WO2011125460A1

WO2011125460A1 - Optical transmitter/receiver

Info

Publication number: WO2011125460A1
Application number: PCT/JP2011/056560
Authority: WO
Inventors: 前多泰成; 鈴木誠; 神戸聡
Original assignee: 株式会社Ｑｄレーザ
Priority date: 2010-04-08
Filing date: 2011-03-18
Publication date: 2011-10-13
Also published as: JP2011221249A; TW201144884A

Abstract

Disclosed is an optical transmitter/receiver which is provided with: a first photodiode (16) which receives receiving light outputted from an optical fiber (20); a second photodiode (17) which has a light receiving surface (42b) that forms the same plane as the light receiving surface (42a) of the first photodiode (16); a laser diode (14) which outputs, toward the first photodiode (16) and the second photodiode (17), transmitting light inputted to the optical fiber (20); and a thin film (18), which is provided on the light receiving surface (42a) of the first photodiode (16), reflects, toward the optical fiber (20), some of the transmitting light outputted from the laser diode (14), and which passes through the receiving light outputted from the optical fiber (20). The second photodiode (17) receives some of other transmitting light outputted from the laser diode (14).

Description

Optical transceiver

The present invention relates to an optical transceiver.

In recent years, an optical transceiver used for single-fiber bidirectional optical communication has been actively developed. For example, a BIDI (bi-directional) optical transceiver module is known. The BIDI type optical transmission / reception module has a structure in which a transmission TO-CAN, a reception TO-CAN, and a wavelength branching filter are individually mounted in a casing. For this reason, the BIDI type optical transceiver module has a large number of parts.

An optical transceiver module in which a laser diode, a photodiode, and a wavelength branching filter are mounted in one TO-CAN is known as an optical transceiver module with a reduced number of parts compared to a BIDI optical transceiver module (for example, Non-Patent Document 1). According to the optical transceiver module having this structure, two TO-CANs and lenses required for the BIDI optical transceiver module can be reduced to one.

Since the laser diode has temperature characteristics, a part of the light emitted by the laser diode is received by the monitoring photodiode so that the light output of the laser diode becomes constant even when the temperature changes, and is fed back to the drive current. The method of applying is known. For example, as in an optical transceiver module according to Non-Patent Document 1, in addition to a photodiode that receives received light emitted from an optical fiber, a monitor for monitoring the optical output of the laser diode on the back side of the laser diode A photodiode is provided.

The optical transmission / reception module according to Non-Patent Document 1 includes a wavelength branch filter and a monitoring photodiode in addition to the laser diode and the photodiode. The wavelength branching filter is disposed on the front side of the laser diode and above the photodiode, and the monitoring photodiode is disposed on the back side of the laser diode. When such a wavelength branching filter and a monitoring photodiode are provided, a region for mounting these is required, and the number of components increases. Therefore, it is difficult to reduce the size and cost of the optical transceiver module according to Non-Patent Document 1.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical transmission / reception apparatus capable of realizing downsizing and cost reduction.

The present invention includes a first photodiode that receives received light emitted from an optical fiber, a second photodiode having a light receiving surface that forms the same surface as the light receiving surface of the first photodiode, A laser diode that emits transmission light incident on the optical fiber toward the first photodiode and the second photodiode; and a laser diode provided on a light-receiving surface of the first photodiode; A thin film that reflects a part of the transmitted light emitted toward the optical fiber and transmits the received light emitted from the optical fiber, wherein the second photodiode is the laser diode It receives the other part of the transmission light emitted by the optical transmission / reception apparatus. According to the present invention, it is possible to realize downsizing and cost reduction of an optical transmission / reception apparatus capable of single-fiber bidirectional optical communication and monitoring the optical output of a laser diode.

In the above structure, the first photodiode and the second photodiode can be formed on the same substrate. According to this configuration, since the first photodiode and the second photodiode can be manufactured at the same time, the cost can be further reduced.

In the above configuration, the thin film provided on the light receiving surface of the first photodiode may be disposed on the optical axis of the transmission light emitted from the laser diode. According to this configuration, most of the transmission light emitted from the laser diode can be reflected by the thin film and incident on the optical fiber.

In the above configuration, the first photodiode may be disposed on the optical axis of the optical fiber. According to this configuration, the reception light emitted from the optical fiber can be efficiently received by the first photodiode.

