JP2010164708A - Optical fiber array and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively provide a two-dimensional optical fiber array which secures a sufficiently small return loss, has an extremely small arraying error by using a simple manufacturing method. <P>SOLUTION: An array substrate 18 is composed of an alignment substrate 16 and a through-hole substrate 17. A key groove 16b is prepared in the engaging hole 16a of the alignment substrate 16. A linear projection 4a of a flange 4 is engaged with the key groove 16b, thereby inclining the end face 3a of a ferrule 3 at the same angle. By engaging the ferrule 3 with the through-hole 17a of the through-hole substrate 17, each optical fiber 2 is arrayed and fixed to the through-hole substrate 17. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical switch, an isolator, an input / output unit of an optical connection device used in optical communication, a semiconductor laser, an optical coupling component of a photodiode and an optical fiber, or an optical fiber array constituting a multi-core optical connector, and It relates to the manufacturing method.

  The backbone network is strongly required to have a large capacity in accordance with a rapid increase in data traffic. In this backbone network, a large-capacity optical network using WDM (wavelength division multiplexing) technology has already been introduced in the transmission path portion. However, the node portion is a system in which an optical signal is once converted into an electrical signal, the route is switched by an electrical switch, and then converted back to an optical signal and returned to the transmission path portion.

  It has been pointed out that such an apparatus for converting an optical signal and an electric signal significantly increases in cost and power consumption as the signal band is improved (see Non-Patent Document 1). For this reason, it has been studied to use an optical switch that switches an optical signal as it is. In particular, a free space type optical switch that uses a light beam for connection inside a switch (optical connection) or connection between switches without using an optical waveguide medium for wiring in the optical switch can be miniaturized. The practical application to the switch part of a large-scale router is being studied.

  FIG. 9 shows a schematic configuration of such a free space type conventional optical switch (see Non-Patent Document 2). The optical switch 110 shown in the figure is composed of an optical fiber array 111, a microlens array 112, a micro movable mirror array 113, and a fixed mirror 114. The optical fiber array 111 is a two-dimensionally or one-dimensionally arranged optical fiber with a certain interval by using a fiber alignment member. In the microlens array 112, the microlenses are arranged two-dimensionally or one-dimensionally at a certain interval, as in the spatial light beam connecting apparatus.

  The micro movable mirror array 113 includes a plurality of micro movable mirrors 115, which are active elements formed on a semiconductor substrate using micromachine technology, arranged in a one-dimensional or two-dimensional manner. Each inclination angle θ can be dynamically changed. In the figure, each part is described as a one-dimensional array in order to avoid complication.

  In such a free space type conventional optical switch 110, the optical signal 116 emitted from each optical fiber of the optical fiber array 111 is converted into parallel light by each microlens of the microlens array 112 and then moved to a micro movable mirror. After being reflected by each micro movable mirror of the array 113, it is reflected by the fixed mirror 114, is reflected again by the micro movable mirror of the micro movable mirror array 113, and passes through the microlens of the microlens array 112. The light is finally focused on the optical fiber.

  In the optical switch 110 configured as described above, the traveling direction of the optical signal 116 is switched by adjusting the tilt angle θ of the micro movable mirror of the micro movable mirror array 113, and the optical signal 116 is changed to the purpose of the optical fiber array 111. To the optical fiber. The optical system used for the conversion or coupling of the optical fiber and the light beam composed of the optical fiber and the microlens shown here is generally called an optical collimator.

  In the optical switch 110, the connection loss between the input and output optical fibers includes the light loss between the optical fiber and the microlens constituting the optical collimator, in addition to the reflection loss at the refractive index boundary surface generated between each optical component and the air gap. The coupling loss between the light beam and the output optical fiber, the vignetting loss from the lens aperture, and the vignetting loss in the micro movable mirror are dominant. Further, the light beam that has caused the optical axis inclination due to the optical axis shift causes crosstalk to the adjacent channel, and causes deterioration in the quality of the optical communication path.

  In particular, in a two-dimensional optical collimator array, the amount of optical axis misalignment between each optical fiber and the lens is greatly affected by a fiber arrangement error in the optical fiber array. For this reason, two-dimensional optical collimator arrays are strongly required to improve the array fabrication accuracy. An apparatus using the optical collimator array shown here is not limited to an optical switch, and is similarly applied to an optical isolator or an optical interconnection apparatus that uses a light beam for connection. It is also applied to a coupling portion between a semiconductor laser or a photodiode and an optical fiber.

  Here, FIG. 10 shows a schematic structure of a conventional example of a two-dimensional optical fiber array used in a free space type optical switch. As shown in the figure, in the two-dimensional optical fiber array 120, the optical fibers 121 are inserted and aligned in the V-shaped groove portions of the V-groove substrate 122, respectively, and temporarily fixed by the fiber holding plates 123. A plurality of V-groove substrates 122 are laminated and bonded together by being fixed with an adhesive filled in a gap formed therebetween. As the V-groove substrate 122, a substrate made of ceramic, glass, silicon, or the like and formed with a V-shaped groove portion using precision processing technology is widely used. The error can be suppressed to 1 μm or less.

