Optical module

Abstract

To prevent the degradation of transmission characteristics.SOLUTION: An optical module comprises: a block 26 having a front face 28 where the tip surface of an optical fiber 22 is exposed; a waveguide substrate 42 where the top of the front face 28 projects upward from a side face 46 and the optical axes of the optical fiber 22 and an optical waveguide 44 match; a base substrate 56 having a top face where the underside of the waveguide substrate 42 is fixed and a projection projecting from the waveguide substrate 42 to below the block 26, with the top face facing the underside of the block 26; and an adhesive 48 with which the block 26 is bonded to the waveguide substrate 42 and the base substrate 56. The adhesive 48 includes an upper portion 52 located at a corner and demarcated by the top of the front face 28 of the block 26 and the top face of the waveguide substrate 42, an intermediate portion 50 interposed between the front face 28 of the block 26 and the side face 46 of the waveguide substrate 42, and a lower portion 54 interposed between the underside of the block 26 and the top face of the base substrate 56.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an optical module. [Background technology]

[0002] In an optical module, the optical axes of the optical fiber and the optical waveguide must be aligned. A fiber block is fixed to the tip of the optical fiber (Patent Documents 1 and 2). The optical waveguide is attached to a waveguide substrate, and the fiber block and the waveguide substrate are fixed in place (Patent Document 3). An adhesive is used to fix the two together (Patent Document 4). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2007-163604 A [Patent Document 2] JP 2016-206308 A [Patent Document 3] JP 2012-58409 A [Patent Document 4] JP 2016-218280 A Summary of the Invention [Problem to be solved by the invention]

[0004] The adhesive is interposed between the fiber block and the waveguide substrate, and also rises above the waveguide substrate. If this rise expands due to heat, the fiber block will tilt, causing the optical axes of the optical fiber and the optical waveguide to no longer coincide, resulting in a deterioration in transmission characteristics.

[0005] An object of the present invention is to prevent the deterioration of transmission characteristics. [Means for solving the problem]

[0006] the optical module comprises: a block attached to an end of an optical fiber and having a front surface from which a tip surface of the optical fiber is exposed; a waveguide substrate into which an optical waveguide is fabricated and having a side surface from which the tip surface of the optical waveguide is exposed, the side surface facing the front surface of the block, an upper portion of the front surface protruding upward from the side surface, and optical axes of the optical fiber and the optical waveguide coinciding; a base substrate having an upper surface to which a lower surface of the waveguide substrate is fixed and having a protruding portion protruding from the waveguide substrate below the block, the upper surface facing the lower surface of the block; and an adhesive for bonding the block to the waveguide substrate and the base substrate, the adhesive including an upper portion located at a corner defined by the upper portion of the front surface of the block and the upper surface of the waveguide substrate, an intermediate portion interposed between the front surface of the block and the side surface of the waveguide substrate, and a lower portion interposed between the lower surface of the block and the upper surface of the base substrate. [Brief description of the drawings]

