Coaxial single-fiber bidirectional optical transceiver

Abstract

The utility model discloses a coaxial single-fiber bidirectional optical transceiver device, which comprises an optical fiber, a light source chip, a filter plate and an optical detector, and the optical fiber, the light source chip, the filter plate and the optical detector are arranged on the same optical axis in sequence from right to left or from left to right. According to the utility model, a 45-degree optical filter in the traditional BOSA is abandoned, the optical detector is directly arranged behind the light source chip with the wavelength division multiplexing function, and a coaxial layout mode is adopted, so that the size of the single-fiber bidirectional optical transceiver device can be further reduced, and the miniaturization and low-cost packaging of the single-fiber bidirectional optical transceiver assembly are realized.

Description

Technical Field

[0001] The utility model relates to the technical field of optical fibers, in particular to a coaxial single-fiber bidirectional optical transceiver device. Background Art

[0002] In recent years, the emergence of various new applications such as live video broadcasting, online classes, virtual reality, and cloud games has put forward higher requirements on the bandwidth, latency, jitter, and stability of existing networks, pushing the fiber optic network closer to the user side. From fiber to the home (FTTH) to fiber to the room (FTTR), while the fiber optic access network and the optical device products behind it are becoming more and more deeply integrated into the daily lives of ordinary people, they are also facing greater pressure on cost reduction and miniaturization on the user side.

[0003] The Bi-directional Optical Sub-Assembly (BOSA) is the core device of the optical fiber access network. It is an optoelectronic conversion device that integrates reception and transmission, and can realize bidirectional transmission of data on a single optical fiber. The traditional BOSA generally includes optical fiber, laser, optical detector, filter, lens and related fixings, and its layout is as follows: Figure 1 As shown, a 45° filter is set between the laser and the optical fiber. The uplink light λ1 emitted from the laser will pass through the 45° filter and enter the optical fiber, while the downlink light λ2 from the optical fiber will be deflected 90° by the 45° filter and then emitted to the light detector located above.

[0004] The key to BOSA's bidirectional transmission and reception is the 45° filter set at the front end of the laser. The filter changes the propagation direction of the downlink light λ2 without changing the propagation direction of the uplink light λ1, thereby separating the transmission and reception paths so that the two can be processed independently. However, the presence of the filter will increase the distance from the optical fiber to the laser and from the optical fiber to the photodetector. The orthogonal dual optical path layout also requires that the lateral width of the BOSA must be expanded to accommodate related components. All of these will result in a larger overall size of the device, so it needs to be improved. Utility Model Content

[0005] The purpose of the utility model is to provide a coaxial single-fiber bidirectional optical transceiver device, which abandons the 45° filter in the traditional BOSA, places the light detector directly behind the light source chip including the wavelength division multiplexing function, and adopts a coaxial layout. The size of the single-fiber bidirectional optical transceiver device can be further reduced, and the miniaturization and low-cost packaging of the single-fiber bidirectional optical transceiver component can be achieved.

[0006] In order to achieve the above purpose, the following technical solutions are adopted:

[0007] A coaxial single-fiber bidirectional optical transceiver device comprises an optical fiber, a light source chip, a filter, and a light detector, wherein the optical fiber, the light source chip, the filter, and the light detector are arranged in sequence from right to left or from left to right on the same optical axis;

[0008] The light source chip includes a semiconductor laser or an optical waveguide including a semiconductor laser; the semiconductor laser is used to generate an uplink light λ1, which is emitted from one end of the light source chip and fed into an optical fiber to enter an external optical communication network; the optical fiber is used to output a downlink light λ2, which enters the light source chip from one end of the light source chip and is emitted from the other end of the light source chip, then passes through a filter and enters a light detector to complete photoelectric conversion;

[0009] The filter is a band-stop filter for the uplink light λ1 and a band-pass filter for the downlink light λ2.

[0010] Furthermore, the wavelength of the uplink light λ1 is between 1260nm and 1360nm, and the wavelength of the downlink light λ2 is between 1480nm and 1580nm; and the angle between the normal direction of the filter surface and the optical axis is less than 15°.