In the above-described configuration, the optical axis of the transmission light reflected by the thin film and the optical axis of the optical fiber can coincide with each other. According to this configuration, the transmission light emitted from the laser diode can be efficiently incident on the optical fiber.

In the above configuration, the laser diode is provided on a plane perpendicular to the optical axis of the optical fiber, and the first photodiode and the second photodiode are optical axes of the optical fiber. It can be set as the structure provided on the surface inclined with respect to. According to this configuration, the laser diode, the first photodiode, and the second photodiode can be easily mounted.

In the above configuration, the optical axis of the transmission light emitted from the laser diode and the optical axis of the reception light emitted from the optical fiber may intersect at an acute angle. According to this configuration, it is possible to improve the light receiving efficiency of the received light emitted from the optical fiber by the first photodiode.

According to the present invention, it is possible to realize downsizing and cost reduction of an optical transmission / reception apparatus capable of single-fiber bidirectional optical communication and monitoring the optical output of the LD.

FIG. 1A is an example of a schematic top view of the optical transceiver according to the first embodiment, and FIG. 1B is an example of a schematic cross-sectional view taken along the line AA in FIG. FIG. 2 is an example of a schematic top view of the first photodiode and the second photodiode. 3A is an example of the light intensity distribution of the transmission light, and FIG. 3B is an example of the light intensity distribution of the reception light. FIG. 3C is an example of the light intensity distribution of the transmission light incident on the light receiving surface of the second photodiode. 4A is an example of a schematic top view of the first photodiode and the second photodiode, and FIG. 4B is a schematic cross-sectional view taken along the line AA in FIG. 4A. It is an example. FIG. 5 is a simulation result illustrating the optical characteristics of the thin film provided on the light receiving surface of the first photodiode. FIG. 6 is an example of a conceptual diagram illustrating propagation of transmission / reception light by the optical transmission / reception apparatus according to the first embodiment. FIG. 7A is an example of a schematic top view of the optical transceiver according to the second embodiment, and FIG. 7B is an example of a schematic cross-sectional view taken along line AA in FIG.

Hereinafter, an optical transceiver employing a CAN package as an embodiment of the optical transceiver according to the present invention will be described with reference to the drawings.

FIG. 1A is an example of a schematic top view of the optical transceiver 100 according to the first embodiment, and FIG. 1B is an example of a schematic cross-sectional view taken along a line AA in FIG. 1A is a schematic top view of the thin film 18, the cap 24, the glass ball lens 22, and the sealing glass 46 seen through. As shown in FIGS. 1A and 1B, the optical transceiver 100 mainly includes a stem 12, a laser diode (hereinafter referred to as an LD) 14, a first photodiode (hereinafter referred to as a first PD). 16), a second photodiode (hereinafter referred to as second PD) 17, a thin film 18, a glass ball lens 22, and a cap 24.

The stem 12 is made of, for example, an iron-based alloy such as ordinary steel (SPCC), and has a columnar base portion 26 and a projection portion 30 protruding in the vertical direction on the reference surface 28 of the base portion 26. The reference plane 28 is a plane perpendicular to the optical axis of the optical fiber 20, and the distance to the LD 14, the first PD 16, and the glass ball lens 22 is set based on this plane. At the tip of the projecting portion 30, there are a surface parallel to the reference surface 28 (hereinafter referred to as the first mounting surface 32) and an inclined surface (hereinafter referred to as the second mounting surface 34). The second mounting surface 34 has an inclination of, for example, 45 ° with respect to the first mounting surface 32. A lead pin 36 is fixedly attached to the stem 12 via an insulator 38 such as glass. For example, four lead pins 36 are provided, one of which is connected to the LD 14 by a wire 39, the other two are connected to the first PD 16 and the second PD 17, respectively, and the other one is connected to the ground. It is connected. In FIG. 1A, illustration of the lead pins connected to the ground is omitted. Further, the number of lead pins 36 is not limited to four, and may be other numbers such as five.

The LD 14 is mounted on a heat sink 40 made of, for example, aluminum nitride (AlN). The heat sink 40 on which the LD 14 is mounted is mounted on the first mounting surface 32 at the tip of the protrusion 30. The first PD 16 and the second PD 17 are mounted on the second mounting surface 34 at the tip of the protrusion 30. Thereby, the light receiving surface 42a of the first PD 16 and the light receiving surface 42b of the second PD 17 are arranged to be inclined by 45 ° with respect to the optical axis of the LD 14. The thin film 18 is coated on the first PD 16 so as to include the light receiving surface 42a.