[0007] [Figure 1] 1 is an overall cross-sectional view of an optical module according to a first embodiment. [Diagram 2] 2 is a partial plan view of the internal structure of the optical module shown in FIG. [Diagram 3] 3 is a cross-sectional view taken along line III-III of the internal structure shown in FIG. 2. [Figure 4] 4 is a cross-sectional view of the block and the optical fiber shown in FIG. 1 taken along the line IV-IV. [Diagram 5] 2 is a cross-sectional view of the waveguide substrate shown in FIG. 1 taken along line VV. [Figure 6A] 1 is a cross-sectional view of a model of a simulation in which thermal stresses of a conventional block and a waveguide substrate are calculated. [Figure 6B] 11 is a cross-sectional view of a model of a simulation in which thermal stress in the block and the waveguide substrate of the present embodiment is calculated. FIG. [Figure 6C] 13A and 13B are diagrams showing the results of a simulation calculating thermal stresses in a conventional block and a waveguide substrate. [Figure 6D]11A and 11B are diagrams showing the results of a simulation in which thermal stresses in the block and the waveguide substrate of the present embodiment are calculated. [Figure 7] 1A to 1C are diagrams illustrating a manufacturing process of an optical module. [Figure 8] FIG. 4 is a partial plan view of the internal structure of an optical module according to a first modified example of the first embodiment. [Figure 9] 9 is a cross-sectional view of the internal structure shown in FIG. 8 taken along line IX-IX. [Figure 10] 11 is a partial cross-sectional view of the internal structure of an optical module according to a second modified example of the first embodiment. FIG. [Figure 11] 11 is a partial cross-sectional view of the internal structure of an optical module according to a third modified example of the first embodiment. FIG. [Figure 12] 11 is a partial cross-sectional view of the internal structure of an optical module according to a second embodiment. FIG. [Figure 13] FIG. 11 is a partial plan view of the internal structure of the optical module according to the third embodiment. [Figure 14] 14 is a cross-sectional view of the internal structure shown in FIG. 13 taken along line XIV-XIV. [Figure 15] FIG. 13 is a partial plan view of the internal structure of an optical module according to a modified example of the third embodiment. [Figure 16] 16 is a cross-sectional view of the internal structure shown in FIG. 15 taken along line XVI-XVI. [Figure 17] FIG. 11 is a partial plan view of the internal structure of the optical module according to the fourth embodiment. [Figure 18] 18 is a cross-sectional view of the internal structure shown in FIG. 17 taken along line XVIII-XVIII. [Figure 19] FIG. 13 is a partial plan view of the internal structure of an optical module according to a modified example of the fourth embodiment. [Figure 20] 20 is a cross-sectional view of the internal structure shown in FIG. 19 taken along the line XX-XX. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. In all the drawings, the same reference numerals are used to denote the same or equivalent functions, and the repeated description thereof will be omitted. Note that the size of the figures does not necessarily correspond to the magnification.

[0009] [First embodiment] FIG. 1 is an overall cross-sectional view of an optical module according to a first embodiment. The optical module is an optical transceiver. The optical transceiver is used as a signal input / output port for optical communication devices such as routers or switches, or for devices. A connector (not shown) attached to a printed circuit board 10 is used for electrical input / output. Inside a case 12, there is an electronic component 14 (e.g., an integrated circuit chip), and solder 16 is used for electrical and physical connection. Wires 18 are used for electrical connection between a transmission line and another transmission line.

[0010] An adapter 20 is attached to the case 12, and a ferrule 24 fixed to the end of an optical fiber 22 is inserted into the adapter 20. Optical input / output is achieved by inserting a ferrule of an external optical fiber (not shown) into the adapter 20. An MPO (Multi-Fiber Push On) connector is used as the optical interface.

[0011] Fig. 2 is a partial plan view of the internal structure of the optical module shown in Fig. 1. Fig. 3 is a cross-sectional view of the internal structure shown in Fig. 2 taken along line III-III.

[0012] The optical fiber 22 includes a core, a cladding, and a coating. The cladding has a lower refractive index than the core. At the end of the optical fiber 22, the coating is removed, leaving only the core and the cladding. A block 26 is attached to the end of the optical fiber 22. One block 26 is attached to the end of a plurality of optical fibers 22. The tip faces of the optical fibers 22 are exposed from a front surface 28 of the block 26.

[0013] 4 is a cross-sectional view of the block 26 and the optical fiber 22 taken along line IV-IV shown in FIG. 1. The block 26 includes a lower substrate 30. The lower substrate 30 has a rear end face 32 opposite the front face 28. The block 26 includes an upper substrate 34 on the lower substrate 30. The optical fiber 22 is sandwiched between the lower substrate 30 and the upper substrate 34. The lower substrate 30 is often thinner than the upper substrate 34. The upper substrate 34 has a V-groove 36 on the surface facing the lower substrate 30. The optical fiber 22 is disposed in the V-groove 36.

[0014] 3, the upper substrate 34 has a protruding lower surface 38 that protrudes from the lower substrate 30. The lower substrate 30 is shorter in length from the front surface 28 of the block 26 than the upper substrate 34. The upper substrate 34 and the lower substrate 30 are bonded together with an adhesive material 40. A portion of the adhesive material 40 is present in a corner defined by the protruding lower surface 38 of the upper substrate 34 and the rear end surface 32 of the lower substrate 30.

