Optical connection structure

Abstract

The present disclosure provides an optical connection structure capable of reducing the degree of decrease in optical coupling efficiency caused by temperature change. The optical connection structure includes: a plurality of optical fibers configured to have end faces side by side in at least a first direction; an optical functional member having a first face opposing the end faces of the plurality of optical fibers and optically coupled to the end faces of the plurality of optical fibers at the first face; a holding member having a second face opposing the first face and directly or indirectly fixed to the first face, a third face opposite to the second face, and a plurality of optical fiber holding holes extending from the third face toward the second face and respectively accommodating the plurality of optical fibers; and a deformation suppression member having a fourth face opposing the third face and directly or indirectly fixed to the third face, the holding member being sandwiched between the deformation suppression member and the optical functional member. A coefficient of thermal expansion of the optical functional member and the deformation suppression member is greater than a coefficient of thermal expansion of the holding member. Alternatively, the coefficient of thermal expansion of the optical functional member and the deformation suppression member is smaller than the coefficient of thermal expansion of the holding member.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an optical connection structure. This application claims priority based on Japanese Application No. 2020-212291 filed on December 22, 2020, and the entire disclosure of which is incorporated herein by reference. BACKGROUND

[0002] A collimating array in which an optical fiber array and a lens array are arranged at intervals is disclosed in Patent Literature 1.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2004-102108 SUMMARY

[0006] The optical connection structure of the present disclosure includes a plurality of optical fibers, an optical functional member, a holding member, and a deformation suppression member. The plurality of optical fibers are arranged side by side in a first direction at end faces of the plurality of optical fibers, and the plurality of optical fibers respectively extend in a second direction intersecting the first direction. The optical functional member has a first face facing the end faces of the plurality of optical fibers and optically coupled to the end faces of the plurality of optical fibers at the first face. The holding member has a second face facing the first face and directly or indirectly fixed to the first face, a third face opposite to the second face, and a plurality of optical fiber holding holes respectively accommodating the plurality of optical fibers and extending from the third face toward the second face. The deformation suppression member has a fourth face facing the third face and directly or indirectly fixed to the third face. In the second direction, the holding member is sandwiched between the optical functional member and the deformation suppression member. A coefficient of thermal expansion of the optical functional member and the deformation suppression member is larger than a coefficient of thermal expansion of the holding member. Alternatively, the coefficient of thermal expansion of the optical functional member and the deformation suppression member is smaller than the coefficient of thermal expansion of the holding member. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 is a cross-sectional view of an optical connection structure of one embodiment of the present disclosure.

[0008] Figure 2 is a perspective view of the optical connection structure.

[0009] Figure 3 is a cross-sectional view showing a configuration in a case where the optical functional member includes only a lens array.

[0010] Figure 4 is a perspective view of the optical connection structure shown in Figure 3

[0011] Figure 5 ​is a sectional view showing the configuration of the optical connection structure in the case where the optical functional member includes the lens array and the optical element.

[0012] Figure 6 is a sectional view showing the configuration of the optical connection structure in the case where the optical functional member includes the lens array, the optical element, and the lens array.

[0013] Figure 7 is a schematic view showing the optical functional member and the holding member in the case where the deformation suppression member is not provided as a comparative example.

[0014] Figure 8 is a view showing the case where the holding member is deformed in the comparative example.

[0015] Figure 9 is a schematic view showing the optical functional member, the holding member, and the deformation suppression member of one embodiment.

[0016] Figure 10 is a graph showing the results of simulation of the deformation of the holding member when the ambient temperature of the optical connection structure shown in Figure 5

[0017] is a graph showing the simulation results in the case where the deformation suppression member is not provided in the optical connection structure shown in Figure 5

[0018] is a perspective view showing a model used for further simulation, which shows the case where the deformation suppression member is not provided. Figure 12

[0019] is a perspective view showing a model used for further simulation, which shows the case where the deformation suppression member is provided. Figure 13

[0020] are Young's moduli, coefficients of thermal expansion, and Poisson's ratios of the optical element (rotator), the lens array, the holding member, the deformation suppression member, and the adhesive used for the simulation. Figure 14

[0021] is a graph showing the relationship between the thickness of the deformation suppression member and the warping amount (maximum deformation amount) as a result of the simulation. Figure 15

[0022] is a graph showing the relationship between the effective Young's modulus calculated from the Young's modulus of the optical element (rotator) and the Young's modulus of the deformation suppression member, the thickness of the deformation suppression member, and the warping amount, based on the simulation results shown in Figure 16 Figure 15 is a graph showing the relationship between the effective Young's modulus calculated from the Young's modulus of the optical element (rotator) and the Young's modulus of the deformation suppression member, the thickness of the deformation suppression member, and the warping amount, based on the simulation results shown in​​ DETAILED DESCRIPTION

[0023] [Problem to be Solved by the Invention]

[0024] In optical coupling of an optical fiber array including a plurality of optical fibers with an optical functional member such as a lens array, it is conceivable to mutually fix a holding member that holds end portions of the optical fibers in the optical fiber array and the optical functional member by adhesion. The holding member has, for example, a plurality of holes that respectively accommodate the plurality of optical fibers. However, sometimes the coefficient of thermal expansion of the holding member greatly differs from the coefficient of thermal expansion of the optical functional member. In this case, a bending deformation occurs in the holding member due to a change in ambient temperature, and a variation occurs in the direction of the optical axes of the plurality of optical fibers. Thereby, the optical coupling efficiency of the optical functional member fixed to the plurality of optical fibers, or the optical coupling efficiency of the optical functional member coupled to the plurality of optical fibers through a space, decreases.

