CN108141284B

CN108141284B - Apparatus and method for processing signal in optical communication system

Info

Publication number: CN108141284B
Application number: CN201580083930.0A
Authority: CN
Inventors: 张亮; 左天健; 毛渊
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2015-10-30
Filing date: 2015-10-30
Publication date: 2020-02-14
Anticipated expiration: 2035-10-30
Also published as: CN108141284A; WO2017070949A1

Abstract

The present invention provides an apparatus and method for processing a signal in an optical communication system, the apparatus including: the signal processing module is used for carrying out digital signal processing on the two paths of digital signals so as to output a first real number signal, a first imaginary number signal, a second real number signal and a second imaginary number signal; the operation module is used for carrying out addition and/or subtraction operation on the two paths of real number signals output by the processing module and outputting a first operation signal and a second operation signal; the digital-to-analog conversion module is used for performing digital-to-analog conversion on the two paths of operation signals to obtain two paths of analog signals; and the single-bias electro-optic modulator is used for realizing single-sideband modulation so as to output a single-sideband modulation signal, wherein the two sidebands of the spectrum of the single-sideband modulation signal respectively bear the data of the two paths of digital signals. The invention realizes single sideband modulation by using a single-bias electro-optic modulator, and can effectively reduce the system cost.

Description

Apparatus and method for processing signal in optical communication system

Technical Field

The present invention relates to the field of communications, and more particularly, to an apparatus and method for processing signals in an optical communication system.

Background

In recent years, short-distance optical communication has rapidly increased, and the increase speed is further increased with the continuous development of the mobile internet. For short-range optical communications, device cost and power consumption are major considerations. In long-distance optical communication, a coherent system has good performance and mature technology, but is not suitable for short-distance application scenes due to high cost and power consumption. Therefore, in short-distance optical communication applications, people aim more at Intensity modulation/direct detection (IM/DD) technology. In the prior art, when IM/DD is implemented, two paths of digital signals are respectively modulated on two orthogonal polarization states of an optical carrier by a double-polarization electro-optical modulator at a transmitter, and the optical carrier is transmitted to a receiver through an optical fiber, so that beat interference (Signal and Signal beat interference, abbreviated as "SSBI") between signals in a Signal obtained by the optical carrier after beat processing of a photodiode of the receiver can fall within the same guard band, and thus Signal performance can be improved.

However, the above solution requires the use of a double-bias electro-optical modulator at the transmitter, and the device cost is high.

Disclosure of Invention

The embodiment of the invention provides a device for processing signals in an optical communication system, which can reduce the system cost.

In a first aspect, an apparatus for processing a signal in an optical communication system is provided, where the optical communication system is configured to process a first path of digital signals and a second path of digital signals, and the apparatus includes: a signal processing module, configured to perform digital signal processing on the first path of digital signal to output a first real signal and a first imaginary signal, and perform digital signal processing on the second path of digital signal to output a second real signal and a second imaginary signal, where frequencies of the first real signal and the first imaginary signal fall into an intermediate frequency X/2 part of a bandwidth of the optical communication system, frequencies of the second real signal and the second imaginary signal fall into a high frequency X/2 part of the bandwidth of the optical communication system, where 1/2 is not less than X2/3, the first imaginary signal is a hilbert transform of the first real signal, and the second imaginary signal is a hilbert transform of the second real signal; an operation module, configured to perform a first operation on the first real number signal and the second real number signal output by the signal processing module to obtain a first operation signal, and perform a second operation on the first imaginary number signal and the second imaginary number signal output by the signal processing module to obtain a second operation signal, where the first operation is an addition operation and the second operation is a subtraction operation, or the first operation is a subtraction operation and the second operation is an addition operation; the digital-to-analog conversion module is used for performing digital-to-analog conversion on the first operation signal to obtain a first analog signal, and performing digital-to-analog conversion on the second operation signal to obtain a second analog signal; and the single-bias electro-optical modulator is used for receiving the first analog signal or the amplified signal of the first analog signal and the amplified signal of the second analog signal or the amplified signal of the second analog signal, and performing electro-optical modulation to obtain a single-sideband modulation signal of an optical domain, wherein two sidebands of a spectrum of the single-sideband modulation signal respectively bear data of the first path of digital signal and the second path of digital signal.

