Optical devices, optical receivers, and optical transceivers

Abstract

The present invention provides an optical device that can suppress the effects of reflected light when multiple cores are optically coupled using a butt joint between a back-side incident optical device. [Solution] The optical device is a back-side-incident type optical device that receives incident light from a plurality of cores arranged in an optical fiber by butt-joint optical coupling with the plurality of cores. The optical device has a first path through which the incident light from the plurality of cores is incident, a light-receiving section that absorbs the incident light incident from the first path, and a separation section that separates the unabsorbed component of the incident light that was not absorbed by the light-receiving section into a second path different from the first path.

Description

Technical Field

[0001] The present invention relates to an optical device, an optical receiver, and an optical transceiver.

Background Art

[0002] In recent years, with the increasing speed, large capacity, and miniaturization of optical transceivers, for example, an optical module equipped with a high-density optical receiver that bat joint optically couples a MCF (Multi Core Fiber) and a two-dimensional array of high-speed photodiodes (PD: Photo Diode) array has been studied. MCF is an optical fiber in which a plurality of cores are provided within one cladding.

[0003] The optical module of the prior art 1 has an optical receiver including a surface incident type PD array that bat joint optically couples with a multi-mode MCF. The surface incident type PD array is a PD array in which a light receiving portion is disposed on the substrate surface that bat joint optically couples with the multi-mode MCF, and the light receiving portion receives incident light from the multi-mode MCF.

[0004] In addition, the optical module has an optical transmitter including a back surface emission type VCSEL (Vertical Cavity Surface Emitting Laser) array that bat joint optically couples with a multi-mode MCF. The back surface emission type VCSEL array is a VCSEL array in which a transmissive substrate that bat joint optically couples with the multi-mode MCF is disposed on the transmissive substrate of the VCSEL array, and the signal light is emitted to the multi-mode MCF through the transmissive substrate. That is, the optical module of the prior art 1 has a back surface emission type VCSEL array and a surface incident type PD array.

[0005] The optical module of Conventional Technology 2 comprises an optical transmitter having a back-side exit type VCSEL array that is butt-joint optically coupled with a single-mode MCF, and an optical receiver having a back-side incident type PD array that is butt-joint optically coupled with a single-mode MCF. The back-side incident type PD array is a PD array in which a light-receiving section is arranged on the back side of a transparent substrate that is butt-joint optically coupled with the single-mode MCF, and receives incident light from the single-mode MCF that passes through the transparent substrate. In other words, the optical module of Conventional Technology 2 has a back-side exit type VCSEL array and a back-side incident type PD array.

[0006] Figure 16 is an explanatory diagram showing an example of a schematic cross-section of a conventional optical receiver 100 of the prior art 2. The optical receiver 100 shown in Figure 16 has a back-side incident PD array 120 that is butt-joint optically coupled with a single-mode MCF 110. The single-mode MCF 110 has a plurality of cores 111, a cladding 112 surrounding the plurality of cores 111, and an end face 113 that is butt-joint optically coupled with the back-side incident PD array 120.

[0007] The back-side incident PD array 120 includes a transparent substrate 121, a light-receiving section 122, an electrode 123, and a wiring pattern 124. The transparent substrate 121 is a substrate that transmits incident light from multiple cores 111 arranged in a single-mode MCF 110 by butt-joint photo-coupling with multiple cores 111.

[0008] The light-receiving unit 122 is built into the back side of the transparent substrate 121 and is a part that absorbs incident light transmitted from the front surface of the transparent substrate 121. When a voltage is applied from the electrode 123, the light-receiving unit 122 absorbs the incident light and converts it into an electric current according to the intensity of the absorbed incident light.

[0009] The electrode 123 is positioned on the back surface of the transparent substrate 121 and on the back surface of the light-receiving unit 122, and electrically connects the light-receiving unit 122 and the wiring pattern 124. For example, it is a metal electrode. The electrode 123 is a part that applies a voltage to the light-receiving unit 122 and outputs a current from the light-receiving unit 122.

[0010] The wiring pattern 124 is located on the back surface of the transparent substrate 121 and is electrically connected to the electrode 123. The light receiving unit 122 converts the light received by the electrode 123 into a current corresponding to the intensity of the light, and outputs the converted current to the wiring pattern 124. The path 125 within the transparent substrate 121 is the path through which incident light from multiple cores 111 enters the light receiving unit 122.

[0011] Conventional technology 2's optical module allows for shorter wiring lengths compared to conventional technology 1's optical module, enabling higher speeds. Furthermore, because it uses a single-mode MCF110, long-distance transmission is facilitated. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent Application Publication No. 9-139512 [Patent Document 2] Special Publication No. 2004-533009 [Patent Document 3] U.S. Patent No. 10120149 [Patent Document 4] U.S. Patent Application Publication No. 2012 / 14639 [Patent Document 5] Japanese Patent Publication No. 2020-027147 [Overview of the project] [Problems that the invention aims to solve]

[0013] However, in the conventional optical receiver 100 of technology 2, a vertical optical system is used to optically couple the single-mode MCF 110 and the back-entry type PD array 120 using a butt joint. Therefore, in the optical receiver 100, a portion of the incident light transmitted through the transparent substrate 121 is not absorbed by the light-receiving section 122, and the unabsorbed component of the incident light that was not absorbed leaks onto the electrode surface of the electrode 123 on the back surface of the light-receiving section 122. Then, at the electrode surface of the electrode 123, the unabsorbed component leaked from the light-receiving section 122 is reflected, and the reflected light may recombine with the incident light that has passed through the transparent substrate 121 and through the core 111 in the single-mode MCF 110. As a result, this reflected light affects the feedback mechanism for outputting a predetermined emission light from the VCSEL in the optical transmitter on the opposing device side that is optically coupled with the single-mode MCF 110. In other words, a method is needed to suppress the effects of reflected light when optically coupling the single-mode MCF 110 and the back-entry type PD array 120 using a butt joint.