The LD 14 is, for example, a quantum well laser. The LD 14 emits transmission light toward the first PD 16 and the second PD 17. A part of the transmission light emitted from the LD 14 is reflected to the optical fiber 20 side by the thin film 18 coated on the first PD 16. The transmission light reflected by the thin film 18 is collected by the glass ball lens 22 and enters the optical fiber 20. Another part of the transmission light emitted from the LD 14 is incident on the light receiving surface 42b of the second PD 17. Also, the received light emitted from the optical fiber 20 is collected by the glass ball lens 22, passes through the thin film 18, and enters the light receiving surface 42 a of the first PD 16. Thus, the thin film 18 functions as a high reflection film for the transmission light emitted from the LD 14 and functions as a low reflection film for the reception light emitted from the optical fiber 20.

Here, the first PD 16 and the second PD 17 will be described with reference to FIG. FIG. 2 is an example of a schematic top view of the first PD 16 and the second PD 17. As shown in FIG. 2, the first PD 16 and the second PD 17 are disposed adjacent to each other, and the light receiving surface 42a of the first PD 16 and the light receiving surface 42b of the second PD 17 form the same surface. The thin film 18 is provided on the first PD 16 so as to include the light receiving surface 42a. On the other hand, the thin film 18 is not provided on the second PD 17. For example, the first PD 16 is a rectangle of 500 μm × 350 μm, and the second PD 17 is a rectangle of 500 μm × 150 μm.

Next, the light intensity distribution between the transmitted light and the received light when entering the first PD 16 and the second PD 17 will be described with reference to FIGS. 3 (a) and 3 (b). 3A is an example of the light intensity distribution of the transmitted light between AA in FIG. 2, and FIG. 3B is an example of the light intensity distribution of the received light between AA in FIG. is there. FIG. 3C is an example of the light intensity distribution of the transmission light incident on the light receiving surface 42b of the second PD 17. The horizontal axis in FIGS. 3A to 3C is the distance (mm) from the center when the center between AA is 0, and the vertical axis is the relative intensity. That is, when the horizontal axis is between −0.1 mm and 0.25 mm, the first PD 16 is used, and when the horizontal axis is between −0.25 mm and −0.1 mm, the second PD 17 is used.

As shown in FIG. 3A, the transmission light emitted from the LD 14 is incident on a wide area over the first PD 16 and the second PD 17. This is because the transmission light emitted from the LD 14 has a certain degree of spread angle. For example, the transmission light emitted from the LD 14 has a full angle at half maximum and a divergence angle of 40 ° in the vertical direction and 20 ° in the horizontal direction.

On the other hand, the received light emitted from the optical fiber 20 is locally incident on the first PD 16 as shown in FIG. This is because the received light emitted from the optical fiber 20 has a small NA (numerical aperture). For example, the NA of the received light emitted from the optical fiber 20 is 0.16.

As described above, the thin film 18 functions as a high reflection film for transmission light emitted from the LD 14 and functions as a low reflection film for reception light emitted from the optical fiber 20. For this reason, as shown in FIG. 2, by providing the thin film 18 on the first PD 16 so as to include the light receiving surface 42a, the received light emitted from the optical fiber 20 is transmitted through the thin film 18 and the light receiving surface 42a of the first PD 16. A part of the transmitted light emitted from the LD 14 can be reflected by the thin film 18 to the optical fiber 20 side.

Further, since the thin film 18 is not provided on the second PD 17, another part of the transmission light emitted from the LD 14 is incident on the light receiving surface 42b of the second PD 17 (see FIG. 3C). For this reason, another part of the transmission light emitted from the LD 14 can be received by the light receiving surface 42b of the second PD 17. Since the transmission light incident on the light receiving surface 42b of the second PD 17 is in the far field region, even if the thin film 18 is provided on the second PD 17, it is reflected by the thin film 18 and enters the optical fiber 20. Not what you get. Therefore, even if a part of transmission light is received by the light receiving surface 42b without providing the thin film 18 on the second PD 17, it does not cause a decrease in coupling efficiency during transmission.

