Silicon-based monolithic integrated direct detection receiving device based on narrow-band filter

Abstract

A silicon-based monolithic integration direct detection receiving device based on a narrow-band filter comprises a signal coupling and beam splitting module, a carrier extraction and signal frequency mixing module and a signal photoelectric conversion module, the signal coupling and beam splitting module divides input light into two parts, and the two parts are coupled to the carrier extraction and signal frequency mixing module; the carrier wave extraction and signal frequency mixing module extracts carrier waves from two paths of input light through a micro-ring resonator and a multi-mode interferometer, carries out frequency mixing on the carrier waves and the input light and then outputs the mixed light to the signal photoelectric conversion module, and the signal photoelectric conversion module carries out photoelectric conversion on optical signals obtained after frequency mixing through a balanced photoelectric detector. According to the invention, second-order signal and signal beat frequency interference can be avoided, performance limitation of a direct detection system is broken through, generation of signal and signal beat frequency interference damage is inhibited fundamentally, and low-cost and high-capacity signal transmission is realized.

Description

Technical Field

[0001] The present invention relates to a technology in the field of optical communication, specifically a silicon-based monolithic integrated direct detection receiving device based on a narrowband filter for a large-capacity and low-cost optical communication system. Background Art

[0002] Existing low-cost silicon-based integrated direct detection receiving devices all suffer from severe signal-to-signal beat interference damage. Since this damage cannot be completely compensated by digital signal processing technology, the residual interference limits the performance of existing silicon-based integrated direct detection receiving devices. Summary of the Invention

[0003] Aiming at the deficiency that the prior art cannot achieve high-performance detection and recovery of complex-valued double-sideband IQ signals based on an integrated narrowband filter receiver, the present invention proposes a silicon-based monolithic integrated direct detection receiving device based on a narrowband filter, which can obtain a pure linear carrier signal beat term, avoid second-order signal-to-signal beat interference, break through the performance limitations of direct detection systems, fundamentally suppress the generation of signal-to-signal beat interference damage, and achieve low-cost and large-capacity signal transmission.

[0004] The present invention is realized through the following technical solutions:

[0005] The present invention relates to a silicon-based monolithic integrated direct detection receiving device based on a narrowband filter, including: a signal coupling and splitting module, a carrier extraction and signal mixing module, and a signal optoelectronic conversion module. Among them: the signal coupling and splitting module divides the input light into two and couples it to the carrier extraction and signal mixing module; the carrier extraction and signal mixing module extracts carriers from the two input lights through a microring resonator and a multimode interferometer respectively, mixes the carriers with the input light, and then outputs to the signal optoelectronic conversion module; the signal optoelectronic conversion module performs optoelectronic conversion on the mixed optical signal through a balanced photodetector.

[0006] The signal coupling and splitting module includes: a grating coupler and a 1×2 multimode interferometer. Among them: the grating coupler couples the light in the optical fiber into the silicon optical waveguide, and the 1×2 multimode interferometer splits the optical signal into 1×2 and then outputs to the carrier extraction and signal mixing module.

[0007] The carrier extraction and signal mixing module includes: a microring resonator and a 4×4 multimode interferometer. Among them: the microring resonator extracts the carrier component from the input optical signal using its bandpass port, and the multimode interferometer performs 90-degree optical mixing of the carrier and the input optical signal and then outputs to the signal optoelectronic conversion module.

[0008] The described signal optoelectronic conversion module includes: two balanced photodetectors, which respectively convert the four outputs of the multimode interferometer into electrical signals, and each balanced photodetector consists of two photodetectors.

[0009] The present invention relates to a signal processing method based on the above receiving device, including:

[0010] Step 1: The carrier-assisted double-sideband signal at the receiving end is c + s, where: c represents the carrier component, s represents the signal component, and this signal is divided into two paths, where: one path is directly input to a 90-degree optical mixer, and the other path passes through a silicon-based bandpass filter to obtain the carrier and then is input to the 90-degree optical mixer, and the output of the silicon-based bandpass filter is c.