[0025] [Effects of the Invention]

[0026] According to the optical connection structure of the present disclosure, the degree of decrease in the optical coupling efficiency of the optical fibers and the optical functional member due to a change in temperature can be reduced.

[0027] [Explanation of Embodiments of the Invention]

[0028] First, an embodiment of the present disclosure will be described. The optical connection structure of one embodiment has a plurality of optical fibers, an optical functional member, a holding member, and a deformation suppression member. The plurality of optical fibers is arranged so that end faces of the plurality of optical fibers are side by side at least in a first direction, and the plurality of optical fibers respectively extend along a second direction that intersects the first direction. The optical functional member has a first face that opposes the end faces of the plurality of optical fibers and is optically coupled to the end faces of the plurality of optical fibers at the first face. The holding member has a second face that opposes the first face and is directly or indirectly fixed to the first face, a third face that opposes the second face, and a plurality of optical fiber holding holes that respectively accommodate the plurality of optical fibers and extend from the third face toward the second face. The deformation suppression member has a fourth face that opposes the third face and is directly or indirectly fixed to the third face. In the second direction, the holding member is sandwiched between the optical functional member and the deformation suppression member. The coefficient of thermal expansion of the optical functional member and the deformation suppression member is greater than the coefficient of thermal expansion of the holding member. Alternatively, the coefficient of thermal expansion of the optical functional member and the deformation suppression member is smaller than the coefficient of thermal expansion of the holding member.

[0029] In the optical connection structure, the optical functional member and the holding member are directly or indirectly fixed to each other. Therefore, in the case where the deformation suppression member is not provided, a bending deformation occurs in the holding member due to a difference in the coefficient of thermal expansion between the optical functional member and the holding member, and a variation occurs in the direction of the optical axes of the plurality of optical fibers. On the other hand, in the case of the optical connection structure of one embodiment, due to a temperature change, a stress caused by the deformation suppression member in the opposite direction to the stress caused by the optical functional member occurs in the holding member. Further, these stresses cancel each other out inside the holding member. Therefore, according to the above-described optical connection structure, the variation in the direction of the optical axes of the plurality of optical fibers caused by a temperature change can be reduced, and the degree of decrease in the optical coupling efficiency between the optical fibers and the optical functional member can be reduced.

[0030] In the above-described optical connection structure, the thickness of the deformation suppression member in the second direction can be 1 mm or more. According to simulation by the present inventor, in the case where the thickness of the deformation suppression member is less than 1 mm, the thicker the deformation suppression member, the more the bending of the holding member is suppressed. In contrast, in the case where the thickness of the deformation suppression member is 1 mm or more, the thickness of the deformation suppression member is less relevant to the bending of the holding member. Therefore, if the thickness of the deformation suppression member is at least 1 mm, the above-described effect can be sufficiently achieved.

[0031] In the above-described optical connection structure, the ratio (Eb / Ec) of the Young's modulus Eb of the deformation suppression member to the effective Young's modulus Ec of the optical functional member can be 0.192 or more. According to simulation by the present inventor, in the case where the ratio (Eb / Ec) satisfies this condition, the above-described effect can be sufficiently achieved.

[0032] In the above-described optical connection structure, the deformation suppression member can hold the plurality of optical fibers. In this case, the plurality of optical fibers can be more securely held.

[0033] The above-described optical connection structure can include an optical fiber ribbon in which the plurality of optical fibers are covered and protected by a resin. The deformation suppression member can include a plurality of optical fiber holding holes in which the plurality of optical fibers are respectively accommodated, and a ribbon holding hole in which the optical fiber ribbon is accommodated. In this case, the plurality of optical fibers can be more securely held via the optical fiber ribbon.

[0034] In the above-described optical connection structure, the deformation suppression member can further include a fifth surface that is opposite the fourth surface in the second direction. The ribbon holding hole can extend toward the fourth surface along the second direction from a bottom surface of a recess formed in the fifth surface. The plurality of optical fiber holding holes can extend along the second direction from the ribbon holding hole to the fourth surface. In this case, the optical fiber ribbon and the plurality of optical fibers can be held by a simple structure that is easy to form.

[0035] In the optical connection structure described above, the optical functional member can include a lens array including the first surface. In this case, the optical fiber array composed of a plurality of optical fibers is optically coupled to the lens array, and an optical connection structure in which a decrease in optical coupling efficiency of the optical fiber array and the lens array caused by a change in temperature is small can be provided.

[0036] In the optical connection structure described above, the lens array can be composed mainly of silicon, the holding member can be composed mainly of glass, and the deformation suppression member can be composed mainly of resin. In this case, both the thermal expansion coefficient of the lens array and the thermal expansion coefficient of the deformation suppression member are larger than the thermal expansion coefficient of the holding member. Thus, the effects described above can be achieved.

