JP2008015040A - Optical waveguide and optical module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical waveguide and an optical module that have a small size and a high optical coupling efficiency. <P>SOLUTION: The optical module has, in addition to a light emitting element 14 and a light receiving element 15, a planar optical waveguide 10 to which an optical fiber ribbon 7 composed of a circular plurality of optical fibers is optically coupled. This optical waveguide 10 is incorporated with a plurality of light emitting waveguide cores 11 having a vertically long cross sectional shape relative to a mounting face of the optical element which is composed of the light emitting element 14 and the light receiving element 15, and similarly incorporated with a plurality of light receiving waveguide cores 12 having a horizontally long cross sectional shape. In the end part of the optical waveguide 10, there is provided a mirror face 10a, wherein reflection of light is performed between the light emitting and light receiving waveguide cores 11, 12, and between the light emitting and light receiving elements 14, 15. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical waveguide and an optical module for optically coupling an optical fiber or the like and an optical element such as a light emitting element or a light receiving element via a waveguide core.

  With the spread and development of information communication technology including the Internet, construction of an optical fiber communication system capable of high-capacity high-speed transmission is progressing. With the increase in the number of optical fiber cables and the increase in the density, it is indispensable to integrate the connections using a multi-fiber connector.

  As such a multi-fiber connector, for example, an optical module in which a plurality of optical waveguide cores are arranged one-dimensionally or two-dimensionally has been proposed (see, for example, Patent Document 1).

The optical module includes a circuit board, and a plurality of photoelectric conversion elements each including a light-emitting element or a light-receiving element and a sheet-like optical waveguide in which a plurality of optical waveguide cores are arranged one-dimensionally or two-dimensionally on the circuit board And are optically coupled to a plurality of photoelectric conversion elements by a mirror surface formed on one end face of the optical waveguide. Since the optical path is folded back by the mirror surface, the thickness can be reduced.
JP 2004-191564 A

  However, in the conventional optical module, when a plurality of waveguide cores and a plurality of optical fibers are coupled due to misalignment of the waveguide with respect to the exterior member, misalignment of the waveguide core due to thermal deformation or manufacturing variations, etc. In addition, the optical coupling efficiency may be reduced. In addition, when a light emitting element is used as a photoelectric conversion element, if a positional shift occurs between the mirror surface and the light emitting element due to thermal expansion of the optical waveguide, light that does not propagate through the optical waveguide core is generated, and the optical coupling efficiency decreases. There is a risk. Further, when a light receiving element is used as the photoelectric conversion element, there is a possibility that the optical coupling efficiency may be lowered due to an irregular shape between the image reflected on the mirror surface and projected onto the light receiving element.

  Accordingly, an object of the present invention is to provide an optical waveguide and an optical module that are small in size and have high optical coupling efficiency.

  In order to achieve the above object, one embodiment of the present invention provides the following optical waveguide and optical module.

[1] In an optical waveguide in which an optical fiber is optically coupled to one end and a light emitting element is optically coupled to the other end, a light emitting waveguide core having cross-sectional shapes having different outer diameters in directions orthogonal to each other, and the light emitting waveguide core An optical waveguide comprising: a mirror surface provided at the other end of the light-emitting waveguide and inclined in a direction in which an outer diameter of a cross-sectional shape of the light-emitting waveguide core is increased and optically coupled to the light-emitting element.

  According to the optical waveguide configured as described above, even if the mirror surface is displaced in the longitudinal direction of the light emitting waveguide core due to thermal expansion, and a positional displacement occurs between the mirror surface and the light emitting device, the light is emitted from the light emitting device and is reflected on the mirror surface. Since most of the reflected light propagates through the optical waveguide core, it is possible to suppress a decrease in optical coupling efficiency (light loss) due to the positional shift. The mirror surface can be formed by dicing the optical waveguide, but a metal film may be formed on the surface.

[2] In an optical waveguide in which an optical fiber is optically coupled to one end and a light receiving element is optically coupled to the other end,
A light receiving waveguide core having a cross-sectional shape with different outer diameters in directions orthogonal to each other, and provided at the other end of the light receiving waveguide core, and inclined so that the outer diameter of the cross-sectional shape of the light receiving waveguide core decreases. And a mirror surface optically coupled to the light receiving element.

  According to the optical waveguide having the above configuration, the light propagating through the light receiving waveguide core and reflected by the mirror surface is distorted into a trapezoid and projected onto the light receiving element, and the length of the projected image in the longitudinal direction of the light receiving waveguide core. Thus, the amount of protrusion from the light receiving element is reduced, and the decrease in optical coupling efficiency (light loss) due to the irregular shape between the projected image and the light receiving portion can be suppressed.