FIG. 11 shows a schematic structure of another conventional example of a two-dimensional optical fiber array (a ferrule of an MT type optical connector). As shown in the figure, in the two-dimensional optical fiber array 130, the optical fibers 131 are respectively inserted into the guide holes 132a for alignment of the ferrules 132, and fixed with the adhesive injected from the adhesive filling holes 132b. Has been. The ferrule 132 is a transfer molding method in which a polymer thermoplastic material (thermoplastic resin) having a small deformation amount during heat shrinkage or after molding is used, and the heated material is extruded into a mold and cooled to mold. It is produced by. In general, a plastic molding technique represented by a transfer molding method is suitable for mass production, and makes it possible to produce a highly accurate optical fiber array at low cost.
ASMorris III, "In search of transparent networks", IEEE Spectrum, pp 47-51 (Oct. 2001) DT Neilson, et. Al., “Fully provisioned 112x112 micro-mechanical optical cross connect with 35.8Tb / s demonstrated capacity”, OFC2000. Paper-PD12-1, (2000)

However, the two-dimensional optical fiber array 120 as shown in FIG. 10 has the following problems. In the following description, the optical axis of the optical fiber is defined as the Z direction, the stacking direction of the V-groove substrate is defined as the Y direction, and the arrangement direction of the optical fibers perpendicular to the Z axis and the Y axis is defined as the X direction.
(1) First, when the V-groove substrate 122 is laminated, the center position of the optical fiber 121 arranged on the substrate is within ± 1 to 2 μm in the horizontal direction (X direction) between the upper and lower substrates. It is necessary to align with accuracy. For this reason, the external accuracy of the V-groove substrate 122 is increased to the same level as described above, and the end of the substrate is brought into contact with a jig or the like. While observing the end surface of the V-groove substrate on the side where the end surface of 121 is exposed, the relative position between the substrates is finely adjusted for alignment, and high-precision machining or mounting technology is required. Furthermore, since the substrates are bonded and fixed after alignment, it is necessary to consider the effect of curing shrinkage due to the adhesive, and it is difficult to control the position by this shrinkage. Further, the substrate itself for forming the V-groove has a thickness variation of about ± 3 to 5 μm. For this reason, in the two-dimensional optical fiber array 120, there is a limit to the improvement of the alignment accuracy of the optical fibers 121, particularly the alignment accuracy with respect to the stacking direction (Y direction) of the V-groove substrate.
(2) When the number of optical fibers 121 is increased in the direction parallel to the V-groove substrate 122 (X direction) as the scale increases, an alignment error of the optical fibers 121 is likely to occur due to warpage of the V-groove substrate 122. Further, when the number of laminated V-groove substrates 122 is increased, an arrangement error of the optical fibers 121 is likely to occur due to variations in the thickness of the V-groove substrate 122 and the thickness of the adhesive. Even if the V-groove substrate 122 is formed with high dimensional accuracy, the overall alignment error becomes large due to variations in the thickness of the adhesive and curing shrinkage. Even if the adhesive layer is thinned to suppress the effects of thickness variation and cure shrinkage, the adhesive properties may be insufficient if long-term reliability is not maintained, and long-term reliability may not be ensured. Control is not easy.
(3) In general, the V-groove substrate 122 is manufactured by forming a V-shaped groove on a semiconductor, glass, ceramics, or other substrate by precision machining or an etching process. A manufacturing method involving a process is not suitable for mass production, and it is difficult to reduce the manufacturing cost.
(4) Also, the outer diameter of the optical fiber 121 aligned with the V-groove substrate 122 is as very thin as 50 μm to 125 μm, and the coating that protects the surface is removed, so that the optical fiber 121 is easily broken. Even if it does not break, a minute scratch may adhere to the surface and cause a disconnection in the future. In addition, the optical fiber drawn to the outside of the V-groove substrate 122 is generally coated with a primary coating of an outer diameter of 250 μm and the surface is protected, but since the mechanical strength is low, a slight tension is applied, The stress sometimes concentrates on the edge of the V-groove substrate 122 and may break. For this reason, disconnection may occur after the optical fibers 121 are arrayed and the manufacturing yield may be lowered, and it is difficult to reduce the assembly cost of the two-dimensional optical fiber array 120 shown in FIG.
(5) In order to sufficiently reduce the reflection loss, a method of preventing the reflected return light from being coupled to the optical fiber core by making the end face of the optical fiber oblique with respect to the optical axis is effective, as in the case of an oblique polishing connector. However, it is extremely difficult to slantly polish the optical fibers 121 having a thin outer diameter as described above, because the tips of the optical fibers are likely to be chipped. It is clear that it is more difficult to align all the polishing directions of optical fibers that have been individually obliquely polished from the viewpoint of handling the optical fibers alone and mounting them by aligning the polished surfaces. In order to avoid this problem, after aligning and fixing the optical fiber 121 to the V-groove substrate 122 to form a one-dimensional optical fiber array, a predetermined angle is set in the direction in which the V-groove substrate is laminated (Y direction). There has also been proposed a method in which the end face of the optical fiber is obliquely polished so as to be laminated to be two-dimensional. However, it is desirable that the arrangement interval of the optical fibers 121 arranged in the two-dimensional optical fiber array 120 can cope with the highest possible density. Therefore, the optical fibers with respect to the stacking direction (Y direction) of the V-groove substrate 122 are desirable. The thickness of the V-groove substrate 122 that restricts the arrangement interval is required to be 500 μm to 1 mm. In such a thin substrate polishing, it is difficult to hold the substrate and adjust the pressing force during polishing. Furthermore, unless a plurality of laminated V-groove substrates are simultaneously obliquely polished, the inclination angle of the inclined polishing surface (inclination formed by the polishing surface with respect to the Y axis on the YZ plane) and the end surface angle error (ideal of the polishing surface) In typical polishing, the polishing end face and the Z-axis are perpendicular to each other on the XZ plane), which makes it difficult to guarantee stable optical characteristics.
For the above reasons, it is technically difficult to provide an inclined end surface for preventing reflection loss in the two-dimensional optical fiber array 120 illustrated in FIG.