[0011] Furthermore, one end of the light source chip close to the filter is coated with a first dielectric film, and the first dielectric film is an anti-reflection film for the downlink light λ2 and an anti-reflection film for the uplink light λ1; one end of the light source chip close to the optical fiber is coated with a second dielectric film, and the second dielectric film is an anti-reflection film for both the uplink light λ1 and the downlink light λ2.

[0012] Furthermore, a distributed Bragg grating structure is fabricated on the semiconductor laser.

[0013] Furthermore, the light source chip includes a first section of optical waveguide having a distributed Bragg grating structure, and the Bragg central wavelength λ corresponding to the Bragg grating structure on the first section of optical waveguide is B The wavelength interval between the uplink light λ1 and the downlink light λ2 is less than 3 nm. When the downlink light λ2 propagates in the light source chip, it passes through the first section of optical waveguide.

[0014] Furthermore, the light source chip includes a second section of optical waveguide, the second section of optical waveguide contains a distributed Bragg grating structure; the Bragg central wavelength λ corresponding to the Bragg grating structure of the second section of optical waveguide B The wavelength interval with the uplink light λ1 is less than 3nm, and the downlink light λ2 needs to pass through the second section of optical waveguide when propagating on the light source chip; the second section of optical waveguide includes an intrinsic active core layer, and the intrinsic active core layer is the gain medium of the uplink light λ1 when current is injected.

[0015] Furthermore, the light source chip also includes an on-chip photodetector; the on-chip photodetector is used to monitor the working state of the semiconductor laser on the light source chip.

[0016] Furthermore, the on-chip photodetector uses the same active layer epitaxial material as the semiconductor laser.

[0017] Furthermore, the on-chip photodetector is a waveguide-type photodetector, and when the downlink light λ2 propagates on the light source chip, it needs to pass through the main waveguide of the on-chip photodetector.

[0018] Furthermore, the light source chip includes a wavelength division multiplexing element; the wavelength division multiplexing element includes port a, port b, and port c; the uplink light λ1 enters the wavelength division multiplexing element through port a and is output from port b in the direction of the optical fiber; after the downlink light λ2 is coupled into the light source chip, it enters the wavelength division multiplexing element through port b and is output from port c in the direction of the filter.

[0019] By adopting the above scheme, the beneficial effects of the utility model are:

[0020] 1) The utility model requires that the downlink light is input from one end of the light source chip and then output from the other end face opposite thereto, so that the light detector usually placed on one side of the light source chip can be moved to the rear of the light source chip. This allows the main components such as the light source chip, filter and light detector to be coaxially arranged in the present application, keeping the light transmission and receiving paths consistent, and achieving a smaller radial size.

[0021] 2) In the utility model, the optical paths of the uplink light and the downlink light overlap between the light source chip and the optical fiber, and coupling elements such as lenses can be shared, which creates conditions for the single package (such as single TO package) of the light source chip, filter and light detector, which is conducive to achieving a smaller device size.

[0022] 3) The utility model abandons the 45° filter of the conventional BOSA, eliminates the space occupied by it, shortens the distance between the optical fiber and the light source chip, and allows the optical fiber end face to be closer to the light-emitting surface of the light source chip, which is conducive to achieving more effective optical coupling. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of a conventional single-fiber bidirectional transceiver device;

[0024] Figure 2 It is a schematic diagram of the structure of the utility model;

[0025] Figure 3 It is a structural schematic diagram of the first embodiment of the utility model;

[0026] Figure 4 It is a structural schematic diagram of the second embodiment of the utility model;

[0027] Figure 5 This is a schematic diagram of a structure further improved on the basis of the second embodiment of the present utility model;

[0028] Figure 6 This is a schematic structural diagram of a third embodiment of the present utility model;

[0029] Figure 7 This is a schematic diagram of the reflection spectrum of the film system in the first embodiment of the utility model;

[0030] The accompanying drawings illustrate:

[0031] 1—photodetector; 2—filter; 3—light source chip; 4—optical fiber; 201—optical waveguide; 301—laser body; 302—first section of optical waveguide; 303—on-chip optical waveguide; 401—on-chip photodetector; 501—semiconductor laser; 502—wavelength division multiplexing element. DETAILED DESCRIPTION

[0032] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0033] Reference Figures 2 to 7 As shown, the utility model provides a coaxial single-fiber bidirectional optical transceiver device, which includes an optical fiber 4, a light source chip 3, a filter 2, and a light detector 1 in a first embodiment. The optical fiber 4, the light source chip 3, the filter 2, and the light detector 1 are arranged on the same optical axis from right to left or from left to right in sequence;