According to the embodiment of the invention, the real part and the imaginary part of the two paths of digital signals are respectively subjected to arithmetic operation, and the operated result is used as two paths of input of a single-bias electro-optical modulator, so that the two side bands of the spectrum of the obtained single-side band modulation signal respectively bear the data of the two paths of digital signals, and the two paths of digital signals are not required to be respectively modulated by the double-bias electro-optical modulator, so that the cost can be saved.

In other words, in the embodiment of the present invention, instead of directly inputting the digital electrical signals to the double-bias electro-optical modulator, the two electrical signals are preprocessed, that is, the two electrical signals are subjected to arithmetic operation of a real part and an imaginary part, and the preprocessed signals obtained after the arithmetic operation are used as the input of the single-bias electro-optical modulator, so that the modulation of the two digital electrical signals can be realized only by one single-bias electro-optical modulator. The double-polarization modulator can be realized by two single-polarization modulators, wherein the polarization states of the two single-polarization modulators are orthogonal to each other, or can also be a specially designed modulator with two orthogonal polarization states, and the device cost is higher in any form of double-polarization modulator, but only one single-polarization modulator is needed in the embodiment of the invention, so that the system cost is reduced.

With reference to the first aspect, in a first implementation manner of the first aspect, the X is 2/3, where frequencies of the first real signal and the first imaginary signal fall within an intermediate frequency 1/3 portion of a bandwidth of the optical communication system, and frequencies of the second real signal and the second imaginary signal fall within a high frequency 1/3 portion of the bandwidth of the optical communication system.

In the embodiment of the invention, the frequencies of the first real signal and the first imaginary signal fall into the intermediate frequency 1/3 part of the bandwidth of the optical communication system, and the frequencies of the second real signal and the second imaginary signal fall into the high frequency 1/3 part of the bandwidth of the optical communication system, so that in the obtained single-sideband modulation signal, only the low frequency 1/3 part is not used for transmitting data and is used as a guard band for accommodating an SSBI (single sideband interference cancellation), and thus, the spectrum resource of 2/3 can be utilized, and good system resource utilization rate is achieved while the signal performance is improved.

With reference to the first aspect or the foregoing implementation manner, in a second implementation manner of the first aspect, the single-bias electro-optical modulator includes an optical input port, an optical output port, a first radio frequency port, a second radio frequency port, and a plurality of dc bias ports, where the optical input port is configured to input a continuous optical signal, the first radio frequency port is configured to input the first analog signal or an amplified signal of the first analog signal, the second radio frequency port is configured to input the second analog signal or an amplified signal of the second analog signal, the plurality of dc bias ports are configured to input dc bias voltages, respectively, and the optical output port is configured to output the single-sideband modulation signal.

And the single-bias electro-optical modulator electro-optically modulates the signals input by the optical input port, the first radio frequency port and the second radio frequency port according to the direct-current bias voltage to obtain a single-sideband modulation signal of an optical domain, and outputs the single-sideband modulation signal through the optical output port, wherein two sidebands of a spectrum of the single-sideband modulation signal respectively bear data of the first path of digital signal and the second path of digital signal.

With reference to the first aspect or the foregoing implementation manner, in a third implementation manner of the first aspect, the single-bias electro-optical modulator is a quadrature IQ modulator, wherein the first rf port is an I port of the IQ modulator and the second rf port is a Q port of the IQ modulator, or the first rf port is a Q port of the IQ modulator and the second rf port is an I port of the IQ modulator, and the plurality of dc bias ports include a first bias port corresponding to the I port, a second bias port corresponding to the Q port, and a third bias port, wherein a dc bias of the first bias port is set at 0.75 pi, a dc bias of the second bias port is set at 0.75 pi, and a dc bias of the third bias port is set at 0.5 pi.

By setting three DC bias voltages of the IQ modulator, the embodiment of the invention can use a commonly used IQ modulator to perform electro-optical modulation operation, wherein the pre-processed real part signal and the pre-processed imaginary part signal are respectively used as I, Q two-way input of the IQ modulator, and the implementation mode is simple and easy.

