Optical fiber module and manufacturing method thereof

Abstract

This optical fiber module (10) is formed by optically connecting a planar light wave circuit (101) and an optical fiber (100), the optical fiber module being characterized in that: the planar light wave circuit (101) has formed on a substrate (102) an optical waveguide (103) which comprises a core (103a) and cladding (103b); a conductive thin film (105) is disposed on an inclined surface which is formed between an end surface of the substrate (102) connected to the optical fiber (100) and a rear surface of the substrate (102); and the optical fiber (100) is fusion-spliced to the planar light wave circuit (101).

Description

[Technical Field]

[0001] The present invention relates to an optical fiber module and a manufacturing method thereof, and more particularly to an optical fiber module formed by fusion-splicing a silica-based planar lightwave circuit and an optical fiber. [Background technology]

[0002] Silica-based planar lightwave circuit (PLC) and optical fiber Connection methods include fixing with UV-curing adhesive and fusing with a laser. Fusion splicing is used especially for quartz-based PLCs for visible wavelengths or high power output, because UV-curing adhesives are altered by visible wavelengths or high power light, increasing connection loss.

[0003] In this type of fusion splicing, the silica-based PLC fiber connection may not melt, or the optical fiber may melt excessively, resulting in deformation, due to the relatively large difference in heat capacity between the silica-based PLC and the optical fiber, and the use of a silicon substrate in the silica-based PLC, which acts as a heat sink.

[0004] For this reason, for example, Patent Document 1 describes a method of suppressing heat dissipation by removing a portion of the silicon substrate of the module. This allows the thermal capacity of the quartz-based PLC and the optical fiber to be matched. It is also known that heating for fusion is performed by external heating (Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2-251916 [Patent Document 2] Japanese Patent Application Publication No. 8-75949 [Patent Document 3] International Publication No. 2014 / 196444 [Patent Document 4] Japanese Patent Application Laid-Open No. 2006-269984 Summary of the Invention [Problem to be solved by the invention]

[0006] However, removing part of the substrate requires photolithography and etching techniques, which makes the process relatively complicated and time-consuming and costly to manufacture.Another problem is that external heating of the quartz-based PLC consumes a lot of power.

[0007] The present invention aims to provide an optical fiber module and a manufacturing method thereof that can more easily remove the substrate in a shorter time and that can reduce the power consumption for heating for melting in the manufacturing of an optical fiber module in which a silica-based PLC and an optical fiber are fused together. [Means for solving the problem]

[0008] One aspect of the optical module of the present invention is an optical fiber module in which a planar lightwave circuit and an optical fiber are optically coupled, characterized in that the planar lightwave circuit has an optical waveguide consisting of a core and a clad formed on a substrate, a conductive thin film is provided on an oblique surface formed between an end face of the substrate that connects to the optical fiber and a back surface of the substrate, and the optical fiber is fusion-spliced ​​to the planar lightwave circuit. [Effects of the Invention]

[0009] According to the present invention, in the manufacture of an optical fiber module in which a silica-based PLC and an optical fiber are fused together, the removal of the substrate can be performed more easily and in a shorter time, and the power consumption for heating for melting can be reduced. [Brief explanation of the drawings]

[0010] [Figure 1]Fig. 1(a) is a diagram illustrating an optical module according to the present invention, and Fig. 1(b) is a diagram illustrating an example of an optical module according to the present invention. [Figure 2] FIG. 2 is a diagram illustrating an optical module according to a first embodiment of the present invention. [Figure 3] Fig. 3(a) is a flowchart showing the steps of manufacturing the optical module according to Example 1. Fig. 3(b) is a diagram showing the steps of manufacturing the optical module 20 according to Example 1. [Figure 4] FIG. 4 is a diagram illustrating an optical module according to a first embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, parts having the same functions are designated by the same reference numerals, and repeated description will be omitted.

[0012] (First embodiment) FIG. 1(a) is a perspective view schematically illustrating an optical module 10 according to a first embodiment of the present invention. The optical module 10 includes at least one optical fiber 100 and a planar lightwave circuit 101, and the optical fiber 100 and the planar lightwave circuit 101 are connected by a fusion splice 106. The planar lightwave circuit 101 includes a substrate 102, an optical waveguide 103 on the substrate 102, which is composed of a core 103a and a clad 103b, a light-shielding groove 104a formed by removing a part of the clad 103b, a light-shielding material 104b filled in the light-shielding groove 104a, and a conductive thin film 105 provided on a slope formed between the connection end face of the optical fiber 100 and the back surface of the substrate. Here, the optical fiber 100 has a core portion 100 a and cladding 100 The light-shielding groove 104a and the light-shielding material 104b filled therein are provided for terminating excess optical power.