[3] A plurality of waveguide cores arranged in a predetermined direction, a plurality of optical fibers are optically coupled to one end of the plurality of waveguide cores, and a light emitting element and the other end of the plurality of waveguide cores In a planar optical waveguide to which a light receiving element is optically coupled, the waveguide core has a cross-sectional shape with different outer diameters in directions orthogonal to each other, and a light emitting guide having a smaller outer diameter arranged in the predetermined direction. The waveguide core and the waveguide core have cross-sectional shapes with different outer diameters in directions orthogonal to each other, the light receiving waveguide core having a larger outer diameter arranged in the predetermined direction, and the predetermined direction. An optical waveguide comprising a mirror surface that is inclined in a vertical direction to optically couple the light emitting waveguide core and the light emitting element and optically couple the light receiving waveguide core and the light receiving element. .

  According to the optical waveguide having the above configuration, similarly to the above [1], it is possible to suppress a decrease in optical coupling efficiency due to a positional shift between the mirror surface and the light emitting element. Further, similarly to the above [2], it is possible to suppress a decrease in optical coupling efficiency due to a different shape between the projected image and the light receiving unit. Therefore, a bidirectional optical waveguide with high optical coupling efficiency can be configured.

[4] The optical waveguide according to [1], wherein the light emitting waveguide core is a plurality of light emitting waveguide cores arranged in a direction in which an outer diameter of a cross-sectional shape decreases. When a plurality of light emitting waveguides are used, misalignment between the mirror surface and the light emitting element is likely to occur. However, the above configuration can provide a great effect of suppressing a decrease in optical coupling efficiency.

[5] The optical waveguide according to [2], wherein the light receiving waveguide core is a plurality of light receiving waveguide cores arranged in a direction in which an outer diameter of a cross-sectional shape increases. When a plurality of light receiving waveguides are used, the total amount of protrusion of the projected image from the plurality of light receiving elements is increased, but the above-described configuration provides a great suppression effect on the decrease in optical coupling efficiency.

[6] The light emitting waveguide core is a plurality of light emitting waveguide cores arranged in the predetermined direction,
The optical waveguide according to [3], wherein the light receiving waveguide core is a plurality of light receiving waveguide cores arranged in the predetermined direction. With the above configuration, it is possible to obtain a large suppression effect on optical loss and optical coupling efficiency reduction.

[7] The light emitting element includes a plurality of light emitting units arranged corresponding to the plurality of light emitting waveguide cores, and the light receiving element includes a plurality of light emitting elements arranged corresponding to the plurality of light receiving waveguide cores. The optical waveguide according to [3], further including a light receiving portion.

[8] The optical waveguide according to [1], [2], or [3], wherein the light emitting waveguide core or the light receiving waveguide core has a rectangular cross-sectional shape. The cross-sectional shape of the core is not limited to a rectangle, and may be a trapezoid or an oval as long as the outer diameters in directions orthogonal to each other are different.

[9] The light guide according to [8], wherein the light emitting waveguide core or the light receiving waveguide core has a difference in length between a long side and a short side of the rectangular cross-sectional shape of 5 μm or more. Waveguide. According to this configuration, when the difference between the lengths of the long side and the short side is 5 μm or more, the effect of suppressing the reduction of the optical coupling efficiency and the optical loss with respect to the optical element is increased.

[10] The optical waveguide according to [1], [2], or [3], wherein the light emitting waveguide core or the light receiving waveguide core has an incident end and an output end having the same cross-sectional shape. According to this configuration, since no mode conversion loss occurs, high light efficiency can be obtained.

[11] The optical waveguide according to [3], wherein the light emitting waveguide core and the light receiving waveguide core have the same outer diameter in a direction perpendicular to the predetermined direction. According to this structure, it can manufacture easily from the same photolithographic mask.

[12] The optical waveguide as described in [1], [2] or [3] above, which is formed from a polymer material. According to this configuration, deformation due to thermal expansion can be suppressed.

[13] The light receiving waveguide core has a rectangular cross-sectional shape, a long side length is larger than a diameter of the optical fiber core, and a short side length is smaller than the diameter of the optical fiber core. The optical waveguide according to [2] or [3], wherein

[14] In an optical module having an optical waveguide having an optical fiber optically coupled at one end and a light emitting element optically coupled to the other end of the optical waveguide, the optical waveguides have different outer diameters in directions orthogonal to each other. A light emitting waveguide core having a cross-sectional shape, and a mirror surface provided at the other end of the optical waveguide and optically coupled to the light emitting element inclined in a direction in which the outer diameter of the cross-sectional shape of the light emitting waveguide core increases. And an optical module.

  According to the optical module having the above configuration, even if the mirror surface is displaced in the longitudinal direction of the light emitting waveguide core due to thermal expansion, and the positional deviation occurs between the mirror surface and the light emitting element, the light is emitted from the light emitting element, Since most of the reflected light propagates through the optical waveguide core, it is possible to suppress a decrease in optical coupling efficiency (light loss) due to the positional shift.

