JP2020160307A - Optical waveguide, optical module and electronic apparatus - Google Patents

Abstract

To provide an optical waveguide small in excessive loss accompanying branching and large in positional deviation admissibility of incident light; an optical module including the optical waveguide and high in reliability; and an electronic apparatus.SOLUTION: An optical waveguide comprises: a core layer including: an incident core part 191; a branch part 192 for branching the incident core part into a main line branch part 1921 and a branch line branch part 1922; a main line core part 193 and a branch line core part 194. When setting a length from a light incident point 1915a to a branch line side light emission point 1946a to L [mm]; a length from the light incident point to a first end 1916 to L1[mm]; a length from the first end to a second end 1926 to L2[mm]; the width of a light incident end 1915 to W [μm]; the width of a main line incident part 1911 to W1 [mum]; the width of a branch line incident part 1912 to W2[μm]; a distance between the main line branch part and a straight line VL to α2; and a distance between the branch line branch part and the straight line to β2, 0.5≤L≤2.0, 0.15≤L1≤0.60, 0.05≤L2≤0.40, 42≤W≤52, 4≤W1/W2≤6 and 0<α2≤β2 are satisfied.SELECTED DRAWING: Figure 3

Description

The present invention relates to optical waveguides, optical modules and electronic devices.

In optical communication using an optical waveguide, light introduced from one end of the core portion is conveyed to the other end while being reflected at the boundary with the clad portion. A light emitting element such as a semiconductor laser is arranged on the incident side of the optical waveguide, and a light receiving element such as a photodiode is arranged on the exit side. The light incident from the light emitting element propagates through the optical waveguide and is received by the light receiving element.

In such optical communication, the characteristics of the light emitting element may change due to the external environment, changes over time, and the like, and the light intensity incident on the optical waveguide may change accordingly. Such a change in light intensity causes a decrease in the stability of optical communication.

Therefore, in Patent Document 1, the light emitting element, the leading waveguide core that propagates the light emitted from the light emitting element, the monitoring waveguide core that branches from the leading waveguide core, and the light emitted from the monitoring waveguide core are received. An optical waveguide module including a light receiving element for the light receiving element and a hole serving as a reflecting surface for changing the propagation direction of light propagating in the leading waveguide core is disclosed. Since this optical waveguide module includes a monitoring waveguide core branched from the leading waveguide core, it is possible to detect a change in the light emitting intensity of the light emitting element with time. This makes it possible to control the drive of the light emitting element so that the light emitting intensity becomes constant, for example.

Japanese Unexamined Patent Publication No. 2007-057760

However, in the optical waveguide module described in Patent Document 1, the Fresnel reflection at the interface (reflection portion) between the lead waveguide core (main line core portion) and the vacancies is used to determine the light propagation direction in the plane of the optical waveguide. I'm converting. For this reason, it is necessary to secure a wide space for arranging the holes and the waveguide core (branch line core portion) for the monitor, and there is a problem that it becomes difficult to miniaturize the optical fiber wave module accordingly.

In particular, when trying to reduce the size of the optical waveguide module, it is necessary to reduce the size of the pores, but it is not easy to improve the surface accuracy of the minute reflecting surface, so there is a problem that the excess loss due to branching is large. There is.

Further, as the size is reduced, the difficulty of aligning the optical waveguide and the light emitting element becomes higher. That is, there is a problem that the tolerance for misalignment is lowered.

An object of the present invention is to provide an optical fiber with a small excess loss due to branching and a large tolerance for misalignment of incident light, and a highly reliable optical module and electronic device including the optical fiber. ..

Such an object is achieved by the present invention of the following (1) to (6).
(1) An incident core portion having a light incident end including a light incident point at the center of the width and a first end and extending linearly along a virtual straight line.
A branching portion provided adjacent to the first end of the incident core portion and branching the incident core portion into a main line branching portion and a branch line branching portion, and a branching start point is located on the virtual straight line. In addition, a branching portion having a second end at a position where the distance between the main line branching portion and the branch line branching portion in the direction orthogonal to the virtual straight line is 4 μm, and
The main line core portion adjacent to the second end of the main line branch portion and
A branch line core portion adjacent to the second end of the branch line branch portion and having a branch line side light emission point, and a branch line core portion.
Has a core layer in which a branching pattern is formed
Let L [mm] be the length along the virtual straight line from the light incident point to the branch line side light emitting point.
Let L1 [mm] be the length along the virtual straight line from the light incident point to the first end.
The length along the virtual straight line from the first end to the second end is L2 [mm].
The width of the light incident end is W [μm].
When the incident core portion is divided into a main line incident portion and a branch line incident portion with the virtual straight line as a boundary, the width of the main line incident portion is W1 [μm] and the width of the branch line incident portion is W2 [μm].
The distance between the main line branching portion and the virtual straight line at the second end is set to α2 [μm].
When the distance between the branch line branch and the virtual straight line at the second end is β2 [μm],
0.5 ≤ L ≤ 2.0,
0.15 ≤ L1 ≤ 0.60,
0.05 ≤ L2 ≤ 0.40,
42 ≤ W ≤ 52,
4 ≦ W1 / W2 ≦ 6, and
0 <α2 ≦ β2,
An optical fiber that meets the requirements.

(2) The distance between the main line core portion and the virtual straight line at the branch line side light emission point is set to α3 [μm].
When the distance between the branch line core portion and the virtual straight line at the branch line side light emission point is β3 [μm],
α2 ≦ α3 ≦ 30, and 20 ≦ β3 ≦ 60,
The optical fiber waveguide according to (1) above.

(3) The average inclination angle of the main line core portion with respect to the virtual straight line between the second end and the branch line side light emission point is
The optical waveguide according to (1) or (2) above, which is larger than the average inclination angle of the main line branch portion with respect to the virtual straight line.

(4) The average inclination angle of the branch line core portion with respect to the virtual straight line is
The optical waveguide according to any one of (1) to (3) above, which is larger than the average inclination angle of the branch line branching portion with respect to the virtual straight line.

(5) The optical fiber waveguide according to any one of (1) to (4) above,
A light emitting element optically connected to the light incident point of the optical waveguide,
A light receiving element optically connected to the branch line side light emitting point of the optical waveguide,
An optical module characterized by having.

(6) An electronic device including the optical module according to (5) above.

According to the present invention, it is possible to obtain an optical fiber that has a small excess loss due to branching and a large tolerance for misalignment of the light emitting element.

Further, according to the present invention, a compact and highly reliable optical module can be obtained.
Further, according to the present invention, a highly reliable electronic device can be obtained.

It is sectional drawing which shows the optical module which concerns on embodiment. It is a top view which shows the part of the optical module shown in FIG. 1 excluding the housing and the receptacle. FIG. 3 is an enlarged plan view showing a part of a core portion included in the optical waveguide shown in FIG. It is a partially enlarged perspective view of the optical fiber shown in FIG. It is a partially enlarged view of FIG. It is a graph which shows the distribution of the loss on the main line side and the distribution of a branching ratio measured about the optical fiber of the optical waveguide of Experimental Example 51 corresponding to Example, and Experimental Example 15, 45, 49 corresponding to Comparative Example.

Hereinafter, the optical waveguide, the optical module, and the electronic device of the present invention will be described in detail based on the preferred embodiments shown in the accompanying drawings.