[0015] The optical module has a waveguide substrate 42. As shown in Fig. 1, an electrical transmission line is formed on the waveguide substrate 42, and electronic components 14 are often mounted on the electrical transmission line. Optoelectronic elements (not shown), such as photodiodes and optical modulators, may also be built into the waveguide substrate 42 to convert one of electrical and optical signals into the other.

[0016] Fig. 5 is a cross-sectional view taken along line VV of the waveguide substrate 42 shown in Fig. 1. An optical waveguide 44 is fabricated in the waveguide substrate 42. The optical waveguide 44 is made up of a core and a clad. The thickness of the clad is at most several tens of microns. The width and thickness of the core are generally several µm for single-mode propagation.

[0017] The tip end face of the optical waveguide 44 is exposed from the side surface 46 of the waveguide substrate 42. The side surface 46 of the waveguide substrate 42 and the front surface 28 of the block 26 face each other. The optical axes of the optical fiber 22 and the optical waveguide 44 are aligned. The upper part of the front surface 28 of the block 26 protrudes upward from the side surface 46 of the waveguide substrate 42. The block 26 is bonded to the waveguide substrate 42 with an adhesive 48. An intermediate portion 50 of the adhesive 48 is interposed between the front surface 28 of the block 26 and the side surface 46 of the waveguide substrate 42. An upper portion 52 of the adhesive 48 is located in a corner defined by the upper part of the front surface 28 of the block 26 and the upper surface of the waveguide substrate 42.

[0018] As shown in Fig. 3, the optical module has a base substrate 56. The base substrate 56 is bonded to the printed circuit board 10 (Fig. 1). The lower surface of the waveguide substrate 42 is fixed to the upper surface of the base substrate 56. An adhesive layer 58 is interposed between the waveguide substrate 42 and the base substrate 56. The base substrate 56 has a protruding portion that protrudes from the waveguide substrate 42 below the block 26. The upper surface of the base substrate 56 faces the lower surface of the block 26. The base substrate 56 is short enough not to overlap the adhesive material 40.

[0019] The distance between the lower surface of block 26 and the upper surface of base substrate 56 is greater than the distance between the lower surface of waveguide substrate 42 and the upper surface of base substrate 56. That is, lower portion 54 of adhesive 48 is greater in thickness than adhesive layer 58. The lower surface of block 26 is higher than the lower surface of waveguide substrate 42. The upper surface of base substrate 56 is flat below block 26 and waveguide substrate 42.

[0020] The block 26 is adhered to the base substrate 56 with adhesive 48. The lower substrate 30 is adhered to the base substrate 56. A lower portion 54 of the adhesive 48 is interposed between the lower surface of the block 26 and the upper surface of the base substrate 56. The adhesive 48 has a larger coefficient of thermal expansion than the base substrate 56.

[0021] Fig. 6A is a model cross-sectional view of a simulation in which thermal stress in a conventional block and a waveguide substrate is calculated, Fig. 6B is a model cross-sectional view of a simulation in which thermal stress in a block and a waveguide substrate of this embodiment is calculated, Fig. 6C is a result of the simulation in which thermal stress in a conventional block and a waveguide substrate is calculated, and Fig. 6D is a result of the simulation in which thermal stress in a block and a waveguide substrate of this embodiment is calculated.

[0022] The waveguide substrate 142 is made of silicon, the block 126 is made of quartz, and the base substrate 156 is made of Kovar. The thermal expansion coefficients of these are 6×10 -6 / K or less. On the other hand, the adhesive 148 is an organic material, and its thermal expansion coefficient is 2×10 -5 / K or more. When the environmental temperature changes from 25° C. to 85° C., in the case of the conventional structure, the block 126 tilts with respect to the waveguide substrate 142 due to thermal expansion of the upper portion 152 of the adhesive 148 as shown in FIG. 6C. As a result, the optical axes of the optical fiber and the optical waveguide are misaligned.