[15] In an optical module having an optical waveguide having an optical fiber optically coupled to one end and a light receiving element optically coupled to the other end of the optical waveguide, the optical waveguides have different outer diameters in directions orthogonal to each other. A light receiving waveguide core having a cross-sectional shape, and a mirror surface provided at the other end of the optical waveguide and optically coupled to the light receiving element inclined in a direction in which the outer diameter of the cross-sectional shape of the light receiving waveguide core decreases. And an optical module.

  According to the optical module having the above configuration, the light propagating through the light receiving waveguide core and reflected by the mirror surface is distorted into a trapezoid and projected onto the light receiving element, and the length of the projected image in the longitudinal direction of the light receiving waveguide core. Thus, the amount of protrusion from the light receiving element is reduced, and the decrease in optical coupling efficiency (light loss) due to the irregular shape between the projected image and the light receiving portion can be suppressed.

[16] A plate-like optical waveguide having a plurality of waveguide cores optically coupled to one end and arranged in a predetermined direction, a light emitting element optically coupled to the other end of the optical waveguide, and a light receiving device In the optical module having an element, the optical waveguide has a cross-sectional shape having different outer diameters in directions orthogonal to each other as the waveguide core, and a light emitting waveguide having a smaller outer diameter arranged in the predetermined direction The core and the waveguide core have cross-sectional shapes having different outer diameters in directions perpendicular to each other, the light receiving waveguide core having a larger outer diameter arranged in the predetermined direction, and perpendicular to the predetermined direction An optical module comprising a mirror surface that is inclined in any direction to optically couple the light emitting waveguide core and the light emitting element and optically couple the light receiving waveguide core and the light receiving element.

  According to the optical module having the above configuration, similarly to [14] above, it is possible to suppress a decrease in optical coupling efficiency due to a positional shift between the mirror surface and the light emitting element. Further, similarly to the above [15], it is possible to suppress a decrease in optical coupling efficiency due to the different shapes of the projected image and the light receiving unit. Therefore, a bidirectional optical module with high optical coupling efficiency can be configured.

[17] The optical waveguide is held by an exterior member (hereinafter referred to as an MT ferrule) obtained by extending an MT (Mechanically Transferable) ferrule used as a ferrule for a multi-core optical fiber to an optical waveguide, and the MT ferrule is The optical module according to [14], [15], or [16], further comprising a guide pin for performing alignment with the optical fiber. According to this configuration, the MT ferrule and the optical fiber can be accurately aligned.

  According to the present invention, an optical waveguide and an optical module that are small and have high optical coupling efficiency can be obtained.

[First Embodiment]
(Configuration of optical module)
FIG. 1 shows a configuration of an optical module according to the first embodiment of the present invention. The optical module 100 includes an optical subassembly 1 including an optical waveguide and an optical element, an optical connector 2 optically coupled to the optical subassembly 1 and connected to an optical fiber from the outside, and an electronic component (not shown). A circuit board 3 mounted on the lower side of the optical subassembly 1 and a flat cable or the like disposed on the lower side of the circuit board 3 and electrically connected to other boards are connected. An electrical connector 4, a housing 5 that houses the above-described members, and a lid 6 that covers the housing 5.

(Configuration of optical subassembly)
FIG. 2 shows the configuration of the optical subassembly. In the figure, (a) is a front view, (b) is a cross-sectional view taken along line AA of (a), and (c) is a cross-sectional view taken along line BB of (a).

  The optical subassembly 1 has a plate-shaped optical waveguide 10 having a plurality of light emitting waveguide cores 11 and light receiving waveguide cores 12, and a built-in optical waveguide 10 and a pair of guide holes 13a provided on both sides thereof. The MT type ferrule 13, a laser diode (LD), or the like, and a light emitting element 14 disposed at the end of the optical waveguide 10, a photodiode (PD) or the like, and a light receiving element 15 disposed adjacent to the light emitting element 14. A holder 16 on which the light-emitting element 14 and the light-receiving element 15 that are optical elements are mounted, a substrate 17 disposed adjacent to the holder 16, and a light-emitting element 14 mounted on the substrate 17 to modulate and emit light. A drive circuit 18, an amplification circuit 19 that amplifies the electrical signal photoelectrically converted by the light receiving element 15, the above-described members, optical elements, and circuits are housed and a lid 20 a is attached. It is constituted by a body 20.

(Configuration of optical waveguide and MT type ferrule)
3A and 3B show details of the optical waveguide and the MT type ferrule, where FIG. 3A is a perspective view and FIG. 3B is a front view of the optical waveguide. In the optical waveguide 10, the light emitting waveguide core 11 and the light receiving waveguide core 12 are provided on the same plane at the center of the clad 10 b at a predetermined interval. One end of the optical waveguide 10 is optically coupled to the end of a ribbon optical fiber 7 inserted into the optical connector 2 of FIG.

  The ribbon optical fiber 7 is configured, for example, by forming a plurality of multi-mode optical fibers 7a having a circular core cross-sectional shape into a ribbon shape.