1. 1. Optical Module First, the optical waveguide according to the embodiment and the optical module according to the embodiment will be described.

FIG. 1 is a cross-sectional view showing an optical module according to an embodiment. FIG. 2 is a plan view showing a portion of the optical module shown in FIG. 1 excluding the housing and the receptacle. In each figure of the present application, the three axes orthogonal to each other are the X-axis, the Y-axis, and the Z-axis. Further, in the following description, the tip end side of the Z axis is also referred to as "upper", the proximal end side is referred to as "lower", the distal end side of the X axis is referred to as "right", and the proximal end side is also referred to as "left".

The optical module 100 (optical module according to the embodiment) shown in FIG. 1 includes an optical waveguide 1 (the optical waveguide according to the embodiment), an electric substrate 2, a light emitting element 31 optically connected to the optical waveguide 1. It has a light receiving element 32, a control element 4, a lens array 5, a receptacle 61, and a housing 7. In such an optical module 100, the light emitted by the light emitting element 31 is introduced into the optical waveguide 1 and internally distributed into the light for communication and the light for monitoring. Then, the light for monitoring is received by the light receiving element 32, and while monitoring the light intensity, sufficient light intensity is secured for the light for communication, and high quality optical communication is possible.

Of these, the electric substrate 2 shown in FIG. 1 includes an insulating substrate 21, a conductive layer 22 provided on the upper surface of the insulating substrate 21, and a contact 23.

Further, a light emitting element 31, a light receiving element 32, and a control element 4 are mounted on the upper surface of the electric substrate 2 shown in FIG. These elements and the conductive layer 22 are electrically connected via a bonding wire (not shown). The connection structure is not limited to the bonding wire, and may be replaced by other structures such as flip chip bonding.

Examples of the light emitting element 31 include a surface emitting laser (VCSEL), a light emitting diode (LED), and an organic EL element.

Further, examples of the light receiving element 32 include a photodiode (PD, APD), a phototransistor, and the like.

Further, examples of the control element 4 include a driver IC, a transimpedance amplifier (TIA), a limiting amplifier (LA), a combination IC in which these elements are combined, and the like.

In addition to the above-mentioned elements, the electric board 2 has various electronic components such as a CPU (central processing unit), MPU (microprocessor unit), LSI, IC, RAM, ROM, capacitor, coil, resistor, and diode. It may be installed.

Further, a contact 23 electrically connected to the conductive layer 22 is provided at the left end of the electric substrate 2 shown in FIG. The portion provided with the contact 23 is inserted into and fitted to the electric connector 82 attached to the right end of the electric wiring 81 shown in FIG. As a result, the electric board 2 and the electric wiring 81 are electrically connected via the electric connector 82. As a result, an external electrical connection is made to the optical module 100.

On the other hand, the optical fiber waveguide 1 shown in FIGS. 1 and 2 has a sheet shape. The core portion 14 formed inside the optical waveguide 1 serves as a light guide path. In FIG. 2, the core portion 14 is shown through.

Further, an MT type optical connector 62 is attached to the right end of the optical waveguide 1. The MT type optical connector 62 is inserted from the left side of the receptacle 61. That is, an MT type receiving portion 611 is formed on the left side of the receptacle 61, and an MT type optical connector 62 is inserted into the MT type receiving portion 611.

The MT-type receiving unit 611 and the MT-type optical connector 62 may be replaced with members that can be fitted to each other and satisfy different connector standards.

Further, the optical waveguide 1 is formed with reflecting portions 16a and 16b. The optical path P1 extending in the left-right direction in FIG. 1 is converted into an optical path P2 extending in the vertical direction in FIG. 1 via the reflecting portions 16a and 16b. The optical path P2 optically connects the optical waveguide 1 to the light emitting element 31 and the light receiving element 32, respectively. The optical paths P1 and P2 shown in FIG. 1 show an example of a path through which light propagates, respectively.

The lens array 5 is provided between the optical waveguide 1 and the electric substrate 2. The lens array 5 shown in FIG. 1 has a container-like shape having a bottom portion 51 at the top and an opening at the bottom, and has a bottom portion 51 and a wall portion 52 erected downward from the edge of the bottom portion 51. , Is equipped. Then, the lower surface of the wall portion 52 is joined to the upper surface of the electric substrate 2, and the optical waveguide 1 is joined to the upper surface of the bottom portion 51. As a result, a cavity 53 surrounded by the bottom portion 51, the wall portion 52, and the electric substrate 2 is formed. Further, the above-mentioned light emitting element 31, light receiving element 32 and control element 4 are housed in the cavity 53. As a result, the light emitting element 31, the light receiving element 32, and the control element 4 can be protected from the external environment, foreign matter adhesion, and the like. The lens array 5 is not limited to the above configuration, and for example, the cavity 53 may be partially open.

The lens array 5 has light transmission and can pass through the optical path P2. Further, a lens 54 is formed on the bottom portion 51. The lens 54 is, for example, a convex lens, and can focus the light propagating in the optical path P2 at a target position.

In addition to the lens 54, the lens array 5 may be provided with a diffraction grating, a polarizer, a prism, a filter, and the like.

An MPO-type receiving unit 612 is formed on the right side of the receptacle 61. An MPO-type optical connector 92 attached to the left end of the optical fiber 91 is inserted and fitted into the MPO-type receiving unit 612. As a result, the optical fiber 91 and the optical waveguide 1 are optically connected. As a result, an external optical connection is made to the optical module 100.

The MPO-type receiving unit 612 and the MPO-type optical connector 92 may be replaced with members that can be fitted to each other and satisfy different connector standards. Further, the optical waveguide 1 and the optical fiber 91 may be directly connected without using the receptacle 61 or the MPO type optical connector 92.

The housing 7 is a box-shaped member that houses all parts except the electric wiring 81, the electric connector 82, the optical fiber 91, and the MPO type optical connector 92. By housing in such a housing 7, each part can be protected from the external environment, and the reliability and portability of the optical module 100 can be improved.

A through hole is provided in a part of the housing 7, and a portion of the electric substrate 2 provided with the contact 23 protrudes from the through hole. As a result, the electric connector 82 can be easily attached to the contact 23. Similarly, the MPO type receiving portion 612 of the receptacle 61 is exposed from a through hole provided in a part of the housing 7. As a result, the optical fiber 91 can be easily connected to the optical module 100 simply by inserting the MPO type optical connector 92 into the MPO type receiving unit 612.

Examples of the constituent material of the housing 7 include metal materials such as stainless steel, aluminum alloy, and titanium alloy, as well as various resin materials and various ceramic materials. Further, the housing 7 may be provided as needed or may be omitted. In that case, the mold resin may be provided so as to cover the lens array 5 and the optical fiber waveguide 1. The mold resin may be provided so as to fill the inside of the housing 7.

1.1 Optical Fiber Next, the optical fiber 1 will be described.

FIG. 3 is an enlarged plan view showing a part of the core portion included in the optical waveguide shown in FIG. FIG. 4 is a partially enlarged perspective view of the optical fiber shown in FIG. FIG. 5 is a partially enlarged view of FIG.