[0011] Step 2: The two inputs of the 90-degree optical mixer are c + s and c, and its four outputs are received by two balanced photodetectors. The photocurrents output by the two balanced photodetectors are respectively Re{c * ·(c + s)} and Im{c * ·(c + s)}, where: Re{·} and Im{·} respectively represent the operations of taking the real part and the imaginary part.

[0012] Step 3: Use offline digital signal processing technology to recover the signal. The two received photocurrents are amplitude-matched and added to obtain (c + s)·c * =|c| 2 + c * ·s, where: the first DC component can be eliminated by subtracting the signal mean value, and the channel response is compensated using adaptive equalization, and finally the transmitted-end signal is demodulated and recovered. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is the schematic diagram of the principle of the present invention;

[0014] Figure 2 is the 3D structural schematic diagram of the silicon-based monolithic integrated receiving device chip in the embodiment;

[0015] Figure 3 is the schematic diagram of the simulation device for comparing the scheme performance in the embodiment;

[0016] Figure 4 is the comparison diagram of the bit error performance between the scheme in the embodiment and the existing representative schemes;

[0017] Figure 5 is the schematic diagram of the bit error rate simulation result in the embodiment;

[0018] Figure 6 is the schematic diagram of the simulation architecture in the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] As Figure 1 and Figure 2As shown in the figure, the silicon-based monolithic integrated direct detection receiving device based on a narrowband filter according to this embodiment includes a grating coupler, a multimode interferometer, a microring resonator, and a balanced photodetector integrated on a silicon-based chip, where: the optical signal in the optical fiber is respectively input into the first input end of a 4×4 multimode interferometer and the microring resonator through the grating coupler, the microring resonator outputs a carrier component to the other input end of the 4×4 multimode interferometer, and after the carrier component is mixed with the received optical signal, they are respectively output to two balanced photodetectors for optoelectronic conversion.

[0020] As Figure 3A shown, the grating coupler includes a grating and a tapered waveguide.

[0021] The period of the grating is 0.63 μm.

[0022] The width of the tapered waveguide varies from 15 μm to 0.5 μm, and the length is 150 μm.

[0023] As Figure 3B shown, the 1×2 multimode interferometer realizes the function of 1×2 beam splitting, and specifically includes an input tapered waveguide, a multimode waveguide region, and an output tapered waveguide.

[0024] The width of the input tapered waveguide varies from 0.5 μm to 1.67 μm; the length of the multimode waveguide region is 14 μm, and the width is 4 μm.

[0025] The width of the output tapered waveguide varies from 1.67 μm to 0.5 μm.

[0026] As Figure 4A shown, the 4×4 multimode interferometer realizes the function of 90-degree optical mixing, and specifically includes an input tapered waveguide, a multimode waveguide region, and an output tapered waveguide.

[0027] The width of the input tapered waveguide varies from 0.5 μm to 2 μm.

[0028] The length of the multimode waveguide region is 180 μm, and the width is 10 μm.

[0029] The width of the output tapered waveguide varies from 2 μm to 0.5 μm.

[0030] As Figure 4B shown, the silicon-based bandpass filter based on a microring structure adopts a cascaded dual-ring structure, the waveguide width is 1.2 μm, the gap between the waveguide and the microring is 0.62 μm, the gap between the microrings is 0.59 μm, and the radius of the microring is 120 μm.

[0031] In order to solve the problem of nonlinear effects caused by high input power, the silicon-based filter is processed in a silicon nitride material with a low thermo-optic coefficient.

[0032] After simulation, the transmitter modulates to generate a 16-order quadrature amplitude modulation (QAM) signal with a baud rate of 28 Gbaud. The carrier signal power ratios are all set to the optimal values. The optical fiber channel is an additive white Gaussian noise channel, and the optical signal-to-noise ratio is set from 14 dB to 26 dB. The receiver reconstructs the signal according to the principles of different receiving schemes, and after channel equalization, the demodulated signal is obtained for recovery, as Figure 5 shown in the simulation results of the system bit error rate. Since this method can fundamentally suppress the generation of signal-to-signal beat frequency interference and break through the performance limitations of direct detection systems, it significantly reduces the signal bit error rate and improves the system performance.