  The optical waveguide 10 has a mirror surface 10a at the other end. The mirror surface 10 a has a mirror surface formed by aluminum vapor deposition or the like, guides light from the light emitting portion 14 a of the light emitting element 14 to the light emitting waveguide core 11, and transmits light from the light receiving waveguide core 12 to the light receiving portion 15 a of the light receiving element 15. An angle that can be led to, for example, 45 ° is set. The angle of the mirror surface 10a is not limited to 45 °.

  Further, as shown in FIG. 3B, the end face 11a of the light-emitting waveguide core 11 is rectangular with respect to the horizontal plane of the optical waveguide 10, in other words, a vertically long rectangle (h1> w1) with respect to the mounting surface of the optical element. The end face 12a of the light receiving waveguide core 12 has a horizontally long rectangular shape (h2 <w2). The cross-sectional shapes of the light emitting waveguide core 11 and the light receiving waveguide core 12 are the same over the entire length. The heights of the light emitting waveguide core 11 and the light receiving waveguide core 12 are equal (h1 = h2). As described above, the cross-sectional shape of the light emitting waveguide core 11 and the light receiving waveguide core 12 is a combination of a vertically long and a horizontally long rectangle, whereby the following effects are obtained in the embodiment of the present invention. .

  The MT type ferrule 13 is made into a plate shape by resin molding or the like, and a recess 13b for arranging the light emitting element 14 and the light receiving element 15 is provided at the rear part. In the MT ferrule 13, a pair of guide pins (not shown) are inserted into a pair of guide holes 13a, and a connector (not shown) that holds the ribbon optical fiber 7 is fixed by the guide pins and a clamp member (not shown).

  The light emitting element 14 includes a plurality of light emitting portions 14 a arranged in a line below the mirror surface 10 a of the optical waveguide 10. The light receiving element 15 includes a plurality of light receiving portions 15a arranged in a row below the mirror surface 10a. Each of the plurality of light emitting units 14a is driven independently, and each of the plurality of light receiving units 15a receives light independently.

(Optical waveguide manufacturing method)
Next, a method for manufacturing an optical waveguide will be described. FIGS. 4A to 4G are manufacturing process diagrams of an optical waveguide.

  First, as shown in FIG. 4A, the master 101 on which the convex portions 102 corresponding to the light emitting waveguide core 11 and the light receiving waveguide core 12 are formed is manufactured by using, for example, a photolithography method.

  Next, as shown in FIG. 4B, the surface of the master 101 on which the convex portion 102 is formed has a light transmittance in the ultraviolet region and the visible region, for example, with a viscosity of about 500 to 7000 mPa · s. A curable resin, for example, a curable organopolysiloxane layer containing a methylsiloxane group, an ethylsiloxane group, or a phenylsiloxane group in the molecule is provided by coating or the like, and then cured to form the cured layer 103.

  Next, as shown in FIG. 4C, the hardened layer 103 is peeled from the master 101, and a mold 105 having a concave portion 104 corresponding to the convex portion 102 is produced.

  Next, as shown in FIG. 4 (d), a resin excellent in adhesion to the mold 105, such as an alicyclic acrylic resin film, an alicyclic olefin resin film, a cellulose triacetate film, A clad film base 106 made of a fluororesin film or the like is adhered.

  Next, as shown in FIG. 4 (e), in the concave portion 104 of the mold 105, for example, an ultraviolet curable or thermosetting monomer, an oligomer or a mixture of a monomer and an oligomer, an epoxy type, a polyimide type, an acrylic type A curable resin 107 made of an ultraviolet curable resin or the like is filled.

  Next, as shown in FIG. 4F, the curable resin 107 in the recess 104 is cured to form the light emitting waveguide core 11 and the light receiving waveguide core 12, and then the mold 105 is peeled off. As a result, the light emitting waveguide core 11 and the light receiving waveguide core 12 are left on the clad film substrate 106.

  Next, as shown in FIG. 4G, a clad layer 108 is provided so as to cover the clad film base 106, the light emitting waveguide core 11, and the light receiving waveguide core 12. Examples of the clad layer 108 include a film, a layer cured by applying a curable resin for clad, and a polymer film formed by applying a solvent solution of a polymer material and drying. Finally, one surface of the optical waveguide 10 where the light emitting waveguide core 11 and the light receiving waveguide core 12 are exposed is cut vertically by a dicer, and the other opposite surface is cut at a predetermined angle by a dicer to obtain a mirror surface 10a. Form. Further, by cutting with a dicer parallel to the optical waveguide core, the optical waveguide 10 with the clad film substrate 106 and the clad layer 108 as the clad 10b is completed.