The optical waveguide 1 according to the present embodiment is a laminated body in which a lower protective layer 17, a clad layer 11, a core layer 13, a clad layer 12, and an upper protective layer 18 are laminated in this order from the lower side of FIG. It has 10. Further, in the core layer 13, a long core portion 14 extending in the left-right direction of FIG. 3 and a side surface provided adjacent to the side surface of the core portion 14 when viewed from the thickness direction of the core layer 13. The clad portion 15 is formed.

On the other hand, as described above, the optical waveguide 1 shown in FIGS. 3 and 4 includes reflecting portions 16a and 16b that mutually convert between the optical path P1 and the optical path P2 shown in FIG. As shown in FIG. 4, the reflecting portions 16a and 16b are a part of the inner surface of the recess 160 which is opened on the upper surface of the laminated body 10 and penetrates the core layer 13. That is, the reflecting portions 16a and 16b are a part of the interface between the hollow recess 160 and the core portion 14. In the reflecting portions 16a and 16b, the optical path P1 and the optical path P2 can be mutually converted by reflection based on the difference in refractive index.

Hereinafter, each part of the optical fiber waveguide 1 will be described in more detail.
1.1.1 Core layer The side surface of the core portion 14 formed in the core layer 13 shown in FIG. 4 is surrounded by the side surface clad portions 15 and the clad layers 11 and 12. The refractive index of the core portion 14 is higher than that of the side clad portions 15 and the clad layers 11 and 12. As a result, light can be confined and propagated in the core portion 14. The side surface clad portion 15 and any one or both of the clad layers 11 and 12 may be integrated.

In the core layer 13, the refractive index distribution in the plane orthogonal to the optical path P1 may be any distribution, for example, a so-called step index (SI) type distribution in which the refractive index changes discontinuously. , The so-called graded index (GI) type distribution in which the refractive index changes continuously may be used.

Further, the cross-sectional shape of the core portion 14 by a plane orthogonal to the optical path P1 is not particularly limited, and is not particularly limited, and is a circle such as a perfect circle, an ellipse, or an oval, a polygon such as a triangle, a quadrangle, a pentagon, or a hexagon, and other variations. It may be in shape.

Further, when the core layer 13 is viewed from the thickness direction, the core portion 14 is branched into two in the middle of the extending direction. As a result, the optical signal can be divided into two. This branch structure will be described in detail later.

The average thickness of the core layer 13 is not particularly limited, but is preferably about 1 to 200 μm, more preferably about 5 to 100 μm, and even more preferably about 10 to 70 μm. As a result, it is possible to reduce the thickness of the optical waveguide 1 while suppressing a decrease in the transmission efficiency of the optical waveguide 1.

Examples of the constituent material (main material) of the core layer 13 include acrylic resin, methacrylic resin, polycarbonate, polystyrene, cyclic ether resin such as epoxy resin and oxetane resin, polyamide, polyimide, polybenzoxazole, and the like. Polysilane, polysilazane, silicone resin, fluororesin, polyurethane, polyolefin resin, polybutadiene, polyisoprene, polychloroprene, polyesters such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), polyethylene succinate, polysulfone, poly Examples thereof include various resin materials such as ether and cyclic olefin resin. Among these, examples of the cyclic olefin-based resin include benzocyclobutene-based resins and norbornene-based resins. As the resin material, a composite material in which materials having different compositions are combined is also used.

1.1.2 Clad layer The average thickness of the clad layers 11 and 12 is preferably about 1 to 200 μm, more preferably about 3 to 100 μm, and even more preferably about 5 to 60 μm. .. As a result, the functions as the clad layers 11 and 12 are ensured while preventing the optical waveguide 1 from becoming thicker than necessary.

Further, as the constituent materials of the clad layers 11 and 12, for example, the same materials as the constituent materials of the core layer 13 described above can be used, but in particular, (meth) acrylic resin, epoxy resin, silicone resin, and the like. It is preferably at least one selected from the group consisting of a polyimide resin, a fluorine resin, a polyolefin resin and a cyclic olefin resin.

The clad layers 11 and 12 may be provided as needed or may be omitted. At this time, for example, if the core layer 13 is exposed to the outside air (air), the outside air functions as the clad layers 11 and 12.

1.1.3 Protective layer In the optical waveguide 1 shown in FIG. 4, the lower protective layer 17 and the upper protective layer 18 protect the core layer 13 and the clad layers 11 and 12, and the core portion 14 is caused by the external environment or the like. It is possible to suppress a decrease in transmission efficiency.

Examples of the constituent materials of the lower protective layer 17 and the upper protective layer 18 include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyolefins such as polyethylene and polypropylene, polyimide, polyamide, and cyclic olefin resins. Examples include materials containing resin.

The average thickness of the lower protective layer 17 and the upper protective layer 18 is not particularly limited, but is preferably about 5 to 500 μm, and more preferably about 10 to 400 μm.

Further, the lower protective layer 17 and the upper protective layer 18 may have the same configuration or different configurations from each other.

The lower protective layer 17 and the upper protective layer 18 may be provided as needed, and at least one of them may be omitted.

1.1.4 The recessed core portion 14 is branched into two as described above. A recess 160 is provided at the end before branching and at one end after branching, respectively. The reflecting portions 16a and 16b provided on the inner surface of the recess 160 are surfaces that are inclined with respect to the optical path P1 of the core portion 14. The conversion angle of the optical path P1 can be adjusted according to the inclination angles of the reflecting portions 16a and 16b.

The recess 160 shown in FIG. 4 has a triangular shape as shown in FIG. 1 when viewed from a direction orthogonal to the optical path P1 in the plane of the core layer 13. Then, as shown in FIG. 4, the reflective portions 16a and 16b are flat, respectively, which are continuously formed from the upper protective layer 18 through the clad layer 12 and the core layer 13 to reach the clad layer 11. It is a face. The shape of the recess 160 is not limited to the shape shown in FIG. 4, and may be any shape. Further, the reflecting portions 16a and 16b are not limited to a flat surface, and may be a curved surface.

The inclination angles of the reflecting portions 16a and 16b are not particularly limited, but when the lower surface of the optical waveguide 1 shown in FIG. 1 is used as a reference plane, the angle formed by the reference plane and the reflecting portions 16a and 16b on the optical path P1 side is 30. It is preferably about 60 °, more preferably about 40 to 50 °. By setting the inclination angle within the above range, the optical path P1 of the core portion 14 can be efficiently converted in the reflecting portions 16a and 16b, and the loss due to the optical path conversion can be suppressed.

The position of the deepest portion of the recess 160 is not particularly limited, but may be at least on the clad layer 11 side of the core layer 13.

Further, in the present embodiment, the recess 160 is hollow, but the recess 160 may be filled with a material having a refractive index lower than that of the core portion 14, and metal films are formed on the reflection portions 16a and 16b. You may be.

Further, instead of the recess 160, a curved waveguide connecting the optical path P1 and the optical path P2 may be provided.

Further, the reflecting portion 16a and the recess 160 in which the reflecting portion 16a is provided may be omitted. In that case, the arrangement of the light emitting element 31 may be appropriately changed so that the light is incident on the light incident end 1915 described later.

1.1.5 Branching pattern Each of the optical fiber waveguides 1 shown in FIGS. 2 and 3 has a core layer 13 in which four core portions 14 including a branched structure are formed. That is, four branch patterns 19 are formed in the core layer 13, and each branch pattern 19 is composed of a core portion 14.

