notch groove 6, that is, the upper surface. The load at the time of pressurization shall be approximately equal to the load required for the plastic deformation of the polymer optical waveguide film 2 to start. [0041] (Action / effect) In the cleaving process, the polymer optical waveguide film 2 is pushed up by the pressurizing member 4, so that a slight plastic deformation occurs. As a result, the notch groove 6 has a very slightly open shape. In the present embodiment, by performing the step of crushing the switching portion, this deformation can be restored and the cut groove 6 can be brought closer to the close contact state. As a result, transmission loss and crosstalk in the transmission state can be reduced. [0042] In the present embodiment, an example is shown in which the polymer optical waveguide film 2 is placed on a flat table 15 when the step of crushing the switching portion is performed. As shown, it may be supported from below by the pressurizing member 4 used for the cleaving process. In that case, the pressurizing member 4 and the pressurizing member 16 perform a crushing process so as to be sandwiched from above and below. [0043] In the crushing process, the pressurization used for the flat table 15 or the cleaving process is as long as the polymer optical waveguide film 2 can be prevented from escaping to the lower side by the pressurization from the upper side. Instead of the member 4, it may be supported from below by another member. [0044] (Embodiment 5) (Constitution) The optical switch according to the fifth embodiment based on the present invention will be described with reference to FIGS. 14 (a) and 14 (b) and 15 (a) and 15 (b). As shown in FIGS. 15 (a) and 15 (b), this optical switch includes a structure in which the polymer optical waveguide film 2 is sandwiched between the holding plates 3h. A through hole 32 is provided in the holding plate 3h, and the core intersection 7 is exposed from the through hole 32. Other configurations are basically the same as those described in the first embodiment. [0045] However, the optical switch in the present embodiment is different in the notch groove 6. The notch groove 6 is not formed by a through hole 32 as a through hole for switching, but is formed by a through hole 31 shown in FIGS. 14 (a) and 14 (b). The holding plate 3 shown in FIGS. 14 (a) and 14 (b) is different from the holding plate provided as an optical switch as a finished product, and is a holding plate for cleaving. The through hole 31 is a through hole for cleaving. That is, the notch groove 6 holds the polymer optical waveguide film 2 so that the core intersection 7 as the switching point is exposed from the through hole 31 as the through hole for cleaving, and the pressure member 4 is pressed from the back side of the starting groove 5. It is formed by causing a cleave by pressing the switching portion with. After forming the notch groove 6 in this way with the cleaving holding plate, the polymer optical waveguide film 2 is taken out and re-sandwiched by the holding plate 3h having the through hole 32 as the switching through hole. [0046] Further, the width A in the direction perpendicular to the notch groove 6 of the through hole 31 as the through hole for cleaving (horizontal direction in FIG. 14A) is perpendicular to the notch groove 6 of the through hole 32 as the through hole for switching. It is larger than the width B in any direction (horizontal direction in FIG. 15 (a)). [0047] The optical switch in this embodiment is assembled in this way. (Action / effect) In the cleaving process, it is necessary to develop cracks, so it is necessary to temporarily generate an excessive stress inside the polymer optical waveguide film 2 by the push-up process. At that time, the portion where the pressurizing member 4 is in contact with the polymer optical waveguide film 2 and the portion 17 near the inner peripheral edge of the through hole of the holding plate holding the polymer optical waveguide film 2 (see FIG. 14 (b)). In, the polymer optical waveguide film 2 may undergo plastic deformation. However, in the present embodiment, the shape of the through hole 31 used for cleaving and the through hole 32 for switching as an actual optical switch are different, and A> B. That is, since the through hole 32 for switching has a narrower width in the direction perpendicular to the notch groove 6 than the through hole 31 for cleaving, the portion 17 where plastic deformation occurs during cleaving is switched. As shown in Fig. 15 (b), it will be sandwiched in the holding plate for use. Therefore, in the state of being assembled as an optical switch, the polymer optical waveguide film 2 is held so as to correct the plastic deformation generated in the portion 17, so that the influence of the plastic deformation during the cleaving process can be reduced. That is, the notch groove 6 formed by the cleave processing becomes easy to close, and it becomes easy to realize the transmission state. [0048] Although some of the above embodiments have been described focusing on only one switching point, the optical switch in the present embodiment has only one switching point in one polymer optical waveguide film. However, it may include a plurality of switching points. In that case, it is preferable that the switching points are arranged in a grid pattern as in the optical switch 100 shown in FIG. 11, but the switching locations may be arranged in a grid pattern. [0049] It should be noted that the above-described embodiment disclosed this time is an example in all respects and is not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and includes all modifications within the meaning and scope equivalent to the scope of claims. [0050] [Effect of the invention] According to the present invention, since the cut groove is formed by causing a cleave without the entry of a cutting tool or the like, the machined surface is smooth without unevenness due to scratching. Therefore, the reflection loss in the reflection state can be reduced. Further, since the cut groove is formed by causing a cleave, there is no cut margin inside the cut groove. Therefore, the transmission loss in the transmission state can be reduced. [Simple explanation of drawings] FIG. 1 is a plan view of an optical switch according to a first embodiment based on the present invention. FIG. 2 is a cross-sectional view of a transmission state of an optical switch according to a first embodiment based on the present invention. FIG. 3 is a cross-sectional view of a reflection state of an optical switch according to a first embodiment based on the present invention. FIG. 4 is a plan view of a state before cleaving in the method for manufacturing an optical switch according to the first embodiment based on the present invention. FIG. 5 is a cross-sectional view of a state before cleaving in the method for manufacturing an optical switch according to the first embodiment based on the present invention. FIG. 6 is a cross-sectional view of a notch groove generated as a result of cleaving in the method for manufacturing an optical switch according to the first embodiment based on the present invention. FIG. 7 is a plan view showing a portion to be pressed when cleaving is performed in the method for manufacturing an optical switch according to the second embodiment based on the present invention. 8 (a) and 8 (b) are side views of how cleaving is performed in the method of manufacturing an optical switch according to the second embodiment based on the present invention, as viewed from two different directions perpendicular to each other. FIG. 9 is a cross-sectional view of a notch groove when a streak is generated in the optical switch according to the first embodiment based on the present invention. FIG. 10 is a cross-sectional view of a notch groove when a streak is generated in the optical switch according to the second embodiment based on the present invention. FIG. 11 is a conceptual diagram of a method for manufacturing an optical switch according to a third embodiment based on the present invention. FIG. 12 is an explanatory diagram of a crushing step included in the method for manufacturing an optical switch according to a fourth embodiment based on the present invention. FIG. 13 is an explanatory diagram of a modified example of a crushing step included in the method for manufacturing an optical switch according to a fourth embodiment based on the present invention. 14 (a) and 14 (b) are explanatory views showing a state of cleaving for forming a notch groove of an optical switch in the fifth embodiment based on the present invention. 15 (a) and 15 (b) are a plan view and a cross-sectional view of an optical switch according to a fifth embodiment based on the present invention. [Explanation of symbols] 1,1a, 1b, 1c, 1d core, 2 polymer optical waveguide film, 3,3h holding plate, 4,4f pressurizing member, 5 origin groove, 6 notch groove, 7 core intersection, 8 bottom, 9a, 9b contact Points, 10,10a, 10b lines, 11 input fibers, 12 output fibers, 13 light sources, 14 power meters, 15 units, 16 pressurizing members (for crushing), 17 parts, 20 switching points, 31,32 through holes , 100 optical switches.