[0014] One aspect of this invention is to provide an optical device that can suppress the effects of reflected light when multiple cores are optically coupled using a butt joint between a back-side incident optical device. [Means for solving the problem]

[0015] One embodiment of the optical device is a back-side-incident optical device that receives incident light from a plurality of cores arranged in an optical fiber by butt-joint optical coupling with the plurality of cores. The optical device has a first path through which the incident light from the plurality of cores is incident, a light-receiving section that absorbs the incident light incident from the first path, and a separation section that separates the unabsorbed component of the incident light that was not absorbed by the light-receiving section into a second path different from the first path. [Effects of the Invention]

[0016] From one perspective, it is possible to suppress the effects of reflected light when multiple cores are optically coupled with a back-illuminated optical device using a butt joint. [Brief explanation of the drawing]

[0017] [Figure 1] Figure 1 is an explanatory diagram showing an example of the optical receiver of Example 1. [Figure 2] Figure 2 is an explanatory diagram showing an example of a schematic cross-section of the optical receiver of Example 1. [Figure 3] Figure 3 is an explanatory diagram showing an example of a schematic cross-section of the optical receiver of Example 2. [Figure 4] Figure 4 is an explanatory diagram showing an example of the optical receiver of Example 3. [Figure 5] Figure 5 is an explanatory diagram showing an example of a schematic cross-section of the optical receiver of Example 3. [Figure 6] Figure 6 is an explanatory diagram showing an example of a schematic cross-section of the PD array of Example 3. [Figure 7] Figure 7 is an explanatory diagram showing an example of the plane of the ring-shaped electrode of Example 3. [Figure 8] Figure 8 is an explanatory diagram showing another example of the plane of the partial electrode of Example 3. [Figure 9] Figure 9 is an explanatory diagram showing an example of a schematic cross-section of the PD array of Example 4. [Figure 10] Figure 10 is an explanatory diagram showing an example of the plane of the transparent electrode of Example 4. [Figure 11] Figure 11 is an explanatory diagram showing an example of a schematic cross-section of the optical receiver of Example 5. [Figure 12] Figure 12 is an explanatory diagram showing an example of a schematic cross-section of the PD array of Example 6. [Figure 13] Figure 13 is an explanatory diagram showing an example of the plane of the scattering electrode of Example 6. [Figure 14] Figure 14 is an explanatory diagram showing an example of a schematic cross-section of an optical circuit in which the optical receiver of Example 7 is mounted. [Figure 15] Figure 15 is an explanatory diagram showing an example of the optical transceiver of this example. [Figure 16] Figure 16 is an explanatory diagram showing an example of a schematic cross-section of the optical receiver of the prior art 2.

Modes for Carrying Out the Invention

[0018] Embodiments of the optical device and the like of the present invention will be described below with reference to the drawings. However, these embodiments do not limit the disclosed technology. Furthermore, the embodiments described below may be combined as appropriate, provided they do not contradict each other. [Examples]

[0019] Figure 1 is an explanatory diagram showing an example of the optical receiver 1 of Example 1, and Figure 2 is an explanatory diagram showing an example of a schematic cross-section of the optical receiver 1 of Example 1. The optical receiver 1 shown in Figure 1 is an optical module having an MCF (Multi Core Fiber) 2 and a two-dimensional array of back-incident type PD (Photo Diode) arrays 3, and butt-joint optical coupling between the MCF 2 and the PD array 3.

[0020] The MCF2 has multiple cores 21, a cladding 22 surrounding the multiple cores, and an end face 23 that butt-jointly optically couples with a back-side incident PD array 3. The MCF2 is a single-mode MCF having a refractive index and core diameter such that the propagation mode is single-mode. The end face 23 is a coupling surface that butt-jointly optically couples with the PD array 3, and the end face 23 is polished obliquely with respect to the core 21. For the sake of explanation, the MCF2 is exemplified as having, for example, seven cores, but it is not limited to this and can be modified as appropriate.

[0021] The PD array 3 is a set of back-incident PD arrays arranged in a two-dimensional array. The PD array 3 includes a transparent substrate 31, a light-receiving section 32, an electrode 33, a wiring pattern 34, and a separation section 37. The transparent substrate 31 is a substrate that transmits incident light from multiple cores 21 arranged in the MCF2 by butt-joint photo-coupling with the multiple cores 21. The transparent substrate 31 is made of a material including, for example, GaAs (gallium arsenide), InGaAs (indium gallium arsenide), Si (silicon), etc.

[0022] The light-receiving unit 32 is built into the back side of the transparent substrate 31 and is a part that absorbs incident light transmitted from the surface of the transparent substrate 31. When a voltage is applied from the electrode 33, the light-receiving unit 32 absorbs the incident light and converts it into an electric current according to the intensity of the absorbed incident light. In the light-receiving unit 32, although the incident light that enters from the transparent substrate 31 is absorbed, a portion of the incident light that is not absorbed will be transmitted to the electrode surface of the electrode 33.

[0023] The electrode 33 is positioned on the back surface of the transparent substrate 31 and the back surface of the light-receiving unit 32, and electrically connects the light-receiving unit 32 and the wiring pattern 34. For example, it is a metal electrode. The electrode 33 is the part that applies a voltage to the light-receiving unit 32 and outputs a current from the light-receiving unit 32. In addition, the electrode surface of the electrode 33 reflects the non-absorbed component, which is a part of the incident light that was not fully received by the light-receiving unit 32.

[0024] The wiring pattern 34 is located on the back surface of the transparent substrate 31 and is electrically connected to the electrode 33. The light receiving unit 32 converts the light received by the electrode 33 into a current corresponding to the intensity of the light received when a voltage is applied to the light receiving unit 32, and outputs the converted current to the wiring pattern 34.

[0025] The first path 35 within the transparent substrate 31 is the path through which incident light from multiple cores 21 enters the light-receiving unit 32. The separation unit 37 separates the unabsorbed component of the incident light that was not absorbed by the light-receiving unit 32 into a second path 36 that is different from the first path 35. The first path 35 and the second path 36 are paths within the transparent substrate 31. The separation unit 37 is the electrode surface of an electrode 33 positioned diagonally to the first path 35, which reflects the unabsorbed component into the second path 36, which is different from the first path 35. Since the second path 36 is a different path from the first path 35, it suppresses the recombination of the unabsorbed component with the incident light passing through the cores 21 in the MCF2.

[0026] For the sake of explanation, the end face 23 of the MCF2 shown in Figure 2 is depicted as being separated from the bonding surface of the transparent substrate 31 of the PD array 3, but it goes without saying that the bonding surface of the MCF2 and the surface of the transparent substrate 31 are joined together with adhesive.

[0027] An optical transmitter in the opposing device (not shown) has, for example, a back-side emission type VCSEL array that is optically connected to the MCF2. The VCSEL array emits signal light that passes through a transparent substrate within the VCSEL array and is emitted to the core 21 in the MCF2.

[0028] Next, the operation of the optical receiver 1 in Example 1 will be described. The VCSEL array in the optical transmitter in the opposing device emits single-mode signal light to the MCF2. The PD array 3 in the optical receiver 1 is butt-joint optically coupled with the MCF2 and receives single-mode incident light from multiple cores 21 in the MCF2.