(Assembling the optical module)
Next, assembly of the optical module 100 will be described. First, as shown in FIG. 2, an MT ferrule 13 with a built-in optical waveguide 10 is prepared. Next, the substrate 17 on which the drive circuit 18 and the amplifier circuit 19 are mounted is installed in the housing 20. Further, the holder 16 is installed in the housing 20, and the light emitting element 14 and the light receiving element 15 are mounted on the holder 16. The light emitting element 14 and the light receiving element 15 may be mounted on the holder 16 in advance. Next, the MT ferrule 13 is installed at a predetermined position of the housing 20, and the optical waveguide 10 is aligned with the light emitting element 14 and the light receiving element 15. Thereby, the optical subassembly 1 is completed.

  Next, as shown in FIG. 1, the optical subassembly 1 is carried into a housing 5 in which the optical connector 2, the circuit board 3, and the electrical connector 4 are already mounted, and the end faces 11 a and 12 b of the optical waveguide 10 are inserted into the optical connector 2. Further, the mirror surface 10a is aligned with the light emitting part 14a of the light emitting element 14 and the light receiving part 15a of the light receiving element 15, and then fixed on the circuit board 3. Finally, the lid 6 is attached to the housing 5 to complete the optical module 100.

(Optical coupling between optical fiber and optical waveguide)
Although the optical waveguide core is formed by the manufacturing method as described above, a certain variation occurs in the distance between the optical waveguide cores due to thermal deformation and process variations during this process. Further, since the outer shape of the optical waveguide is formed by a dicer or the like as described above, the distance from the end surface of the optical waveguide to the optical waveguide core has a certain variation due to variations during dicing. Further, the formed optical waveguide is displaced in the position of the optical waveguide core due to thermal expansion or the like according to the surrounding environment. These positional shifts increase in the optical waveguide core arrangement direction (X direction in FIG. 3B). As shown in FIG. 3B, the end face of the light emitting waveguide core has a vertically long rectangle (h1> w1). ) And the end face 12a of the light receiving waveguide core 12 has a horizontally long rectangular shape (h2 <w2), so that optical coupling with an optical fiber is possible even if a positional deviation in the X direction occurs. Is less likely to cause

(Light reception operation)
FIG. 5 shows an optical path when light is incident on the light receiving element from the optical waveguide. In the figure, (a) shows the case of the light receiving waveguide core in the present embodiment, and (b) shows the case of the comparative example in which the cross sectional shape of the light receiving waveguide core is a square.

  As shown in FIG. 5A, the light from the light receiving waveguide core 12 having a horizontally long rectangular cross-sectional shape is reflected by the mirror surface 10a, and then the projected image 15b is projected onto the light receiving portion 15a of the light receiving element 15. To do. Since the reflected light from the mirror surface 10a is generally distorted in a trapezoidal shape, the optical coupling efficiency is likely to deteriorate. However, since the amount of protrusion in the short side direction of the projected image 15b is small, the deterioration of the optical coupling efficiency can be suppressed.

  On the other hand, as shown in FIG. 5B, in the case of the light receiving waveguide core 12 ′ having a square cross-sectional shape, the projected image 15b on the light receiving element 15 having the same size as the light receiving portion 15a in FIG. Since the entire light receiving unit 15a is covered, the amount of light leaking from the light receiving unit 15a increases, and the optical coupling efficiency deteriorates. For this reason, the light receiving efficiency is lowered as compared with the configuration of FIG. If the cross-sectional shape of the optical waveguide core is a square with the short side of the light receiving waveguide core 12 in FIG. 5A as one side, the optical coupling efficiency between the optical waveguide and the light receiving element can be further improved. In this case, the optical coupling efficiency between the optical fiber and the optical waveguide is deteriorated.

(Light emission operation)
FIG. 6 shows an optical path when light is emitted from the light emitting element to the optical waveguide. In the figure, (a) shows the case of the light emitting waveguide core in the present embodiment, and (b) shows the case of the comparative example in which the cross sectional shape of the light emitting waveguide core is a square.

  As shown in FIG. 6A, the light from the light emitting element 14 having a vertically long rectangular cross-sectional shape is reflected by the mirror surface 10 a and then enters the light emitting waveguide core 11. Even if the optical waveguide 10 is thermally expanded in the longitudinal direction of the light emitting waveguide core 11 due to heat generation of the light emitting element 14 and a positional shift occurs between the light emitting element 14 and the light emitting waveguide core 11, the light emitting waveguide. Since the core 11 is vertically long, a decrease in optical coupling efficiency between the light emitting element 14 and the light emitting waveguide core 11 is suppressed.

  On the other hand, as shown in FIG. 6B, in the case of the light emitting waveguide core 11 ′ having a square cross-sectional shape, the light from the light emitting element 14 is reflected on the mirror surface 10a as in the case of FIG. After reflection, the light enters the light emitting waveguide core 11 ′. At this time, since the cross-sectional shape of the light emitting waveguide core 11 ′ is square, when a positional shift occurs between the optical waveguide 10 and the light emitting element 14, part of the light from the light emitting element 14 is emitted from the light emitting waveguide. Since the light leaks from the upper part of the core 11 ′, the amount of light incident on the light emitting waveguide core 11 ′ from the light emitting element 14 is reduced as compared with the case of FIG. That is, the optical coupling efficiency decreases. In addition, although the optical coupling efficiency may be lowered due to the mirror surface misalignment on the light receiving element side, the misalignment occurs in the present invention as can be seen by similarly shifting the mirror surface position in FIG. However, the optical coupling efficiency is not easily lowered.

