Silicon photonic chips and XGSPON optical modules based on wavelength division multiplexing

Abstract

The present invention belongs to the field of optical communication technology, and in particular relates to a silicon photonic chip and an XGSPON optical module based on wavelength division multiplexing. The BOSA position in the original mainstream technical solution is replaced by a silicon photonic chip with WDM function and built-in APD. At the same time, the LD chip, TIA chip and optical fiber adapter encapsulated in BOSA in the mainstream solution are mounted around the silicon photonic chip, reducing the cost and uncertainty of manual installation; at the same time, the solution has high integration, and the chip volume is one order of magnitude smaller than that of BOSA.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical communications, and in particular relates to a silicon photonic chip and an XGSPON optical module based on wavelength division multiplexing. Background Art

[0002] At present, my country's fixed broadband access network has basically achieved full fiber optic access, and the access rate has gradually increased from 100M to 1G in recent years. At the same time, mobile broadband has gradually acquired 1G access capabilities with the large-scale commercialization of 5G worldwide. In this market context, domestic and foreign broadband operators have begun to deploy 10G / 10G+ PON technology (Note: PON refers to Passive Optical Network), with the goal of providing 1G access capabilities to each household as the broadband development goal.

[0003] As the XG(S)-PON (Note: XG-PON is a 10G PON with asymmetric upstream and downstream, and XGS-PON is a 10G PON with symmetric upstream and downstream) industry chain has matured, the current mainstream XGSPON optical module solution uses BOSA optical devices (Note: BOSA refers to Bi-Directional Optical Sub-Assembly, a single-fiber bidirectional optical transmitting and receiving component) based on TO coaxial packaging (Note: TO refers to Transistor Outline, a coaxial packaging device, and the number behind it represents the tube diameter) to realize the core transceiver functions.

[0004] The active part of this technical solution is packaged into TO46 / TO56 for transmitting / receiving, respectively, to realize the function of electrical-optical or optical-electrical conversion. The transmitting LD chip (Note: LD refers to Laser Diode) and MPD chip (Note: MPD refers to Monitor PD, used to monitor the backlight power of LD) are packaged in the transmitting TO, and the receiving PD chip (Note: PD refers to Photonic Diode, used for photoelectric conversion, divided into APD and PIN) and TIA chip (Note: TIA refers to Transimpedance Amplifier, used to convert photocurrent into voltage and amplify the output) are packaged in the receiving TO. The TO packaging process includes: tube socket clamping, mounting pads, eutectic mounting chips, wire bonding, capping and other processes, plus various tests such as airtightness inspection (gross leak, fine leak), aging test, LIV test.

[0005] The passive optical path of this technical solution adopts the solution of base + filter. The transmitting optical path is sequentially set with transmitting TO, isolator, 0° filter, and fiber adapter output, and the receiving optical path is sequentially set with fiber adapter input, 45° filter, and receiving TO. In this way, the discrete optical components are assembled to obtain BOSA. The manufacturing process of BOSA includes: transmitting TO crimping, penetration welding, transmitting coupling, receiving coupling and other processes, plus various tests such as LIV test, TC / TE test, sensitivity test, etc.

[0006] The driving control circuit of this technical solution is usually packaged into SFP+ specifications, such as Figure 1 This is a schematic block diagram of the driving control circuit of the prior art solution. BOSA is electrically connected to the PCB board through wire bonding or a flexible circuit board, and cooperates with the driving circuit to realize the transceiver function of the optical module. In the transmitting function, the external digital electrical signal TD+ / - is input through the electrical interface and converted into the driving electrical signal LD+ / - of LD through the electrical driving chip to drive the transmitting optical path of BOSA; in the receiving function, BOSA receives light and outputs the photoelectric signal DIN+ / -, which is converted into the digital electrical signal RD+ / - by the electrical driving chip and output through the electrical interface.

[0007] It can be seen that the above technical solution has the following shortcomings: 1. The process is cumbersome and requires TO packaging, BOSA assembly, and module packaging, and multiple processes require manual installation, which has high labor costs and low reliability; 2. The integration is low and the volume is large.