  On the other hand, the two-dimensional optical fiber array 130 as shown in FIG. 11 has the following problems. In general, a non-reflective coating film composed of a dielectric multilayer film is formed on the refractive index boundary surface between the optical fiber and lens constituting the optical collimator and the air, in order to avoid the influence of reflection. In many cases, a vapor deposition method is used for the formation of the non-reflective coating film. However, in the vapor deposition method, the formation target is generally exposed to a high temperature environment of several hundred degrees Celsius or more in the film formation process. .

  When the ferrule 132 shown in FIG. 11 is used, a plurality of optical fibers 131 are inserted into the guide holes 132a, and the optical input / output end surfaces of the optical fibers 131 are polished in a state where the optical fibers 131 are held by the ferrule 132. Alternatively, a non-reflective coating film is formed on the polished light incident / exit end face. However, the thermoplastic resin constituting the ferrule 132 has a glass transition temperature in the vicinity of 180 to 200 ° C., and it is difficult to form an antireflective coating film using the vapor deposition method together with the ferrule 132 in terms of heat resistance. .

  Even if an anti-reflection coating film is formed, in order to suppress reflection over a wavelength range of several tens of nm required in the communication wavelength band, the reflectance is at least about 0.05%. This is the limit, and when this is converted into reflection loss, it is approximately -33 dB. Therefore, it is very difficult to realize a reflection loss of −40 dB or less as required for a normal communication device using only a non-reflective coating film. As means for solving this problem, instead of forming a non-reflective coating film on the light incident / exit end face of the optical fiber 131, the ferrule 132 and the plurality of optical fibers 131 held in the ferrule are generally referred to as MPO connectors. The optical fiber end face is inclined with respect to the optical axis by polishing in the same manner as the multi-core oblique polishing optical connector, and a method for preventing the reflected return light from being coupled to the optical fiber core can be easily mentioned. it can.

  According to this means, the optical fiber alignment error and the tilt angle variation of the slant polishing surface, which are problems in the two-dimensional optical fiber array 120 as shown in FIG. Is possible. However, in the two-dimensional optical fiber array 130 as shown in FIG. 11, since the optical fiber 131 is inserted into the ferrule 132 without being covered, there is a problem that the assembly becomes difficult as the number of optical fibers arranged increases. . Specifically, the optical fiber 131 breaks inside the guide hole 132a of the ferrule and clogs the guide holes, or some of the optical fibers come off before being fixed to all the guide holes 132a through the optical fiber 131. As a result, there is a problem that the inserted optical fiber is reinserted into the guide hole that has been removed while scraping the base of the optical fiber. For this reason, the assembly yield is reduced and the assembly time is increased, and there is a limit in reducing the assembly cost. In addition, since an uncoated optical fiber is handled, the surface of the optical fiber may be damaged during assembly, resulting in a decrease in long-term reliability.

  The present invention has been made in order to solve the above-described problems. A two-dimensional optical fiber array having a very small array error with a sufficiently small return loss is reduced by a simple manufacturing method. The purpose is to provide at a cost.

  In order to achieve this object, the present invention comprises a plurality of optical fibers, and a plurality of optical fiber splicing means provided in the center with a through hole for an optical fiber in which each of these optical fibers is fitted and held, And an alignment substrate provided with a plurality of through guide holes into which each of the optical fiber joint means is fitted, and the light incident / exit end face exposed from the alignment substrate of the optical fiber is orthogonal to the central axis of the optical fiber. Inclined by a predetermined angle with respect to the surface to be moved.

  According to the present invention, in the above invention, the optical fiber joint means is constituted by a ferrule that holds the optical fiber and a flange that protects the ferrule.

  In the invention according to any one of the inventions described above, the light incident / exit end face of the optical fiber is covered with a non-reflective coating film.

  According to the present invention, in any one of the above inventions, the key means for aligning the direction of inclination of the light incident / exit end face of each optical fiber between the optical fiber joint means and the through guide hole of the alignment substrate. Is provided.

  The present invention provides the alignment substrate according to any one of the above inventions, wherein the alignment substrate includes key means for determining a direction of inclination of the light incident / exit end face of the optical fiber with the optical fiber joint means; And a through-hole substrate having a through-hole into which each of the optical fiber joint means is fitted.

  The present invention is the invention according to any one of the above inventions, wherein the alignment substrate is formed by a transfer molding method.

  In order to achieve this object, the present invention provides a first step of fixing an optical fiber to an optical fiber splicing means, and a light incident / exit end face of the optical fiber and the optical fiber splicing means with a predetermined angle of inclination. A second step of forming a surface and a plurality of the optical fiber joint means are fitted into the respective through guide holes of the alignment substrate, and the positions of the light incident / exit end faces of the optical fiber joint means are aligned on the same surface. It consists of a third step.

  According to the present invention, a first step of fixing an optical fiber to an optical fiber joint means, a plurality of the optical fiber joint means are fitted into each through guide hole of the alignment substrate, and a light incident / exit end face is separated from the alignment substrate. A second step of exposing, a third step of forming an inclined surface at a predetermined angle on the light incident / exit end surface of the optical fiber and the optical fiber splicing means, and a light incident / exit end surface of the optical fiber splicing means And a fourth step of aligning the positions on the same plane.

  According to the present invention, in any one of the above inventions, the step of aligning the position of the light incident / exit end face of the optical fiber joint means on the same surface is performed by exposing the light incident / exit end face of the optical fiber of the alignment substrate. The optical fiber joint means is inserted into the guide hole of the alignment substrate until the light incident / exit end surface is abutted against the abutting member abutted against the end surface on the side to be aligned.