(Effects of the first embodiment)
According to the first embodiment, the following effects are obtained.
(A) Since the cross-sectional shape of the light emitting waveguide core 11 is made long with respect to the mounting surface of the optical element, even if a positional deviation occurs between the light emitting waveguide core 11 and the optical fiber 7a, the light emitting waveguide Even if a positional shift occurs between the core 11 and the light emitting element 14, a decrease in light loss can be suppressed.
(B) Since the cross-sectional shape of the light receiving waveguide core 12 is laterally long with respect to the mounting surface of the optical element, even if a positional shift occurs between the light receiving waveguide core 12 and the optical fiber 7a, the light receiving portion 15a And the optical coupling efficiency can be improved.
(C) Since the light emitting waveguide core 11 and the light receiving waveguide core 12 have the same height, they can be easily manufactured from the same photolithography mask.
(D) Since the cross-sectional shapes of the light-emitting waveguide core 11 and the light-receiving waveguide core 12 are kept constant over the entire length, it is possible to suppress the occurrence of mode conversion loss due to the change of the cross-sectional shape.
(E) Since it is folded back by the mirror surface 10a and optically coupled to the light emitting element 14 and the light receiving element 15, a thin optical module can be realized.

[Second Embodiment]
FIG. 7 shows the structure of the optical waveguide and MT ferrule of the optical module according to the second embodiment of the present invention. In the figure, (a) shows the light emitting side assembly, and (b) shows the light receiving side assembly. In the present embodiment, the light emitting side assembly 8 and the light receiving side assembly 9 are separated and independent from each other in the first embodiment, and these are combined with the drive circuit 18 and the amplifier circuit 19 so that the light emitting and light receiving optical subassemblies 1 are combined. The other configuration is the same as that of the first embodiment.

  As shown in FIG. 7A, the optical waveguide 10 in the light emitting side assembly 8 includes only a plurality of (here, eight) light emitting waveguide cores 11 having a vertically long rectangular cross-sectional shape, and the light emitting element 14. Has a number of light emitting portions 14a corresponding to the number of cores.

  Similarly, as shown in FIG. 7B, the optical waveguide 10 in the light-receiving side assembly 9 is composed of only a plurality of (here, eight) light-receiving waveguide cores 12 having a horizontally-long rectangular cross-sectional shape, The light receiving element 15 has a number of light receiving portions 15a corresponding to the number of cores.

(Configuration of optical subassembly using light-receiving side assembly)
FIG. 8 shows a configuration of a light receiving optical subassembly configured using the light receiving side assembly. In the light receiving optical subassembly 1, in FIG. 2 of the first embodiment, the optical waveguide 10 is configured by only the light receiving waveguide core 12, and the light receiving element 15 having eight light receiving portions 15 a is provided in the holder 16. It is arranged.

  In addition, the light-emitting optical subassembly 1 using the light-emitting side assembly 8 has a configuration in which the optical waveguide 10 includes only the light-emitting waveguide core 11 in FIG. 8, and the light-emitting element 14 having eight light-emitting portions 14 a in the holder 16. Further, it can be configured by mounting the drive circuit 18 on the substrate 17 instead of the amplifier circuit 19. If the light emitting waveguide core 11 and the light receiving waveguide core 12 have the same height, the same MT ferrule can be used on the light emitting side and the light receiving side.

  According to the second embodiment, it is possible to configure the optical module 100 specialized for light reception or light emission depending on the application or the like.

  FIG. 9 shows the relationship between the cross-sectional shape of the light emitting and receiving waveguide core and the optical coupling efficiency (overlap loss excluding Fresnel loss), (a) shows the optical coupling efficiency characteristics in this example, (b) Indicates the optical coupling efficiency characteristics of the comparative example. In the figure, TX indicates a light emitting waveguide core, and RX indicates a light receiving waveguide core. The ribbon optical fiber 7 is referred to as an optical fiber.

  The characteristic of FIG. 9A according to the present embodiment is when the optical module 100 is optically coupled to a multi-mode optical fiber having a diameter of 50 μm. The optical waveguide 10 has a light emitting waveguide core 11 with a width of 30 μm and a high The light receiving waveguide core 12 has a width of 60 μm and a height of 45 μm.

  As is clear from FIG. 9A, according to the embodiment of the present invention, the positions of the optical fiber and the optical waveguide core are, for example, in the in-plane direction (X direction) in which misalignment is a problem. It can be seen that even with a deviation of 10 μm, an optical loss of 0.6 dB or less is sufficient.