With reference to the first aspect or the foregoing implementation manner, in a fourth implementation manner of the first aspect, the single-bias electro-optical modulator is a parallel dual-electrode mach-zehnder modulator DD-MZM, where the first rf port is an upper arm rf input port of the DD-MZM and the second rf port is a lower arm rf input port of the DD-MZM, or the first rf port is a lower arm rf input port of the DD-MZM and the second rf port is an upper arm rf input port of the DD-MZM, the plurality of dc bias ports include a first bias port corresponding to the upper arm rf input port and a second bias port corresponding to the lower arm rf input port, where the first bias port is grounded and a dc bias voltage of the second bias port is set at 0.25 pi.

By setting two direct current bias voltages of the DD-MZM, the embodiment of the present invention can use a commonly used DD-MZM to perform an electro-optical modulation operation, wherein the pre-processed real part signal and the pre-processed imaginary part signal are respectively used as two input paths of an upper arm and a lower arm of the DD-MZM, and the implementation manner is relatively simple and easy.

With reference to the first aspect or the foregoing implementation manner, in a fifth possible implementation manner of the first aspect, an electrical domain modulation manner of the first real signal, the first imaginary signal, the second real signal, and the second imaginary signal is Direct Multi-tone Technology (DMT) modulation or Carrierless Amplitude Phase (CAP) modulation.

For signal transmission and processing, before electro-optical modulation, electrical domain modulation processing (e.g., quadrature amplitude mapping) may be included in the digital signal processing in the electrical domain to obtain the real and imaginary signals. The embodiment of the present invention does not limit the electrical domain modulation method of the real number signal and the imaginary number signal, and may be DMT modulation or CAP modulation, which are mature and easy to use, but may also adopt other suitable modulation methods.

With reference to the first aspect or the foregoing implementation manner, in a sixth possible implementation manner of the first aspect, the first path of digital signal and the second path of digital signal are Pseudo Random Binary Sequence (PRBS) digital signals. Such PRBS signals are a common data format in communications and are conveniently used to simulate random codes in real systems.

With reference to the first aspect or the foregoing implementation manner, in a seventh possible implementation manner of the first aspect, the signal processing module, the operation module, and the Digital-to-analog conversion module may be implemented by a Digital Signal Processor (DSP). The mode only needs one DSP, so that the equipment space can be saved, and the cost is reduced. Of course, the embodiments of the present invention may also use other ways to implement these several modules. For example, the signal processing module may be implemented by a DSP or a dedicated chip, the operation module may be implemented by an adder circuit and a subtractor, and the Digital-to-Analog conversion module may be implemented by an Analog-to-Digital Converter (ADC).

In a second aspect, a method for processing signals in an optical communication system is provided, where the optical communication system is configured to process a first path of digital signals and a second path of digital signals, and the method includes: performing digital signal processing on the first path of digital signal to output a first real signal and a first imaginary signal, and performing digital signal processing on the second path of digital signal to output a second real signal and a second imaginary signal, wherein the frequencies of the first real signal and the first imaginary signal fall into an intermediate frequency X/2 part of the bandwidth of the optical communication system, the frequencies of the second real signal and the second imaginary signal fall into a high frequency X/2 part of the bandwidth of the optical communication system, wherein X is greater than or equal to 1/2 and less than or equal to 2/3, the first imaginary signal is a Hilbert transform of the first real signal, and the second imaginary signal is a Hilbert transform of the second real signal; performing a first operation on the first real signal and the second real signal output by the signal processing module to obtain a first operation signal, and performing a second operation on the first imaginary signal and the second imaginary signal output by the signal processing module to obtain a second operation signal, wherein the first operation is an addition operation and the second operation is a subtraction operation, or the first operation is a subtraction operation and the second operation is an addition operation; performing digital-to-analog conversion on the first operation signal to obtain a first analog signal, and performing digital-to-analog conversion on the second operation signal to obtain a second analog signal; and performing single-sideband modulation by using a single-bias electro-optical modulator, wherein the single-bias electro-optical modulator is used for receiving the first analog signal or the amplified signal of the first analog signal and the second analog signal or the amplified signal of the second analog signal, and performing electro-optical modulation to obtain a single-sideband modulation signal of an optical domain, and two side bands of a spectrum of the single-sideband modulation signal respectively bear data of the first path of digital signal and the second path of digital signal.