[0023] In contrast, in this embodiment, the expansion pressure of the upper portion 152 of the adhesive 148 is pushed back by the expansion pressure of the lower portion 154. As a result, the angular displacement α between the block 126 and the waveguide substrate 142 is suppressed as shown in Fig. 6D, and is reduced to about 1 / 18 compared to the conventional example, so there is little fluctuation in the optical coupling efficiency. This stabilizes the optical coupling. The following table compares the thermal stress simulation results of the conventional example and this embodiment, focusing particularly on the displacement of point A in the Z-axis direction and the angular displacement α of the block relative to the optical waveguide substrate.

[0024] [Table 1]

[0025] 7 is an explanatory diagram of an example of a manufacturing process for an optical module. The block 26 is fixed to the optical fiber 22, and the waveguide substrate 42 is fixed to the base substrate 56. Then, the optical fiber 22 and the optical waveguide 44 are aligned. The alignment is performed while monitoring the optical output, thereby achieving optical coupling. Then, the block 26 is bonded to the waveguide substrate 42 and the base substrate 56. The adhesive 48 is a photocurable adhesive, and is cured by irradiating it with ultraviolet light from an ultraviolet light 60. If the block 26 is made of a light-transmitting material, it is easy to irradiate it with ultraviolet light.

[0026] [Modification 1 of the first embodiment] FIG. 8 is a partial plan view of the internal structure of the optical module according to the first modified example of the first embodiment. FIG. 9 is a cross-sectional view of the internal structure shown in FIG. 8 along the line IX-IX. The upper surface of the base substrate 56 has a groove 62A. The groove 62A extends along the lower end of the side surface 46 of the waveguide substrate 42. The groove 62A faces the lower surface of the waveguide substrate 42. An adhesive layer 58 is interposed between the waveguide substrate 42 and the base substrate 56. The end of the adhesive layer 58 is located inside the groove 62A. This prevents the adhesive 48 from contacting the adhesive layer 58, thereby avoiding adverse effects caused by the contact between the two. In addition, the adhesive layer 58 is prevented from flowing out toward the block 26 side from the side surface 46, which prevents adverse effects caused when the block 26 is bonded to the waveguide substrate 42.

[0027] [Modification 2 of the first embodiment] FIG. 10 is a partial cross-sectional view of the internal structure of an optical module according to the second modification of the first embodiment. The upper surface of the base substrate 56 has a groove 62B. The groove 62B extends along the lower end of the side surface 46 of the waveguide substrate 42. The groove 62B faces the lower surface of the block 26. An adhesive layer 58 is interposed between the waveguide substrate 42 and the base substrate 56. The end of the adhesive layer 58 is located inside the groove 62B. This prevents the adhesive layer 58, which is located on the block 26 side rather than the side surface 46, from swelling in the height direction when the block 26 is bonded to the waveguide substrate 42, from adversely affecting assembly. This can be applied when there is no problem even if the adhesive 48 comes into contact with the adhesive layer 58.

[0028] [Third Modification of the First Embodiment] 11 is a partial cross-sectional view of the internal structure of an optical module according to the third modification of the first embodiment. The upper surface of the base substrate 56 has a groove 62C. The groove 62C extends along the lower end of the side surface 46 of the waveguide substrate 42. The groove 62C is located directly below the side surface 46 of the waveguide substrate 42. An adhesive layer 58 is interposed between the waveguide substrate 42 and the base substrate 56. An end of the adhesive layer 58 is located inside the groove 62C. As a result, the adhesive 48 does not come into contact with the adhesive layer 58, which avoids adverse effects such as material mixing, and thus makes it possible to prevent the above-mentioned adverse effects on assembly.

[0029] [Second embodiment] FIG. 12 is a partial cross-sectional view of the internal structure of the optical module according to the second embodiment. The lower surface of the block 226 is located lower than the lower surface of the waveguide substrate 242. However, the upper surface of the base substrate 256 is lower below the block 226 than below the waveguide substrate 242. This allows a space to be secured between the lower surface of the block 226 and the upper surface of the base substrate 256, and allows the adhesive 248 to be placed. The space can be secured even if the waveguide substrate 242 is thin and the lower substrate 230 of the block 226 is thick. On the upper surface of the base substrate 256, the bottom surface of the adhesive layer 258 stops at the boundary of the height difference. This prevents the adhesive layer 258 from contacting the adhesive 248. The contents of the first embodiment are applicable to other details.