[0029] The transparent substrate 31 in the PD array 3 transmits incident light from multiple cores 21 in the MCF2, and this incident light enters the light-receiving unit 32 via a first path 35 through which it passes. The light-receiving unit 32 absorbs the incident light when a voltage is applied from the electrode 33, and converts the absorbed incident light into a current according to its intensity. In the light-receiving unit 32, although the incident light entering from the transparent substrate 31 is absorbed, a portion of the incident light that is not absorbed leaks onto the electrode surface of the electrode 33.

[0030] Since the electrode surface of electrode 33 is inclined at an angle with respect to the first path 35 in the transparent substrate 31, the non-absorbent component of the incident light that enters the light-receiving unit 32 via the first path 35 is reflected to the second path 36. As a result, the non-absorbent component reflected to the second path 36 is reflected to a second path 36 that is different from the first path 35, thus suppressing recombination with the incident light passing through the core 21 in the MCF2.

[0031] In the optical receiver 1 of Example 1, the end face 23 of the MCF2 is polished obliquely to the core 21, and the surface of the transparent substrate 31 of the PD array 3 is butt-joint optically coupled to the polished, inclined optical coupling surface. Furthermore, the electrode surface of the electrode 33 of the transparent substrate 31 is inclined obliquely to the first path 35 within the transparent substrate 31, so that the non-absorbed component of the incident light that enters the light receiving unit 32 via the first path 35 is reflected to the second path 36. As a result, the influence of the reflected light of the non-absorbed component when butt-joint optical coupling is performed between the MCF2 and the PD array 3 can be suppressed. Moreover, by reflecting the reflected light of the non-absorbed component to the second path 36 while butt-joint optical coupling is performed between the MCF2 and the PD array 3, not only is miniaturization and high density possible, but the influence of reflected light can also be suppressed.

[0032] Furthermore, the optical receiver 1 obliquely polishes the end face 23 of the MCF2 and performs butt-joint optical coupling between the end face 23 and the transparent substrate 31 of the PD array 3. As a result, the gap between the PD array 3 and the MCF2 is reduced, suppressing coupling loss, while the recombination of non-absorbing components to the MCF2 can be suppressed without the use of additional parts.

[0033] In the first embodiment, the optical receiver 1 was illustrated in which the end face 23 of the MCF2 was polished at an angle, and the surface of the transparent substrate 31 of the PD array 3 was butt-joint optically coupled to the polished, inclined optical coupling surface. However, the invention is not limited to this, and the end face 23 of the MCF2 may be polished perpendicular to the core 21, and the transparent substrate 31 may be positioned such that the surface of the transparent substrate 31 of the PD array 3 is at an angle to the polished, horizontal optical coupling surface. This embodiment will be described below as the second embodiment. [Examples]

[0034] Figure 3 is an explanatory diagram showing an example of a schematic cross-section of the optical receiver 1A of Example 2. Note that components identical to those of the optical receiver 1 of Example 1 are denoted by the same reference numerals, and explanations of their overlapping components and operations are omitted. The difference between the optical receiver 1 of Example 1 and the optical receiver 1A of Example 2 lies in the fact that the transparent substrate 31 of the PD array 3A is positioned so that its surface is oblique to the optical coupling surface, which is the horizontal end face 23A of the MCF 2A, and butt-joint optical coupling is performed between the MCF 2A and the transparent substrate 31.

[0035] The separation section 37A is the electrode surface of the electrode 33, which is located on the back surface of the transparent substrate 31, where the end face 23A of the MCF2A is polished perpendicularly to the core 21 and the substrate is positioned diagonally with respect to the horizontal optical coupling surface. In the separation section 37A, the non-absorbent component is reflected from the electrode surface and separated into the second path 36.

[0036] Next, the operation of the optical receiver 1A in Example 2 will be described. The VCSEL array in the optical transmitter in the opposing device emits single-mode signal light to the MCF2A. The PD array 3A in the optical receiver 1A is butt-joint optically coupled with the MCF2A and receives single-mode incident light from multiple cores 21 in the MCF2A.

[0037] The transparent substrate 31 in the PD array 3A transmits incident light from multiple cores 21 in the MCF2A, and this incident light enters the light-receiving unit 32 via a first path 35 through which it passes. The light-receiving unit 32 absorbs the incident light when a voltage is applied from the electrode 33, and converts the absorbed incident light into a current according to its intensity. In the light-receiving unit 32, although the incident light entering from the transparent substrate 31 is absorbed, a portion of the incident light that is not absorbed leaks onto the electrode surface of the electrode 33.

[0038] Since the electrode surface of electrode 33 is inclined at an angle with respect to the first path 35 in the transparent substrate 31, the non-absorbent component of the incident light that enters the light-receiving section 32 via the first path 35 is reflected to the second path 36. As a result, the non-absorbent component reflected to the second path 36 is reflected to a second path 36 that is different from the first path 35, thus suppressing recombination with the incident light passing through the core 21 of MCF2A.

[0039] In the optical receiver 1A of Example 2, the end face 23A of the MCF2A is polished perpendicular to the core 21, and the MCF2A and the transparent substrate 31 are butt-joint optically coupled such that the surface of the transparent substrate 31 of the PD array 3A is oblique to the polished horizontal optical coupling surface. The electrode surface of the electrode 33 in the transparent substrate 31 is inclined obliquely with respect to the first path 35 in the transparent substrate 31, so that the non-absorbed component of the incident light that enters the light receiving unit 32 via the first path 35 is reflected to the second path 36. As a result, the influence of the reflected light of the non-absorbed component when the MCF2A and the PD array 3A are butt-joint optically coupled can be suppressed.

[0040] Furthermore, by arranging the electrode surface of the PD array 3 at an angle, the optical receiver 1A can suppress the recombination of non-absorbent components with MCF2 without using additional parts.

[0041] In Example 2, the example shown was that in the light receiver 1A, the non-absorbent component of the incident light transmitted through the first path 35 is reflected at the electrode surface and separated into a second path 36 that is different from the first path 35. However, an embodiment in which the non-absorbent component of the incident light transmitted through the first path 35 is transmitted, rather than reflected at the electrode surface, will be described below as Example 3. [Examples]

[0042] Figure 4 is an explanatory diagram showing an example of the optical receiver 1B of Example 3, and Figure 5 is an explanatory diagram showing an example of a schematic cross-section of the optical receiver 1B of Example 3. Note that components identical to those of the optical receiver 1A of Example 2 are denoted by the same reference numerals, and explanations of their overlapping components and operations are omitted. The difference between the optical receiver 1A of Example 2 and the optical receiver 1B of Example 3 is that, instead of reflecting the non-absorbed component of the incident light transmitted through the first path 35 at the electrode surface, it is transmitted through a second path 36B that is different from the first path 35.