[0037] In the optical connection structure described above, the optical functional member can further include an optical element different from the lens array, the lens array can be sandwiched between the holding member and the optical element in the second direction, and the optical element can be directly or indirectly fixed to the lens array. In this case, an optical connection structure in which various operations on light incident to or emitted from each optical fiber are performed can be provided. In this case, the optical element can be at least one of a rotator, an optical filter, an optical isolator, and an optical path conversion member.

[0038] In the optical connection structure described above, the second surface can be bonded to the first surface by an adhesive. In this case, the second surface can be indirectly fixed to the first surface.

[0039] In the optical connection structure described above, the fourth surface can be bonded to the third surface by an adhesive. In this case, the fourth surface can be indirectly fixed to the third surface.

[0040] [Details of Embodiments of the Present Disclosure]

[0041] Hereinafter, specific examples of the optical connection structure of the present disclosure will be described with reference to the drawings. Note that the present disclosure is not limited to these examples, but is shown by the claims, and is intended to include all modifications within the scope equivalent to the claims. In the following description, the same reference numerals are applied to the same elements in the description of the drawings, and repetitive description is omitted. In the following description, the light-transmitting property means a property of transmitting light of an object wavelength by 95% or more at a thickness of 1 mm. In the following embodiments, the object wavelength is, for example, 1260 nm or more and 1360 nm or less.

[0042] Figure 1 is a cross-sectional view of an optical connection structure 1 of one embodiment of the present disclosure. Figure 2 is a perspective view of the optical connection structure 1. As Figure 1 and Figure 2 shown, the optical connection structure 1 includes an optical functional member 10 (inFigure 2 The N pieces of optical fiber ribbons (ribbon cores) 40 are arranged in parallel in a direction D2 intersecting the direction Dl. The direction D2 is, for example, orthogonal to the direction Dl. The end faces 42 of the optical fibers 41 constituting the optical fiber ribbons 40 are flush with the end faces 42 of the optical fibers 41 constituting the other optical fiber ribbons 40, and these end faces 42 are arranged in parallel in the direction D2. Each of the optical fibers 41 is, for example, a single-mode optical fiber. Each of the optical fibers 41 extends along a direction D3 (second direction) intersecting both the direction Dl and the direction D2. In other words, the central axis of each of the optical fibers 41 is along the direction D3. The direction D3 is, for example, orthogonal to both the direction Dl and the direction D2. A certain length of region in the tip end portion of each of the optical fibers 41 is exposed from the resin covering of the optical fiber ribbon 40.

[0043] The optical functional member 10 is a block-shaped optical passive member having a light-transmitting property. The optical functional member 10 has a face 11 (first face) extending along the direction Dl and the direction D2 and intersecting the direction D3. The face 11 opposes each of the end faces 42 of the optical fibers 41 of the N pieces of optical fiber ribbons 40. In one example, the face 11 is flat. The normal direction of the face 11 can coincide with the direction D3 or can be slightly inclined with respect to the direction D3. The optical functional member 10 is optically coupled at the face 11 to each of the end faces 42 of the optical fibers 41 of the N pieces of optical fiber ribbons 40.

[0044] The holding member 20 holds at least a portion including the end face 42 in the portion of the optical fiber 41 exposed from the resin covering of the optical fiber ribbon 40. The holding member 20 is a flat-plate-shaped or cuboid-shaped member. The holding member 20 has a face 21 (second face) extending along the direction Dl and the direction D2 and intersecting the direction D3, and a face 22 (third face) opposing the face 21 and extending along the direction Dl and the direction D2 and intersecting the direction D3. In one example, the faces 21 and 22 are flat. In one example, the faces 21 and 22 are parallel to each other. The thickness of the holding member 20 in the direction D3, i.e., the interval between the faces 21 and 22, is, for example, in the range of 0.5 mm to 3.0 mm. The normal direction of the face 21 can coincide with the direction D3 or can be slightly inclined with respect to the direction D3.

[0045] The face 21 opposes the face 11 of the optical functional member 10 and is directly or indirectly fixed to the face 11. In one example, the face 21 is bonded to the face 11 by an adhesive 51. In other words, the adhesive 51 is interposed between the face 21 and the face 11. The adhesive 51 has a light-transmitting property. The adhesive 51 is, for example, a resin adhesive. The adhesive 51 is selected so that the difference in refractive index between the constituent material of the optical functional member 10 and the constituent material of the optical fiber 41 is zero or extremely small. As examples of the adhesive 51, an epoxy resin-based adhesive, an acrylic resin-based adhesive, and a silicone resin-based adhesive can be listed. The thickness of the adhesive 51 in the direction D3 is, for example, in the range of 0.01 mm to 0.1 mm.

[0046] The holding member 20 has a plurality of, i.e., M x N, optical fiber holding holes 23. Each optical fiber holding hole 23 extends from the face 22 toward the face 21 and, in one example, penetrates between the face 22 and the face 21. The M x N optical fiber holding holes 23 correspond one-to-one to the M x N optical fibers 41. Each optical fiber holding hole 23 accommodates and holds at least a portion of the exposed portion of the resin coating of the corresponding optical fiber 41.