The branch pattern 19 shown in FIG. 3 includes an incident core portion 191 extending linearly along the Y axis, a branch portion 192 that branches the incident core portion 191 into two, and a Y-axis tip side from the branch portion 192, respectively. It includes a main line core portion 193 and a branch line core portion 194 extending toward. The main line core portion 193 is located closer to the tip of the X-axis than the branch line core portion 194. Further, in the branch portion 192 shown in FIG. 3, the point where the branch starts is set as the branch start point D. That is, the first terminal 1916, which is the end of the incident core portion 191 and the start point D of the branch, which is the start of the branch, are at the same position along the Y axis. Then, a straight line passing through the start point D of this branch and parallel to the extending direction of the incident core portion 191 is defined as a virtual straight line VL.

The incident core portion 191 has a light incident end 1915 located at the base end of the Y axis and a first terminal 1916 located at the tip of the Y axis, and extends linearly along a virtual straight line VL. Further, the center point of the length, that is, the width of the light incident end 1915 along the X-axis direction is defined as the light incident point 1915a.

Further, a virtual straight line VL penetrates the incident core portion 191 so as to pass through the light incident end 1915 and the first terminal 1916, respectively. Then, in the incident core portion 191, a portion located on the X-axis tip end side is referred to as a main line incident portion 1911 and a portion located on the X-axis base end side is designated as a branch line incident portion 1912 with the virtual straight line VL as a boundary.

The branch portion 192 is provided adjacent to the first terminal 1916 of the incident core portion 191 and has a main line branch portion 1921 and a branch line branch portion 1922 formed by branching the incident core portion 191 into two. That is, the main line branching portion 1921 is connected to the first terminal 1916 of the main line incident portion 1911, and the branch line branching portion 1922 is connected to the first terminal 1916 of the branch line incident portion 1912.

The main line branching portion 1921 and the branch line branching portion 1922 are configured to extend from the starting point D of the branch toward the tip end side of the Y axis and gradually separate from each other in the X-axis direction. The branch portion 192 has a second terminal 1926 provided at a position where the distance between the main line branch portion 1921 and the branch line branch portion 1922 is 4 μm in the X-axis direction, that is, in the direction orthogonal to the virtual straight line VL. There is.

The main line core portion 193 is provided so as to be adjacent to the second terminal 1926 of the main line branch portion 1921. Then, it extends from the second terminal 1926 toward the tip end side of the Y axis and is gradually displaced toward the tip end side of the X axis. Further, the main line core portion 193 has a main line side light emission point 1936a located at the tip of the Y axis. The main line side light emission point 1936a is the center point of the length, that is, the width of the Y-axis tip of the main line core portion 193 along the X-axis.

The branch line core portion 194 is provided so as to be adjacent to the second terminal 1926 of the branch line branch portion 1922. Then, it extends from the second terminal 1926 toward the tip end side of the Y axis and is gradually displaced toward the base end side of the X axis. As a result, the main line core portion 193 and the branch line core portion 194 are configured to gradually separate from each other in the X-axis direction toward the tip end side of the Y-axis. Further, the branch line core portion 194 has a branch line side light emission point 1946a located at the tip of the Y axis. The branch line side light emission point 1946a is the center point of the length, that is, the width of the Y-axis tip of the branch line core portion 194 along the X-axis.

When light is incident on the branch pattern 19 as described above from the light incident point 1915a, the light is distributed into two at the branch portion 192 via the incident core portion 191. Then, the light distributed to the main line core portion 193 side is emitted from the main line side light emission point 1936a, and is received by an optical component such as a light receiving element or an optical fiber (not shown). On the other hand, the light distributed to the branch line core portion 194 side is emitted from the branch line side light emission point 1946a and received by a light receiving element described later.

The light distributed to the main line core portion 193 side can be used, for example, as light for communication. That is, optical communication can be performed by receiving light incident from the light incident point 1915a and emitted from the main line side light emitting point 1936a. On the other hand, the light distributed to the branch line core portion 194 side can be used, for example, as light for a monitor. The light for the monitor is received by the light receiving element 32 and is used for inspecting the quality of the light for communication and the like without affecting the light for communication. Specifically, for example, the soundness of the light emitting element 31 can be monitored by detecting the intensity of the light for the monitor.
The optical fiber waveguide 1 may be used for purposes other than the above.

Further, at the light incident point 1915a, the reflecting portion 16a is located so as to overlap the light incident point 1915a. As a result, the light from the Z-axis base end to the Z-axis tip can be reflected by the reflecting portion 16a and incident on the incident core portion 191 from the light incident point 1915a.

Further, a reflecting portion 16b is located at the branch line side light emitting point 1946a so as to overlap the light emitting point 1946a. As a result, the light that propagates through the branch line core portion 194 and reaches the branch line side light emission point 1946a can be reflected by the reflection portion 16b and emitted as light from the Z-axis tip toward the Z-axis base end.

Here, in the branch pattern 19, the dimensions of each part are defined as follows. In the description described later, the "width" means a length along the X-axis.

First, let L [mm] be the length along the virtual straight line VL from the light incident point 1915a to the branch line side light emitting point 1946a.

Further, the length along the virtual straight line VL from the light incident point 1915a to the first terminal 1916 is L1 [mm].

Further, the length along the virtual straight line VL from the first terminal 1916 to the second terminal 1926 is L2 [mm].
Further, the width of the light incident end 1915 is W [μm].

Further, when the incident core portion 191 is divided into the main line incident portion 1911 and the branch line incident portion 1912 with the virtual straight line VL as a boundary, the width of the main line incident portion 1911 is W1 [μm] and the width of the branch line incident portion 1912 is W2 [. μm].

Further, the distance between the main line branch portion 1921 and the virtual straight line VL at the second terminal 1926 is set to α2 [μm].

Further, the distance between the branch line branch portion 1922 and the virtual straight line VL at the second terminal 1926 is set to β2 [μm].

At this time, the branch pattern 19 according to the present embodiment satisfies all six conditions represented by the following inequalities [1] to [6].

[1] 0.5 ≤ L ≤ 2.0
[2] 0.15 ≤ L1 ≤ 0.60
[3] 0.05 ≤ L2 ≤ 0.40
[4] 42 ≦ W ≦ 52
[5] 4 ≦ W1 / W2 ≦ 6
[6] 0 <α2 ≦ β2

Hereinafter, [1] to [6] will be described in order.
[1] 0.5 ≤ L ≤ 2.0
As described above, the length L is the length along the virtual straight line VL from the light incident point 1915a to the branch line side light emitting point 1946a. When this length is 0.5 mm or more and 2.0 mm or less, the distance between the reflecting portion 16a and the reflecting portion 16b becomes short. As a result, the distance between the light emitting element 31 and the light receiving element 32 along the Y axis can be shortened, so that the optical module 100 can be miniaturized, and particularly the portion where the light emitting element 31 and the light receiving element 32 are arranged can be miniaturized. It is possible to realize an optical waveguide 1.