[0013] The slope of the substrate 102 is formed by mechanical polishing, and the slope exists from the connection end face that constitutes the fused portion 106 of the planar lightwave circuit 101. Then, by providing the conductive thin film 105 on this slope, the conductive thin film 105 can be brought close to the fused portion 106.

[0014] For example, as shown in Figure 1(b), for a planar lightwave circuit with a substrate thickness of 1 mm and a substrate length (longitudinal direction of the fiber) of 4 mm, if only an area with a substrate thickness of 0.9 mm and a substrate length of 2 mm (half the total length of the substrate) is polished to ensure the mechanical strength of the planar lightwave circuit, especially the mechanical strength of the area where the light-shielding groove is formed, the polishing angle should be set to approximately 66°.

[0015] The core 103a and clad 103b are made of a quartz-based material, the substrate 102 is made of a quartz-based material or silicon, and the light-shielding material 104b is made of a resin with light-shielding properties. The conductive thin film 105 is a thin film containing conductive particles such as metal and carbon, or semiconductor particles, or a thin film of an ink or paste-like dispersion in which a conductor or semiconductor is dispersed, and can be heated instantaneously by microwave irradiation (Patent Document 3).

[0016] As described above, the silicon substrate 102 can be removed by machining (polishing), i.e., the portion of the substrate that forms the slope can be removed. This makes it possible to more easily and quickly remove the substrate in order to reduce the difference in heat capacity between the planar lightwave circuit and the optical fiber when fusion-splicing the planar lightwave circuit and the optical fiber.

[0017] Furthermore, since the conductive thin film 105 is formed on the slope of the substrate 102, it is possible to use microwave heating to heat the substrate for fusion bonding. As a result, unlike conventional external heating using a heater or the like, the conductive thin film 105 itself generates heat, making it possible to perform localized and rapid heating with low power consumption, thereby reducing power consumption for fusion bonding. Furthermore, by heating the connection end faces of the planar lightwave circuit 101 and the optical fiber 100 with microwave irradiation and simultaneously heating and fusing the optical fiber 100 with laser light, only the fused portion 106 is selectively heated, and the entire planar lightwave circuit 101 does not reach a temperature of several hundred degrees Celsius or higher, suppressing heat dissipation and providing light shielding. This can prevent the material 104b from volatilizing and deteriorating.

[0018] In this embodiment, the conductive thin film 105 is formed on the entire slope of the substrate 102, but the conductive thin film may be formed on a part of the slope of the substrate 102 near the fused portion.

[0019] According to the present invention, photolithography and etching techniques are not required to remove the substrate to reduce heat capacity, and it can be produced using simple machining techniques.Furthermore, a conductive thin film is formed on the substrate portion of the planar lightwave circuit, and by irradiating it with microwaves, it is possible to selectively heat only the fused portion.

[0020] In this embodiment, the grooves are formed by mechanically polishing the substrate, so there is no need to form grooves in the substrate by patterning, which makes it possible to simplify the process, shorten the time, and reduce costs.

[0021] (Second embodiment) Fig. 2 is a perspective view showing an optical module 20 according to a second embodiment of the present invention. In the optical module 10 shown in Fig. 1(a), by forming a heat insulating groove 202a by removing a part of the substrate 102 on the connection side of the optical fiber 100 relative to the light-shielding groove 104a, heat dissipation is suppressed, and the optical module 20 in which the optical fiber 100 is fused can be produced using a lower-power laser beam.

[0022] Figure 2 shows the board 202The planar lightwave circuit is made of silicon, and the core 103a and clad 103b are made of silica-based materials. 201 , an optical fiber 100 is shown, and a planar lightwave circuit 201 The substrate 202 is formed with a light-shielding groove 104a where the cladding 103b has been removed, and the light-shielding groove 104a is filled with a light-shielding material 104b. The portion of the substrate on the connection end face side of the optical fiber 100 is polished obliquely, and a conductive thin film 105 is formed on the polished oblique surface (slope). 201 Back side (board 202 On the back surface of the substrate, a heat insulating groove 202a is formed by removing the substrate on the optical fiber 100 connection side of the light blocking groove 104a. In this embodiment, the light blocking material 104b is made of resin mixed with carbon particles, and the conductive thin film 105 is made of a thin film containing carbon particles. Furthermore, in order to enable fusion bonding with a low-power laser, 202 A heat insulating groove 202a is formed in the

[0023] According to the present invention, in the manufacture of an optical fiber module in which a silica-based PLC and an optical fiber are fused together, the substrate can be removed more easily and in a shorter time, and the power consumption required for heating for melting can be reduced.