[0030] [Third embodiment] Fig. 13 is a partial plan view of the internal structure of the optical module according to the third embodiment. Fig. 14 is a cross-sectional view taken along line XIV-XIV of the internal structure shown in Fig. 13. The block 326 is a plurality of blocks 326. The optical waveguide 344 fabricated in the waveguide substrate 342 is a plurality of optical waveguides 344. The optical fiber 322 to which each of the plurality of blocks 326 is attached is one or more optical fibers 322.

[0031] The upper surface of the base substrate 356 has a convex portion 364 between adjacent blocks 326, and has a convex portion 346 on the outside of all blocks 326. The adhesive 348 does not reach the convex portions 346, 364. In other words, the convex portions 346, 364 can stop the lateral flow of the adhesive 348 before hardening, and the shape of the adhesive 348 can be more controlled. The bonding of the multiple blocks 326 may be performed one by one. In that case, the convex portions 364 prevent the adhesive 348 used in the previous bonding from flowing into the adjacent bonding area, enabling the next appropriate bonding. If the convex portions 346, 364 are provided on both sides of the block 326, the adhesive 348 can be partitioned, and the amount of the adhesive 348 can be appropriately controlled. The contents of the first embodiment can be applied to other details.

[0032] [Modification of the third embodiment] FIG. 15 is a partial plan view of the internal structure of an optical module according to a modified example of the third embodiment. FIG. 16 is a cross-sectional view of the internal structure shown in FIG. 15 along line XVI-XVI. The upper surface of the base substrate 356 has recesses 366 on both sides of the block 326. The upper surface of the base substrate 356 has edges adjacent to the recesses 366. The tip of the bottom surface of the adhesive 348 is aligned with the edge. In other words, the recesses 366 stop the flow of the adhesive 348 before it hardens. The bonding of multiple blocks 326 may be performed one by one. In that case, the recesses 366 prevent the adhesive 348 used in the previous bonding from flowing into the adjacent bonding area, enabling the next proper bonding. If there are recesses 366 on both sides of the block 326, the adhesive 348 can be partitioned, so that the amount of the adhesive can be properly managed.

[0033] [Fourth embodiment] FIG. 17 is a partial plan view of the internal structure of the optical module according to the fourth embodiment. FIG. 18 is a cross-sectional view of the internal structure shown in FIG. 17 along line XVIII-XVIII. The block 426 is a plurality of blocks 426. The optical waveguide 444 fabricated in the waveguide substrate 442 is a plurality of optical waveguides 444. The optical fiber 422 to which each of the plurality of blocks 426 is attached is one or more optical fibers 422. The base substrate 456 has a main body to which the waveguide substrate 442 is fixed. The base substrate 456 has a plurality of protrusions 468 protruding from the main body. The plurality of blocks 426 are bonded to the plurality of protrusions 468, respectively.

[0034] The base substrate 456 has a notch 470 between adjacent protrusions 468. Without the notch 470, the planar shape of the base substrate 456 is rectangular. The upper surface of the base substrate 456 has an edge adjacent to the notch 470. The tip of the bottom surface of the adhesive 448 is aligned with the edge. In other words, the notch 470 stops the flow of the adhesive 448 before hardening. This allows the adhesive 448 to be partitioned, so that the amount can be appropriately controlled. The bonding of the multiple blocks 426 may be performed one by one. In that case, the notch 470 prevents the adhesive 448 used in the previous bonding from flowing into the adjacent bonding area, enabling the next appropriate bonding. The contents of the first embodiment can be applied to other details.

[0035] [Modification of the fourth embodiment] Fig. 19 is a partial plan view of the internal structure of an optical module according to a modified example of the fourth embodiment. Fig. 20 is a cross-sectional view of the internal structure shown in Fig. 19 taken along the line XX-XX. Each of the blocks 426 is located at the center of a corresponding one of the protrusions 468A in the direction in which the protrusions 468A are arranged. The protrusions 468A are narrower in width than the protrusions 468A shown in Fig. 18. Therefore, the tip of the bottom surface of the adhesive 448 is aligned with the edges on both sides of the protrusions 468A. Therefore, the amount of adhesive 448 can be more appropriately managed.

