Method for manufacturing optical module

Abstract

To provide a technique of attaching a block and an optical circuit substrate to each other while suppressing the axial displacement amount in an optical module.SOLUTION: The method for manufacturing an optical module includes: an application step of applying a photo-curing adhesive between a block in which a light guide is inserted and an optical circuit substrate in which an optical waveguide is formed, the adhesive being applied between a side surface in which an edge surface of the light guide is exposed of the side surface of the block and a side surface in which an edge surface of the optical waveguide is exposed of the side surface of the optical circuit substrate; and an attachment step of inputting light of a wavelength which cures the adhesive, into the light guide.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a method for manufacturing an optical module. [Background technology]

[0002] Patent Document 1 discloses a method for manufacturing an optical module in which a block into which an optical fiber is inserted and an optical circuit board on which an optical waveguide is formed are bonded together with a photocurable adhesive. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-194802 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology of Patent Document 1, the block and the optical circuit board are bonded by irradiating ultraviolet light from the periphery of the bonding surfaces of the block and the optical circuit board to harden the adhesive. With this technology, it is difficult to irradiate the bonding surfaces with ultraviolet light evenly. This causes a problem that the adhesive shrinks unevenly during hardening, resulting in a large axial misalignment between the central axis of the optical fiber inserted in the block and the central axis of the optical waveguide formed in the optical circuit board. This specification provides a technology that can bond the block and the optical circuit board in an optical module while suppressing the axial misalignment. [Means for solving the problem]

[0005] The manufacturing method of an optical module disclosed in this specification may include a coating step of applying a photocurable adhesive between a block into which a light guide is inserted and an optical circuit board on which an optical waveguide is formed, wherein the adhesive is applied between one of the side surfaces of the block at which an end face of the light guide is exposed and one of the side surfaces of the optical circuit board at which an end face of the optical waveguide is exposed, and a bonding step of inputting light of a wavelength at which the adhesive hardens into the light guide.

[0006] When the light is input to the light guide in the bonding process, the adhesive between the block and the optical circuit board hardens and spreads from the center of the light guide to the periphery. Therefore, the hardening shrinkage of the adhesive can occur evenly around the light guide. According to the manufacturing method, the hardening shrinkage of the adhesive is less biased, so that the amount of axial misalignment between the central axis of the light guide and the central axis of the optical waveguide is reduced. [Brief description of the drawings]

[0007] [Figure 1] FIG. 2 is a schematic plan view of a portion of the optical module. [Diagram 2] FIG. 2 is a schematic cross-sectional view of a portion of the optical module, the cross-sectional view corresponding to line II-II in FIG. [Diagram 3] FIG. 2 is a cross-sectional view of an optical fiber as viewed from the optical axis direction, illustrating the positional relationship between the optical fiber and an optical waveguide. [Figure 4] 11 is a diagram showing the results of measuring the incidence efficiency of signal light incident from an optical fiber to an optical waveguide after the adhesive is cured. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] 1 and 2, the optical module 1 includes an optical fiber 2, a block 3, an optical circuit board 4, and an optical waveguide 5. The block 3 and the optical circuit board 4 are bonded together via an adhesive 6. In the optical module 1, the optical fiber 2 and the optical waveguide 5 are optically joined together, and the optical module 1 is configured such that signal light that has passed through the optical fiber 2 is input to the optical waveguide 5.

[0009] The optical fiber 2 is not particularly limited, but may be, for example, a single mode optical fiber. The operating wavelength of the optical fiber 2 may be, for example, near infrared of 1510 nm to 1620 nm. One end of the optical fiber 2 is inserted into the block 3 and fixed to the block 3. The optical fiber 2 is an example of a light guide.

[0010] The block 3 is not particularly limited, and may be, for example, a glass block having a rectangular parallelepiped shape. A through hole through which the optical fiber 2 is inserted is formed in the block 3. One end face 2a of the optical fiber 2 is exposed flush with one side face 3S of the block 3 on which the opening edge of the through hole is formed.

[0011] The optical circuit board 4 is a board on which an optical waveguide 5 is formed on the surface. The optical circuit board 4 may be a single-layer board made of a single material, or may be a laminated board made of multiple materials. At least the portion of the optical circuit board 4 that contacts the optical waveguide 5 is made of a material that has a lower refractive index than the optical waveguide 5, and functions as a cladding layer. The optical circuit board 4 is equipped with optical circuit elements for processing signals input from the optical fiber 2.