  The present invention includes a first step of fixing an optical fiber to the optical fiber joint means, a second step of fixing the optical fiber joint means to the alignment substrate, the optical fiber joint means, and the optical fiber. And a third step of forming an inclined surface having a predetermined angle on the light incident / exit end surface.

  According to the present invention, the optical fiber is fitted into the optical fiber joint means and is inserted into the through guide hole provided in the alignment substrate. Therefore, the arrangement accuracy of the optical fiber array is determined by the arrangement accuracy of the through guide holes arranged on the alignment substrate and the dimensional accuracy of the optical fiber joint means. As a result, it is possible to provide a two-dimensional optical fiber array with a very small arrangement error at a low cost.

  Moreover, the yield can be remarkably improved by holding the optical fiber by the optical fiber joint means and then forming the array after oblique polishing. For example, according to one aspect of the present invention, a heat-resistant material in which a plurality of through guide holes are formed in an alignment substrate made of a polymer-based thermoplastic material (thermoplastic resin), and an optical fiber is held in the through guide holes. An optical fiber array was constructed by inserting a cylindrical optical fiber joint means comprising As a result, the arrangement error of the optical fibers can be extremely reduced at a low cost.

  In addition, a non-reflective coating can be attached to the light incident / exit end face of the optical fiber together with the tip of the optical fiber joint means while being held by the optical fiber joint means. Thereby, it is possible to further improve the reflection loss. Alternatively, the oblique polishing angle can be reduced by non-reflective coating treatment. In addition, the smaller the angle of oblique polishing of the light incident / exit end face of the optical fiber, the smaller the angle deviation of the beam caused by the beam exiting from the optical fiber being refracted on the inclined face, thereby relaxing the orientation accuracy of the ferrule end face in the oblique direction. It is possible to reduce the assembly cost. Thus, if a non-reflective coating is formed at the tip of the optical fiber joint means, the optical fiber array of the present invention can be used as an input / output unit of a spatial optical system optical switch used in optical communication or the like. The present invention can be applied to an optical coupling portion with a light emitting element typified by a laser.

  According to another aspect of the present invention, in the configuration of the optical fiber array described above, a key and a key groove structure are provided in the through guide hole and the ferrule of the alignment substrate, so that the orientation in the oblique direction of the end surface can be easily aligned. be able to. In addition, by preparing a new alignment substrate and providing key means for aligning the inclination direction of the light input / output end face of each optical fiber between the optical fiber joint means and the alignment substrate, a more accurate optical fiber array can be obtained. It can be provided at low cost. Further, for example, in any configuration of the optical fiber array described above, if the alignment substrate is manufactured by a transfer molding method, it is easy to extremely reduce the optical fiber arrangement error at low cost.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
An optical fiber array generally indicated by reference numeral 1 in FIG. 1 includes a plurality of optical fibers 2, an optical fiber joint means 5 comprising a ferrule 3 and a flange 4 for holding each optical fiber 2, and an optical fiber via the ferrule 3. And an alignment substrate 6 that holds 2 in parallel with each other at a predetermined interval. As shown in FIG. 2, in the ferrule 3, the coating of the tip end portion of the optical fiber 2 is removed, and the exposed portion of the waveguide composed of the core and the clad is inserted. Further, on the side of the ferrule 3 where the optical fiber 2 is inserted, a flange 4 is provided from the ferrule 3 to the optical fiber 2 to protect them. The through hole provided in the center of the flange 4 is composed of a thick portion and a thin portion with an inner diameter, a portion of the ferrule 3 is inserted into the thick portion with an inner diameter, and the coated optical fiber 2 is inserted into the thin portion. Yes.

  The optical fiber 2 is fitted into the through-hole of the ferrule 3, is fixed by a thermosetting adhesive widely used for assembling the optical connector, and is held inside the ferrule 3. The entrance of the through hole of the ferrule 3 is provided with a taper for introducing the optical fiber 2 into the hole so that the surface of the optical fiber without a coating can be inserted without scratching. The surface of the optical fiber 2 is protected from the entrance of the through-hole of the ferrule 3 to the end of the ferrule on the side where the flange 4 is mounted by a primary coating having a diameter of about 250 μm. The mechanical strength is ensured by overlapping the secondary coating. For this reason, when inserting the ferrule 3 holding the optical fiber 2 into a through guide hole 6a arranged on the alignment substrate 6 to be described later, the optical fiber 2 can be easily handled without breaking or scratching.

  As shown in FIG. 3, the alignment substrate 6 is provided with a plurality of through guide holes 6 a in a matrix shape. The inner shape of the through guide holes 6 a is formed to be substantially the same as the outer shape of the ferrule 3. Yes. Therefore, by inserting the cylindrical ferrule 3 provided at the distal end portion of the optical fiber 2 into the through guide hole 6a, the plurality of optical fibers 2 are parallel to each other via the ferrule 3 on the alignment substrate 6. It is attached. The optical fiber 2 is fitted into a through-hole penetrating the center of the ferrule 3, and the light incident / exit end face 2a of the optical fiber 2 is exposed to the end face 3a side of the ferrule 3, and each end face 2a, 3a is obliquely polished. It is made into an inclined surface. The light incident / exit end faces 2a of the plurality of optical fibers 2 are aligned to be parallel to each other.