[0036] The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the configurations described in the embodiments can be replaced with substantially the same configurations, configurations that provide the same effects, or configurations that can achieve the same purpose.

[0037] [Outline of the embodiment] (1) A block 26 is attached to an end of an optical fiber 22 and has a front surface 28 on which a tip surface of the optical fiber 22 is exposed, an optical waveguide 44 is formed, the front surface 28 has a side surface 46 on which the tip surface of the optical waveguide 44 is exposed, the side surface 46 faces the front surface 28 of the block 26, an upper portion of the front surface 28 protrudes upward from the side surface 46, and the optical axes of the optical fiber 22 and the optical waveguide 44 are aligned, and a waveguide substrate 42 has an upper surface to which a lower surface of the waveguide substrate 42 is fixed, and a protruding portion protrudes from the waveguide substrate 42 below the block 26. an optical module in which the upper surface has a base substrate 56 facing the lower surface of the block 26 and an adhesive 48 that adheres the block 26 to the waveguide substrate 42 and the base substrate 56, the adhesive 48 including an upper portion 52 located at a corner defined by the upper portion of the front surface 28 of the block 26 and the upper surface of the waveguide substrate 42, an intermediate portion 50 interposed between the front surface 28 of the block 26 and the side surface 46 of the waveguide substrate 42, and a lower portion 54 interposed between the lower surface of the block 26 and the upper surface of the base substrate 56.

[0038] The expansion of the upper portion 52 of the adhesive 48 applies a tilting force to the block 26, but the expansion of the lower portion 54 applies an opposite force to the block 26. This prevents the block 26 from tilting, and stabilizes the optical coupling between the optical fiber 22 and the optical waveguide 44.

[0039] (2) An optical module as described in (1), wherein the distance between the lower surface of the block 26 and the upper surface of the base substrate 56 is greater than the distance between the lower surface of the waveguide substrate 42 and the upper surface of the base substrate 56.

[0040] (3) The optical module according to (2), wherein the lower surface of the block 26 is located higher than the lower surface of the waveguide substrate 42.

[0041] (4) An optical module according to (3), wherein the top surface of the base substrate 56 is flat beneath the block 26 and the waveguide substrate 42.

[0042] (5) The optical module according to (2), wherein the lower surface of the block 226 is located lower than the lower surface of the waveguide substrate 242.

[0043] (6) The optical module according to (5), wherein the top surface of the base substrate 256 is lower below the block 226 than below the waveguide substrate 242.

[0044] (7) An optical module as described in any one of (1) to (6), further comprising an adhesive layer 58 interposed between the waveguide substrate 42 and the base substrate 56, the upper surface of the base substrate 56 having a groove 62A, and an end of the adhesive layer 58 positioned inside the groove 62A.

[0045] (8) The optical module according to (7), wherein the groove 62A extends along the lower end of the side surface 46 of the waveguide substrate 42.

[0046] (9) The optical module according to (8), wherein the groove 62A faces the lower surface of the waveguide substrate 42.

[0047] (10) An optical module according to (8), wherein the groove (62B) faces the lower surface of the block (26).

[0048] (11) An optical module according to (8), wherein the groove 62C is located directly below the side surface 46 of the waveguide substrate 42.

[0049] (12) An optical module according to any one of (1) to (11), wherein the block 326 is a plurality of blocks 326, the optical waveguide 344 fabricated in the waveguide substrate 342 is a plurality of optical waveguides 344, and the optical fiber 322 to which each of the plurality of blocks 326 is attached is one or more optical fibers 322.

[0050] (13) The optical module according to (12), wherein the upper surface of the base substrate 356 has a protrusion 364 between adjacent blocks 326.

[0051] (14) The optical module according to (13), wherein the adhesive 348 does not extend onto the protrusion 364.

[0052] (15) An optical module according to (12), wherein the upper surface of the base substrate 356 has a recess 366 between adjacent blocks 326.

[0053] (16) An optical module as described in (15), wherein the top surface of the base substrate 356 has an edge adjacent to the recess 366, and the tip of the bottom surface of the adhesive 348 is aligned with the edge.