  On the other hand, the comparative example shown in FIG. 9B is a case where the light emitting waveguide core 11 and the light receiving waveguide core 12 are both optical waveguides 10 having a 45 μm square specification. This comparative example is the most efficient from the viewpoint of optical coupling, but it can be seen that a loss of 1.3 dB or more is generated only by shifting by 10 μm.

  FIG. 10 is a diagram in which the optical coupling efficiency when the position of the optical fiber and the optical waveguide core is shifted by 10 μm in the X direction is plotted with respect to the difference between the long side and the short side length of the rectangular cross section. As is clear from the figure, the rectangular (difference> 0) has a smaller decrease in the optical coupling efficiency than the square (difference = 0), and if the difference is 5 μm or more, there is an improvement effect of 0.3 dB or more. I understand.

  Next, when the distance h0 (FIG. 3B) from the bottom surface of the optical waveguide to the lower end of the optical waveguide core is 50 μm and the diameter of the light receiving element is 80 μm, the light reflected from the mirror surface and exiting the optical waveguide is received by the light receiving element. The light loss (overlap loss) at the time of incidence on the light was about 0.6 dB (corresponding to FIG. 5A). On the other hand, when the cross section of the optical waveguide core is a square of 60 μm square (corresponding to FIG. 5B), the same optical loss is about 1.0 dB, and the structure of this embodiment is adopted. It can be seen that a decrease in optical coupling efficiency with respect to the light receiving element can be suppressed.

  From the above results, the light emitting waveguide core 11 and the light receiving waveguide core 12 have a difference in length between the long side and the short side of the rectangular cross section in consideration of the cutting accuracy of the optical waveguide 10 and the mechanical accuracy of the MT ferrule 13. It can be seen that if the thickness is 5 μm or more, the effect of suppressing the decrease in optical coupling efficiency is enhanced.

[Other embodiments]
The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention. For example, the combination of the components between the embodiments can be arbitrarily performed.

It is sectional drawing which shows the structure of the optical module which concerns on the 1st Embodiment of this invention. The structure of an optical subassembly is shown, (a) is a front view, (b) is (a) AA sectional view, (c) is BB sectional drawing of (a). The details of an optical waveguide and MT type ferrule are shown, (a) is a perspective view and (b) is a front view of an optical waveguide. The manufacturing method of an optical waveguide is shown, (a)-(g) is a manufacturing process figure. The optical path when light is incident on the light receiving element from the optical waveguide is shown, (a) is a path diagram of the light receiving waveguide core in the present embodiment, and (b) is a square cross section of the light receiving waveguide core. It is a route diagram of a comparative example. The light path when irradiating light from a light emitting element to an optical waveguide is shown, (a) is a path diagram of the light emitting waveguide core in the present embodiment, and (b) is a cross sectional shape of the light emitting waveguide core. It is a route diagram of a comparative example. The structure of the optical waveguide and MT type ferrule of the optical module which concerns on the 2nd Embodiment of this invention is shown, (a) is a perspective view which shows the assembly by the side of light emission, (b) is a perspective view which shows the assembly by the side of light reception. It is. It is sectional drawing which shows the structure of the optical subassembly for light reception comprised using the light reception side assembly. The relationship between the cross-sectional shape of the light emitting and receiving waveguide core and the optical coupling efficiency is shown, (a) is a characteristic diagram in the present embodiment, (b) is a characteristic diagram of a comparative example. It is the figure which plotted the optical coupling efficiency when the position of an optical fiber and an optical waveguide core shifted | deviated by 10 micrometers in the X direction with respect to the difference of the length of the long side of a rectangular cross section, and a short side.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical subassembly 2 Optical connector 3 Circuit board 4 Electrical connector 5 Case 6 Lid 7 Ribbon optical fiber 7a Optical fiber 8 Light emission side assembly 9 Light reception side assembly 10 Optical waveguide 10a Mirror surface 10b Clad 11, 11 'Light emission waveguide core 11a , 12b End face 12, 12 ′ Light receiving waveguide core 13 MT ferrule 13a Guide hole 13b Recess 14 Light emitting element 14a Light emitting part 15 Light receiving element 15a Light receiving part 15b Projected image 16 Holder 17 Substrate 18 Drive circuit 19 Amplifying circuit 20 Housing 20a Lid DESCRIPTION OF SYMBOLS 100 Optical module 101 Master 102 Convex part 103 Hardened layer 104 Concave part 105 Mold 106 Clad film base material 107 Curable resin 108 Clad layer

Claims (17)