  In general, an optical fiber array has a return loss of −40 dB or less, which is a required value of a general communication device, so that the light incident / exit end surface of the optical fiber and the ferrule end surface on the side where the optical fiber array is exposed are optical The inclined surface forms a predetermined angle with respect to the optical axis direction of the fiber. The inclined surface may be formed by polishing the ferrule alone following the step of fixing the optical fiber to the ferrule, or after polishing the entire alignment substrate after inserting the ferrule fixing the optical fiber into the alignment substrate, Alternatively, the ferrule may be protruded from the alignment substrate and only the ferrule tip may be polished. When the optical path length variation of the beam emitted from the optical fiber has an adverse effect on the optical characteristics, for example, after inserting the ferrule into the alignment substrate, the ferrule tip is brought into contact with a smooth surface such as an optical flat so that the tip of the ferrule The position can also be aligned with the optical axis direction (Z direction) of the optical fiber.

  The ferrule 3 is an optical fiber holding part and is currently commercially available. This generally available ferrule has an extremely high accuracy with an eccentricity amount of 1 μm or less, which is a deviation amount between the center of the inner diameter and the center of the outer diameter. The light incident / exit end face 2a of the optical fiber 2 fitted in the ferrule 3 is obliquely polished together with the end face of the ferrule 3, or a non-reflective coating film is further formed on the oblique polished face. The light incident / exit end surface 2 a is in a state of forming the same plane as the end surface 3 a of the ferrule 3.

  In this embodiment, since the ferrule 3 is made of a material having high heat resistance such as zirconia, for example, the optical fiber 2 enters the optical fiber 2 while being held by the ferrule 3 as described above. It becomes possible to form a non-reflective coating film by a vapor deposition method on the emission end face 2a. The ferrule 3 may be composed of other materials such as alumina, metal, crystallized glass, etc. in addition to zirconia.

  The alignment substrate 6 is made of, for example, a polymer-based thermoplastic material (thermoplastic resin), and has a plurality of through guide holes 6a arranged as shown in FIG. The inner diameter of the through guide hole 6 a corresponds to the outer diameter of the ferrule 3, and the hole shape is substantially equal to the outer shape of the ferrule 3. The alignment substrate 6 may be made of metal, ceramic, or glass in addition to the polymer thermoplastic material. By machining these materials or molding them using a mold, the positions of the guide holes can be arranged with high accuracy of ± 2 μm or less in the entire area of a two-dimensional array of 10 rows and 10 columns, for example. Is possible. In particular, when the alignment substrate 6 is made of a thermoplastic resin, it can be manufactured at low cost while maintaining high accuracy by a transfer molding method.

  In the optical fiber array 1 in the first embodiment described above, for example, the position and shape of the through guide hole 6a of the alignment substrate 6 are formed with high dimensional accuracy. In addition, if the outer shape of the ferrule 3 and the inner diameter and eccentricity of the through guide hole 6a are formed with high accuracy, the plurality of optical fibers 2 fixed to the alignment substrate 6 via the ferrule 3 can be in a state with extremely small errors. It will be arranged in two dimensions. As described above, according to the first embodiment, the ferrule 3 and the through guide hole 6a of the alignment substrate 6 formed with high accuracy are used, so that a two-dimensional optical fiber that has a very small arrangement error. An array can be obtained. In the optical fiber array 1, the arrangement accuracy of the optical fibers 2 is determined by the arrangement accuracy of the through guide holes 6 a arranged in the alignment substrate 6 and the dimensional accuracy of the ferrule 4.

  The end face of the optical fiber may be subjected to antireflection coating after being obliquely polished. This makes it possible to further improve the reflection loss. Alternatively, the oblique polishing angle can be reduced by non-reflective coating treatment. Actually, the optical fiber 2 was inserted into the ferrule 3 and the end face was polished at an inclination angle of 2 ° to form a normal quality non-reflective coating film (reflectance 0.1%). When there is no film, the return loss of about −17 dB is set to −40 dB or less, and the angle deviation θ ′ of the beam generated by the beam exiting from the optical fiber being refracted on the inclined surface is set to be less than 1 °. did it. Further, as the angle deviation of the beam is smaller, it is possible to relax the alignment accuracy in the oblique direction of the ferrule end face, so that the effect of reducing the assembly cost can be obtained.

Note that the angle of the inclined surface of the ferrule may be approximately 8 ° or more in order to satisfy the required value of the return loss. However, when the light incident / exit end face of the optical fiber is an inclined surface, the optical axis of the beam emitted from the optical fiber is inclined due to refraction at the interface between the optical fiber core and air. For example, if the inclination angle θ of the optical fiber end face is 8 ° and the refractive index of the optical fiber core is 1.46, the angle θ ′ formed by the beam emitted from the optical fiber with respect to the optical axis of the optical fiber is Snell's formula. Using the following calculation formula derived from the above, it is calculated to be approximately 3.7 °.
θ ′ = | sin ⁻¹ (1.46 × sin θ) −θ |

  The optical fiber array according to the present invention is equal to the optical fiber array according to the present invention on one side, for example, when the optical axes are aligned so that the inclined surfaces are in contact with each other so that the oblique polishing optical connectors are fitted to each other. When the flat surface has an inclined surface and the other surface is combined with a flat microlens array in which microlenses are arranged at an equal interval to the optical fiber core on the plane without providing a gap, the gap between the optical fiber core and the air layer. Therefore, there is no need to consider the optical axis inclination of the outgoing beam.

  However, when the optical fiber array according to the present invention is applied to a spatial optical system in which an optical fiber and a lens, for example, are optically coupled through a space, the optical axis inclination θ ′ of the beam emitted from the optical fiber is directly applied to the beam. Further, the beam center position shifts after propagating a certain distance, which increases the optical coupling loss. In particular, the beam angle deviation θ ′ is a major cause of loss in the spatial optical system, so it is desirable to make it as small as possible. From this point of view, in the optical fiber array according to the present invention, an inclined surface is formed on the light incident / exit end surface of the optical fiber, and a non-reflective coating film is formed on the inclined surface, so that reflection attenuation is also achieved at a smaller inclination angle. The amount was suppressed to -40 dB or less of the required value, and at the same time, the optical axis inclination of the beam emitted from the optical fiber was reduced.