[0008] At present, there are XGSPONs on the market that use silicon photonic chips and COB technology (Note: COB, Chip on board, refers to the process of fixing the exposed chip directly on the printed circuit board, then bonding it with gold wires, and then encapsulating and protecting the chip and wires with organic glue) for integrated packaging to replace the previous mainstream BOSA solution, but there are the following two difficulties:

[0009] 1. Conventional COB technology is mostly used for CWDM / DWDM wavelength division multiplexing high-speed optical modules. The wavelength division multiplexing function is generally realized by AWG (Arrayed waveguide gratings) array waveguide grating solution, including an input waveguide, an input star coupler, an output star coupler and dozens of output waveguides. This solution is difficult to implement for wide wavelength multiplexing / demultiplexing (1270nm & 1577nm) of PON products and has a large volume;

[0010] 2. In terms of achieving efficient coupling between silicon-based waveguides and optical fibers, due to the small size of silicon nano-optical waveguides, their mode spot size is only on the order of 0.1 μm2, which is far from the optical fiber mode spot size (tens of μm2). Therefore, the core issue of efficient coupling between silicon-based waveguides and optical fibers lies in how to achieve effective mode spot size conversion. Summary of the invention

[0011] The purpose of the present invention is to provide a silicon photonic chip and XGSPON optical module based on wavelength division multiplexing, replacing the BOSA position in the original mainstream technical solution with a silicon photonic chip with WDM function and built-in APD, and at the same time, the LD chip, TIA chip and optical fiber adapter encapsulated in BOSA in the mainstream solution are mounted around the silicon photonic chip (Note: WDM refers to Wavelength Division Multiplexing, a wavelength division multiplexer used to separate multiple optical channels according to wavelength, and is used to separate the transmitted and received light waves in this solution).

[0012] In order to achieve the above object, the technical solution of the present invention is as follows:

[0013] A silicon photonic chip based on wavelength division multiplexing includes a silicon-based substrate, on which a mode spot converter, a beam splitter, an MPD device, an APD device, a silicon-based optical wavelength division filter, and an inverted tapered end face coupler are arranged;

[0014] The pattern spot converter 1 is used as a light source input interface to match the input pattern spot;

[0015] The optical splitter splits the input optical signal in proportion, a part of the optical signal is transmitted to the MPD device, and the other part of the optical signal is transmitted to the silicon-based optical wavelength division filter;

[0016] The MPD device is used to monitor the input optical signal and convert the optical signal into a photocurrent output;

[0017] The silicon-based optical wavelength division filter realizes a single optical path bidirectional function. On the one hand, it receives the optical signal output by the optical splitter and transmits it to the inverted tapered end face coupler. On the other hand, it receives the optical signal output by the inverted tapered end face coupler and transmits it to the APD device.

[0018] The APD device is used to convert the received optical signal into a photocurrent and output it;

[0019] The inverted tapered end face coupler is used for coupling a waveguide with an external optical fiber to achieve the output of an optical signal. The optical fiber port of the inverted tapered end face coupler is provided with a second mode spot converter.

[0020] An XGSPON optical module, comprising an electrical interface 1, an electrical driver chip, an LD chip, a TIA chip, an optical fiber adapter and the silicon photonic chip described in claim 1;

[0021] The external digital electrical signal is input to the electric driving chip through the electrical interface 1. The electric driving chip converts the digital electrical signal into a driving electrical signal, which directly drives the modulated LD chip. The LD chip inputs an optical signal into the silicon photonic chip according to the driving electrical signal. The silicon photonic chip outputs the optical signal to the optical fiber adapter through the optical fiber.

[0022] The external optical signal is input to the silicon photonic chip through the optical fiber adapter and optical fiber. The silicon photonic chip outputs the photocurrent to the TIA chip. The TIA chip converts the photocurrent into an amplified voltage signal and inputs it to the electric drive chip. The electric drive chip processes the voltage signal to obtain a digital electrical signal and outputs it through electrical interface 1.

[0023] Furthermore, the optical ports of the LD chip and the silicon photonic chip are edge coupled.