The various steps of the method of the second aspect may also be referred to various operations of the corresponding modules and/or devices of the apparatus of the first aspect and are not repeated here.

In a third aspect, an optical communication system is provided, where the optical communication system is configured to process a first path of digital signals and a second path of digital signals, the optical communication system includes a transmitter, a receiver, and an optical fiber link connected between the transmitter and the receiver, the transmitter includes a signal processing module, an arithmetic module, a digital-to-analog conversion module, and a single-bias electro-optical modulator, and the receiver includes a photodiode, an amplifier, and a signal recovery module.

The signal processing module is configured to perform digital signal processing on the first path of digital signal to output a first real signal and a first imaginary signal, and perform digital signal processing on the second path of digital signal to output a second real signal and a second imaginary signal, where frequencies of the first real signal and the first imaginary signal fall into an intermediate frequency X/2 part of a bandwidth of the optical communication system, frequencies of the second real signal and the second imaginary signal fall into a high frequency X/2 part of the bandwidth of the optical communication system, where 1/2 is not less than X2/3, the first imaginary signal is a hilbert transform of the first real signal, and the second imaginary signal is a hilbert transform of the second real signal; the operation module is configured to perform a first operation on the first real number signal and the second real number signal output by the signal processing module to obtain a first operation signal, and perform a second operation on the first imaginary number signal and the second imaginary number signal output by the signal processing module to obtain a second operation signal, where the first operation is an addition operation and the second operation is a subtraction operation, or the first operation is a subtraction operation and the second operation is an addition operation.

The digital-to-analog conversion module is used for performing digital-to-analog conversion on the first operation signal to obtain a first analog signal, and performing digital-to-analog conversion on the second operation signal to obtain a second analog signal.

The single-bias electro-optical modulator is configured to receive the first analog signal or an amplified signal of the first analog signal and the second analog signal or an amplified signal of the second analog signal, perform electro-optical modulation to obtain a single-sideband modulation signal of an optical domain, and output the single-sideband modulation signal to an optical fiber link through the single-bias electro-optical modulator, where two sidebands of a spectrum of the single-sideband modulation signal respectively carry data of the first path of digital signal and the second path of digital signal. The photodiode receives the single-sideband modulation signal from the optical fiber link and performs photoelectric conversion processing on the single-sideband modulation signal to obtain a beat frequency signal, wherein an intermediate frequency X/2 part of the bandwidth of the beat frequency signal carries data of the first path of digital signal, a high frequency X/2 part of the bandwidth of the beat frequency signal carries data of the second path of digital signal, and a low frequency 1-X part of the bandwidth of the beat frequency signal is used as a guard band of beat frequency interference SSBI of signals and signals. The amplifier is used for amplifying the beat frequency signal to obtain an amplified beat frequency signal; the signal recovery module is used for recovering the data of the first path of digital signal and the second path of digital signal from the amplified beat frequency signal.

With reference to the third aspect, in an implementation manner of the third aspect, the optical communication system is a short-range optical communication system. In the field of optical communication, a short-distance optical communication system refers to an optical communication system in which the total length of the optical fiber link is less than 80 km. The embodiment of the invention is particularly suitable for the short-distance optical communication system adopting the direct detection technology at the receiving end. According to the embodiment of the invention, the real part and the imaginary part of the two paths of digital signals are respectively subjected to arithmetic operation, and the operated result is used as two paths of input of a single-bias electro-optical modulator, so that the two side bands of the spectrum of the obtained single-side band modulation signal respectively bear the data of the two paths of digital signals, and the two paths of digital signals are not required to be respectively modulated by the double-bias electro-optical modulator, so that the cost can be saved.