  Next, a method for assembling the optical fiber array 1 in the first embodiment configured as described above will be described with reference to FIG. First, as shown in FIG. 3A, the alignment substrate 6 is temporarily fixed to a reference plate (optical flat) 7 as a contact member via a spacer 8. Next, as shown in FIG. 6B, the end face 3a is obliquely polished after the fiber is held in advance, or the tip of the ferrule 3 on which the non-reflective coating film is further formed on the obliquely polished surface is used as the reference plate 7 The ferrules 3 are inserted into the through guide holes 6a of the alignment substrate 6 while applying pressure so as to be in contact with the upper surface of each.

  Next, as shown in FIG. 3C, an adhesive 9 is applied to the joint between the ferrule 3 and the alignment substrate 6, and the ferrule 3 is fixed to the alignment substrate 6. Thereafter, the alignment substrate 6 is removed from the reference plate 7. Thereby, the optical fiber array 1 can be produced. In this way, the optical fiber held in advance by the ferrule is end-face processed in units of single core, and then arrayed, so that optical fiber breaks and scratches on the end face of the optical fiber during polishing are checked and removed before installation. Therefore, the yield of manufacturing the optical fiber array can be increased. Also, the assembly method as described above makes it possible to produce a fiber array in which the end face positions of the optical fibers are aligned with high accuracy in the optical fiber optical axis direction (Z direction).

  Furthermore, as shown in FIG. 4D, an inclined surface 7a corresponding to the inclined end surface of each ferrule 3 is provided in advance on the reference plate 7, and the ferrule 3 is rotated and inserted so as to abut against the inclined surface 7a. It becomes possible to match the inclination direction of each ferrule 3. In the case where the alignment substrate 6 is made of a material having sufficient heat resistance, the ferrule 3 that has been obliquely polished is aligned and fixed to the alignment substrate 6 by the assembly method as described above, and then the end face 3a of each ferrule 3 is used. A non-reflective coating film may be collectively formed on the end surface of the alignment substrate 6 including

  Thus, the optical fiber array 1 according to the first embodiment can be easily manufactured. Therefore, according to the first embodiment, by using the ferrule 3 formed with high dimensional accuracy and the through guide hole 6a of the alignment substrate 6, a two-dimensional optical fiber array that has a very small arrangement error. Can be obtained at low cost.

 In the first embodiment, the optical fiber array 1 is manufactured by protruding the tip of the ferrule 3 from the alignment substrate 6 by using a structure in which the reference plate 7 and the spacer 8 are overlapped. However, it is not limited to this. For example, if the spacer 8 is omitted and only the reference plate 7 is used, the tip of the ferrule 3 is disposed on the surface of the alignment substrate 6. In other words, the end surface 3a of the ferrule 3 and the surface of the array substrate 6 are the same. An optical fiber array in which a plane is formed can be manufactured.

  Next, another assembling method of the optical fiber array 1 according to the first embodiment will be described with reference to FIG. First, as shown in FIG. 2A, a reference plate (optical flat) 10 having an inclined surface 10a inclined obliquely by a predetermined angle with respect to the axis of the through guide hole 6a of the alignment substrate 6 is interposed via a spacer 11. Then, the alignment substrate 6 is temporarily fixed. Next, as shown in FIG. 4B, the ferrule 3 is passed through the alignment substrate 6 so that the tip of the ferrule 3 holding the fiber 2 before the end surface is obliquely polished is abutted against the inclined surface 10a of the reference plate 10. Each is inserted into the guide hole 6a while applying pressure.

  Subsequently, as shown in FIG. 2C, the aligned ferrule 3 and the optical fiber 2 held by the ferrule 3 are polished at a predetermined angle that is inclined with respect to the optical axis of the optical fiber. Next, as shown in FIG. 4D, the ferrule 3 is pressed against the upper surface of the reference plate 7 having the upper surface perpendicular to the axis of the through guide hole 6a of the alignment substrate 6 with the tip 3a of the ferrule 3 being pressed. After aligning the protruding length of the tip 3 a of the ferrule 3 from the alignment substrate 6, an adhesive 9 is applied to the joint portion with the alignment substrate 6, and the ferrule 3 is fixed to the alignment substrate 6. By performing the oblique polishing process after the fibers are arrayed in this way, it is not necessary to match the inclination directions of the optical fibers, and assembling can be simplified.

  Note that after the step of FIG. 10C, the alignment substrate 6 and the ferrule 3 may be bonded and fixed, and the step of FIG. Further, when the alignment substrate 6 is made of a material having sufficient heat resistance, the obliquely polished ferrule 3 is bonded and fixed to the alignment substrate 6 and then deposited on the end surface of the alignment substrate 6 including each ferrule end surface 3a. The antireflective coating film may be formed in a lump.

[Second Embodiment]
When an inclined surface is previously formed on a single ferrule and inserted into an alignment substrate, it is necessary to align the inclined surface of each ferrule in the same direction, but this is a protrusion that indicates the direction of the inclined surface on the ferrule. This can be easily solved by providing a key or a key groove, providing a key groove or key that matches the key or the key groove in the guide hole of the alignment board, and inserting the keys or the key groove so as to fit each other. A protruding key or key groove indicating the direction of the inclined surface of the ferrule may be provided on the flange. In this case, the key or key groove is arranged substantially equal to the outer shape of the flange provided with the key or key groove. When a board having a key hole or a guide hole with a key is prepared, and this is attached to a surface opposite to the surface where the inclined surface of the ferrule is exposed, the ferrule is inserted into the guide hole of the alignment substrate. As a guide, the inclined surface of the ferrule can be aligned.