[0033] As Figure 6 shown, the simulation architecture involved in this embodiment includes: a laser, an IQ modulator, a digital-to-analog converter, a channel, a receiving device, and digital signal processing technologies at the transmitter and receiver. Among them: the laser provides an optical carrier input to the IQ modulator. The transmitter generates a signal and inputs it to the IQ modulator through a digital-to-analog converter for optoelectronic modulation. The modulated optical signal is input into the channel for transmission. After the signal at the receiver is received, a digital signal processing algorithm is used to demodulate and recover the signal.

[0034] The digital-to-analog converter converts the digital signal into an analog electrical signal.

[0035] The IQ modulator modulates the electrical signal onto the optical carrier.

[0036] The channel is an additive white Gaussian noise channel.

[0001] The above specific implementation can be locally adjusted by those skilled in the art in different ways without departing from the principles and purposes of the present invention. The protection scope of the present invention is subject to the claims and is not limited by the above specific implementation. All implementation solutions within its scope are subject to the constraints of the present invention.

Claims

1. A silicon-based monolithic integrated direct detection receiving device based on narrowband filter, characterized in that: include: A signal coupling and splitting module, a carrier extraction and signal mixing module, and a signal photoelectric conversion module, wherein: the signal coupling and splitting module splits the input light into two and couples it to the carrier extraction and signal mixing module; the carrier extraction and signal mixing module extracts the carrier from the two input lights respectively through a microring resonator and a multimode interferometer and mixes the carrier with the input light and then outputs it to the signal photoelectric conversion module; the signal photoelectric conversion module performs photoelectric conversion on the mixed optical signal through a balanced photodetector.

2. The silicon-based monolithic integrated direct detection receiving device based on narrowband filter according to claim 1 is characterized in that: The signal coupling and splitting module includes: a grating coupler and a 1×2 multimode interferometer, wherein: the grating coupler couples the light in the optical fiber into the silicon optical waveguide, and the 1×2 multimode interferometer performs 1×2 splitting on the optical signal and outputs it to the carrier extraction and signal mixing module.

3. The silicon-based monolithic integrated direct detection receiving device based on narrowband filter according to claim 1 is characterized in that: The carrier extraction and signal mixing module includes: a microring resonator and a 4×4 multimode interferometer, wherein: the microring resonator uses its bandpass port to extract the carrier component from the input optical signal, and the multimode interferometer performs 90-degree optical mixing on the carrier and the input optical signal and outputs the result to the signal photoelectric conversion module.

4. The silicon-based monolithic integrated direct detection receiving device based on narrowband filter according to claim 1 is characterized in that: The signal photoelectric conversion module comprises: two balanced photoelectric detectors, which respectively convert the four outputs of the multi-mode interferometer into electrical signals, and each balanced photoelectric detector is composed of two photoelectric detectors.

5. A signal processing method based on the receiving device according to any one of claims 1 to 4, characterized in that: include: Step 1: The carrier-assisted double-sideband signal at the receiving end is c+s, where c represents the carrier component and s represents the signal component. The signal is divided into two paths, one of which is directly input to the 90-degree optical mixer and the other is input to the 90-degree optical mixer after obtaining the carrier through the silicon-based bandpass filter. The output of the silicon-based bandpass filter is c; Step 2: The two inputs of the 90-degree optical mixer are c+s and c, and its four outputs are received by two balanced photodetectors. The photocurrents output by the two balanced photodetectors are Re{c * ·(c+s)} and Im{c * ·(c+s)}, where: Re{·} and Im{·} represent the real part and imaginary part operations respectively; Step 3: Use offline digital signal processing technology to restore the signal, match the amplitudes of the two received photocurrents and add them to obtain (c+s)·c * =|c| 2 +c * ·s, where: The first DC component is eliminated by subtracting the signal mean, and the channel response is compensated using adaptive equalization, and finally the transmitter signal is restored by demodulation.

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