Thus, the light receiving surface 42a of the first PD 16 and the light receiving surface 42b of the second PD 17 are arranged adjacent to each other so as to form the same surface, the thin film 18 is provided on the light receiving surface 42a, and the thin film is formed on the light receiving surface 42b. By adopting a structure in which 18 is not provided, a part of the transmission light can be incident on the optical fiber 20 and another part of the transmission light can be received by the light receiving surface 42b of the second PD 17, and the received light can be received by the light receiving surface of the first PD 16. 42a can receive light. In order to easily obtain such an effect, the light receiving surface 42a of the first PD 16 and the light receiving surface 42b of the second PD 17 are arranged adjacent to each other in the wide direction in the FFP (Far Field Pattern) of the transmission light emitted from the LD 14. It is preferable.

1 (a) and 1 (b), the light receiving surface 42a of the first PD 16 is disposed on the optical axis of the optical fiber 20, and is disposed on the optical axis of the transmission light emitted from the LD 14. That is, the thin film 18 provided on the light receiving surface 42a of the first PD 16 is disposed on the optical axis of the transmission light emitted from the LD 14. The optical axis of the transmission light reflected by the thin film 18 is coincident with the optical axis of the optical fiber 20. Thereby, the transmission light emitted from the LD 14 can be efficiently incident on the optical fiber 20. Also, the received light emitted from the optical fiber 20 can be efficiently received by the first PD 16. In this case, the optical axis of the transmission light reflected by the thin film 18 and the optical axis of the reception light emitted from the optical fiber 20 also coincide with each other.

The cap 24 is made of metal, for example, and has a cylindrical shape. The upper surface 44 of the cap 24 is provided with a hole, and the glass ball lens 22 is fitted into the hole. A sealing glass 46 is provided on the upper surface 44 of the cap 24 so as to cover the hole around the glass ball lens 22, and the hole is sealed by the sealing glass 46 and the glass ball lens 22. Thereby, the LD 14, the first PD 16 and the second PD 17 can be sealed with the cap 24 and sealed by fixing the lower portion 48 of the cap 24 to the stem 12 by welding. Although the inside of the cap 24 may be filled with air, it is preferable that the cap 24 is filled with nitrogen gas for the purpose of suppressing the deterioration of the LD 14, the first PD 16 and the second PD 17.

Here, it is assumed that the optical transceiver 100 according to the first embodiment is used in an FTTH (Fiber To The Home) system. In FTTH, the wavelength band of 1.31 μm is generally used for the upstream and the wavelength band of 1.49 μm is used for the downstream. Therefore, the LD 14 of the optical transceiver 100 emits transmission light of the 1.31 μm wavelength band, The first PD 16 receives received light in the 1.49 μm wavelength band emitted from the optical fiber 20, and the second PD 17 receives transmission light in the 1.31 μm wavelength band emitted from the LD 14. Therefore, the thin film 18 coated on the first PD 16 is required to have an optical characteristic of reflecting light in the 1.31 μm wavelength band and transmitting light in the 1.49 μm wavelength band.

The LD 14 that emits transmission light having a wavelength of 1.31 μm includes, for example, a lower cladding layer made of an n-type InP layer, an active layer made of an InGaAsP-MQW (Multiple Quantum Wells) layer, and an upper cladding made of a p-type InP layer. And a quantum well laser comprising a layer.

Next, a description will be given of the first PD 16 that receives received light in the 1.49 μm wavelength band and is coated with the thin film 18 so as to include the light receiving surface 42a, and the second PD 17 that receives transmitted light in the 1.31 μm wavelength band. . FIG. 4A is an example of a schematic top view of the first PD 16 and the second PD 17, and FIG. 4B is an example of a schematic cross-sectional view taken along the line AA of FIG. 4A.

As shown in FIG. 4A, the anode electrode 76 for the first PD 16 and the anode electrode 80 for the second PD 17 are both provided on the first PD 16. The anode electrode 76 for the first PD 16 is connected to the light receiving surface 42 a of the first PD 16 via the wiring 78. The anode electrode 80 for the second PD 17 is connected to the light receiving surface 42 b of the second PD 17 via the wiring 79. For example, a transimpedance amplifier (TIA) is connected to the anode electrode 76 via a wire. The transimpedance amplifier converts the current generated when the first PD 16 receives the reception light emitted from the optical fiber 20 into a voltage. For example, an APC (Auto Power Control) circuit is connected to the anode electrode 80 via a wire. The APC circuit applies feedback to the drive current of the LD 14 based on the detected light output in order to keep the light output of the LD 14 constant.