[0034] The light source chip 3 includes a semiconductor laser or an optical waveguide 201 including a semiconductor laser (the semiconductor laser is a part of the continuous optical waveguide 201); the semiconductor laser is used to generate an uplink light λ1, which is emitted from one end of the light source chip 3 and fed into the optical fiber 4 to enter the external optical communication network; the optical fiber 4 is used to output a downlink light λ2, which enters the light source chip 3 from one end of the light source chip 3, and is emitted from the other end of the light source chip 3, and then passes through the filter 2 and enters the photodetector 1 to complete the photoelectric conversion;

[0035] The filter 2 is a band-stop filter 2 for the uplink light λ1 and a band-pass filter for the downlink light λ2.

[0036] Continue to refer to Figure 2As shown, the optical fiber 4, the light source chip 3, the filter 2 and the optical detector 1 are arranged on the same optical axis from right to left in sequence, and further explained. In this embodiment, the semiconductor laser of the light source chip 3 generates an uplink light λ1, which is emitted from the right end face of the light source chip 3, coupled into the optical fiber 4 and propagated along the optical fiber 4. Part of the uplink light λ1 is also emitted from the left end face of the light source chip 3, which will be blocked by the filter 2 to avoid entering the optical detector 1 and causing interference; the downlink light λ2 from the optical fiber 4 is emitted from the optical fiber 4, coupled into the light source chip 3, propagated along the optical waveguide 201 on the light source chip 3, and then emitted from the left end face of the light source chip 3, and then passed through the filter, and then entered the optical detector 1 to complete the photoelectric conversion. At the same time, the uplink light λ1 and the downlink light λ2 share the optical path between the light source chip 3 and the optical fiber 4, which may include elements such as lenses introduced to improve the optical coupling efficiency. At the same time, the optical path between the light source chip 3 and the optical detector 1 may also introduce elements such as lenses to improve the optical response of the optical detector 1 to the downlink light λ2.

[0037] At the same time, the normal direction of the filter is consistent with the optical axis or maintains a certain small inclination angle (the angle between the normal direction of the surface of the filter 2 and the optical axis is less than 15°) to weaken the reflected light of the uplink light λ1 returning along the original path; the wavelength of the uplink light λ1 is generally between 1260nm and 1360nm, and the wavelength of the downlink light λ2 is generally between 1480nm and 1580nm. With such a design, it can be ensured that the downlink light λ2 passes through the gain medium adapted to the uplink light λ1 with lower loss, and appropriate band separation also helps to realize a wavelength division multiplexing component with high isolation.

[0038] In another embodiment, one end of the light source chip 3 close to the filter 2 is coated with a first dielectric film, and the first dielectric film is an anti-reflection film for the downlink light λ2 and an anti-reflection film for the uplink light λ1; one end of the light source chip 3 close to the optical fiber 4 is coated with a second dielectric film, and the second dielectric film is an anti-reflection film for both the uplink light λ1 and the downlink light λ2.

[0039] like Figure 3 As shown, in this embodiment, the left end face of the light source chip 3 is coated with a multilayer dielectric film (first dielectric film), and the film layer is designed to be an anti-reflection film for the downstream light λ2 and an anti-reflection film for the upstream light λ1; the right end face of the light source chip 3 is coated with another multilayer dielectric film (second dielectric film), and the film layer is designed to be an anti-reflection film for both the upstream light λ1 and the downstream light λ2; in a preferred embodiment, the first dielectric film on the left end face of the light source chip 3 has a reflectivity of >50% for the upstream light λ1, and a transmittance of >95% for the downstream light λ2.

[0040] like Figure 7As shown in FIG. 1 , a film layer design example of this embodiment is shown. This example is for XG-PON ONU application, where the upstream optical wavelength λ1 = 1270nm, the downstream optical wavelength λ2 = 1577nm; Figure 7 It can be seen that for the left end face of the light source chip 3, a five-layer composite film based on SiO2 / Si / SiNx with a total thickness of 456nm is used, which can achieve a reflectivity greater than 70% at λ1, while ensuring a reflectivity less than 1% at λ2; for the right end face of the light source chip 3, a three-layer composite film based on SiO2 / Si with a total thickness of 356nm is used, which can achieve a wide bandwidth anti-reflection film covering λ1 and λ2 with a reflectivity <1%.