[0024] Fig. 3(a) is a flowchart showing the steps of the process for fabricating the optical module 20 according to the first embodiment. Fig. 3(b) is a diagram showing the steps of the process for fabricating the optical module 20 according to the first embodiment.

[0025] The wafer process S101 will now be described. The planar lightwave circuit 101 made of a quartz-based material used in this example was fabricated by using photolithography and etching techniques to sequentially form a lower clad layer and a core 103a layer on a silicon wafer 302, then etching the core 103a layer while leaving the portion that will become the optical waveguide 103, and then depositing an upper clad layer. The light-shielding groove 104a was also formed by photolithography and etching (S1: Next, the light blocking material 104b was filled using a microdispenser (S2: filling process of the light blocking material). Since the heat insulating groove 202a is a simple pattern, in this embodiment, Etching was performed simply using masking tape without using photolithography (S3: (Insulation groove formation process).

[0026] Next, the strip-forming process S102 will be described. The silicon wafer 302 was diced into strips (S4: strip-forming process). The end faces for fiber connection were polished. In this specification, the angle between the end face (substrate end face) on the fiber connection side and the angled polishing is referred to as the polishing angle θ. The polishing angle can be determined based on the amount of heat to be suppressed and the mechanical strength required for the optical module and the planar lightwave circuit. In this embodiment, the polishing angle θ was set to 45°. The larger the polishing angle θ, the greater the effect of suppressing heat dissipation. The polishing angle θ may be in the range of 45° or more and less than 90° (S5: angled polishing process). When the planar lightwave circuit and the fiber are fused, heat at the fused fiber transfers toward the substrate 102 (e.g., a silicon substrate), which has high thermal conductivity. To suppress this transfer, the portion of the substrate 102 on the fused fiber portion 106 side of the planar lightwave circuit 101 is removed. An angle of 45° or more is assumed, assuming that approximately half of the substrate directly below the fused fiber portion is removed.

[0027] The conductive thin film 105 was formed on the polished surface by depositing carbon using a carbon deposition device (S6: conductive thin film forming step).

[0028] Next, the chip process S103 will be described. The rectangular wafer was diced into chips to form planar lightwave circuits 101 to be used in optical fiber modules (S7: chip formation step).

[0029] Thereafter, the planar lightwave circuit 101 and the optical fiber 100 were fixed on a stage and aligned so as to enable optical connection (S8: fiber axial alignment step). The alignment method for optically connecting the planar lightwave circuit 101 and the optical fiber 100 was the same as the conventional method of fixing with a UV curable adhesive and the conventional fusion method.

[0030] Thereafter, a microwave heating device was used to irradiate the planar lightwave circuit 101 with microwaves having a wavelength of 2.45 GHz, and only the conductive thin film 105 patterned on the polished surface was instantaneously and selectively heated (S9: microwave heating step). The laser was focused on the fusion splice 106 with 00, and fusion splicing was performed (S10: fusion splicing step).

[0031] In this embodiment, the substrate of the planar lightwave circuit 101 is made of silicon, but silicon is not transparent to microwaves, so microwave energy is absorbed. The absorbed energy is converted into heat, briefly raising the temperature of the planar lightwave circuit 101 around the substrate. This temperature rise causes volume expansion of the planar lightwave circuit 101, including the substrate, which may result in misalignment of the optical axis of the optical fiber 100. If the mode field at the connection point between the planar lightwave circuit 101 and the optical fiber 100 is large, a slight misalignment (<1 μm) is not a problem, but if the mode field is small, it may become a problem. Therefore, when a silicon substrate is used for the planar lightwave circuit 101, a material containing a mixture of metal-based particles and carbon-based particles (Patent Documents 3 and 4) may be used as the conductive thin film 105 to further enhance the selective heating properties of microwave heating. As a result, only the conductive thin film 105 is selectively heated by microwave irradiation, and temperature rise can be suppressed even in a planar lightwave circuit 101 using a silicon substrate, and misalignment between the planar lightwave circuit 101 and the optical fiber 100 can be suppressed.