If the length L is less than the lower limit, the distance between the light emitting element 31 and the light receiving element 32 is too short, so that the light emitting element 31 and the light receiving element 32 interfere with each other or the curvature of the branch line core portion 194 becomes large. This may increase the bending loss. On the other hand, if the length L exceeds the upper limit value, the optical module 100 may not be miniaturized.
The length L is preferably 0.5 mm or more and 1.0 mm or less.

[2] 0.15 ≤ L1 ≤ 0.60
As described above, the length L1 is the length of the incident core portion 191 extending linearly. Since the incident core portion 191 is a portion where the light incident at the light incident point 1915a first propagates, it is required to extend linearly for a certain length. Therefore, by setting the length L1 within the above range, it is possible to stabilize the propagation of light immediately after the incident. As a result, even if the incident position of the light with respect to the light incident point 1915a shifts, the branch ratio at the branch portion 192 is less likely to fluctuate. As a result, a constant amount of light can be easily distributed to the branch line branch portion 1922 side.

If the length L1 is less than the lower limit, the light propagation in the incident core portion 191 may not be stable, so that the transmission efficiency of the core portion 14 may decrease. In addition, the branching ratio tends to fluctuate according to the incident position of light. On the other hand, if the length L1 exceeds the upper limit value, the distance from the light incident point 1915a to the branch portion 192 becomes long, so that the optical module 100 may not be miniaturized.

The length L1 is preferably 0.15 mm or more and 0.40 mm or less, and more preferably 0.15 mm or more and 0.35 mm or less.

[3] 0.05 ≤ L2 ≤ 0.40
The length L2 is the length of the branch portion 192 as described above. By optimizing the length L2, it is possible to reduce the size of the optical module 100 while suppressing an increase in excess loss due to branching.

If the length L2 is less than the lower limit, the curvature of the branch line branch portion 1922 at the branch portion 192 becomes large, so that the bending loss may increase. On the other hand, if the length L2 exceeds the upper limit value, the optical module 100 may not be miniaturized.

The length L2 is preferably 0.10 mm or more and 0.30 mm or less, and more preferably 0.10 mm or more and 0.25 mm or less.

[4] 42 ≦ W ≦ 52
The width W is the width of the light incident end 1915 as described above. By optimizing the width W, a balance with the spread width of the light incident on the light incident end 1915 can be achieved. Therefore, the branching ratio is less likely to fluctuate according to the incident position of the light with respect to the incident point 1915a, while preventing the alignment accuracy from becoming too high.

If the width W is less than the lower limit, the width W becomes too narrow, so that when the incident position of the light with respect to the light incident point 1915a shifts, the amount of light incident on the light incident end 1915 tends to decrease. Therefore, it is necessary to improve the accuracy of the alignment of the light emitting element 31 with respect to the optical waveguide 1, which may increase the difficulty of the work. On the other hand, if the width W exceeds the upper limit value, the width W becomes too wide, and the branching ratio may easily fluctuate.
The width W is preferably 45 μm or more and 50 μm or less.

[5] 4 ≦ W1 / W2 ≦ 6
The width W1 is the width of the main line incident portion 1911 as described above. Further, the width W2 is the width of the branch line incident portion 1912. The ratio W1 / W2 is the ratio of the width W1 to the width W2. Since this ratio W1 / W2 affects the branching ratio of the branching pattern 19, the ratio W1 / W2 is appropriately set according to the amount of light required for the monitor light.

If the ratio W1 / W2 is less than the lower limit, the amount of light for the monitor becomes too small, so that the S / N ratio of the monitor decreases, and the purpose of monitoring the soundness of the light emitting element 31 can be achieved. There is no risk. On the other hand, if the ratio W1 / W2 exceeds the upper limit value, the amount of light for monitoring becomes too large, so that the amount of light for communication becomes relatively small, and the S / N ratio of communication may decrease. is there.
The ratio W1 / W2 is preferably 4.5 or more and 5.5 or less.

[6] 0 <α2 ≦ β2
The distance α2 is, as described above, the distance between the main line branch portion 1921 and the virtual straight line VL at the second terminal 1926. Specifically, it is the distance between the position on the most virtual straight line VL side of the main line branch portion 1921 and the virtual straight line VL in the direction orthogonal to the virtual straight line VL (X-axis direction) at the position of the second terminal 1926.

Further, the distance β2 is, as described above, the distance between the branch line branch portion 1922 and the virtual straight line VL at the second terminal 1926. Specifically, it is the distance between the position on the most virtual straight line VL side of the branch line branching portion 1922 and the virtual straight line VL in the direction orthogonal to the virtual straight line VL at the position of the second terminal 1926.

Then, when the distance α2 and the distance β2 satisfy the above inequality, both the main line branching portion 1921 and the branch line branching portion 1922 extend so as to gradually separate from the virtual straight line VL. Then, while shortening the length of the branch portion 192 along the Y axis as much as possible, it is possible to sufficiently secure the distance between the main line branch portion 1921 and the branch line branch portion 1922 at the second terminal 1926. As a result, the size of the optical module 100 can be reduced while suppressing an excessive loss in the branch portion 192.

If the distance α2 is larger than the distance β2, the main line branch portion 1921 bends sharply, so that the bending loss at the main line branch portion 1921 may increase. When the distance α2 is 0 or less, the branch line branching portion 1922 is sharply bent in order to secure a sufficient distance between the main line branching portion 1921 and the branch line branching portion 1922 at the second terminal 1926. Since there is a need, bending loss at the branch line branch portion 1922 may increase.

The total of the distance α2 and the distance β2 is 4 μm as described above. Therefore, β2 [μm] = 4 [μm] -α2 [μm] holds.
Further, it is preferably 0.5 ≦ α2 ≦ β2.

The optical fiber waveguide 1 according to the present embodiment, which satisfies all the six conditions represented by the above inequality [1] to [6], has a small excess loss due to branching, and when aligning the light emitting element 31. The tolerance for misalignment is large. Therefore, the assembly work when assembling the optical module 100 is easy, the internal loss is small, and the optical module 100 with high reliability can be realized.

Further, since the tolerance for misalignment is large, it is possible to suppress variations in the intensity of light for communication and variations in the branch ratio between the branch patterns 19 to a small extent. As a result, an optical fiber waveguide 1 that is easy to use can be obtained.

Further, since the excess loss due to branching is small, sufficient light intensity can be secured even if the width of the main line core portion 193 is narrowed. As a result, it is possible to increase the coupling efficiency with the optical component connected to the main line side light emission point 1936a. Similarly, since the width of the branch line core portion 194 can be narrowed, for example, at the connection portion between the branch line branch portion 1922 and the branch line core portion 194, even if the branch line core portion 194 is bent, bending loss is suppressed as compared with the case where the width is wide. can do.

Further, the optical module 100 according to the present embodiment is optically connected to the optical waveguide 1, the light emitting element 31 optically connected to the optical incident point 1915a of the optical waveguide 1, and the branch line side light emitting point 1946a of the optical waveguide. It has a light receiving element 32 connected to the light receiving element 32. Such an optical module 100 is compact and highly reliable because the optical waveguide 1 has the above-mentioned effects.

On the other hand, the distance between the main line core portion 193 and the virtual straight line VL at the branch line side light emission point 1946a is set to α3 [μm].

Further, the distance between the branch line core portion 194 and the virtual straight line VL at the branch line side light emission point 1946a is set to β3 [μm].