[0043] The MCF2A has an end face 23A that is polished perpendicular to the core 21 and has a horizontal optical coupling surface. The transparent substrate 31 of the PD array 3B has a horizontal surface. The optical receiver 1B is butt-joint optically coupled between the horizontal optical coupling surface of the MCF2A and the horizontal surface of the transparent substrate 31.

[0044] The PD array 3B includes a transparent substrate 31, a light-receiving section 32, an electrode 33, and a separation section 37B. The separation section 37B is an anti-reflective section positioned at the center of the electrode surface of the electrode 33, and non-absorbent components pass through the anti-reflective section and are separated into a second path 36B.

[0045] Next, the anti-reflective portion will be explained in detail. Figure 6 is an explanatory diagram showing an example of a substantially cross-sectional view of the PD array 3B1 of Example 3, and Figure 7 is an explanatory diagram showing an example of a plan view of the ring-shaped electrode 33B of Example 3. The ring-shaped electrode 33B shown in Figure 7 has a wiring portion 33B1 that is electrically connected to the wiring pattern 34, a ring-shaped electrode surface 33B2 that is electrically connected to the wiring portion 33B1, and an opening 33B3 formed in the center of the electrode surface 33B2. The ring-shaped electrode 33B is an electrode with the outer circumference of the opening 33B3 as the electrode surface 33B2. The opening 33B3 is the anti-reflective portion.

[0046] The separation section 37B is an opening 33B3 formed in the center of the electrode surface 33B2, through which the non-absorbent component passes through the opening 33B3 and separates into the second path 36B.

[0047] Next, the operation of the optical receiver 1B in Example 3 will be described. The VCSEL array in the optical transmitter in the opposing device emits single-mode signal light to the MCF2A. The PD array 3B1 in the optical receiver 2B is butt-joint optically coupled with the MCF2A and receives single-mode incident light from multiple cores 21 in the MCF2A.

[0048] The transparent substrate 31 in the PD array 3B1 transmits incident light from multiple cores 21 in the MCF2A, and this incident light enters the light-receiving unit 32 via a first path 35 through which it passes. The light-receiving unit 32 absorbs the incident light when a voltage is applied from the ring-shaped electrode 33B, and converts the absorbed incident light into a current according to its intensity. In the light-receiving unit 32, although the incident light entering from the transparent substrate 31 is absorbed, a portion of the incident light that is not absorbed leaks onto the electrode surface 33B2 of the ring-shaped electrode 33B.

[0049] The opening 33B3 of the electrode surface 33B2 transmits the non-absorbent component of the incident light that enters the light-receiving section 32 via the first path 35. As a result, the non-absorbent component that passes through the opening 33B3 is transmitted to a second path 36B that is different from the first path 35, thereby suppressing recombination with the incident light passing through the core 21 in the MCF2A.

[0050] In the optical receiver 1B of Example 3, even when the MCF 2A and the transparent substrate 31 are butt-joint optically coupled, the non-absorbent component is transmitted to the second path 36B through the opening 33B3 located at the center of the electrode surface 33B2. As a result, the effect of the return light of the non-absorbent component when the MCF 2A and the PD array 3B1 are butt-joint optically coupled can be suppressed. Moreover, in the optical receiver 1B, the optical path and the electrode 33B can be made perpendicular, so there is no need to worry about the pitch misalignment between the cores 21 that occurs when the light is incident at an oblique angle.

[0051] Since the optical receiver 1B transmits non-absorbing components through the aperture 33B3 located in the center of the electrode surface, in the region with the strongest light intensity among the non-absorbing components, the influence of reflected light from the non-absorbing components can be suppressed. Moreover, since the same electrode material as the wiring pattern 34 on the PD array 3B1 can be used, manufacturing becomes relatively easy.

[0052] In Example 3, the ring-shaped electrode 33B of the PD array 3B1 is an example of a ring-shaped electrode having an opening 33B3 at the center of the electrode surface 33B2 and the outer circumference being the electrode surface 33B2. However, it is not limited to a ring-shaped electrode 33B; any electrode having an opening 33B3 that allows non-absorbing components to pass through at the center of the electrode surface 33B2 is acceptable, and can be modified as appropriate.

[0053] Figure 8 is an explanatory diagram showing another example of the plan view of the partial electrode 33C of Example 3. The partial electrode 33C shown in Figure 8 has a wiring portion 33C1 that is electrically connected to the wiring pattern 34, a semicircular ring-shaped electrode surface 33C2 that is electrically connected to the wiring portion 33C1, and an opening 33C3 formed in the center of the electrode surface 33C2. The partial electrode 33C is a semicircular ring-shaped electrode with the outer circumference of the opening 33C3 as the electrode surface 33C2. In the partial electrode 33C, the opening 33C3 located in the center of the electrode surface 33C2 transmits non-absorbent components to the second path 36B. As a result, the influence of the return light of non-absorbent components when the MCF2A and the PD array 3B1 are butt-joint photocoupled can be suppressed.

[0054] Furthermore, in the PD array 3B1 of Example 3, the case in which a ring-shaped electrode 33B that transmits non-absorbable components is used was illustrated. However, the example is not limited to this, and a transparent electrode 33D that transmits non-absorbable components may also be used, and such an embodiment will be described below as Example 4. [Examples]

[0055] Figure 9 is an explanatory diagram showing an example of a schematic cross-section of the PD array 3B3 of Example 4, and Figure 10 is an explanatory diagram showing an example of a plan view of the transparent electrode 33D of Example 4. Note that components identical to those of the optical receiver 1B of Example 3 are denoted by the same reference numerals, and explanations of their overlapping components and operations are omitted. The difference between the optical receiver 1B of Example 3 and the optical receiver 1C of Example 4 is that the transparent electrode 33D is used instead of the ring-shaped electrode 33B as an anti-reflective section located on the back surface of the light-receiving section 32 within the transparent substrate 31.

[0056] The transparent electrode 33D, positioned on the back surface of the light-receiving section 32, is an anti-reflective section that transmits non-absorbent components to the second path 36B. The transparent electrode 33D is made of a material including, for example, indium tin oxide (ITO), tin oxide, tungsten-doped tin oxide, etc. The transparent electrode 33D is an electrode that transmits infrared light. The transparent electrode 33D has a wiring section 33D1 at one end that is electrically connected to the wiring pattern 34, and a transparent electrode surface 33D2 that transmits non-absorbent components. The separation section 37B shown in Figure 9 is the transparent electrode 33D, through which non-absorbent components are transmitted to the second path 36B.