[0047] The holding member 20 is composed of a material having a thermal expansion coefficient smaller than that of the optical functional member 10 or a material having a thermal expansion coefficient larger than that of the optical functional member 10. The holding member 20 can have a light-transmitting property or can not have a light-transmitting property. The holding member 20 has glass as a main constituent material and, in one example, is composed only of glass. The glass is, for example, Pyrex glass (Pyrex is a registered trademark). Note that the thermal expansion coefficient of the Pyrex glass is in the range of 3 x 10 －6 K －1 to 4 x 10 －6 K －1 , and the Young's modulus of the Pyrex glass is 65,500 MPa. The shape of the holding member 20 can be formed, for example, by a method such as cutting or etching.

[0048] The deformation suppression member 30 is a substantially rectangular parallelepiped member for counteracting the bending stress applied to the holding member 20. The deformation suppression member 30 of the present embodiment also has a function of holding the N optical fiber ribbons 40 and the N x M optical fibers 41. The holding member 20 is sandwiched between the optical functional member 10 and the deformation suppression member 30 in the direction D3. The deformation suppression member 30 has a surface 31 extending in the direction D1 and the direction D2 and intersecting the direction D3, and a surface 32 opposite to the surface 31 in the direction D3. In one example, the surface 31 is flat. The thickness of the deformation suppression member 30 in the direction D3, i.e., the interval of the surface 31 and the surface 32, is, for example, in the range of 1 mm to 5 mm. The surface 31 opposes the surface 22 of the holding member 20 and is directly or indirectly fixed to the surface 22. In one example, the surface 31 is bonded to the surface 22 by an adhesive 52. In other words, the adhesive 52 is interposed between the surface 31 and the surface 22. The adhesive 52 can or can not have light transmissivity. The adhesive 52 is, for example, resin, and in one example, is an epoxy resin-based, an acrylic resin-based, or a silicone resin-based. The thickness of the adhesive 52 in the direction D3 is, for example, in the range of 0.01 mm to 0.1 mm.

[0049] The deformation suppression member 30 has N x M optical fiber holding holes 33 each of which accommodates the N x M optical fibers 41, and N ribbon holding holes 34 each of which accommodates the N optical fiber ribbons 40. Each of the ribbon holding holes 34 extends from the bottom surface of the recess 35 formed in the surface 32 toward the surface 31 in the direction D3. Each of the optical fiber holding holes 33 extends from the corresponding ribbon holding hole 34 in the direction D3 to the surface 31.

[0050] In the case where the coefficient of thermal expansion of the optical functional member 10 is larger than that of the holding member 20, the coefficient of thermal expansion of the deformation suppression member 30 is also larger than that of the holding member 20. In the case where the coefficient of thermal expansion of the optical functional member 10 is smaller than that of the holding member 20, the coefficient of thermal expansion of the deformation suppression member 30 is also smaller than that of the holding member 20. The coefficient of thermal expansion of the deformation suppression member 30 can be larger or smaller than that of the optical functional member 10. The Young's modulus of the deformation suppression member 30 is smaller than that of each of the optical functional member 10 and the holding member 20.

[0051] The deformation suppression member 30 can or can not have light transmissivity. The deformation suppression member 30 of the present embodiment is mainly composed of resin, and in one example, is composed of resin. As the resin constituting the deformation suppression member 30, for example, liquid crystal polymer (LCP), polyphenylene sulfide (PPS), or the like can be cited. The coefficient of thermal expansion of LCP is, for example, in the range of 10 x 10 －6 K－1 up to 20 x 10 －6 K －1 The Young's modulus of the LCP is 20500 MPa. The deformation suppression member 30 can be formed, for example, by molding using a mold having a plurality of pins for forming the optical fiber holding holes 33 and the tape holding holes 34.

[0052] In Figure 1 and Figure 2 the optical connection structure 1 shown in FIG. 1, the light L emitted from the end face 42 of each optical fiber 41 is incident on the optical functional member 10. Inside the optical functional member 10, a predetermined action is imparted to the light L. Thereafter, the light L is emitted from the face 13 of the optical functional member 10 opposite the face 11. Alternatively, inside the optical functional member 10, a predetermined action is imparted to the light L incident on the face of the optical functional member 10 opposite the face 11. Thereafter, the light L is incident on the end face 42 of each optical fiber 41.

[0053] Figure 3 is a sectional view showing the configuration in the case where the optical functional member 10 includes only the lens array 12. Figure 4 is Figure 3 a perspective view of the optical connection structure 1 shown in FIG. 1. In Figure 4 , the deformation suppression member 30 is indicated by a broken line. The lens array 12 has the aforementioned face 11 and a face 13 opposite the face 11, and is in the form of a flat plate or a rectangular parallelepiped. The face 13 extends along the direction Dl and the direction D2, and intersects the direction D3. In one example, the face 13 is parallel to the face 11. The thickness of the lens array 12 in the direction D3, i.e., the interval between the face 11 and the face 13, is, for example, in the range of 0.5 mm to 3.0 mm.

[0054] M x N lenses 131 corresponding to the M x N optical fibers 41 are formed on the face 13. Each lens 131 is a convex lens protruding from the face 13, and is optically coupled to the corresponding optical fiber 41. That is, the M x N lenses 131 are arranged in a two-dimensional manner in the direction Dl as the row direction and in the direction D2 as the column direction, over M rows and N columns. In one example, the lens array 12 is composed mainly of silicon (Si), and in one embodiment, is composed of silicon. The coefficient of thermal expansion of silicon is 3 x 10 －6 K －1 The Young's modulus of silicon is 131000 MPa.