At this time, it is preferable that the branch pattern 19 satisfies both of the two conditions represented by the following inequalities [7] and [8].
[7] α2 ≦ α3 ≦ 30
[8] 20 ≦ β3 ≦ 60

Hereinafter, [7] and [8] will be described in order.
[7] α2 ≦ α3 ≦ 30
As described above, the distance α3 is the distance between the main line core portion 193 and the virtual straight line VL at the branch line side light emission point 1946a. Specifically, at the position of the branch line side light emission point 1946a, the distance between the position on the most virtual straight line VL side of the main line core portion 193 and the virtual straight line VL in the direction orthogonal to the virtual straight line VL (X-axis direction). is there.

Further, as described above, the distance α2 is the distance between the main line branch portion 1921 and the virtual straight line VL at the second terminal 1926.

Then, when the distance α2 and the distance α3 satisfy the above inequality, the main line core portion 193 is configured so that the main line core portion 193 is separated to a position sufficiently distant from the branch line side light emission point 1946a. Therefore, when the reflecting portion 16b as shown in FIG. 3 is provided in the range centered on the branch line side light emitting point 1946a, it is possible to secure a space for providing the reflecting portion 16b having a sufficient width. As a result, it becomes easy to form the reflecting portion 16b having high surface accuracy, and it becomes easy to increase the coupling efficiency between the optical waveguide 1 and the light receiving element 32 through the reflection by the reflecting portion 16b.

Further, when the distance α3 is equal to or less than the upper limit value, the curvature of the main line core portion 193 is unlikely to increase, so that it is possible to prevent an increase in bending loss of the main line core portion 193.

[8] 20 ≦ β3 ≦ 60
As described above, the distance β3 is the distance between the branch line core portion 194 and the virtual straight line VL at the branch line side light emission point 1946a. Specifically, it is the distance between the position on the most virtual straight line VL side of the branch line core portion 194 and the virtual straight line VL in the direction orthogonal to the virtual straight line VL at the position of the branch line side light emission point 1946a.

Then, when the distance β3 satisfies the above inequality, the branch line side light emission point 1946a can be sufficiently separated from the main line core portion 193. As a result, when the reflecting portion 16b as shown in FIG. 3 is provided in the range centered on the branch line side light emitting point 1946a, it is possible to secure a space for providing the reflecting portion 16b having a sufficient width. As a result, it becomes easy to form the reflecting portion 16b having high surface accuracy, and it becomes easy to increase the coupling efficiency between the optical waveguide 1 and the light receiving element 32 through the reflection by the reflecting portion 16b.

If the distance β3 is less than the lower limit, it becomes difficult to secure a sufficient space, so that the surface accuracy of the reflecting portion 16b may decrease. On the other hand, when the distance β3 exceeds the upper limit value, the curvature of the branch line core portion 194 becomes large, so that the bending loss may increase.

Further, as shown in FIG. 5, the average inclination angle α4 with respect to the virtual straight line VL of the main line branch portion 1921 can be obtained from the length L2 and the distance α2.

Further, the length along the virtual straight line VL from the second terminal 1926 to the branch line side light emission point 1946a is L3 [mm]. Then, due to the difference (α3-α2) between the distance α3 and the distance α2 and the length L3, the inclination of the main line core portion 193 when the main line core portion 193 separates from the virtual straight line VL, that is, the second end 1926 and the branch line side. The average inclination angle α5 with respect to the virtual straight line VL of the main line core portion 193 with respect to the light emission point 1946a can be obtained.

In the branch pattern 19 according to the present embodiment, the average tilt angle α5 may be smaller than the average tilt angle α4, but it is preferably larger. As a result, the inclination angle is gradually increased from the main line branch portion 1921 to the main line core portion 193, so that the bending method of the light for communication propagating through them can also be gradually increased. By performing such a bending method, an increase in bending loss can be suppressed, and a decrease in the S / N ratio of communication can be suppressed.

The average tilt angle α4 can be obtained by tan ^-1 (α2 / L2 / 1000). Further, the average inclination angle α5 can be obtained by tan ^-1 {(α3-α2) / L3 / 1000}.

The length L3 is preferably 0.5 mm or more and 0.9 mm or less, and more preferably 0.6 mm or more and 0.8 mm or less.

Further, as shown in FIG. 5, the average inclination angle β4 with respect to the virtual straight line VL of the branch line branching portion 1922 can be obtained from the length L2 and the distance β2.

Further, due to the difference between the distance β3 and the distance β2 (β3-β2) and the length L3, the inclination of the branch line core portion 194 when the branch line core portion 194 separates from the virtual straight line VL, that is, the virtual straight line of the branch line core portion 194. The average tilt angle β5 with respect to VL can be obtained.

In the branch pattern 19 according to the present embodiment, the average tilt angle β5 may be smaller than the average tilt angle β4, but it is preferably larger. As a result, the inclination angle is gradually increased from the branch line branch portion 1922 to the branch line core portion 194, so that the bending method of the monitor light propagating there can also be gradually increased. By performing such a bending method, an increase in bending loss can be suppressed, and a decrease in the S / N ratio of the monitor can be suppressed.

The average tilt angle β4 can be obtained by tan ^-1 (β2 / L2 / 1000). The average tilt angle β5 can be obtained by tan ^-1 {(β3-β2) / L3 / 1000}.

Further, the total length LL of the optical waveguide 1, that is, the length along the virtual straight line VL from the light incident point 1915a to the main line side light emitting point 1936a is not particularly limited, but is 3.0 mm or more and 100.0 mm or less. It is preferable that it is 4.0 mm or more and 50.0 mm or less.

The main line branch portion 1921 and the main line core portion 193 may each have a linear pattern, may have a curved pattern, or both may be mixed.

Similarly, the branch line branching portion 1922 and the branch line core portion 194 may also have a linear pattern, a curved pattern, or a mixture of both.

Further, the number of branch patterns 19 included in the optical waveguide 1 may be 1 to 3 or 5 or more. When the number of branch patterns 19 is large, the optical fiber waveguide 1 may be multi-layered as needed. The core layer and the clad layer may be alternately laminated on the clad layer 12 shown in FIG.

The pitch of the branch patterns 19 adjacent to each other, that is, the distance L4 between the virtual straight lines VL of the adjacent branch patterns 19 shown in FIG. 2 is preferably 100 μm or more and 300 μm or less, and more preferably 150 μm or more and 250 μm or less. .. The arrangement density of the branch patterns 19 can be sufficiently increased while avoiding interference between the branch patterns 19. As a result, it is possible to achieve both miniaturization and multi-channelization of the optical waveguide 1. Further, it is possible to prevent the leakage light from affecting each other between the branch patterns 19. As a result, it is possible to suppress a decrease in the detection accuracy of the light intensity of the light for the monitor and a decrease in the quality of the optical communication.

Further, the intensity of the communication light when it is assumed that the main line side light emission point 1936a is at the same position as the branch line side light emission point 1946a is defined as the main line emission intensity, and the monitor light emitted from the branch line side light emission point 1946a. The ratio of the branch line emission strength to the main line emission strength (branch ratio) is preferably -30 dB or more, and more preferably 25 to -15 dB. With such a branching ratio, the balance between the intensity of the communication light emitted from the main line core portion 193 and the intensity of the monitor light emitted from the branch line core portion 194 becomes particularly good. That is, it is possible to sufficiently secure the light intensity for the monitor without significantly deteriorating the quality of optical communication. As a result, it is possible to continue to monitor the soundness of the light emitting element 31 more accurately while performing good optical communication.