[0057] Next, the operation of the optical receiver 1C in Example 4 will be described. The VCSEL array in the optical transmitter in the opposing device emits single-mode signal light to the MCF2A. The PD array 3B2 in the optical receiver 1C is butt-joint optically coupled with the MCF2A and receives single-mode incident light from multiple cores 21 in the MCF2A.

[0058] The transparent substrate 31 in the PD array 3B2 transmits incident light from multiple cores 21 in the MCF2A, and this incident light enters the light-receiving unit 32 via a first path 35 through which it passes. The light-receiving unit 32 absorbs the incident light when a voltage is applied from the transparent electrode 33D, and converts the absorbed incident light into a current according to its intensity. In the light-receiving unit 32, although the incident light entering from the transparent substrate 31 is absorbed, a portion of the incident light that is not absorbed leaks onto the transparent electrode surface 33D2 of the transparent electrode 33D.

[0059] The transparent electrode surface 33D2 of the transparent electrode 33D transmits the non-absorbent component of the incident light that enters the light-receiving unit 32 via the first path 35 to the second path 32B. As a result, the non-absorbent component that has passed through the transparent electrode surface 33D2 is transmitted to the second path 36B, which is different from the first path 35, thus suppressing recombination with the incident light passing through the core 21 in the MCF2A.

[0060] In the optical receiver 1C of Example 4, even when the MCF 2A and the transparent substrate 31 are butt-joint optically coupled, the transparent electrode surface 33D2 of the transparent electrode 33D transmits the non-absorbent component to the second path 36B. As a result, the influence of the return light of the non-absorbent component when the MCF 2A and the PD array 3B2 are butt-joint optically coupled can be suppressed. Moreover, since the transparent electrode 33D is made of a material that transmits infrared light throughout the entire electrode, the reflection of the non-absorbent component of the entire electrode can be suppressed.

[0061] In addition, while the example of Example 4 illustrates the arrangement of a transparent electrode 33D as the anti-reflective portion within the PD array 3B2, an anti-reflective coating portion may also be placed on the back surface of the transparent electrode 33D to prevent reflection of non-absorbent components that have passed through the transparent electrode surface 33D2, and this can be modified as appropriate. As a result, by using the anti-reflective coating portion, reflection of non-absorbent components at the interface between the transparent electrode 33D and the anti-reflective coating portion can be prevented. Furthermore, an anti-reflective coating portion may also be provided on the back surface of the ring-shaped electrode 33B to prevent reflection of non-absorbent components that have passed through the opening 33B3 of the ring-shaped electrode 33B, and this can be modified as appropriate. As a result, by using the anti-reflective coating portion, reflection of non-absorbent components at the interface between the ring-shaped electrode 33B and the anti-reflective coating portion can be prevented.

[0062] A light-absorbing portion that absorbs non-absorbent components transmitted through the transparent electrode surface 33D2 may be placed on the back surface of the transparent electrode 33D, and this can be changed as appropriate. Alternatively, a light-absorbing portion that absorbs non-absorbent components transmitted through the opening 33B3 of the ring-shaped electrode 33B may be provided on the back surface of the ring-shaped electrode 33B, and this can be changed as appropriate.

[0063] A light-scattering section may be placed on the back surface of the transparent electrode 33D to scatter non-absorbent components that have passed through the transparent electrode surface 33D2, and this can be changed as appropriate. As a result, since the light-scattering section is placed on the back surface of the transparent electrode 33D, the reflection of the transmitted non-absorbent components can be suppressed. Alternatively, a light-scattering section may be provided on the back surface of the ring-shaped electrode 33B to scatter non-absorbent components that have passed through the opening 33B3 of the ring-shaped electrode 33B, and this can be changed as appropriate. As a result, since the light-scattering section is placed on the back surface of the ring-shaped electrode 33B, the reflection of the transmitted non-absorbent components can be suppressed.

[0064] In Example 4, the optical receiver 1C exemplifies a case where the horizontal optical coupling surface of the MCF2A and the surface of the horizontal transparent substrate 31 are butt-joint optically coupled. However, the inclined optical coupling surface of the MCF2 shown in Figure 2 and the surface of the horizontal transparent substrate 31 may also be butt-joint optically coupled, and such an embodiment will be described below as Example 5. [Examples]

[0065] Figure 11 is an explanatory diagram showing an example of a schematic cross-section of the optical receiver 1D of Example 5. Components identical to those of the optical receiver 1C of Example 4 are denoted by the same reference numerals, and explanations of the redundant components and operations are omitted. The difference between the optical receiver 1D of Example 5 and the optical receiver 1C of Example 4 lies in the butt-joint optical coupling of the inclined optical coupling surface of the MCF2 with the surface of the horizontal transparent substrate 31, thereby transmitting the non-absorbent component to the transparent electrode 33D on the back surface of the transparent substrate 31.

[0066] Next, the operation of the optical receiver 1D in Example 5 will be described. The VCSEL array in the optical transmitter in the opposing device emits single-mode signal light to the MCF2. The PD array 3D in the optical receiver 1D is butt-joint optically coupled with the MCF2 and receives single-mode incident light from multiple cores 21 in the MCF2.

[0067] The transparent substrate 31 in the PD array 3D transmits incident light from multiple cores 21 in the MCF2, and this incident light enters the light-receiving unit 32 via a first path 35 through which it passes. The light-receiving unit 32 absorbs the incident light when a voltage is applied from the transparent electrode 33D, and converts the absorbed incident light into a current according to its intensity. In the light-receiving unit 32, although the incident light entering from the transparent substrate 31 is absorbed, a portion of the incident light that is not absorbed is transmitted to the transparent electrode surface 33D2 of the transparent electrode 33D.

[0068] The transparent electrode surface 33D2 of the transparent electrode 33D transmits the non-absorbent component of the incident light that enters the light-receiving section 32 via the first path 35. As a result, the non-absorbent component that has passed through the transparent electrode surface 33D2 is transmitted to a second path 36B that is different from the first path 35, thereby suppressing recombination with the incident light passing through the core 21 of the MCF2.

[0069] In the optical receiver 1D of Example 5, even when the MCF2 and the transparent substrate 31 are butt-joint optically coupled, the transparent electrode 33D transmits the non-absorbent component to the second path 36B. As a result, the influence of the return light of the non-absorbent component when the MCF2 and the PD array 3D are butt-joint optically coupled can be suppressed.