[0032] Furthermore, in this embodiment, the planar lightwave circuit 101, in which the layer of the optical waveguide 103 at the connecting end face of the optical fiber 100 is vertical and the substrate portion is polished at an angle, is fusion-spliced ​​to the optical fiber 100 having a vertical end face. However, if it is desired to further reduce reflection, it is possible to further reduce the return loss by polishing the layer of the optical waveguide 103 of the planar lightwave circuit 101 and the optical fiber 100 at an angle of several degrees (about 8°).

[0033] The light-blocking material can also be filled after the optical fiber is fused. However, since it cannot be filled during the wafer process, throughput does not increase. In addition, filling the light-blocking material into the light-blocking groove with the fiber attached is a complicated process, and requires space and time. These problems can be solved by using the method of this embodiment.

[0034] (Third embodiment) In addition, in order to further reduce the heat capacity in the planar lightwave circuit 401 of this embodiment shown in Fig. 4, after chipping, the portions other than the connection portion (fused portion 106) of the optical fiber 100, the optical waveguide 103, and the light-shielding groove 104a can be removed by dicing or the like, thereby obtaining a planar lightwave circuit 401 in Fig. 4 in which the lateral length of the end face of the optical module 40 on the connection side of the optical fiber 100 is shorter than the lateral length of the end face of the optical module 40 opposite to that end face, and which has a conductive thin film 405 adjacent to the underside of the end face of the optical module 40 on the connection side of the optical fiber 100. The optical module 40 can also be fusion-spliced ​​with a lower-power laser.

[0035] According to the present invention, in the manufacture of an optical fiber module in which a silica-based PLC and an optical fiber are fused together, the removal of the substrate can be performed more easily and in a shorter time, and the power consumption for heating for melting can be reduced.

[0036] In the above examples, laser fusion was used for fusion, but the present invention is not limited to this and discharge fusion can also be used. As an alternative to microwave heating, millimeter waves can be used. Furthermore, although an optical fiber was connected to a silica-based optical waveguide formed on a silicon substrate as the optical waveguide, this method can also be applied to a silica-based optical waveguide formed on a quartz substrate. Furthermore, this method can be applied not only to single-core optical fibers but also to multi-core optical fiber fusion splicing.

Claims

1. An optical fiber module in which a planar lightwave circuit and an optical fiber are optically coupled, The planar lightwave circuit has an optical waveguide formed on a substrate, the optical waveguide comprising a core and a clad, a conductive thin film is provided on an inclined surface formed between the end surface of the substrate that is connected to the optical fiber and the back surface of the substrate; an optical module, wherein the optical fiber is fusion-spliced ​​to the planar lightwave circuit;

2. 2. The optical module according to claim 1, wherein the substrate in the planar lightwave circuit has a heat insulating groove formed therein.

3. 3. The optical module according to claim 1, wherein the substrate is a silicon substrate or a quartz substrate, and the conductive thin film is a thin film containing metal and carbon conductor particles, or semiconductor particles, or a thin film of an ink or paste dispersion in which a conductor or semiconductor is dispersed.

4. 3. The optical module according to claim 1, wherein the lateral length of the end face of the optical module on the connection side of the optical fiber is shorter than the lateral length of the end face of the optical module opposite the end face.

5. A method for manufacturing an optical module in which a planar lightwave circuit and at least one optical fiber are optically coupled, the method comprising the steps of: obliquely polishing a portion of a substrate on the optical fiber connection end face side of the planar lightwave circuit; patterning a conductive thin film on the obliquely polished surface; heating the conductive thin film by laser fusion or discharge fusion; and fusion-splicing the optical fiber to the planar lightwave circuit.

6. 6. The method for manufacturing an optical module according to claim 5, wherein the laser fusion method is performed by irradiating microwaves or millimeter waves.

7. 7. The method for fabricating an optical module according to claim 5, further comprising the step of removing a portion of the substrate to form a heat insulating groove in the planar lightwave circuit.

8. 7. The method for producing an optical module according to claim 5, wherein an angle formed between the end face of the substrate and the oblique polishing is equal to or greater than 45 degrees and less than 90 degrees.

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