[0055] In Figure 3 and Figure 4 the optical connection structure 1 shown in FIG. 1, the light L emitted from the end face 42 of each optical fiber 41 is incident on the lens array 12. The light L is parallelized (collimated) by each lens 131 of the lens array 12, and is emitted from the face 13. Alternatively, the light L incident on the face 13 of the lens array 12 as parallel light is condensed by each lens 131, and is incident on the end face 42 of each optical fiber 41.

[0056] Figure 5 is a sectional view showing the configuration of the optical connection structure 1 in the case where the optical functional member 10 includes the lens array 12 and the optical element 14. The lens array 12 is sandwiched between the holding member 20 and the optical element 14 in the direction D3. The optical element 14 is directly or indirectly fixed to the lens array 12. Specifically, the optical element 14 has a face 15 opposite to the face 13 of the lens array 12 and a face 16 opposite to the face 15. The face 15 extends along the direction Dl and the direction D2 and intersects the direction D3. In one example, the face 15 is flat. The normal direction of the face 15 can coincide with the direction D3 or can be slightly inclined with respect to the direction D3. The thickness of the optical element 14 in the direction D3, i.e., the interval between the face 15 and the face 16, is, for example, in the range of 0.5 mm to 10 mm. The optical element 14 is, for example, at least one of a rotator, an optical filter, an optical isolator, and an optical path conversion member.

[0057] The face 15 is opposite to the face 13 of the lens array 12 and is directly or indirectly fixed to the face 13. In one example, the face 15 is bonded to the face 13 by an adhesive 53. In other words, the adhesive 53 is interposed between the face 15 and the face 13. The adhesive 53 has optical transparency. The adhesive 53 is, for example, a resin adhesive. As the adhesive 53, an adhesive having a difference in refractive index with the constituent material of the optical element 14 of zero or a minimum is selected. As examples of the adhesive 53, an epoxy resin-based adhesive, an acrylic resin-based adhesive, and a silicone resin-based adhesive can be listed. The thickness of the adhesive 53 in the direction D3 is, for example, in the range of 0.01 mm to 0.1 mm.

[0058] In the optical connection structure 1 shown in FIG. 8, Figure 5 In the optical connection structure 1 shown in FIG. 8, the light L emitted from the end face 42 of each optical fiber 41 is incident on the lens array 12. The light L is parallelized (collimated) by each lens 131 of the lens array 12 and is emitted from the face 13. Thereafter, the light L is incident on the optical element 14, is subjected to a prescribed action inside the optical element 14, and is emitted from the face 16. Alternatively, the light L incident on the face 16 of the optical element 14 as parallel light is subjected to a prescribed action inside the optical element 14, is condensed by each lens 131 of the lens array 12, and is incident on the end face 42 of each optical fiber 41.

[0059] Figure 6is a sectional view showing the configuration of the optical connection structure 1 in the case where the optical functional member 10 includes the lens array 12, the optical element 14, and the lens array 17. The lens array 17 has a face 18 and a face 19 opposite to the face 18, and is in a flat plate shape or a cuboid shape. The faces 18 and 19 extend along a direction Dl and a direction D2, and intersect a direction D3. In one example, the face 19 is parallel to the face 18. The thickness of the lens array 17 in the direction D3, i.e., the interval of the faces 18 and 19, is, for example, in the range of 0.5 mm to 3.0 mm.

[0060] The face 18 is opposed to the face 16 of the optical element 14, and is directly or indirectly fixed to the face 16. In one example, the face 18 is bonded to the face 16 by an adhesive 54. In other words, the adhesive 54 is interposed between the face 18 and the face 16. As the adhesive 54, the same adhesive as the adhesive 53 described above can be used.

[0061] In the face 18, M x N lenses 181 corresponding to the M x N optical fibers 41 are formed. Each lens 181 is a convex lens protruding from the face 18, and is optically coupled to the corresponding optical fiber 41 via the lens 131. That is, the M x N lenses 181 are arranged in a two-dimensional manner in the direction Dl as a row direction and in the direction D2 as a column direction, over M rows and N columns. In one example, the lens array 17 is mainly composed of, for example, silicon (Si), and in one embodiment, is composed of silicon.

[0062] In Figure 6 In the optical connection structure 1 shown in the drawing, the light L emitted from the end face 42 of each optical fiber 41 is incident on the lens array 12. The light L is parallelized (collimated) by each lens 131 of the lens array 12, and is emitted from the face 13. Thereafter, the light L is incident on the optical element 14, is subjected to a prescribed action inside the optical element 14, and is condensed by each lens 181 of the lens array 17, and is emitted from the face 19. Alternatively, the light L incident on the face 19 of the lens array 17 as divergent light is parallelized (collimated) by each lens 181 of the lens array 17, is subjected to a prescribed action inside the optical element 14, and is condensed by each lens 131 of the lens array 12, and is incident on the end face 42 of each optical fiber 41.

[0063] An effect obtained by the optical connection structure 1 of the present embodiment having the above configuration will be described. Figure 7 is a schematic view showing the optical functional member 10 and the holding member 20 in the case where the deformation suppression member 30 is not provided as a comparative example. As such, when the optical functional member 10 and the holding member 20 are fixed to each other, since the difference in the coefficients of thermal expansion of the optical functional member 10 and the holding member 20, as shown in Figure 8As shown, the face 21 of the holding member 20 is deformed. Thereby, the direction of the optical axis of each optical fiber 41 is varied, and the optical coupling efficiency of each optical fiber 41 to the optical functional member 10, particularly to the lens array 12, is decreased.