[0024] The advantages of the present invention are:

[0025] 1. This solution abandons BOSA, avoids the cumbersome TO packaging and BOSA assembly process, and directly performs modular packaging on the chip. Since the chip mounting and coupling can be completed by machines, the cost and uncertainty of manual installation are reduced; at the same time, this solution has a high degree of integration, and the chip volume is one order of magnitude smaller than BOSA;

[0026] 2. Use silicon-based optical wavelength division filter (WDM-filter) to achieve single optical path bidirectional function, which can be used for wide wavelength multiplexing / demultiplexing (1270nm & 1577nm) of PON products and reduce the chip size;

[0027] 3. Use spot mode converter to achieve efficient coupling between silicon-based waveguide and optical fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic block diagram of a drive control circuit of a prior art solution in the background technology;

[0029] Figure 2 It is a schematic block diagram of a driving control circuit of the technical solution in the embodiment;

[0030] Figure 3 Schematic diagram of the internal structure of the silicon photonic chip in the embodiment. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below with reference to the embodiments.

[0032] like Figure 2As shown, this embodiment proposes an XGSPON optical module structure based on silicon photonic chip, including a PCB board, on which an electrical interface 1, an electrical driver chip, a silicon photonic chip and an optical fiber adapter are provided. In the transmitting function, the external digital electrical signal TD+ / - is input to the electrical driver chip through the electrical interface 1, and is converted by the electrical driver chip into the driving electrical signal LD+ / - of LD to directly modulate and drive the LD chip. The LD chip transmits the light source to the silicon photonic chip. While the light source is input to the silicon photonic chip, the chip has an integrated MPD built into the chip to monitor the input optical power, and converts it into a photocurrent and inputs it into the electrical driver chip. The silicon photonic chip outputs an optical signal to the optical fiber adapter through an optical fiber; in the receiving function, the external optical signal is input to the silicon photonic chip through the optical fiber adapter and the optical fiber, and the silicon photonic chip outputs a photocurrent to the TIA chip. The TIA chip is packaged on the PCB by patching and wire bonding. The TIA chip converts the photocurrent into an amplified voltage signal DIN+ / - and inputs it to the electrical driver chip. The electrical driver chip processes the voltage signal to obtain a digital electrical signal RD+ / -, and outputs it through the electrical interface 1.

[0033] like Figure 3 As shown, the silicon photonic chip includes a silicon-based substrate, on which are arranged a spot mode converter - SSC, a spectrometer, an MPD device, an APD device, a silicon-based optical wavelength division filter, and an inverted tapered end face coupler.

[0034] Silicon-based optical wavelength division filter WDM-filter uses silicon-based waveguide grating design to couple the energy of light at the resonant wavelength to the reverse mode, so that it appears in the band-stop region during forward transmission. From the transmission end, it is a band-stop filter, and from the reflection end, it is a bandpass filter. Using the working principle of the apodized multimode waveguide grating (MWG) structure, the input TE0 mode is converted into TE1 mode through the apodized multimode waveguide, and the TE1 mode near the center wavelength of the Bragg grating is reflected and converted into TE0 mode and downloaded. Multi-channel wavelength division multiplexing can be achieved by cascading multiple apodized multimode waveguide grating structures.

[0035] The spot converter SSC uses a horizontal tapered transition structure instead of a vertical transition structure to reduce the core thickness of the passive waveguide. This solution does not require complex photolithography processes and difficult etching processes. After simulating and optimizing the spot conversion structure using the BPM method, we found that the designed structure has a large process tolerance. The inverse tapered waveguide coupler structure consists of two parts. One is a silicon core area with a constant height and a gradually decreasing width; the other is a polymer or SiN optical waveguide with a cross-sectional size of about 3μm×3 μm located above the silicon core area. The two are combined to form a dual-core hybrid tapered waveguide. Using this gradient structure, the silicon nano-optical waveguide mode field can be gradually converted into a polymer or SiN optical waveguide mode, thereby achieving the expansion of the light field spot and improving the coupling efficiency with the optical fiber. The characteristics of the tapered waveguide coupler are: high coupling efficiency, suitable for wide-band and dual-polarization operation, and the structure is only made using contact exposure, with a simple process and high tolerance.

[0036] The mode spot converter is used as the light source input interface. It is designed to match the mode spot and divergence angle of the LD chip. Based on the high-precision COB process, the LD chip and silicon photonic chip are mounted on the PCB board. The LD chip and the silicon photonic chip optical port are edge coupled, and high precision (sub-micron) is used to ensure the coupling efficiency.