  This will be described with reference to the second embodiment of the present invention shown in FIG. In the figure, the same or equivalent members described in the first embodiment shown in FIGS. 1 to 5 described above are denoted by the same reference numerals, and detailed description thereof is omitted. As shown in FIG. 6, the ferrule 3 is provided with a notch 3b constituting key means obtained by cutting off a part of the circular portion on the outer periphery in order to indicate the inclination direction of the end face 3a. With respect to the ferrule 3, for example, the notch 3b is used as a reference for determining the direction of the inclined surface, and the notch 3b and the polished surface are mounted by attaching to a polishing jig holding the ferrule outer periphery including the notch 3b and performing oblique polishing. Can be accurately aligned among a plurality of ferrules. The polishing jig may be configured to polish a single ferrule or to simultaneously polish a plurality of ferrules at a time. Further, if the key structure is not particularly complicated, after the cylindrical ferrule is obliquely polished, for example, the reference surface (for example, the direction of the polishing surface is obliquely set at a predetermined angle as in the first embodiment described above) The notched portion 3b may be produced by abutting the optical flat) to fix the direction of the inclined surface and cutting the ferrule outer shape in a predetermined direction.

  In addition, a flat portion 6b constituting a key means that engages with the notch portion 3b of the ferrule 3 is provided in a part of the inner peripheral portion of the through guide hole 6a of the alignment substrate 6. It is provided at the same position in the circumferential direction of the through guide hole 6a. Thus, since the flat part 6b is provided in the same position in the circumferential direction of each penetration guide hole 6a, each ferrule 3 is inserted in the penetration guide hole 6a of the alignment board | substrate 6, and each optical fiber end surface is inserted. The directions of 3a can be easily aligned, and the light beam emission directions from the fiber array can be made parallel.

  In the second embodiment, the cutout portion 3b is provided in a part of the cylindrical portion of the ferrule 3, and the flat portion 6b is provided in a part of the inner peripheral portion of the through guide hole 6a of the alignment substrate 6. The structure is not limited to this. For example, a protrusion is provided on a part of the outer periphery of the ferrule 3, and a groove for engaging the protrusion is provided on a part of the inner periphery of the through guide hole 6a. As long as the content of the present embodiment is not impaired, an appropriate design change is possible.

  In the second embodiment, the key means is provided on the ferrule 3. However, the flange 4 may be press-fitted into the through guide hole 6 a of the alignment substrate 6, and the key means may be provided on the flange 4. . Since a ferrule with a cylindrical shape is commercially available as a normal product, it is possible to realize high-precision machining at a lower cost by providing a key structure on the flange than performing additional processing such as providing a key means on the ferrule. .

  According to the second embodiment, the same effect as that of the first embodiment described above can be obtained, and the arrangement of the ferrules 3 can be simplified by providing the key means. This can be realized by work, and the cost can be further reduced as compared with the first embodiment.

[Third Embodiment]
Next, an optical fiber array according to the third embodiment of the present invention will be described with reference to FIG. In the figure, the same or equivalent members described in the first and second embodiments shown in FIGS. 1 to 6 described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the third embodiment, as shown in FIG. 7, a convex strip as a key means for aligning the direction of inclination of the end surface 3 a of each ferrule 3 with a part of the outer peripheral portion of the flange 4 holding the ferrule 3. 4a is provided. Further, the alignment substrate 18 has an alignment substrate 16 having key means for aligning the direction of inclination of the end face 3a of the ferrule 3 with the ferrule 3, and a through hole 17a into which each of the ferrules 3 is fitted. It is characterized by comprising a through-hole substrate 17 on which the ferrules 3 are arranged.

  The alignment substrate 16 is provided with a plurality of insertion holes 16a into which the flanges 4 are inserted, and a part of the inner peripheral portion of the insertion holes 16a is provided with a key groove 16b that constitutes key means. 16 is fixed to the side of the through-hole substrate 17 where the ferrule 3 is inserted. On the other hand, the through hole substrate 17 is provided with a plurality of through holes 17a into which the ferrule 3 is fitted. In such a configuration, the rotation direction of the flange 4 fitted in the fitting hole 16a of the alignment substrate 16 is determined by engaging the convex body 4a with the key groove 16b, and the ferrule 3 is fitted into the through hole 17a. Is attached to the through-hole substrate 17. Therefore, by providing the key means between the alignment substrate 16 and the flange 4, the ferrules 3 attached to the through-hole substrate 17 have the same inclination of the end surface 3a.

  In this 3rd Embodiment, since the protruding item | line 4a as a key means is provided in the flange 4, it can process cheaply. In addition, by providing a key groove 16b constituting the ridges 4a and key means in a separate component called the alignment substrate 16, the through guide hole of the alignment substrate, which requires extremely high processing accuracy, is made into a simple shape such as a cylindrical shape. Therefore, high precision machining can be easily performed and cost reduction can be expected. The alignment substrate 16 may be removed from the through-hole substrate 17 after assembly.