In an optical waveguide in which an optical fiber is optically coupled to one end and a light emitting element is optically coupled to the other end,
A light emitting waveguide core having a cross-sectional shape with different outer diameters in directions orthogonal to each other;
A mirror surface that is provided at the other end of the light emitting waveguide core and is inclined in a direction in which an outer diameter of a cross-sectional shape of the light emitting waveguide core is increased and is optically coupled to the light emitting element. Optical waveguide. In an optical waveguide in which an optical fiber is optically coupled to one end and a light receiving element is optically coupled to the other end,
A light receiving waveguide core having a cross-sectional shape with different outer diameters in directions orthogonal to each other;
A mirror surface that is provided at the other end of the light receiving waveguide core and is inclined in a direction in which an outer diameter of a cross-sectional shape of the light receiving waveguide core is reduced and is optically coupled to the light receiving element. Optical waveguide. A plurality of waveguide cores arranged in a predetermined direction; a plurality of optical fibers are optically coupled to one end of the plurality of waveguide cores; and a light emitting element and a light receiving element are disposed at the other end of the plurality of waveguide cores. In a planar optical waveguide to be optically coupled,
The waveguide core has a cross-sectional shape with different outer diameters in directions orthogonal to each other, and a light emitting waveguide core in which a smaller outer diameter is disposed in the predetermined direction;
As the waveguide core, the light receiving waveguide core having a cross-sectional shape having different outer diameters in directions orthogonal to each other, and a larger outer diameter arranged in the predetermined direction;
A mirror surface that is inclined in a direction perpendicular to the predetermined direction, optically couples the light emitting waveguide core and the light emitting element, and optically couples the light receiving waveguide core and the light receiving element. Characteristic optical waveguide.   The optical waveguide according to claim 1, wherein the light emitting waveguide core is a plurality of light emitting waveguide cores arranged in a direction in which an outer diameter of a cross-sectional shape decreases.   The optical waveguide according to claim 2, wherein the light receiving waveguide core is a plurality of light receiving waveguide cores arranged in a direction in which an outer diameter of a cross-sectional shape increases. The light emitting waveguide core is a plurality of light emitting waveguide cores arranged in the predetermined direction,
The optical waveguide according to claim 3, wherein the light receiving waveguide core is a plurality of light receiving waveguide cores arranged in the predetermined direction. The light emitting element includes a plurality of light emitting portions arranged corresponding to the plurality of light emitting waveguide cores,
The optical waveguide according to claim 3, wherein the light receiving element includes a plurality of light receiving portions arranged corresponding to the plurality of light receiving waveguide cores.   4. The optical waveguide according to claim 1, wherein the light emitting waveguide core or the light receiving waveguide core has a rectangular cross-sectional shape.   9. The optical waveguide according to claim 8, wherein the light emitting waveguide core or the light receiving waveguide core has a difference in length between a long side and a short side of the rectangular cross-sectional shape of 5 [mu] m or more.   4. The optical waveguide according to claim 1, wherein the light emitting waveguide core or the light receiving waveguide core has an incident end and an emission end having the same cross-sectional shape.   The optical waveguide according to claim 3, wherein the light emitting waveguide core and the light receiving waveguide core have the same outer diameter in a direction perpendicular to the predetermined direction.   4. The optical waveguide according to claim 1, 2 or 3, wherein the optical waveguide is made of a polymer material.   The light receiving waveguide core has a rectangular cross-sectional shape, wherein a length of a long side is larger than a diameter of the core of the optical fiber, and a length of a short side is smaller than the diameter of the core of the optical fiber. The optical waveguide according to claim 2 or 3. In an optical module having an optical waveguide in which an optical fiber is optically coupled to one end and a light emitting element optically coupled to the other end of the optical waveguide,
The optical waveguide is a light emitting waveguide core having a cross-sectional shape with different outer diameters in directions orthogonal to each other, and a direction in which the outer diameter of the cross-sectional shape of the light emitting waveguide core is increased at the other end of the optical waveguide. And a mirror surface that is optically coupled to the light emitting element. In an optical module having an optical waveguide having an optical fiber optically coupled to one end and a light receiving element optically coupled to the other end of the optical waveguide,
The optical waveguide includes a light receiving waveguide core having a cross-sectional shape with different outer diameters in directions orthogonal to each other, and a direction in which the outer diameter of the cross-sectional shape of the light receiving waveguide core is reduced at the other end of the optical waveguide. And a mirror surface that is optically coupled to the light receiving element. A plate-shaped optical waveguide having a plurality of waveguide cores optically coupled to one end and arranged in a predetermined direction, and a light emitting element and a light receiving element optically coupled to the other end of the optical waveguide. In an optical module having
The optical waveguide has, as the waveguide core, cross-sectional shapes having different outer diameters in directions orthogonal to each other, a light emitting waveguide core having a small outer diameter arranged in the predetermined direction, and the waveguide core The light receiving waveguide core having a cross-sectional shape having different outer diameters in directions orthogonal to each other, and a larger outer diameter disposed in the predetermined direction, and a direction perpendicular to the predetermined direction, An optical module comprising: a light emitting waveguide core and the light emitting element; and a mirror surface for optically coupling the light receiving waveguide core and the light receiving element.   The optical waveguide is held by an MT (Mechanically Transferable) ferrule, and the MT ferrule includes a guide pin for alignment with the optical fiber. The optical module as described.

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