[0037] The optical splitter splits the input optical signal in proportion, with one part of the optical signal being sent to the MPD device and the other part being sent to the silicon-based optical wavelength division filter. The MPD device is used to monitor the input optical signal, convert the optical signal into a photocurrent, and output it to the electric drive chip through the electrical interface two. The silicon-based optical wavelength division filter realizes a single optical path bidirectional function. On the one hand, it receives the optical signal output by the optical splitter and transmits it to the inverted tapered end face coupler. On the other hand, it receives the optical signal output by the inverted tapered end face coupler and transmits it to the APD device. The APD device is used to convert the received optical signal into a photocurrent and output it through the electrical interface four.

[0038] The inverted tapered end face coupler is used to couple the waveguide with the external optical fiber to achieve the output of the optical signal. However, the MFD (fiber mode field diameter) at the tip of the inverted tapered coupler is about 2-3um, which still cannot match the 9um single-mode optical fiber well. Therefore, in this embodiment, a mode spot converter 2 is provided at the optical fiber port of the inverted tapered end face coupler, and edge coupling is adopted with the optical fiber end face to achieve efficient coupling of the silicon-based waveguide and the optical fiber. The other end of the optical fiber is connected to the optical fiber adapter.

[0039] The above embodiments are only used to explain the concept of the present invention, rather than to limit the protection of the rights of the present invention. Any non-substantial changes to the present invention using this concept shall fall within the protection scope of the present invention.

Claims

1. A silicon photonic chip based on wavelength division multiplexing, comprising a silicon-based substrate, characterized in that: A pattern spot converter, a spectrometer, an MPD device, an APD device, a silicon-based optical wavelength division filter, and an inverted tapered end face coupler are arranged on the silicon-based substrate; The pattern spot converter 1 is used as a light source input interface to match the input pattern spot; The optical splitter splits the input optical signal in proportion, a part of the optical signal is transmitted to the MPD device, and the other part of the optical signal is transmitted to the silicon-based optical wavelength division filter; The MPD device is used to monitor the input optical signal and convert the optical signal into a photocurrent output; The silicon-based optical wavelength division filter realizes a single optical path bidirectional function. On the one hand, it receives the optical signal output by the optical splitter and transmits it to the inverted tapered end face coupler, and on the other hand, it receives the optical signal output by the inverted tapered end face coupler and transmits it to the APD device. The silicon-based optical wavelength division filter (WDM-filter) uses a silicon-based waveguide grating design to couple the energy of light at the resonant wavelength to the reverse mode, so that a band-stop region appears in the forward transmission. From the transmission end, it is a band-stop filter, and from the reflection end, it is a bandpass filter. Using the working principle of the apodized multimode waveguide grating (MWG) structure, the input TE0 mode is converted into the TE1 mode through the apodized multimode waveguide, and the TE1 mode near the center wavelength of the Bragg grating is reflected and converted into the TE0 mode and downloaded, and the cascade of multiple apodized multimode waveguide grating structures is used to realize multi-channel wavelength division multiplexing. The APD device is used to convert the received optical signal into a photocurrent and output it; The inverted tapered end face coupler is used for coupling a waveguide with an external optical fiber to achieve the output of an optical signal. The optical fiber port of the inverted tapered end face coupler is provided with a second mode spot converter.

2. An XGSPON optical module, characterized in that: It includes an electrical interface 1, an electrical drive chip, an LD chip, a TIA chip, an optical fiber adapter and the silicon photonic chip described in claim 1; The external digital electrical signal is input to the electric driving chip through the electrical interface 1. The electric driving chip converts the digital electrical signal into a driving electrical signal, which directly drives the modulated LD chip. The LD chip inputs an optical signal into the silicon photonic chip according to the driving electrical signal. The silicon photonic chip outputs the optical signal to the optical fiber adapter through the optical fiber. The external optical signal is input to the silicon photonic chip through the optical fiber adapter and optical fiber. The silicon photonic chip outputs the photocurrent to the TIA chip. The TIA chip converts the photocurrent into an amplified voltage signal and inputs it to the electric drive chip. The electric drive chip processes the voltage signal to obtain a digital electrical signal and outputs it through electrical interface 1.

3. An XGSPON optical module as claimed in claim 2, characterized in that: The optical ports of the LD chip and the silicon photonic chip are edge coupled.

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