[0041] In addition, the light source chip 3 can be a DFB laser. At the same time, a distributed Bragg grating is made on the laser. The grating is used to match and generate the uplink light λ1. The coating layer on the left end face of the light source chip 3 is a reflection-enhancing film for the uplink light λ1, which constitutes the rear reflector of the DFB laser.

[0042] In the second embodiment, if Figure 4 As shown, the light source chip 3 includes a first optical waveguide 302 having a distributed Bragg grating structure, and the Bragg central wavelength λ corresponding to the Bragg grating structure on the first optical waveguide 302 is B The wavelength interval between the uplink light λ1 and the downlink light λ2 is less than 3 nm. When the downlink light λ2 propagates in the light source chip 3 , it passes through the first section of the optical waveguide 302 .

[0043] In this embodiment, a light source chip 3 with a wavelength division multiplexing function is implemented based on DBR, which utilizes the narrowband filtering characteristics of a distributed Bragg reflector to reflect the uplink light λ1 while transmitting the downlink light λ2. DBR is a distributed Bragg reflector, which refers to an optical waveguide with a periodic grating structure in the waveguide propagation direction. It has the characteristics of narrowband reflection and can be used as a reflector for a laser.

[0044] In this embodiment, the first section of the optical waveguide 302 of the light source chip 3 is arranged at one end of the laser body 301 close to the filter 2, and it serves as a rear-end reflector (DBR reflector) and together with the laser body 301 constitutes a semiconductor laser of the light source chip 3. After the downlink light λ2 is coupled into the light source chip 3, it propagates along the on-chip optical waveguide 303 of the laser body 301, and passes through the laser body 301 and the first section of the optical waveguide 302 (DBR reflector) in sequence to reach the end of the light source chip 3 close to the filter 2, that is, the left end face of the light source chip 3.

[0045] Meanwhile, the laser body 301 may include a second optical waveguide, wherein the second optical waveguide includes a distributed Bragg grating structure; the Bragg center wavelength λ corresponding to the Bragg grating structure of the second optical waveguide is B The wavelength interval with the uplink light λ1 is less than 3nm, and the downlink light λ2 needs to pass through the second section of optical waveguide when propagating on the light source chip 3; the second section of optical waveguide includes an intrinsic active core layer, and the intrinsic active core layer is the gain medium of the uplink light λ1 when current is injected; the distributed Bragg grating structure of the first section of optical waveguide 302 and the second section of optical waveguide can be continuously distributed.

[0046] In addition, the left and right end faces of the light source chip 3 are coated with multilayer dielectric films, which are anti-reflection films for both the uplink light λ1 and the downlink light λ2, which will reduce the insertion loss of the downlink light λ2 and improve the stability of the laser by reducing unnecessary reflected light.

[0047] In addition, if Figure 5 As shown, the light source chip 3 may further include an on-chip photodetector 401 ; the on-chip photodetector 401 is used to monitor the working state of the semiconductor laser on the light source chip 3 .

[0048] Preferably, the on-chip photodetector 401 is a waveguide-type photodetector, which is located at one end of the first section of the optical waveguide 302 close to the filter 2. Most of the uplink light λ1 entering the first section of the optical waveguide 302 will be reflected, and a small amount of transmitted uplink light λ1 will enter the on-chip photodetector 401 and be absorbed by the active layer therein and converted into photocurrent, which can be used to characterize the working state of the on-chip laser. At the same time, the downlink light λ2 can pass through the main waveguide of the on-chip photodetector 401 when propagating on the light source chip 3.

[0049] Preferably, the on-chip photodetector 401 uses the same active layer epitaxial material as the semiconductor laser.

[0050] In the third embodiment, Figure 6 As shown, the light source chip 3 includes a wavelength division multiplexing element 502; the wavelength division multiplexing element 502 includes port a, port b, and port c; the uplink light λ1 generated by the semiconductor laser 501 enters the wavelength division multiplexing element 502 through port a, and is output from port b in the direction of the optical fiber 4; after the downlink light λ2 is coupled into the light source chip 3, it enters the wavelength division multiplexing element 502 through port b, and is output from port c in the direction of the filter 2.