[0070] In the PD array 3B2 of Example 4, a transparent electrode 33D was used as an example of an anti-reflective portion located near the back side of the transparent substrate 31. However, the invention is not limited to the transparent electrode 33D, and an embodiment of this is described below as Example 6. [Examples]

[0071] Figure 12 is an explanatory diagram showing an example of a schematic cross-section of the PD array 3E of Example 6, and Figure 13 is an explanatory diagram showing an example of a plan view of the scattering electrode 33E of Example 6. Note that components identical to those of the optical receiver 1C of Example 4 are denoted by the same reference numerals, and explanations of their overlapping components and operations are omitted. The difference between the optical receiver 1E of Example 6 and the optical receiver 1C of Example 4 is that, instead of a transparent electrode 33D, the electrode surface 33E2 of the scattering electrode 33E covering the light-receiving portion 32 in the transparent substrate 31 is composed of an uneven surface 33E3 including multiple protrusions that scatter non-absorbent components.

[0072] The light-receiving unit 32A has a light-receiving unit body 32A1 and an uneven surface 32A2 on its back surface that includes a plurality of protrusions. The scattering electrode 33E covering the back surface of the light-receiving unit 32A is an electrode having a wiring portion 33E1 that is electrically connected to the wiring pattern 34, an electrode surface 33E2 that is electrically connected to the wiring portion 33E1, and an uneven surface 33E3 on the electrode surface 33E2 that includes a plurality of protrusions.

[0073] The scattering electrode 33E, positioned on the uneven surface 32A2 on the back surface of the light-receiving section 32A, is an anti-reflection section that scatters non-absorbent components into the second path 36C. The anti-reflection section consists of the uneven surface 32A2 of the light-receiving section 32A and the uneven surface 33E3 of the scattering electrode 33E. In the separation section 37, non-absorbent components leaking from the uneven surface 32A2 of the light-receiving section 32A are scattered by the uneven surface 33E3 of the scattering electrode 33E and separated into the second path 36C.

[0074] Next, the operation of the optical receiver 1E in Example 6 will be described. The VCSEL array in the optical transmitter in the opposing device emits single-mode signal light to the MCF2A. The PD array 3E in the optical receiver 1E is butt-joint optically coupled with the MCF2A and receives single-mode incident light from multiple cores 21 in the MCF2A.

[0075] The transparent substrate 31 in the PD array 3E transmits incident light from multiple cores 21 in the MCF2A, and this incident light passes through a first path 35 to the light-receiving unit 32A. The light-receiving unit 32A absorbs the incident light when a voltage is applied from the scattering electrode 33E, and converts the absorbed incident light into a current according to its intensity. In the light-receiving unit 32A, although the incident light that enters from the transparent substrate 31 is absorbed, a portion of the incident light that is not absorbed leaks onto the electrode surface 33E2 of the scattering electrode 33E.

[0076] The uneven surface 32E3 within the electrode surface 33E2 of the scattering electrode 33E scatters the non-absorbent component incident from the light-receiving section 32A via the first path 35 to the second path 36C. As a result, the non-absorbent component scattered by the scattering electrode 33E is scattered to the second path 36C, which is different from the first path 35, thus suppressing recombination with the incident light passing through the core 21 in the MCF2A.

[0077] In Example 6, even when butt-joint optical coupling is performed between the MCF2A and the transparent substrate 31, the optical receiver 1E scatters the non-absorbent component to the second path 36C with the scattering electrode 33E. As a result, the influence of the return light of the non-absorbent component when butt-joint optical coupling is performed between the MCF2A and the PD array 3E can be suppressed.

[0078] Furthermore, this method is also applicable to an optical circuit 40 in which the optical receiver 1B of Example 3 is flip-chip mounted on a substrate 41, and such an embodiment will be described below as Example 7. [Examples]

[0079] Figure 14 is an explanatory diagram showing an example of a schematic cross-section of an optical circuit 40 on which the optical receiver 1B of Example 7 is mounted. Note that components identical to those of the optical receiver 1B of Example 3 are denoted by the same reference numerals, and the explanation of their overlapping components and operations is omitted. The optical circuit 40 shown in Figure 14 is a semiconductor device in which the optical receiver 1B is flip-chip mounted on a substrate 41 via an underfill 44. The optical circuit 40 comprises the optical receiver 1B, a substrate 41, solder bumps 43 that electrically connect the wiring pattern 34 on the back surface of the transparent substrate 31 within the optical receiver 1B to the wiring pattern 42 on the substrate 41, and an underfill 44 that joins the transparent substrate 31 and the substrate 41.

[0080] An underfill 44 is placed on the back surface of the transparent electrode 33D, which is located on the back surface of the transparent substrate 31 of the PD array 3B in the optical receiver 1B. The underfill 44 is, for example, an optical resin layer. The underfill 44 becomes a light absorbing portion that absorbs non-absorbent components that pass through the transparent electrode 33D.

[0081] Next, the operation of the optical circuit 40 in Example 7 will be described. The VCSEL array in the optical transmitter in the opposing device emits single-mode signal light to the MCF2A. The PD array 3B2 in the optical receiver 1C is butt-joint optically coupled with the MCF2A and receives single-mode incident light from multiple cores 21 in the MCF2A.

[0082] The transparent substrate 31 in the PD array 3B2 transmits incident light from multiple cores 21 in the MCF2A, and this incident light enters the light-receiving unit 32 via a first path 35 through which it passes. The light-receiving unit 32 absorbs the incident light when a voltage is applied from the transparent electrode 33D, and converts the absorbed incident light into a current according to its intensity. In the light-receiving unit 32, although the incident light entering from the transparent substrate 31 is absorbed, a portion of the incident light that is not absorbed leaks onto the transparent electrode surface 33D2 of the transparent electrode 33D.

[0083] The transparent electrode surface 33D2 transmits the non-absorbent component of the incident light that enters the light-receiving section 32 via the first path 35. Furthermore, the underfill 44 on the back surface of the transparent electrode surface 33D2 absorbs the non-absorbent component that has passed through the transparent electrode surface 33D2. As a result, the non-absorbent component that has passed through the transparent electrode 33D is absorbed by the underfill 44, thereby suppressing its recombination with the incident light passing through the core 21 in the MCF2A.

[0084] In the optical circuit 40 of Example 7, even when the MCF2A and the transparent substrate 31 are butt-joint optically coupled, the transparent electrode 33D transmits the non-absorbent component to the second path 36B. The underfill 44 on the back surface of the transparent electrode 33D absorbs the non-absorbent component that has passed through the transparent electrode 33D. As a result, the influence of the return light of the non-absorbent component when the MCF2A and the PD array 3B2 are butt-joint optically coupled can be suppressed.