As shown in FIG. 4B, the first PD 16 and the second PD 17 are formed on the same substrate 56. The substrate 56 is, for example, an n-type InP substrate. An n-type InP buffer layer 58 and an n-type InGaAs layer 60 are sequentially formed on the substrate 56. A cathode electrode 77 is provided on the back surface of the substrate 56. The n-type InP buffer layer 58, the n-type InGaAs layer 60, and the cathode electrode 77 are common to the first PD 16 and the second PD 17.

In the first PD 16, a p-type region 64 in which p-type carriers are introduced into n-type InP is formed on the n-type InGaAs layer 60, and a pn junction 66 is formed between the n-type InGaAs layer 60 and the p-type region 64. Is done. A diffusion blocking region 68 is formed around the p-type region 64. The thin film 18 that is a multilayer film is coated so as to cover the upper surface of the p-type region 64 that is the light receiving surface 42a.

In the second PD 17, a p-type region 64 in which p-type carriers are introduced into n-type InP is formed on the n-type InGaAs layer 60, and a pn junction 66 is formed between the n-type InGaAs layer 60 and the p-type region 64. Is done. A diffusion blocking region 68 is formed around the p-type region 64. The first PD 16 and the second PD 17 are separated from each other by the diffusion blocking region 68. The thin film 18 is not provided on the upper surface of the p-type region 64 that is the light receiving surface 42b.

The first PD 16 and the second PD 17 are simultaneously manufactured in the same process. For this reason, the upper surface of the p-type region 64 of the first PD 16 and the upper surface of the p-type region 64 of the second PD 17 form the same plane. Therefore, the light receiving surface 42a of the first PD 16 and the light receiving surface 42b of the second PD 17 form the same plane.

Table 1 is an example of the structure of the thin film 18 which is a multilayer film, and shows the material, film thickness, and refractive index of each layer of the multilayer film. As shown in Table 1, the thin film 18 has a structure in which, for example, a silicon layer (Si layer) and a silicon oxide layer (SiO ₂ layer) are repeatedly provided on an aluminum oxide layer (Al ₂ O ₃ layer). Specifically, a silicon layer having a thickness of 53.5 nm and a refractive index of 3.56 is formed on an aluminum oxide layer having a thickness of 58.0 nm and a refractive index of 1.58, and a refractive index of 1.45 having a thickness of 348.0 nm. A silicon oxide layer, a silicon layer having a thickness of 36.9 nm and a refractive index of 3.56, and a silicon oxide layer having a thickness of 182.3 nm and a refractive index of 1.45 are sequentially stacked. Further thereon, a silicon layer having a thickness of 73.7 nm and a refractive index of 3.56 and a silicon oxide layer having a thickness of 182.3 nm and a refractive index of 1.45 are repeatedly formed five times. As the uppermost layer, a silicon layer having a thickness of 36.9 nm and a refractive index of 3.56 is formed.

FIG. 5 shows the reflection characteristics of the thin film 18 when the thin film 18 having the structure shown in Table 1 is formed on a GaAs substrate having a refractive index of 3.42 and light is incident on the thin film 18 at an incident angle of 45 °. It is the simulation result which calculated the transmission characteristic and the loss characteristic. The horizontal axis of FIG. 5 represents the wavelength (nm) of light incident on the thin film 18, and the vertical axis represents the light reflectance (%), transmittance (%), and loss rate (%). As shown in FIG. 5, the reflection characteristics and transmission characteristics of the thin film 18 depend on the wavelength. The thin film 18 functions as a high-reflection film that reflects light with a high reflectance with respect to light in the 1300 nm wavelength band, and as a low-reflection film that transmits light with high transmittance without substantially reflecting with respect to light in the 1500 nm wavelength band. Function. Regarding the loss characteristics, it is 0% in the wavelength band of 1150 nm to 1650 nm. As described above, the thin film 18 having the structure shown in Table 1 functions as a highly reflective film with respect to the 1.31 μm wavelength band transmission light emitted from the LD 14 and has a 1.49 μm wavelength band emitted from the optical fiber 20. It functions as a low reflection film for received light.