On the other hand, the optical communication system of the embodiment of the invention adopts direct detection receiving at the receiving end, and only one photodiode is needed, so that the cost is lower. Moreover, after the beat frequency of the receiving end, the SSBI falls into a protection frequency band, so that the interference to effective signals is reduced, the SSBI can be eliminated in a physical layer without digital processing, and the signal processing performance is improved.

The modules of the optical communication system of the third aspect may be implemented by referring to the corresponding modules of the apparatus of the first aspect, and are not described herein again to avoid repetition.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a schematic block diagram of an optical communication system according to an embodiment of the present invention.

Fig. 2 is a spectral diagram of the optical domain of a dual polarization modulated output signal.

Fig. 3 is a diagram of the electrical domain spectrum of a signal after photoelectric conversion of a dual polarization modulated output signal.

Fig. 4 is a schematic block diagram of an apparatus for processing a signal in an optical communication system according to an embodiment of the present invention.

Fig. 5 is a graph of the optical domain spectrum of an output signal according to an embodiment of the present invention.

Fig. 6 is another schematic block diagram of an apparatus for processing a signal in an optical communication system according to an embodiment of the present invention.

Fig. 7 is still another schematic block diagram of an apparatus for processing a signal in an optical communication system according to an embodiment of the present invention.

Fig. 8 is a schematic block diagram of a receiver according to an embodiment of the present invention.

Fig. 9 is a schematic block diagram of an IQ-modulator according to an embodiment of the invention.

FIG. 10 is a schematic diagram of an output signal according to an embodiment of the invention.

FIG. 11 is a schematic block diagram of a DD-MZM modulator according to an embodiment of the present invention.

Fig. 12 is a schematic block diagram of a method of processing a signal in an optical communication system according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, shall fall within the scope of protection of the present invention.

The technical scheme of the invention can be applied to various optical communication systems, such as: a Plesiochronous Digital Hierarchy (PDH) optical communication system, a Synchronous Digital Hierarchy (SDH) optical communication system, a Dense Wavelength Division Multiplexing (DWDM) optical communication system, an all-optical network optical communication system, and the like. The embodiment of the invention is mainly described by taking an application scenario as a short-distance wired optical communication system as an example. The short-distance optical communication system refers to an optical communication system with the total length of an optical fiber below 80 km.

As shown in fig. 1, a short-range wired optical communication system 100 applied to an embodiment of the present invention may include a transmitter 110, an optical fiber link 120, and a receiver 130. The transmitter 110 may include a signal processing circuit 111, an optical source 112, and a modulator 113, the fiber link 120 may be composed of an optical fiber 121 and a repeater 122, and the receiver 130 may include a photodiode 131, an amplifier 132, and a signal recovery unit 133. It should be noted that the signal processing circuit 111 may not be included in the system 100, in other words, the electrical input signal may be directly input to the modulator 113 to modulate the optical signal generated by the optical source 112. In the optical communication system 100, the transmitter 110 is used to convert an electrical input signal into an optical signal so that the optical signal can be transmitted over the optical fiber link 120. The receiver 130 is configured to receive the optical signal and convert the optical signal into a raw electrical signal, i.e., the electrical output signal in fig. 1. In addition, in this system 100, the length of the optical fiber 121 is less than 80km and the receiver 130 employs direct detection techniques.

In the direct detection technology, in order to improve the spectral efficiency, one method is to map two paths of digital signals X1 and X2 to be transmitted to two paths of digital signals X3 and X4 whose frequencies fall into a low-frequency 1/3 bandwidth part and a high-frequency 1/3 bandwidth part of the system 100, respectively, or to process one path of digital signal to be transmitted into the two paths of signals X1 and X2, at the transmitter 110 end. As shown in fig. 2, the two signals X3 and X4 are modulated on two optical carriers that are normally off orthogonal by the modulator 113, so that SSBI can fall within the low frequency 1/3 guard band at the receiver 130 end, as shown in fig. 3. Therefore, the spectrum efficiency can be improved from 1/2 to 2/3 while the interference of the SSBI to the signal part is eliminated. In fig. 3, B represents the basic bandwidth, for example, B may be 50GHz or 100GHz, the sum of signals a1 and a2 is signal X3, and the sum of signals B1 and B2 is signal X4.