[0064] Figure 9 is a schematic view showing the optical functional member 10, the holding member 20, and the deformation suppressing member 30 of the present embodiment. In the optical connection structure 1 of the present embodiment, the holding member 20 is sandwiched between the optical functional member 10 and the deformation suppressing member 30 in order to solve the above-mentioned problem. Further, the thermal expansion coefficient of the optical functional member 10 and the deformation suppressing member 30 is larger than or smaller than the thermal expansion coefficient of the holding member 20. In this case, due to the temperature change, in the holding member 20, in addition to the stress caused by the optical functional member 10, the stress in the opposite direction to the above-mentioned stress caused by the deformation suppressing member 30 is generated. As a result, the deformation generated in the face 21 of the holding member 20 is reduced. Therefore, according to the optical connection structure 1 of the present embodiment, the variation of the direction of the optical axis of each optical fiber 41 caused by the temperature change can be reduced, and the decrease of the optical coupling efficiency of each optical fiber 41 to the optical functional member 10, particularly to the lens array 12, can be reduced.

[0065] As the present embodiment, it can also be that the thickness of the deformation suppressing member 30 in the direction D3 is 1 mm or more. As shown in the example described later, according to the simulation by the present inventor, in the case where the thickness of the deformation suppressing member 30 is less than 1 mm, the thicker the deformation suppressing member 30, the more the bending of the holding member 20 is suppressed regardless of the Young's modulus of the deformation suppressing member 30. On the contrary, in the case where the thickness of the deformation suppressing member 30 is 1 mm or more, the thickness of the deformation suppressing member 30 is less related to the bending of the holding member 20 regardless of the Young's modulus of the deformation suppressing member 30. Therefore, if the thickness of the deformation suppressing member 30 is at least 1 mm, the above-mentioned effect can be sufficiently obtained.

[0066] As the present embodiment, it can also be that the deformation suppressing member 30 holds a plurality of optical fibers 41. In this case, the deformation suppressing member 30 cooperates with the holding member 20, and thereby the plurality of optical fibers 41 can be more firmly held.

[0067] As the present embodiment, it can also be that the optical functional member 10 includes the lens array 12 including the face 11. In this case, the plurality of optical fibers 41 are optically coupled to the lens array 12, and the optical connection structure 1 in which the decrease of the optical coupling efficiency of each optical fiber 41 to the lens array 12 caused by the temperature change is small can be provided.

[0068] As in this embodiment, the lens array 12 may be primarily made of silicon (Si), the retaining member 20 may be primarily made of glass, and the deformation suppression member 30 may be primarily made of resin. In this case, both the coefficients of thermal expansion of the lens array 12 and the deformation suppression member 30 are greater than those of the retaining member 20. Therefore, the aforementioned effects can be achieved.

[0069] As in this embodiment, the optical functional component 10 may also include an optical element 14, which is different from the lens array 12. Alternatively, the lens array 12 may be sandwiched between the holding member 20 and the optical element 14 in direction D3, and the optical element 14 may be directly or indirectly fixed to the lens array 12. In this case, an optical connection structure 1 can be provided to perform various operations on the light L incident on each optical fiber 41 or the light L emitted from each optical fiber 41.

[0070] As in this embodiment, the optical connection structure 1 may also include an optical fiber ribbon 40 formed by coating and protecting multiple optical fibers 41 with resin. Alternatively, the deformation suppression member 30 may have multiple optical fiber holding holes 33 for accommodating the multiple optical fibers 41 and ribbon holding holes 34 for accommodating the optical fiber ribbon 40. In this case, the multiple optical fibers 41 can be held more securely via the optical fiber ribbon 40.

[0071] As in this embodiment, the deformation suppression member 30 may also have a surface 32 opposite to the surface 31 in the direction D3. Alternatively, the ribbon retaining hole 34 may extend from the bottom surface of the recess 35 formed in the surface 32 towards the surface 31 along the direction D3. Alternatively, a plurality of fiber retaining holes 33 may extend from the ribbon retaining hole 34 along the direction D3 to the surface 31. In this case, the fiber ribbon 40 and the plurality of fibers 41 can be retained by a simple structure that is easy to form.

[0072] As in this embodiment, surface 21 can also be bonded to surface 11 using adhesive 51. In this case, surface 21 can be indirectly fixed to surface 11.

[0073] As in this embodiment, surface 31 can also be bonded to surface 22 using adhesive 52. In this case, surface 31 can be indirectly fixed to surface 22.

[0074] [Example]

[0075] Here, the simulation of the optical connection structure 1 of the above embodiment and the results are explained.