[Fourth embodiment]
Next, a fourth embodiment of the present invention will be described with reference to FIG. Also in the third embodiment, as in the third embodiment described above, the alignment substrate 21 is provided with key means for aligning the direction of the inclination of the end surface 3a of the ferrule 3 with the ferrule 3. 20 and a through-hole substrate 17 having a through-hole 17a into which each of the ferrules 3 is fitted and in which the ferrules 3 are arranged. And in this 3rd Embodiment, as shown in FIG. 8, as a key means which aligns the inclination of the end surface 3a of the ferrule 3, the flat part 4b of the shape where a part of outer peripheral part of the flange 4 was cut off by the plane was used. Provided. On the other hand, the orientation substrate 20 is provided with four rectangular holes 20a vertically as key means extending in the left-right direction in the figure with which the flat portion 4b of the flange 4 engages. With such a key means structure, the shape of the holes 20a of the alignment substrate 20 can be simplified, and it is only necessary to form one hole 20a per row unit, so that the processing can be simplified. Further, in any configuration of the optical fiber array described above, if the alignment substrate is manufactured by the transfer molding method, it is easy to extremely reduce the optical fiber arrangement error at low cost.

  In the present embodiment, the ferrule 3 and the flange 4 are formed as separate members, but may be formed as a single member.

1 is a perspective view showing a first embodiment of an optical fiber array according to the present invention. It is a perspective view which shows the optical fiber assembly in 1st Embodiment of the optical fiber array which concerns on this invention. 1 is an exploded perspective view showing a first embodiment of an optical fiber array according to the present invention. It is a top view for demonstrating the assembly method of 1st Embodiment of the optical fiber array which concerns on this invention. FIG. 10 is a plan view for explaining another assembling method in the first embodiment of the optical fiber array according to the present invention. It is a perspective view which decomposes | disassembles and shows 2nd Embodiment of the optical fiber array which concerns on this invention. It is a perspective view which decomposes | disassembles and shows 3rd Embodiment of the optical fiber array which concerns on this invention. It is a perspective view which decomposes | disassembles and shows 4th Embodiment of the optical fiber array which concerns on this invention. It is a block diagram which shows schematic structure of the free space type conventional optical switch. It is a perspective view which shows the schematic structure of the conventional two-dimensional optical fiber array. It is a perspective view which shows the schematic structure of the conventional two-dimensional optical fiber array.

DESCRIPTION OF SYMBOLS 1 ... Optical fiber array, 2 ... Optical fiber, 2a ... Light entrance / exit end surface, 3 ... Ferrule, 3a ... End surface, 3b ... Flat part (key means), 4 ... Flange, 4a ... Projection body (key means), 5 ... optical fiber joint means, 6, 18, 21 ... alignment substrate, 6a ... penetrating guide hole, 6b ... flat part (key means), 7, 10 ... reference plate (butting member), 16, 20 ... orientation substrate, 16a ... insertion hole, 16b ... key groove (key means), 20a ... hole (key means).

Claims (10)

A plurality of optical fibers;
A plurality of optical fiber splicing means provided in the center with an optical fiber through hole in which each of these optical fibers is fitted and held;
An alignment substrate provided with a plurality of through guide holes into which each of these optical fiber joint means is fitted,
An optical fiber array, wherein a light incident / exit end surface exposed from the alignment substrate of the optical fiber is inclined by a predetermined angle with respect to a surface orthogonal to a central axis of the optical fiber. The optical fiber array of claim 1, wherein
An optical fiber array, wherein the optical fiber joint means comprises a ferrule that holds the optical fiber and a flange that protects the ferrule. The optical fiber array according to claim 1 or 2,
An optical fiber array, wherein the light incident / exit end face of the optical fiber is coated with a non-reflective coating film. The optical fiber array according to any one of claims 1 to 3,
An optical fiber array comprising key means for aligning the direction of inclination of the light incident / exit end face of each optical fiber between the optical fiber joint means and the through guide hole of the alignment substrate. The optical fiber array according to any one of claims 1 to 3,
The alignment substrate has an alignment substrate having key means for aligning the direction of inclination of the light incident / exit end face of each optical fiber with the optical fiber joint means, and each of the optical fiber joint means. An optical fiber array comprising a through-hole substrate having through-holes on which the optical fibers are arranged. The optical fiber array according to any one of claims 1 to 5,
An optical fiber array, wherein the alignment substrate is formed by a transfer molding method. A first step of fixing the optical fiber to the optical fiber joint means;
A second step of forming an inclined surface of a predetermined angle on a light incident / exit end surface of the optical fiber and the optical fiber joint means;
And a third step of fitting a plurality of the optical fiber joint means into the respective through guide holes of the alignment substrate, and aligning the positions of the light incident / exit end faces of the optical fiber joint means on the same surface. A method for manufacturing an optical fiber array. A first step of fixing the optical fiber to the optical fiber joint means;
A second step of fitting a plurality of the optical fiber joint means into each through guide hole of the alignment substrate and exposing the light incident / exit end face from the alignment substrate;
A third step of forming an inclined surface of a predetermined angle on a light incident / exit end surface of the optical fiber and the optical fiber joint means;
And a fourth step of aligning the positions of the light incident / exit end faces of the optical fiber joint means on the same plane. In the manufacturing method of the optical fiber array of Claim 7 or 8,
The step of aligning the position of the light incident / exit end face of the optical fiber joint means on the same plane,
The optical fiber joint means is inserted into the guide hole of the alignment substrate until the light incident / exit end surface is abutted against the abutting member abutted against the end surface of the alignment substrate where the light incident / exit end surface of the optical fiber is exposed. A method for manufacturing an optical fiber array. A first step of fixing the optical fiber to the optical fiber joint means;
A second step of fixing the optical fiber joint means to the alignment substrate;
And a third step of forming an inclined surface having a predetermined angle on the light incident / exit end surface of the optical fiber.

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