2. 2. Electronic device According to the optical waveguide of the present invention as described above, as described above, the light intensity of the light for the monitor can be monitored, and the light intensity of the light for communication is sufficiently secured. Therefore, it is possible to easily add a function of monitoring the soundness of the light emitting element 31 to an electronic device having an optical communication function. Moreover, since the optical waveguide 1 has a small excess loss due to branching and has a high tolerance for misalignment of the light emitting element 31, high-quality optical communication is possible and the optical module 100 provided with the optical waveguide 1 is provided. The ease of assembly can be improved, and the ease of assembly of electronic devices can be improved. Furthermore, according to the optical waveguide 1, since the optical module 100 can be miniaturized, the electronic device can also be miniaturized. Therefore, by providing the optical module 100, a highly reliable electronic device (electronic device of the present invention) can be obtained.

Examples of the electronic device of the present invention include electronic devices such as smartphones, tablet terminals, mobile phones, game machines, router devices, WDM devices, personal computers, televisions, servers, and supercomputers.

Although the optical waveguide, the optical module, and the electronic device of the present invention have been described above based on the illustrated embodiments, the present invention is not limited thereto.

For example, in the above embodiment, the lens is arranged between the optical waveguide and the light emitting / receiving element, but this lens may be provided as needed and may be omitted.

Further, as the electric substrate, a resin substrate such as a rigid substrate or a flexible substrate is often used, but a ceramic substrate, a glass substrate, or the like may be used.

Next, specific examples of the present invention will be described.
1. 1. Fabrication of Optical Waveguide (Experimental Example 1)
First, the optical fiber shown in FIG. 3 was produced. The numerical values representing the branching pattern of this optical waveguide are as follows.

-Length L (= length LL): 1.0 mm
・ Length L1: 0.10 mm
・ Length L2: 0.10 mm
・ Width W: 48 μm
・ Width W1: 32 μm
・ Width W2: 16 μm
-Ratio W1 / W2: 2
・ Distance α2: 0 μm
・ Distance β2: 4 μm

For the convenience of evaluation, the prepared optical waveguide has a length L and a length LL equal to each other. That is, the position of the branch line side light emission point 1946a in the Y-axis direction and the position of the main line side light emission point 1936a in the Y-axis direction are made the same.

In addition, the main line branch portion and the main line core portion each have a shape extending in a straight line, and the width thereof is taken over by the width W1 of the main line incident portion as it is.

Further, the branch line branching portion and the branch line core portion are also formed to extend linearly, and the width thereof is taken over by the width W2 of the branch line incident portion as it is.

(Experimental Examples 2 to 6)
An optical fiber wave was obtained in the same manner as in Experimental Example 1 except that the lengths L1 and L2 were changed as shown in Table 1, respectively.

(Experimental Example 7)
An optical waveguide was obtained in the same manner as in Experimental Example 1 except that the widths W1 and W2 were changed as shown in Table 1.

(Experimental Examples 8 to 12)
An optical fiber wave was obtained in the same manner as in Experimental Example 7, except that the lengths L1 and L2 were changed as shown in Table 1, respectively.

(Experimental Example 13)
An optical waveguide was obtained in the same manner as in Experimental Example 1 except that the widths W1 and W2 were changed as shown in Table 1.

(Experimental Examples 14-18)
An optical fiber wave was obtained in the same manner as in Experimental Example 13 except that the lengths L1 and L2 were changed as shown in Table 1, respectively.

(Experimental Example 19)
An optical waveguide was obtained in the same manner as in Experimental Example 1 except that the distances α2 and β2 were changed as shown in Table 1.

(Experimental Examples 20 to 24)
An optical fiber wave was obtained in the same manner as in Experimental Example 19 except that the lengths L1 and L2 were changed as shown in Table 1, respectively.

(Experimental Examples 25 to 54)
An optical fiber wave having a branching pattern was produced in the same manner as in Experimental Example 1, except that the lengths L1, L2, widths W1, W2, distances α2, and β2 were changed as shown in Table 1, respectively.

In each of the above experimental examples, the distance α3 and the distance β3 satisfy α2 ≦ α3 ≦ 30 and 20 ≦ β3 ≦ 60.

2. 2. Evaluation of Optical Waveguide Next, a graded index type optical fiber having a diameter of 50 μm connected to a light emitting element (VCSEL) was connected to the light incident point 1915a of the optical waveguide obtained in each experimental example.

Further, a graded index type optical fiber having a diameter of 50 μm connected to a light receiving element (PD) was connected to each of the main line side light emitting point 1936a and the branch line side light emitting point 1946a of the optical waveguide.

Next, a laser beam having a wavelength of 850 nm was emitted from the light emitting element, and the light emitted at the main line side light emitting point 1936a and the branch line side light emitting point 1946a, respectively, was received by the light receiving element through the optical waveguide. Then, the main line emission strength and the branch line emission strength were measured, respectively, and the following evaluations were made.

2.1 Evaluation of loss on the main line First, the distribution of loss on the main line was measured while shifting the position of the optical fiber connected to the light emitting element within a range of at least ± 10 μm in the width direction around the light incident point 1915a. Then, the maximum value of the distribution was defined as "main line side loss" and evaluated in light of the following evaluation criteria. The evaluation results are shown in Table 1.

(Evaluation criteria)
A: Main line side loss is 1.25 dB or less B: Main line side loss is more than 1.25 dB and 2.00 dB or less C: Main line side loss is more than 2.00 dB

2.2 Evaluation of branching ratio Next, the ratio of the branch line emission intensity to the main line emission intensity while shifting the position of the optical fiber connected to the light emitting element within a range of at least ± 10 μm in the width direction around the light incident point 1915a. Each branch ratio was measured. Then, the measured branching ratio was evaluated against the following evaluation criteria. The maximum value of the distribution was used for the main line emission intensity when calculating the branching ratio. The evaluation results are shown in Table 1.

(Evaluation criteria)
A: Branch ratio is -25 dB or more and -15 dB or less B: Branch ratio is more than -15 dB or less than -10 dB or -30 dB or more and less than -25 dB C: Branch ratio is more than -10 dB or less than -30 dB

2.3 Evaluation of standard deviation σ of loss on the main line Next, the width of the light incident end was divided into sections of 2 μm, and the loss on the main line when the optical fiber was located in each section was calculated. Subsequently, the mean value and deviation were obtained from the main line side loss of each section, and the "standard deviation σ" was calculated. Then, the calculated standard deviation σ was evaluated against the following evaluation criteria. The evaluation results are shown in Table 1.

(Evaluation criteria)
A: Standard deviation σ is 0.1667 or less B: Standard deviation σ is more than 0.1667 and 0.3000 or less C: Standard deviation σ is more than 0.3000

2.4 Evaluation of standard deviation σ of branching ratio Next, the width of the light incident end was divided into sections of 2 μm, and the branching ratio when the optical fiber was located in each section was obtained. Subsequently, the mean value and the deviation were obtained from the branch ratio of each section, and the "standard deviation σ" was calculated. Then, the calculated standard deviation σ was evaluated against the following evaluation criteria. The evaluation results are shown in Table 1.