[0076] Figure 10 It means to indicate that... Figure 5 The graph shows the results of simulating the deformation of the surface 21 of the retaining member 20 when the ambient temperature of the light connection structure 1 is raised from 25°C to 110°C.Figure 11 indicates the result in the case where the deformation suppression member 30 is not provided in the optical connection structure 1 shown in Figure 5 In these figures, the vertical axis indicates the height of the surface 21, i.e., the position of each portion of the surface 21 in the direction D3 (unit: pm), and the horizontal axis indicates the width direction position, i.e., the position of each portion of the surface 21 in the direction Dl (unit: pm). In this simulation, the optical element 14 was assumed to be a rotator, and the thickness of the rotator in the direction D3 was assumed to be 6 mm. The material of the rotator was yttrium iron garnet. The thickness of the holding member 20 in the direction D3 was assumed to be 1 mm, and the thickness of the deformation suppression member 30 in the direction D3 was assumed to be 3 mm. The material of the holding member 20 was borosilicate glass. The material of the deformation suppression member 30 was liquid crystal polymer (LCP).

[0077] As shown in Figure 11 , in the case where the deformation suppression member 30 was not provided, the amount of warping of the surface 21 of the holding member 20, i.e., the maximum deformation amount, was 0.99 pm. In contrast, as shown in Figure 10 , in the case where the deformation suppression member 30 was provided, the amount of warping of the surface 21, i.e., the maximum deformation amount, was 0.26 pm. Thus, according to the optical connection structure 1 of the above-described embodiment, by providing the deformation suppression member 30, it is possible to reduce the bending of the surface 21 of the holding member 20.

[0078] Figure 12 and Figure 13 is a perspective view showing a model used for another simulation. Figure 12 indicates a model in the case where the deformation suppression member 30 is not provided, Figure 13 indicates a model in the case where the deformation suppression member 30 is provided. In this simulation, the cross section of the lens array 12, the optical element 14 (rotator), the holding member 20, and the deformation suppression member 30 of the optical connection structure 1 shown in Figure 5 was assumed to be a square of 6 mm x 6 mm. Also, the thickness Z of the lens array 12, the optical element 14 (rotator), and the holding member 20 in the direction D3 was assumed to be 1 mm, 6 mm, and 1 mm, respectively. The thickness of the deformation suppression member 30 in the direction D3 was changed in the range of 0.0 mm to 5.0 mm. The thickness of the adhesives 51, 52, and 53 was assumed to be 30 pm, respectively. Figure 14 indicates the Young's modulus, the coefficient of thermal expansion, and the Poisson's ratio of the optical element 14 (rotator), the lens array 12, the holding member 20, the deformation suppression member 30, and the adhesives 51, 52, and 53 used for this simulation.

[0079] Figure 15is a graph showing the relationship between the thickness of the deformation suppressing member 30 and the amount of warping of the face 21, i.e., the maximum amount of deformation, as a result of the simulation. The horizontal axis shows the thickness of the deformation suppressing member 30 (unit: mm), and the vertical axis shows the amount of warping, i.e., the maximum amount of deformation (unit: pm). The lines Al to A5 in the graph show the cases where the Young's modulus of the deformation suppressing member 30 is 5000 MPa, 10000 MPa, 20500 MPa, 40000 MPa, and 80000 MPa, respectively. Referring to Figure 15 It is understood that, in the case where the deformation suppressing member 30 is present, the warping of the face 21 is reduced, as compared to the case where the deformation suppressing member 30 is not present (thickness 0 mm). Further, it is understood that the greater the Young's modulus of the deformation suppressing member 30, the more the warping of the face 21 is reduced.

[0080] Further, referring to Figure 15 In the case where the thickness of the deformation suppressing member 30 is less than 1 mm, the thicker the deformation suppressing member 30, the more the warping of the face 21 is suppressed. In contrast, in the case where the thickness of the deformation suppressing member 30 is 1 mm or more, the relationship between the thickness of the deformation suppressing member 30 and the amount of warping of the face 21 is small. Therefore, it is understood that if the thickness of the deformation suppressing member 30 is at least 1 mm, the effects of the above-described embodiments can be sufficiently achieved.

[0081] Figure 16 is a graph showing the relationship between the effective Young's modulus Ec calculated from the Young's modulus Ea of the optical element 14 (rotator) and the Young's modulus Eb of the deformation suppressing member 30, the thickness of the deformation suppressing member 30, and the amount of warping of the face 21, based on the simulation results shown in Figure 15 Figure 16 In the graph, the horizontal axis shows the thickness of the deformation suppressing member 30 (unit: mm), and the vertical axis shows the ratio (Eb / Ec), showing a plurality of regions divided according to the amount of warping of the face 21. The regions Bl to B6 in the graph show the region where the amount of warping of the face 21 is 0.0 pm to 0.1 pm, the region where the amount of warping of the face 21 is 0.1 pm to 0.2 pm, the region where the amount of warping of the face 21 is 0.2 pm to 0.3 pm, the region where the amount of warping of the face 21 is 0.3 pm to 0.4 pm, the region where the amount of warping of the face 21 is 0.4 pm to 0.5 pm, and the region where the amount of warping of the face 21 is 0.5 pm to 0.6 pm.

[0082] Referring to Figure 16 It is understood that, in the range where the thickness of the deformation suppressing member 30 is 1 mm or more, if the ratio (Eb / Ec) is 0.192 or more, the amount of warping of the face 21 falls within the range of 0.0 to 0.2, and the amount of warping of the face 21 can be effectively reduced. Figure 16 ​The Young's modulus Ea of the optical element 14 (rotator) and the Young's modulus Eb of the deformation suppression member 30 can be used to calculate the longitudinal axis of the optical fiber 41 according to the composite law of composite materials.