[0085] In the optical circuit 40, the back-incident PD array 3B2 is flip-chip mounted on the substrate 41, so that the transmitted non-absorbent components are not reflected by the substrate 41, and the recombination to MCF2A can be suppressed by the underfill 44.

[0086] For the sake of explanation, the underfill 44 is made of a material that absorbs non-absorbent components transmitted through the transparent electrode surface 33D2, but it is not limited to this; a material that scatters non-absorbent components may also be used, and this can be changed as appropriate. Furthermore, the underfill 44 and other light-scattering parts may be placed on the back surfaces of the transparent electrode 33D, the ring-shaped electrode 33B, or the partial electrode 33C, and this can be changed as appropriate.

[0087] Next, an optical transceiver 50 employing the optical receiver 1 of this embodiment will be described. Figure 15 is an explanatory diagram showing an example of the optical transceiver 50 of this embodiment. The optical transceiver 50 shown in Figure 15 has an optical transceiver 51 and a DSP (Digital Signal Processor) 52. The optical transceiver 51 has an optical modulator element 54, a driver circuit 55, an optical receiver element 56, and a TIA (Transimpedance Amplifier) ​​57. The optical transceiver 51 has an optical transmitter and an optical receiver. The DSP 52 controls the entire optical transceiver 51. The DSP 52 is an electrical component that performs digital signal processing, performing modulation processing of the transmitted signal and demodulation processing of the received signal.

[0088] The DSP52 performs processing such as encoding the transmission data, generates an electrical signal containing the transmission data, and outputs the generated electrical signal to the driver circuit 55. The driver circuit 55 drives the optical modulator element 54 according to the electrical signal from the DSP52. The optical modulator element 54 optically modulates the signal light. The optical modulator element 54 is butt-joint optically coupled with the second optical fiber 62 and emits the optically modulated signal light into the second optical fiber 62. The optical transmitter incorporates at least the optical modulator element 54.

[0089] The optical receiver element 56 uses an optical signal to acquire signal light from the received light and converts the acquired signal light into electrical light. The optical receiver element 56 is butt-joint optically coupled with the first optical fiber 61 and receives signal light from the first optical fiber 61. The optical receiver incorporates at least the optical receiver element 56. The TIA 57 amplifies the electrical signal after electrical conversion and outputs the amplified electrical signal to the DSP 52. The DSP 52 performs processing such as decoding of the electrical signal acquired from the TIA 57 to obtain received data.

[0090] For the sake of explanation, the optical transceiver 50 is shown as an example in which an optical module 53 containing an optical modulator element 54 and an optical receiver element 56 is incorporated. However, the optical transceiver 50 may also be an optical transmitter incorporating only the optical modulator element 54, or an optical receiver incorporating only the optical receiver element 56, and can be changed as appropriate.

[0091] Furthermore, while MCF2 is used as an example of an optical fiber, the invention is not limited to this, and a two-dimensional array of fiber optics with multiple cores 21 can also be used, and can be changed as appropriate. Also, while MCF2 is used as an example of a single-mode MCF having a refractive index and core diameter such that the propagation mode is single-mode, the invention is not limited to this, and a multi-mode MCF can also be used, and can be changed as appropriate. The transparent substrate 31 is used as an example of a substrate that transmits single-mode incident light from multiple cores 21, but a substrate that transmits multi-mode incident light can also be used, and can be changed as appropriate.

[0092] Furthermore, the components of each part shown in the diagram do not necessarily have to be physically configured as depicted. In other words, the specific forms of distribution and integration of each part are not limited to those shown in the diagram, and all or part of them can be functionally or physically distributed and integrated in any unit according to various loads, usage conditions, etc.

[0093] Furthermore, the various processing functions performed by each device may be executed in whole or in part on a CPU (Central Processing Unit) (or a microcomputer such as an MPU (Micro Processing Unit) or MCU (Micro Controller Unit)). It goes without saying that the various processing functions may also be executed in whole or in part on a program analyzed and executed by the CPU (or a microcomputer such as an MPU or MCU), or on wired logic hardware.

[0094] Furthermore, the following additional information is disclosed regarding the above embodiments.

[0095] (Note 1) A back-incident optical device that receives incident light from multiple cores arranged in an optical fiber by butt-joint optical coupling, A first path through which the incident light from the plurality of cores is incident, A light-receiving unit that absorbs incident light entering from the first path described above, A separation unit separates the unabsorbed component of the incident light that was not absorbed by the light-receiving unit into a second path different from the first path, An optical device characterized by having the following features.

[0096] (Note 2) A transparent substrate that is butt-joint optically coupled with the plurality of cores and transmits incident light from the plurality of cores, The light receiving unit is arranged on the back side of the transparent substrate and absorbs the incident light transmitted from the surface of the transparent substrate, An electrode is disposed on the back surface of the transparent substrate and the back surface of the light-receiving portion, and is electrically connected to the light-receiving portion, The first path in the transparent substrate through which the incident light from the plurality of cores is incident on the light receiving unit, The optical device according to Appendix 1, characterized by having the following features.

[0097] (Note 3) The separation part is The optical device according to Appendix 2, characterized in that the electrode surface of the electrode is arranged obliquely to the first path, and the non-absorbing component is reflected from the electrode surface and separated into the second path.

[0098] (Note 4) The separation part is, The optical device according to Appendix 3, characterized in that the electrode surface of the electrode is arranged on the transparent substrate which is joined to the end face of the optical fiber which has been beveled, and the non-absorbing component is reflected from the electrode surface and separated into the second path.

[0099] (Note 5) The separation part is, The optical device according to Appendix 3, wherein the electrode surface of the electrode is arranged on the transparent substrate to which the end face of the optical fiber is joined in a state where the end face of the optical fiber is polished perpendicularly and the electrode surface is positioned obliquely to the end face, the non-absorbing component is reflected from the electrode surface and separated into the second path.

[0100] (Note 6) The separation part is, The optical device according to Appendix 2, characterized in that an anti-reflective portion is formed on the electrode surface of the electrode, wherein the non-absorbing component passes through the anti-reflective portion and is separated into the second path.

[0101] (Note 7) The anti-reflective part is The optical device according to Appendix 6, characterized in that an opening is formed at the center of the electrode surface, and the non-absorbent component passes through the opening and is separated into the second path.

[0102] (Note 8) The anti-reflective part is The optical device according to Appendix 6, characterized in that the electrode material of the electrode is a transparent electrode that transmits infrared light, and the non-absorbing component passes through the transparent electrode and is separated into the second path.