(Evaluation criteria)
A: Standard deviation σ is 1.667 or less B: Standard deviation σ is more than 1.667 and 3.000 or less C: Standard deviation σ is more than 3.000 The above evaluation results are shown in Table 1.

Of Experimental Examples 1 to 54 shown in Table 1, the range surrounded by a thick line corresponds to "Example", and the rest corresponds to "Comparative Example".

In each of the optical fiber waveguides of the examples, it was found that the loss on the main line side was sufficiently small and the standard deviation σ of the loss on the main line side was also sufficiently small. As a result, it was confirmed that the optical fiber of the example can sufficiently secure the intensity of light for communication and can prevent a decrease in the S / N ratio of communication. It was also found that even if the incident light is misaligned, the effect on the main line side loss and its standard deviation σ can be suppressed to a small extent. Therefore, it was confirmed that the optical fiber of the example has a large tolerance for misalignment of the incident light with respect to the loss on the main line side and the degree of dispersion thereof.

Further, it was found that in each of the optical fiber waveguides of the examples, the branching ratio was within a necessary and sufficient range, and the standard deviation σ of the branching ratio was also sufficiently small. As a result, it was confirmed that the optical fiber of the example can secure the necessary and sufficient intensity as the light for the monitor. Furthermore, it was found that even if the incident light is displaced, the influence on the branching ratio and its standard deviation σ can be suppressed to a small extent. Therefore, it was confirmed that the optical fiber of the example has a large tolerance for misalignment of incident light with respect to the branching ratio and the degree of dispersion thereof.

When the loss on the main line side and the branching ratio were combined, it was found that in the optical fiber of the example, the excess loss due to branching was also suppressed to a small value.

Here, an example of the above evaluation results is shown in a graph.
FIG. 6A is a graph showing the distribution of the main line side loss and the distribution of the branching ratio measured for the optical fiber of Experimental Example 51 corresponding to the example. The vertical axis in the center is the loss on the main line side, and the vertical axis on the right is the branch ratio. Further, the horizontal axis represents the amount of deviation from the light incident point at the light incident end, plus indicates that the deviation is toward the branch line incident portion, and minus indicates that the deviation is toward the main line incident portion.

On the other hand, FIG. 6 (b) corresponds to Experimental Example 15 corresponding to Comparative Example, FIG. 6 (c) corresponds to Experimental Example 45 corresponding to Comparative Example, and FIG. 6 (d) corresponds to Comparative Example. Corresponds to Experimental Example 49 corresponding to.

As is clear from FIG. 6, in the example, since the distribution of the loss on the main line side and the distribution of the branching ratio are relatively flat in the range of ± 10 μm, it can be seen that the allowable displacement of the incident light is large. .. On the other hand, in the comparative example, it can be seen that the distribution of the loss on the main line side or the distribution of the branching ratio fluctuates, and the tolerance for misalignment of the incident light is not large.

Although not shown in Table 1, the same evaluation was performed on the optical fiber waveguide manufactured in the same manner as above except that the width W was changed to 54 μm, and the same result as the evaluation result shown in Table 1 was obtained. It was.

1 Optical waveguide 2 Electric substrate 4 Control element 5 Lens array 7 Housing 10 Laminated body 11 Clad layer 12 Clad layer 13 Core layer 14 Core part 15 Side clad part 16a Reflection part 16b Reflection part 17 Lower protection layer 18 Upper protection layer 19 Branch pattern 21 Insulation substrate 22 Conductive layer 23 Contact 31 Light emitting element 32 Light receiving element 51 Bottom 52 Wall 53 Cavity 54 Lens 61 Receptacle 62 MT type optical connector 81 Electrical wiring 82 Electrical connector 91 Optical fiber 92 MPO type optical connector 100 Optical module 160 Recess 191 Incident core part 192 Branch part 193 Main line core part 194 Branch line core part 611 MT type receiving part 612 MPO type receiving part 1911 Main line incident part 1912 Branch line incident part 1915 Light incident end 1915a Light incident point 1916 First terminal 1921 Main line branch 1922 Branch line branch 1926 Second end 1936a Main line side light emission point 1946a Branch line side light emission point D Start point L4 Distance LL Total length P1 Optical path P2 Optical path VL Virtual straight line α2 Distance α3 Distance α4 Average tilt angle α5 Average tilt angle β2 Distance β3 Distance β4 Average tilt angle β5 Average tilt angle

Claims (6)

A light incident end including a light incident point at the center of the width, and an incident core portion having a first end and extending linearly along a virtual straight line.
A branching portion provided adjacent to the first end of the incident core portion and branching the incident core portion into a main line branching portion and a branch line branching portion, and a branching start point is located on the virtual straight line. In addition, a branching portion having a second end at a position where the distance between the main line branching portion and the branch line branching portion in the direction orthogonal to the virtual straight line is 4 μm, and
The main line core portion adjacent to the second end of the main line branch portion and
A branch line core portion adjacent to the second end of the branch line branch portion and having a branch line side light emission point, and a branch line core portion.
Has a core layer in which a branching pattern is formed
Let L [mm] be the length along the virtual straight line from the light incident point to the branch line side light emitting point.
Let L1 [mm] be the length along the virtual straight line from the light incident point to the first end.
The length along the virtual straight line from the first end to the second end is L2 [mm].
The width of the light incident end is W [μm].
When the incident core portion is divided into a main line incident portion and a branch line incident portion with the virtual straight line as a boundary, the width of the main line incident portion is W1 [μm] and the width of the branch line incident portion is W2 [μm].
The distance between the main line branching portion and the virtual straight line at the second end is set to α2 [μm].
When the distance between the branch line branch and the virtual straight line at the second end is β2 [μm],
0.5 ≤ L ≤ 2.0,
0.15 ≤ L1 ≤ 0.60,
0.05 ≤ L2 ≤ 0.40,
42 ≤ W ≤ 52,
4 ≦ W1 / W2 ≦ 6, and
0 <α2 ≦ β2,
An optical fiber that meets the requirements. The distance between the main line core portion and the virtual straight line at the branch line side light emission point is set to α3 [μm].
When the distance between the branch line core portion and the virtual straight line at the branch line side light emission point is β3 [μm],
α2 ≦ α3 ≦ 30, and 20 ≦ β3 ≦ 60,
The optical fiber waveguide according to claim 1. The average inclination angle of the main line core portion with respect to the virtual straight line between the second end and the branch line side light emission point is
The optical waveguide according to claim 1 or 2, wherein the main line branch portion has a larger average inclination angle with respect to the virtual straight line. The average inclination angle of the branch line core portion with respect to the virtual straight line is
The optical waveguide according to any one of claims 1 to 3, which is larger than the average inclination angle of the branch line branching portion with respect to the virtual straight line. The optical fiber waveguide according to any one of claims 1 to 4.
A light emitting element optically connected to the light incident point of the optical waveguide,
A light receiving element optically connected to the branch line side light emitting point of the optical waveguide,
An optical module characterized by having. An electronic device comprising the optical module according to claim 5.

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