[0083] The optical connection structure of the present disclosure is not limited to the above-described embodiments, and various modifications can be made. For example, in the above-described embodiments, the optical functional member 10 and the holding member 20 are fixed only via the adhesive 51. Without being limited to this, another member can be interposed between the optical functional member 10 and the holding member 20, and the optical functional member 10 and the holding member 20 are indirectly fixed via the other member. Similarly, in the above-described embodiments, the holding member 20 and the deformation suppression member 30 are fixed only via the adhesive 52. Without being limited to this, another member can be interposed between the holding member 20 and the deformation suppression member 30, and the holding member 20 and the deformation suppression member 30 are indirectly fixed via the other member.

[0084] In the above-described embodiments, the deformation suppression member 30 has a function of holding a plurality of optical fibers 41. Without being limited to this, the deformation suppression member can not have a function of holding a plurality of optical fibers 41. For example, the deformation suppression member can have a through-hole for the N pieces of optical fiber ribbons 40 and the N x M optical fibers 41 to be inserted together instead of the optical fiber holding holes 33 and the ribbon holding holes 34.

[0085] In the above-described embodiments, the optical functional member 10 and the holding member 20 are indirectly fixed via the adhesive 51. Without being limited to this, the optical functional member 10 and the holding member 20 can be directly fixed. As a method of direct fixation, for example, laser welding can be cited. Similarly, in the above-described embodiments, the holding member 20 and the deformation suppression member 30 are indirectly fixed via the adhesive 52. Without being limited to this, the holding member 20 and the deformation suppression member 30 can be directly fixed. As a method of direct fixation, for example, laser welding can be cited.

[0086] Explanation of Reference Signs

[0087] 1: Optical connection structure

[0088] 10: Optical functional member

[0089] 11: First surface

[0090] 12: Lens array

[0091] 13, 15, 16, 18, 19, 31, 32: Surface

[0092] 14: Optical element

[0093] 17: Lens array

[0094] 20: Holding member

[0095] 21: second surface

[0096] 22: third surface

[0097] 23, 33: optical fiber holding hole

[0098] 30: deformation suppressing member

[0099] 34: tape holding hole

[0100] 35: recess

[0101] 40: optical fiber tape

[0102] 41: optical fiber

[0103] 42: end surface

[0104] 51, 52, 53, 54: adhesive

[0105] 131, 181: lens

[0106] A1 to A5: line

[0107] B1 to B6: region

[0108] D1: first direction

[0109] D2: direction

[0110] D3: second direction

[0111] L: light

Claims

1. An optical connection structure comprising: a plurality of optical fibers configured to have end faces side by side in a first direction, the plurality of optical fibers respectively extending along a second direction intersecting the first direction; an optical functional member having a first face opposing the end faces of the plurality of optical fibers, the end faces of the plurality of optical fibers being optically coupled at the first face; a holding member having a second face opposing the first face and directly or via an adhesive fixed to the first face, a third face opposite the second face, and a plurality of optical fiber holding holes respectively accommodating the plurality of optical fibers extending from the third face toward the second face; and a deformation suppressing member having a fourth face opposing the third face and directly or via an adhesive fixed to the third face, the holding member being sandwiched between the deformation suppressing member and the optical functional member in the second direction, a coefficient of thermal expansion of the optical functional member and the deformation suppressing member being greater than a coefficient of thermal expansion of the holding member, or a coefficient of thermal expansion of the optical functional member and the deformation suppressing member being less than a coefficient of thermal expansion of the holding member.

2. The optical connection structure according to claim 1, wherein a thickness of the deformation suppressing member in the second direction is 1 mm or more.

3. The optical connection structure according to claim 2, wherein a ratio Eb / Ec of a Young's modulus Eb of the deformation suppressing member to an effective Young's modulus Ec of the optical functional member is 0.192 or more.

4. The optical connection structure according to claim 1, wherein the deformation suppressing member holds the plurality of optical fibers.

5. The optical connection structure according to claim 4, comprising an optical fiber ribbon in which the plurality of optical fibers are covered and protected by a resin, wherein the deformation suppressing member has a plurality of optical fiber holding holes respectively accommodating the plurality of optical fibers and a ribbon holding hole accommodating the optical fiber ribbon.

6. The optical connection structure according to claim 5, wherein the deformation suppressing member further has a fifth face opposite the fourth face in the second direction, the ribbon holding hole extends from a bottom face of a recess formed in the fifth face toward the fourth face along the second direction, and the plurality of optical fiber holding holes extend from the ribbon holding hole along the second direction to the fourth face.

7. The optical connection structure according to any one of claims 1 to 6, wherein the optical functional member includes a lens array including the first face.

8. The optical connection structure according to claim 7, wherein the lens array has silicon as a main constituent material, the holding member has glass as a main constituent material, and the deformation suppressing member has a resin as a main constituent material.

9. The optical connection structure according to claim 7, wherein the optical functional member further includes an optical element different from the lens array, the lens array is sandwiched between the holding member and the optical element in the second direction, and the optical element is directly or indirectly fixed to the lens array.

10. The optical connection structure according to claim 9, wherein ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The optical element is at least one of a rotator, an optical filter, an optical isolator, and an optical path converting member.

Images