[0054] (17) An optical module as described in (12), wherein the base substrate 456 has a main body to which the waveguide substrate 442 is fixed, the base substrate 456 has a plurality of protrusions 468 protruding from the main body, the base substrate 456 has notches 470 between adjacent protrusions 468, and the plurality of blocks 426 are respectively adhered to the plurality of protrusions 468.

[0055] (18) An optical module as described in (17), wherein the top surface of the base substrate 456 has an edge adjacent to the cutout 470, and a tip of the bottom surface of the adhesive 448 is aligned with the edge.

[0056] (19) An optical module as described in (17) or (18), wherein each of the plurality of blocks 426 is located at the center of a corresponding one of the plurality of protrusions 468 in the direction in which the plurality of protrusions 468A are arranged.

[0057] (20) An optical module as described in any one of (1) to (19), wherein the block 26 includes a lower substrate 30 adhered to the base substrate 56 and an upper substrate 34 on the lower substrate 30, the optical fiber 22 is sandwiched between the lower substrate 30 and the upper substrate 34, and the lower substrate 30 is thinner than the upper substrate 34.

[0058] (21) The optical module according to (20), wherein the upper substrate 34 has a V-groove 36 in which the optical fiber 22 is disposed on the surface facing the lower substrate 30.

[0059] (22) An optical module according to (20) or (21), wherein the lower substrate 30 is shorter than the upper substrate 34 in length from the front surface 28 of the block 26.

[0060] (23) An optical module as described in (22), further comprising an adhesive material 40 for adhering the upper substrate 34 and the lower substrate 30, the upper substrate 34 having a protruding lower surface 38 protruding from the lower substrate 30, the lower substrate 30 having a rear end surface 32 opposite the front surface 28, and a portion of the adhesive material 40 being located in a corner defined by the protruding lower surface 38 and the rear end surface 32.

[0061] (24) An optical module according to (23), wherein the base substrate 56 is long enough not to overlap the portion of the adhesive material 40.

[0062] (25) An optical module according to any one of (1) to (24), wherein the block 26 is made of a light-transmitting material and the adhesive 48 is a photocurable adhesive.

[0063] (26) The optical module according to any one of (1) to (25), wherein the adhesive 48 has a thermal expansion coefficient larger than that of the base substrate 56. [Explanation of symbols]

[0064] 10 printed circuit board, 12 case, 14 electronic components, 16 solder, 18 wire, 20 adapter, 22 optical fiber, 24 ferrule, 26 block, 28 front, 30 lower board, 32 rear end, 34 upper board, 36 V-groove, 38 protruding lower surface, 40 adhesive material, 42 waveguide board, 44 optical waveguide, 46 side, 48 adhesive, 50 middle part, 52 upper part, 54 lower part, 56 base board, 58 adhesive layer, 60 ultraviolet light, 62A groove, 62B groove, 62C groove, 126 block, 142 waveguide board, 148 adhesive, 152 upper part, 156 base board, 226 block, 230 lower board, 242 waveguide board, 248 adhesive, 256 Base substrate, 258 adhesive layer, 322 optical fiber, 326 block, 342 waveguide substrate, 344 optical waveguide, 346 protrusion, 348 adhesive, 356 base substrate, 364 protrusion, 366 recess, 422 optical fiber, 426 block, 442 waveguide substrate, 444 optical waveguide, 448 adhesive, 456 base substrate, 468 protrusion, 468A protrusion, 470 notch.

Claims

1. a block attached to an end of an optical fiber and having a front surface on which a tip surface of the optical fiber is exposed; a waveguide substrate having an optical waveguide formed therein, the waveguide substrate having a side surface on which a tip surface of the optical waveguide is exposed, the side surface facing the front surface of the block, an upper portion of the front surface protruding upward from the side surface, and optical axes of the optical fiber and the optical waveguide being aligned; a base substrate having an upper surface to which a lower surface of the waveguide substrate is fixed, the base substrate having a protruding portion protruding from the waveguide substrate below the block, the upper surface facing the lower surface of the block; an adhesive for adhering the block to the waveguide substrate and the base substrate; having an optical module including: an upper portion at a corner defined by the top of the front surface of the block and the upper surface of the waveguide substrate; an intermediate portion interposed between the front surface of the block and the side surface of the waveguide substrate; and a lower portion interposed between the lower surface of the block and the upper surface of the base substrate.