FIG. 6 is an example of a conceptual diagram illustrating light transmission / reception when the optical transmission / reception apparatus 100 according to the first embodiment is used in an FTTH system. For the purpose of clarifying the figure, the optical axis of the transmission light and the optical axis of the reception light are shifted from each other, but in reality, the optical axis of the transmission light and the optical axis of the reception light coincide with each other. . The optical transmitter / receiver 100 according to the first embodiment receives the LD 14 that emits transmission light having a wavelength of 1.31 μm, the first PD 16 that receives reception light having a wavelength of 1.49 μm, and the transmission light having a wavelength of 1.31 μm. And the thin film 18 having the structure shown in Table 1 on the light receiving surface 42a of the first PD 16. As shown in FIG. 6, a part of the 1.31 μm wavelength transmission light emitted from the LD 14 is reflected by the thin film 18 coated on the first PD 16, collected by the glass ball lens 22, and then the optical fiber 20. Is incident on. Further, the other part of the 1.31 μm wavelength transmission light emitted from the LD 14 is incident on the light receiving surface 42 b of the second PD 17. On the other hand, the 1.49 μm wavelength received light emitted from the optical fiber 20 is collected by the glass ball lens 22, passes through the thin film 18, and enters the light receiving surface 42 a of the first PD 16.

As described above, according to the optical transceiver 100 according to the first embodiment, as shown in FIGS. 1 and 6, the LD 14 transmits toward the light receiving surface 42 a of the first PD 16 and the light receiving surface 42 b of the second PD 17. Emits light. The thin film 18 is provided on the light receiving surface 42 a of the first PD 16. The thin film 18 functions as a highly reflective film for transmission light emitted from the LD 14. For this reason, the thin film 18 reflects part of the transmission light emitted from the LD 14 toward the optical fiber 20. Further, the thin film 18 functions as a low reflection film for the received light emitted from the optical fiber 20. For this reason, the thin film 18 transmits the received light emitted from the optical fiber 20. Thereby, a part of the transmission light emitted from the LD 14 is made incident on the optical fiber 20, and the reception light emitted from the optical fiber 20 can be received by the first PD 16. Therefore, single-fiber bidirectional optical communication is possible without separately mounting the wavelength branching filter.

Further, the light receiving surface 42b of the second PD 17 forms the same surface as the light receiving surface 42a of the first PD 16. And the thin film 18 is not provided in the light-receiving surface 42b of 2nd PD17. For this reason, as explained in FIG. 3C, the second PD 17 can receive a part of the transmission light emitted from the LD. Thereby, the second PD 17 can monitor the light output of the LD 14. Further, since the light receiving surface 42b of the second PD 17 forms the same surface as the light receiving surface 42a of the first PD 16, the first PD 16 and the second PD 17 can be provided in the direction in which the LD 14 emits transmission light. Compared to the structure described in No. 1, the size can be reduced.

As described above, according to the optical transmission / reception device 100 according to the first embodiment, it is possible to reduce the size and the cost of the optical transmission / reception device capable of performing one-fiber bidirectional optical communication and monitoring the optical output of the LD. It can be realized.

Further, as shown in FIG. 4B, the first PD 16 and the second PD 17 are formed on the same substrate 56. Thereby, since 1st PD16 and 2nd PD17 can be manufactured simultaneously, cost reduction can be implement | achieved more.

As shown in FIGS. 1 and 6, the thin film 18 provided on the light receiving surface 42 a of the first PD 16 is preferably disposed on the optical axis of the transmission light emitted from the LD 14. Thereby, most of the transmission light emitted from the LD 14 can be reflected by the thin film 18 and incident on the optical fiber 20.

As shown in FIGS. 1 and 6, the first PD 16 is preferably disposed on the optical axis of the optical fiber 20. Thereby, the received light emitted from the optical fiber 20 can be efficiently received by the first PD 16. Further, it is preferable that the optical axis of the transmission light reflected by the thin film 18 and the optical axis of the optical fiber 20 coincide with each other. Thereby, the transmission light emitted from the LD 14 can be efficiently incident on the optical fiber 20.