[0012] The optical waveguide 5 is formed on the surface of the optical circuit board 4 and has a thin wire shape. In this example, the optical waveguide 5 is disposed so as to be embedded in a groove formed on the surface of the optical circuit board 4. Alternatively, the optical waveguide 5 may be a thin layer disposed on the flat surface of the optical circuit board 4. One end face 5a of the optical waveguide 5 is exposed toward one side face 4S of the side faces of the optical circuit board 4. Here, "one end face 5a of the optical waveguide 5 is exposed toward the side face 4S of the optical circuit board 4" is interpreted in a broad sense including a case where one end face 5a of the optical waveguide 5 is exposed to the outside at the side face 4S, as well as a case where one end face 5a of the optical waveguide 5 is disposed away from the side face 4S of the optical circuit board 4 and toward the side face 4S. In this example, one end face 5a of the optical waveguide 5 is disposed away from the side face 4S of the optical circuit board 4. Alternatively, one end face 5a of the optical waveguide 5 may extend to the side face 4S of the optical circuit board 4. In this example, one end face 5a of the optical waveguide 5 has a tapered shape in which the line width narrows toward the side face 4S of the optical circuit board 4. The optical waveguide 5 having such a shape increases the effective surface area of ​​the end face 5a in the traveling direction of the signal light, and therefore can efficiently receive the signal light emitted from the end face 2a of the optical fiber 2. Alternatively, one end face 5a of the optical waveguide 5 may be configured to have a constant line width.

[0013] FIG. 3 is a schematic cross-sectional view of the optical fiber 2 as viewed in the optical axis direction. Point 7 is the central axis of the optical fiber 2, and is also the center of the core in the optical fiber 2. When viewed in the optical axis direction of the optical fiber 2, the central axis 7 of the optical fiber 2 is arranged to coincide with the central axis of the optical waveguide 5. Here, dashed line 12 indicates the position of the optical fiber 2 when an axial misalignment occurs. When such an axial misalignment occurs, the incidence efficiency of the signal light incident from the optical fiber 2 to the optical waveguide 5 is significantly reduced. As will be described below, in the optical module 1 manufactured using the manufacturing method disclosed in this specification, the amount of axial misalignment between the optical fiber 2 and the optical waveguide 5 is suppressed.

[0014] A method for manufacturing the optical module 1 will be described below. First, the block 3 and the optical circuit board 4 into which the optical fiber 2 is inserted are held by using a jig such as a clamp and / or a suction chuck. While holding the block 3 and the optical circuit board 4, the block 3 and the optical circuit board 4 are moved relative to each other to bring the side surface 3S of the block 3 and the side surface 4S of the optical circuit board 4 closer to each other. Next, a photocurable adhesive 6 is applied between the side surface 3S of the block 3 and the side surface 4S of the optical circuit board 4. The adhesive 6 is an adhesive made of a material that cures in the wavelength range of visible light. Next, while holding the block 3 and the optical circuit board 4, the block 3 and the optical circuit board 4 are moved relative to each other to adjust the positions of the block 3 and the optical circuit board 4 (optical axis adjustment) so that the central axis of the optical fiber 2 and the central axis of the optical waveguide 5 coincide with each other.

[0015] Next, visible light is input to the optical fiber 2. Although not particularly limited, for example, visible light with a wavelength of 457 nm may be input at 10 mW for 5 minutes. This causes the adhesive 6 to harden due to the visible light emitted from the end face 2a of the optical fiber 2, and the block 3 and the optical circuit board 4 are bonded together. The adhesive 6 hardens and spreads from the center of the optical fiber 2 to the periphery. Therefore, the hardening shrinkage of the adhesive 6 can occur evenly around the optical fiber 2. Since there is little bias in the hardening shrinkage of the adhesive 6, the axial misalignment between the central axis of the optical fiber 2 and the central axis of the optical waveguide 5 is suppressed.