2. 2. The optical module according to claim 1, An optical module, wherein a distance between the lower surface of the block and the upper surface of the base substrate is greater than a distance between the lower surface of the waveguide substrate and the upper surface of the base substrate.

3. 3. The optical module according to claim 2, An optical module in which the bottom surface of the block is located higher than the bottom surface of the waveguide substrate.

4. 4. The optical module according to claim 3, An optical module, wherein the top surface of the base substrate is flat beneath the block and the waveguide substrate.

5. 3. The optical module according to claim 2, An optical module in which the bottom surface of the block is located lower than the bottom surface of the waveguide substrate.

6. 6. An optical module according to claim 5, An optical module, wherein the top surface of the base substrate is lower below the block than below the waveguide substrate.

7. 2. The optical module according to claim 1, Further comprising an adhesive layer interposed between the waveguide substrate and the base substrate; the top surface of the base substrate has a groove; An optical module in which an end of the adhesive layer is located inside the groove.

8. 8. An optical module according to claim 7, The groove extends along a lower edge of the side surface of the waveguide substrate.

9. 9. An optical module according to claim 8, The groove faces the lower surface of the waveguide substrate.

10. 9. An optical module according to claim 8, The groove faces the lower surface of the block.

11. 9. An optical module according to claim 8, The groove is disposed directly below the side surface of the waveguide substrate.

12. 2. The optical module according to claim 1, the block is a plurality of blocks, the optical waveguide formed in the waveguide substrate is a plurality of optical waveguides, An optical module, wherein the optical fiber to which each of the plurality of blocks is attached is one or more optical fibers.

13. 13. An optical module according to claim 12, The upper surface of the base substrate has a protrusion between adjacent blocks.

14. 14. An optical module according to claim 13, The adhesive does not reach onto the protruding portion.

15. 13. An optical module according to claim 12, The optical module includes a top surface of the base substrate having recesses between adjacent blocks.

16. 16. An optical module according to claim 15, the top surface of the base substrate has an edge adjacent the recess; The tip of the bottom surface of the adhesive is aligned with the edge of the optical module.

17. 13. The optical module according to claim 12, the base substrate has a body to which the waveguide substrate is fixed; the base substrate has a plurality of protrusions protruding from the main body, the base substrate has a notch between adjacent ones of the protruding portions, The plurality of blocks are respectively bonded to the plurality of protrusions.

18. 18. An optical module according to claim 17, the top surface of the base substrate has an edge adjacent the notch; The tip of the bottom surface of the adhesive is aligned with the edge of the optical module.

19. 18. An optical module according to claim 17, An optical module, wherein each of the plurality of blocks is located at the center of a corresponding one of the plurality of protrusions in the direction in which the plurality of protrusions are arranged.

20. 2. The optical module according to claim 1, The block includes a lower substrate bonded to the base substrate and an upper substrate on the lower substrate; the optical fiber is sandwiched between the lower substrate and the upper substrate; The lower substrate is thinner than the upper substrate.

21. 21. The optical module according to claim 20, The upper substrate has a V-groove, in which the optical fiber is disposed, on a surface facing the lower substrate.

22. 21. The optical module according to claim 20, The lower substrate is an optical module having a length from the front surface of the block shorter than that of the upper substrate.

23. 23. An optical module according to claim 22, comprising: Further comprising an adhesive material for bonding the upper substrate and the lower substrate; the upper substrate has a protruding lower surface protruding from the lower substrate, the lower substrate has a rear end surface opposite the front surface; A portion of the adhesive material is at a corner defined by the protruding lower surface and the rear end surface of the optical module.

24. 24. An optical module according to claim 23, The base substrate is long enough not to overlap the portion of the adhesive material.

25. 25. An optical module according to any one of claims 1 to 24, the block is made of a light-transmitting material; The optical module, wherein the adhesive is a light-curing adhesive.

26. 25. An optical module according to any one of claims 1 to 24, The adhesive has a thermal expansion coefficient greater than that of the base substrate.

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