As shown in FIG. 1, the LD 14 is provided on a first mounting surface 32 that is a surface perpendicular to the optical axis of the optical fiber 20, and the first PD 16 and the second PD 17 are arranged on the optical axis of the optical fiber 20. It is provided on the second mounting surface 34 that is a surface inclined obliquely. The LD 14 is mounted on the first mounting surface 32 perpendicular to the optical axis of the optical fiber 20, and the first PD 16 and the second PD 17 are mounted on the second mounting surface 34 inclined obliquely with respect to the optical axis of the optical fiber 20. This can be easily implemented as compared with the case where the LD 14 and the first PD 16 and the second PD 17 are mounted on a surface inclined obliquely with respect to the optical axis of the optical fiber 20 as in Example 2 described later. Further, the stem 12 having a structure in which the reference surface 28 and the first mounting surface 32 are parallel to each other and only the second mounting surface 34 is inclined is manufactured more easily than in the case of Example 2 described later. be able to.

In Example 1, the thin film 18 is shown as an example of a multilayer film of an aluminum oxide layer, a silicon layer, and a silicon oxide layer having a structure as shown in Table 1. However, the present invention is not limited to this. As long as it is a thin film having the property of reflecting the transmission light emitted from the LD 14 and transmitting the reception light emitted from the optical fiber 20, it may be made of other film structures or materials. In particular, when the optical transceiver 100 according to the first embodiment is used in the FTTH system, the thin film 18 reflects the transmission light of the wavelength band of 1.31 μm emitted from the LD 14 and emits the 1.49 μm of light emitted from the optical fiber 20. The case where it has the optical characteristic which permeate | transmits the received light of a wavelength band is preferable. In the FTTH system, the wavelength band of 1.31 μm is used for the upstream and the wavelength band of 1.55 μm is used for the downstream, the wavelength band of 1.49 μm or 1.55 μm is used for the upstream, and the wavelength of 1.31 μm is used for the downstream. A band may be used. Accordingly, the thin film 18 has an optical characteristic of reflecting the transmission light in the wavelength band of 1.31 μm and transmitting the reception light in the wavelength band of 1.55 μm, or transmitting in the wavelength band of 1.49 μm or 1.55 μm. It may have an optical characteristic of reflecting light and transmitting received light having a wavelength band of 1.31 μm.

In order to monitor the optical output of the LD 14, it is preferable that the second PD 17 receives an optical output of about 5% with respect to the total output of the transmission light emitted by the LD 14. Therefore, it is preferable that the positions of the first PD 16 and the second PD 17 are determined with respect to the optical axis emitted from the LD 14 so that about 5% of the transmission light emitted from the LD 14 is incident on the second PD 17.

Although the case where the LD 14 is a quantum well laser has been described as an example, the LD 14 may be another semiconductor laser such as a quantum dot laser. Further, it may be a DFB (Distributed Feedback) type laser or a Fabry-Perot type laser.

For example, a protective film is preferably provided on the second PD 17 so as to include the light receiving surface 42b. It is preferable that the protective film has an optical characteristic that becomes a low reflection film with respect to the transmission light emitted from the LD 14 so that the second PD 17 can receive the transmission light emitted from the LD 14.

The case where the light receiving surface 42a of the first PD 16 is inclined 45 ° with respect to the optical axis of the LD 14 is illustrated as an example because the second mounting surface 34 is inclined 45 ° with respect to the first mounting surface 32. In this case, the optical axis of the transmission light reflected by the thin film 18 coated on the light receiving surface 42a can be matched with the optical axis of the optical fiber 20, and the transmission light emitted from the LD 14 is efficiently transmitted to the optical fiber 20. It can be made incident. However, the inclination is not limited to 45 °, and the transmission light emitted from the LD 14 may have another inclination within a range in which the transmission light is reflected by the thin film 18 and is incident on the optical fiber 20. For example, the inclination may be within a range of 30 ° to 60 °.

FIG. 7A is an example of a schematic top view of the optical transceiver 200 according to the second embodiment, and FIG. 7B is an example of a schematic cross-sectional view taken along line AA in FIG. 7A. 7A is a schematic top view of the thin film 18, the cap 24, the glass ball lens 22, and the sealing glass 46 seen through. As shown in FIGS. 7A and 7B, the tip of the protrusion 30 of the stem 12 has a dogleg shape and is a third surface that is inclined obliquely with respect to the reference surface 28. A mounting surface 82 and a fourth mounting surface 84 are provided. That is, the third mounting surface 82 and the fourth mounting surface 84 are surfaces inclined obliquely with respect to the optical axis of the optical fiber 20. Both the third mounting surface 82 and the fourth mounting surface 84 have an inclination of, for example, 30 ° with respect to the reference surface 28.