However, the above method requires the use of a double-bias electro-optical modulator, and the system cost is high. The embodiment of the invention provides a device for processing signals in an optical communication system, which solves the problem of high system cost in the prior art. The following will be described in detail with reference to specific examples.

Fig. 4 shows a schematic block diagram of an apparatus 200 for processing a signal in an optical communication system according to an embodiment of the present invention. The optical communication system is used for transmitting two paths of digital signals, namely a first path of digital signal X1 and a second path of digital signal X2, wherein the first path of digital signal X1 and the second path of digital signal X2 may be two independent digital signals, or two paths of digital signals obtained by processing one path of digital signal. The present invention is not limited to the specific processing procedure of the digital signal.

The apparatus 200 is an example of the transmitter 110 of fig. 1, and is used for processing the first digital signal X1 and the second digital signal X2. As shown in fig. 4, the apparatus 200 includes a signal processing module 210, an operation module 220, a digital-to-analog conversion module 230, and a single-bias electro-optic modulator 240.

In the embodiment of the present invention, the signal processing module 210, the operation module 220, and the digital-to-analog conversion module 230 in the apparatus 200 may be a specific example of the signal processing circuit 111 in the transmitter 110 in fig. 1, configured to pre-process the first digital signal X1 and the second digital signal X2 to output a desired signal; the single-bias electro-optic modulator 240 in the apparatus 200 may be a specific example of the modulator 113 in the transmitter 110 in fig. 1.

The signal processing module 210 is configured to perform digital signal processing on the first path of digital signal X1 to output a first real signal I1 and a first imaginary signal Q1, and perform digital signal processing on the second path of digital signal X2 to output a second real signal I2 and a second imaginary signal Q2.

In the embodiment of the invention, the frequencies of the first real signal I1 and the first imaginary signal Q1 fall within the intermediate frequency X/2 part of the bandwidth of the optical communication system, and the frequencies of the second real signal I2 and the second imaginary signal Q2 fall within the high frequency X/2 part of the bandwidth of the optical communication system, wherein X is 1/2 ≦ 2/3. In the embodiment of the present invention, the first imaginary signal QI is a hilbert transform of the first real signal I1, and the second imaginary signal Q2 is a hilbert transform of the second real signal I2.

The operation module 220 is configured to perform a first operation on the first real signal I1 and the second real signal I2 output by the signal processing module 210 to obtain a first operation signal D1, and perform a second operation on the first imaginary signal Q1 and the second imaginary signal Q2 output by the signal processing module to obtain a second operation signal D2.

The first operation is an addition operation and the second operation is a subtraction operation, or the first operation is a subtraction operation and the second operation is an addition operation. In the embodiment of the present invention, the operation module 220 is configured to add the two real signals I1 and I2 to obtain a first operation signal I1+ I2, that is, D1-I1 + I2, and subtract the two imaginary signals Q1 and Q2 to obtain second operation signals Q1-Q2, that is, D2-Q1-Q2. Or the operation module 120 is configured to perform subtraction operation on the two real number signals I1 and I2 to obtain first operation signals I1-I2, that is, D1-I1-I2, and perform addition operation on the two imaginary number signals Q1 and Q2 to obtain a second operation signal Q1+ Q2, that is, D2-Q1 + Q2.

The digital-to-analog conversion module 230 is configured to perform digital-to-analog conversion on the first operation signal D1 to obtain a first analog signal Y1, and perform digital-to-analog conversion on the second operation signal D2 to obtain a second analog signal Y2.

The single-bias electro-optical modulator 240 is configured to receive the first analog signal Y1 or the amplified signal of the first analog signal Y1, and the second analog signal Y2 or the amplified signal of the second analog signal Y2, and perform electro-optical modulation to obtain a single-sideband modulation signal Eout in an optical domain, where two sidebands of a spectrum of the single-sideband modulation signal Eout respectively carry data of the first path of digital signal X1 and the second path of digital signal X2.

Optionally, in an embodiment of the present invention, X ═ 2/3, where the frequencies of the first real signal and the first imaginary signal fall within the intermediate frequency 1/3 portion of the bandwidth of the optical communication system, and the frequencies of the second real signal and the second imaginary signal fall within the high frequency 1/3 portion of the bandwidth of the optical communication system.