[0051] The left and right end faces of the light source chip 3 are coated with a multilayer dielectric film, which is an anti-reflection film for both the uplink light λ1 and the downlink light λ2; at the same time, the three-port wavelength division multiplexing (WDM) element can be implemented in a variety of ways such as a directional coupler, a multimode interference coupler, a Mach-Zehnder interferometer, and an arrayed waveguide grating.

[0052] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A coaxial single-fiber bidirectional optical transceiver device, comprising an optical fiber, a light source chip, a filter, and a light detector, characterized in that: The optical fiber, light source chip, filter and light detector are arranged on the same optical axis from right to left or from left to right in sequence; The light source chip includes a semiconductor laser or an optical waveguide including a semiconductor laser; The semiconductor laser is used to generate uplink light λ1, which is emitted from one end of the light source chip and fed into the optical fiber to enter the external optical communication network; the optical fiber is used to output downlink light λ2, which enters the light source chip from one end of the light source chip and is emitted from the other end of the light source chip, then passes through the filter and enters the photodetector to complete the photoelectric conversion; The filter is a band-stop filter for the uplink light λ1 and a band-pass filter for the downlink light λ2.

2. The coaxial single-fiber bidirectional optical transceiver device according to claim 1, characterized in that: The wavelength of the uplink light λ1 is between 1260nm and 1360nm, and the wavelength of the downlink light λ2 is between 1480nm and 1580nm; the angle between the normal direction of the filter surface and the optical axis is less than 15°.

3. The coaxial single-fiber bidirectional optical transceiver device according to claim 1, characterized in that: One end of the light source chip close to the filter is coated with a first dielectric film, which is an anti-reflection film for the downlink light λ2 and an anti-reflection film for the uplink light λ1; one end of the light source chip close to the optical fiber is coated with a second dielectric film, which is an anti-reflection film for both the uplink light λ1 and the downlink light λ2.

4. The coaxial single-fiber bidirectional optical transceiver device according to claim 3, characterized in that: A distributed Bragg grating structure is manufactured on the semiconductor laser.

5. The coaxial single-fiber bidirectional optical transceiver device according to claim 1, characterized in that: The light source chip comprises a first section of optical waveguide having a distributed Bragg grating structure, and the Bragg central wavelength λ corresponding to the Bragg grating structure on the first section of optical waveguide B The wavelength interval between the uplink light λ1 and the downlink light λ2 is less than 3 nm. When the downlink light λ2 propagates in the light source chip, it passes through the first section of optical waveguide.

6. The coaxial single-fiber bidirectional optical transceiver device according to claim 5, characterized in that: The light source chip includes a second section of optical waveguide, the second section of optical waveguide contains a distributed Bragg grating structure; the Bragg center wavelength λ corresponding to the Bragg grating structure of the second section of optical waveguide B The wavelength interval with the uplink light λ1 is less than 3nm, and the downlink light λ2 needs to pass through the second section of optical waveguide when propagating on the light source chip; the second section of optical waveguide includes an intrinsic active core layer, and the intrinsic active core layer is the gain medium of the uplink light λ1 when current is injected.

7. The coaxial single-fiber bidirectional optical transceiver device according to claim 1, characterized in that: The light source chip also includes an on-chip photodetector; the on-chip photodetector is used to monitor the working state of the semiconductor laser on the light source chip.

8. The coaxial single-fiber bidirectional optical transceiver device according to claim 7, characterized in that: The on-chip photodetector uses the same active layer epitaxial material as that of the semiconductor laser.

9. The coaxial single-fiber bidirectional optical transceiver device according to claim 7, characterized in that: The on-chip photodetector is a waveguide-type photodetector. When the downlink light λ2 propagates on the light source chip, it needs to pass through the main waveguide of the on-chip photodetector.

10. The coaxial single-fiber bidirectional optical transceiver device according to claim 1, characterized in that: The light source chip includes a wavelength division multiplexing element; the wavelength division multiplexing element includes port a, port b, and port c; the uplink light λ1 enters the wavelength division multiplexing element through port a and is output from port b in the direction of the optical fiber; after the downlink light λ2 is coupled into the light source chip, it enters the wavelength division multiplexing element through port b and is output from port c in the direction of the filter.

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