The heat sink 40 on which the LD 14 is mounted is mounted on the third mounting surface 82 at the tip of the protrusion 30. As a result, the angle θ between the optical axis of the transmission light emitted from the LD 14 and the optical axis of the reception light emitted from the optical fiber 20 is an acute angle of 60 °. The first PD 16 and the second PD 17 are mounted on the fourth mounting surface 84 of the protrusion 30. Thereby, the light receiving surface 42a of the first PD 16 and the light receiving surface 42b of the second PD 17 are arranged obliquely with respect to the optical axis of the LD 14. The other configuration is the same as that of the first embodiment and is shown in FIG.

As described above, according to the optical transmission / reception device 200 according to the second embodiment, the LD 14 is inclined with respect to the optical axis of the optical fiber 20 as illustrated in FIGS. 7A and 7B. The optical axis of the transmission light emitted from the LD 14 and the optical axis of the reception light emitted from the optical fiber 20 intersect each other at an acute angle. As a result, the light receiving surface 42a of the first PD 16 is closer to being perpendicular to the optical axis of the optical fiber 20 than in the first embodiment. Therefore, the received light emitted from the optical fiber 20 is easily transmitted through the thin film 18 provided on the light receiving surface 42a of the first PD 16, and the intensity of the received light incident on the light receiving surface 42a is increased. That is, the light receiving efficiency of the received light by the first PD 16 is improved.

In the second embodiment, the case where the third mounting surface 82 and the fourth mounting surface 84 are inclined by 30 ° with respect to the reference surface 28 is shown as an example, but the present invention is not limited to this case. The transmission light emitted from the LD 14 may be reflected by the thin film 18 and have another inclination within a range where it is incident on the optical fiber 20. In particular, when the optical axis of the transmission light reflected by the thin film 18 and the optical axis of the optical fiber 20 are matched, the angle of the third mounting surface 82 with respect to the reference surface 28 increases, and the optical axis of the transmission light emitted from the LD 14 And the angle θ of the fourth mounting surface 84 with respect to the reference surface 28 is reduced as the angle θ formed between the optical axis of the received light emitted from the optical fiber 20 and the light receiving surface 42a of the first PD 16 is reduced. Must be close to perpendicular to the axis. In this case, the light receiving efficiency of the received light by the first PD 16 is improved. Therefore, it is preferable that the inclination of the third mounting surface 82 with respect to the reference surface 28 is large and the inclination of the fourth mounting surface 84 is small.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to such specific embodiments, and various modifications can be made within the scope of the gist of the present invention described in the claims.・ Change is possible.

Claims

A first photodiode that receives received light emitted from the optical fiber;
A second photodiode having a light receiving surface forming the same surface as the light receiving surface of the first photodiode;
A laser diode that emits transmission light incident on the optical fiber toward the first photodiode and the second photodiode;
Provided on the light receiving surface of the first photodiode, reflects a part of the transmission light emitted by the laser diode toward the optical fiber, and transmits the reception light emitted from the optical fiber. A thin film,
The second photodiode receives an other part of the transmission light emitted from the laser diode.
The optical transceiver according to claim 1, wherein the first photodiode and the second photodiode are formed on the same substrate.
3. The optical transmission / reception according to claim 1, wherein the thin film provided on the light receiving surface of the first photodiode is disposed on an optical axis of the transmission light emitted from the laser diode. apparatus.
The optical transmission / reception apparatus according to claim 3, wherein the first photodiode is disposed on an optical axis of the optical fiber.
The optical transceiver according to claim 4, wherein an optical axis of the transmission light reflected by the thin film coincides with an optical axis of the optical fiber.
The laser diode is provided on a plane perpendicular to the optical axis of the optical fiber, and the first photodiode and the second photodiode are inclined with respect to the optical axis of the optical fiber. The optical transmission / reception apparatus according to claim 1, wherein the optical transmission / reception apparatus is provided on a surface inclined toward the surface.
6. The optical transmission / reception according to claim 1, wherein an optical axis of the transmission light emitted from the laser diode and an optical axis of the reception light emitted from the optical fiber intersect at an acute angle. apparatus.