[0103] (Note 9) The separation part is The optical device according to Appendix 2, characterized in that an anti-reflective portion is formed on the electrode surface of the electrode, which is arranged on the transparent substrate to which the end face of the optical fiber is joined, the end face of which is beveled, and the non-absorbing component passes through the anti-reflective portion and is separated into the second path.

[0104] (Note 10) An optical device according to any one of Notes 6 to 9, characterized in that it has an anti-reflective coating portion disposed on the back surface of the anti-reflective portion, which prevents the reflection of the non-absorbing component that has passed through the anti-reflective portion.

[0105] (Note 11) An optical device according to any one of Notes 6 to 9, characterized in that it has a light absorbing portion disposed on the back surface of the anti-reflective portion and absorbing the non-absorbent component that has passed through the anti-reflective portion.

[0106] (Note 12) An optical device according to any one of Notes 6 to 9, characterized in that it has a light scattering portion disposed on the back surface of the anti-reflective portion, which scatters the non-absorbent component that has passed through the anti-reflective portion to the second path.

[0107] (Note 13) The optical device is flip-chip mounted on a substrate via underfill, The aforementioned light-absorbing section is The optical device according to Appendix 11, characterized in that it is composed of the aforementioned underfill.

[0108] (Note 14) The optical device is flip-chip mounted on a substrate via underfill, The aforementioned light scattering unit is The optical device according to Appendix 12, characterized in that it is composed of the aforementioned underfill.

[0109] (Note 15) The separation part is, The optical device according to Appendix 2, characterized in that a plurality of protrusions are formed on the back surface of the light-receiving portion and on the electrode surface of the electrode covering the back surface of the light-receiving portion in a region where the non-absorbing component strikes, and the non-absorbing component is scattered and separated into the second path depending on the presence or absence of the protrusions.

[0110] (Note 16) The optical fiber is, The optical device according to Appendix 1, characterized in that it is a two-dimensional array of fiber or a multicore fiber.

[0111] (Note 17) The transparent substrate is The optical device according to Appendix 2, characterized in that it transmits single-mode incident light from the plurality of cores.

[0112] (Note 18) Each core in the optical fiber is The optical device according to Appendix 2, characterized in that it has a refractive index and core diameter such that the propagation mode is single-mode.

[0113] (Note 19) An optical receiver comprising a back-incident optical device that receives incident light from a plurality of cores arranged in an optical fiber by butt joint optical coupling, The optical device is A first path through which incident light from the plurality of cores is incident, A light-receiving unit that absorbs incident light entering from the first path described above, A separation unit separates the unabsorbed component of the incident light that was not absorbed by the light-receiving unit into a second path different from the first path, An optical receiver characterized by having the following features.

[0114] (Note 20) An optical transceiver having an optical receiver equipped with a back-incident optical device that receives incident light from a plurality of cores arranged in a first optical fiber by butt joint optical coupling with the plurality of cores, and an optical transmitter that optically connects to a second optical fiber, The optical device is A first path through which incident light from the plurality of cores is incident, A light-receiving unit that absorbs incident light entering from the first path described above, A separation unit separates the unabsorbed component of the incident light that was not absorbed by the light-receiving unit into a second path different from the first path, An optical transceiver characterized by having the following features. [Explanation of Symbols]

[0115] 1. Optical receiver 2 MCF 3 PD array 21 cores 31 Transparent substrate 32 Light receiving part 33 electrode 35 The first route 36. Second Route 37 Separation section

Claims

1. A back-incident optical device that receives incident light from multiple cores arranged in an optical fiber by butt-joint optical coupling, A first path through which the incident light from the plurality of cores is incident, A light-receiving unit that absorbs incident light entering from the first path, A separation unit separates the unabsorbed component of the incident light that was not absorbed by the light-receiving unit into a second path different from the first path, An optical device characterized by having the following features.

2. A transparent substrate that is butt-joint optically coupled with the plurality of cores and transmits incident light from the plurality of cores, The light receiving unit is arranged on the back side of the transparent substrate and absorbs the incident light transmitted from the surface of the transparent substrate, An electrode is disposed on the back surface of the transparent substrate and the back surface of the light-receiving portion, and is electrically connected to the light-receiving portion, The first path in the transparent substrate through which the incident light from the plurality of cores is incident on the light receiving unit, The optical device according to claim 1, characterized by having the following features.

3. The aforementioned separation unit is The optical device according to claim 2, characterized in that the electrode surface of the electrode is arranged obliquely to the first path, and the non-absorbing component is reflected from the electrode surface and separated into the second path.

4. The aforementioned separation unit is The optical device according to claim 3, characterized in that the electrode surface of the electrode is arranged on the transparent substrate which is joined to the end face of the optical fiber which has been beveled, and the non-absorbing component is reflected from the electrode surface and separated into the second path.

5. The aforementioned separation unit is The optical device according to claim 3, wherein the electrode surface of the electrode is arranged on the transparent substrate to which the end face of the optical fiber is joined in a state where it is positioned obliquely to the end face which the end face of the optical fiber is polished perpendicularly, and the non-absorbing component is reflected from the electrode surface and separated into the second path.

6. The aforementioned separation unit is The optical device according to claim 2, characterized in that an anti-reflective portion is formed on the electrode surface of the electrode, wherein the non-absorbing component passes through the anti-reflective portion and is separated into the second path.

7. The anti-reflective portion is The optical device according to claim 6, characterized in that an opening is formed in the center of the electrode surface, and the non-absorbent component passes through the opening and is separated into the second path.

8. The anti-reflective portion is The optical device according to claim 6, characterized in that the electrode material of the electrode is a transparent electrode that transmits infrared light, and the non-absorbing component passes through the transparent electrode and is separated into the second path.

9. An optical receiver comprising a back-incident optical device that receives incident light from multiple cores arranged in an optical fiber by butt-joint optical coupling, wherein The optical device is A first path through which incident light from the plurality of cores is incident, A light-receiving unit that absorbs incident light entering from the first path, A separation unit separates the unabsorbed component of the incident light that was not absorbed by the light-receiving unit into a second path different from the first path, An optical receiver characterized by having the following features.

10. An optical transceiver comprising an optical receiver equipped with a back-incident optical device that receives incident light from a plurality of cores arranged in a first optical fiber by butt-joint optical coupling with the plurality of cores, and an optical transmitter that optically connects to a second optical fiber, The optical device is A first path through which incident light from the plurality of cores is incident, A light-receiving unit that absorbs incident light entering from the first path, A separation unit separates the unabsorbed component of the incident light that was not absorbed by the light-receiving unit into a second path different from the first path, An optical transceiver characterized by having the following features.

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