[0016] FIG. 4 shows the result of measuring the incidence efficiency of the signal light incident from the optical fiber 2 to the optical waveguide 5 after the block 3 and the optical circuit board 4 are bonded. The comparative example is an example in which the adhesive 6 is cured by irradiating the block 3 and the optical circuit board 4 with visible light from around them. The incidence efficiency of the comparative example was 83.7% on average, whereas the incidence efficiency of this example was 93.7% on average. When the amount of axial misalignment is estimated from the incidence efficiency, the amount of axial misalignment of the comparative example is about 1.8 μm, whereas the amount of axial misalignment of this example is about 1.0 μm. Thus, by irradiating the adhesive 6 with visible light through the optical fiber 2, the amount of axial misalignment is significantly reduced, and the incidence efficiency is significantly improved.

[0017] The core diameter of a single-mode optical fiber is approximately 8 μm, whereas the optical waveguide 5 is a submicron rectangular shape, and the incidence efficiency drops significantly when an axial misalignment occurs. For this reason, the manufacturing method disclosed in this specification is particularly useful when the optical fiber 2 is a single-mode optical fiber and the optical waveguide 5 is a submicron rectangular shape.

[0018] The optical fiber 2 has low transmittance for ultraviolet light. For this reason, when an ultraviolet light curing adhesive is used as the material for the adhesive 6, it may be difficult to sufficiently cure the adhesive 6 even when ultraviolet light is input to the optical fiber 2. In the manufacturing method disclosed in this specification, a visible light curing adhesive is used as the adhesive 6, and the adhesive 6 can be satisfactorily cured by inputting visible light to the optical fiber 2. The light input to the optical fiber 2 may be in a wavelength range that cures the adhesive 6, and may be ultraviolet light as necessary.

[0019] The features of the technology disclosed in this specification are summarized below. Note that the technical elements described below are independent technical elements that exhibit technical usefulness alone or in various combinations.

[0020] (Feature 1) A method for manufacturing an optical module, comprising the steps of: a coating step of coating a photocurable adhesive between a block into which a light guide is inserted and an optical circuit board on which an optical waveguide is formed, the adhesive being coated between one of the side surfaces of the block at which an end face of the light guide is exposed and one of the side surfaces of the optical circuit board at which an end face of the optical waveguide is exposed; and an adhesive step of inputting light having a wavelength at which the adhesive hardens into the light guide.

[0021] (Feature 2) 2. The method for manufacturing an optical module according to claim 1, wherein the coating step includes adjusting a relative positional relationship between the block and the optical circuit board so that a central axis of the light guide and a central axis of the optical waveguide coincide with each other.

[0022] (Feature 3) 3. The method for producing an optical module according to feature 1 or 2, wherein the light guide is a single-mode optical fiber.

[0023] (Feature 4) 4. The method for producing an optical module according to any one of Features 1 to 3, wherein the wavelength of the light input to the light guide in the bonding step is in the visible light range.

[0024] (Feature 5) 5. The method for manufacturing an optical module according to any one of features 1 to 4, wherein the end face of the optical waveguide is disposed away from the side face of the optical circuit board and has a shape that tapers toward the side face of the optical circuit board.

[0025] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. Furthermore, the technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives is itself technically useful. [Explanation of symbols]

[0026] 1: Optical module, 2: Optical fiber, 3: Block, 4: Optical circuit board, 5: Optical waveguide, 6: Adhesive

Claims

1. A method for manufacturing an optical module, comprising the steps of: a coating step of coating a photocurable adhesive between a block into which a light guide is inserted and an optical circuit board on which an optical waveguide is formed, the adhesive being coated between one of the side surfaces of the block at which an end face of the light guide is exposed and one of the side surfaces of the optical circuit board at which an end face of the optical waveguide is exposed; and an adhesive step of inputting light having a wavelength at which the adhesive hardens into the light guide.

2. 2. The method for manufacturing an optical module according to claim 1, wherein the coating step includes adjusting a relative positional relationship between the block and the optical circuit board so that a central axis of the light guide and a central axis of the optical waveguide coincide with each other.

3. The method for manufacturing an optical module according to claim 1 , wherein the light guide is a single mode optical fiber.

4. The method for manufacturing an optical module according to claim 1 , wherein the wavelength of the light input to the light guide in the bonding step is in the visible light range.

5. 5. The method for manufacturing an optical module according to claim 1, wherein the end face of the optical waveguide is disposed away from the side face of the optical circuit board and has a shape that tapers toward the side face of the optical circuit board.

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