Alternatively, in the embodiment of the present invention, as shown in fig. 4, the single-bias electro-optical modulator 240 may include an optical input port EI, an optical output port EO, a first RF port RF1, a second RF port RF2 and a plurality of dc bias ports bias, the optical input port EI is used for inputting the continuous optical signal Ein, the first RF port RF1 is used for inputting the first analog signal Y1 or the amplified signal of the first analog signal Y1, the second RF port is used for inputting the second analog signal Y2 or the amplified signal of the second analog signal Y2, and the plurality of dc bias ports bias are used for inputting dc bias voltages, respectively.

In the embodiment of the present invention, the single-bias electro-optical modulator 240 is configured to electro-optically modulate signals input by the optical input port EI, the first RF port RF1 and the second RF port RF2 according to the dc bias voltage to obtain a single-sideband modulation signal Eout of an optical domain. The single-sideband modulated signal Eout ═ Ein ═ (I1+ Q1+ I2-Q2), is output via the optical output port EO, and the two sidebands of the spectrum of the single-sideband modulated signal Eout carry the data of the first digital signal X1 and the second digital signal X2, respectively. As shown in FIG. 5, the output left sideband signal includes signals I2-Q2, the output right sideband signal includes signals I1+ Q1, and the signals I1+ Q1 carry the data of the first digital signal X1, and the signals I2-Q2 carry the data of the second digital signal X2.

According to the embodiment of the invention, the real part and the imaginary part of the two paths of digital signals are respectively subjected to arithmetic operation, and the operated result is used as two paths of input of the single-bias electro-optical modulator, so that the two side bands of the spectrum of the obtained single-side band modulation signal respectively bear the data of the two paths of digital signals, and the two paths of digital signals are not required to be respectively modulated by the two single-bias electro-optical modulators, so that the cost can be saved.

The function of the signal processing module 210 in the embodiment of the present invention may be implemented by a DSP, or may be implemented by another chip or device having a digital signal processing function. In addition, the operation module 220 in the embodiment of the present invention may be implemented by an adder and a subtractor, and may also be implemented by a DSP, and similarly, the digital-to-analog conversion module 230 may be implemented by a digital-to-analog converter DAC, and may also be implemented by a DSP having a digital-to-analog conversion function. The embodiment of the present invention does not limit the specific implementation form of the operation module 220 and the digital-to-analog conversion module 230.

Fig. 6 is a schematic diagram of an exemplary structure of an apparatus for processing a signal in an optical communication system according to an embodiment of the present invention. DSP 211 and DSP 212 in fig. 6 may correspond to an implementation of signal processing block 210 in fig. 4, adder 221 and subtractor 222 may correspond to an implementation of operation block 220 in fig. 4, and DAC231 and DAC132 may correspond to an implementation of digital-to-analog conversion block 230 in fig. 4.

The DSP 211 in fig. 6 may perform a series of processing on the first digital signal X1, such as serial-to-parallel conversion, Quadrature Amplitude Modulation (QAM) mapping, subcarrier mapping, i.e., signal Modulation, Inverse Fourier Transform (IFFT), cyclic prefix CP addition, parallel-to-serial conversion, and the like; the DSP 212 in fig. 6 may perform serial-to-parallel conversion, QAM mapping, subcarrier mapping, i.e., signal modulation, IFFT, CP adding, parallel-to-serial conversion, and the like on the second path digital signal X2. In the embodiment of the present invention, the specific processing steps and sequence of the DSP 211 for the first digital signal X1 and the DSP 212 for the second digital signal X2 are not limited.

Specifically, the DSP 211 may output a first real signal I1 and a first imaginary signal Q1 by performing serial-to-parallel conversion, QAM mapping, subcarrier mapping, i.e., signal modulation, IFFT, CP adding, parallel-to-serial conversion, and the like on the first path of digital signal X1, where the frequencies of I1 and Q1 fall into the intermediate frequency 1/3 portion of the bandwidth of the optical communication system, and Q1 is hilbert transform of I1; similarly, the DSP 212 may perform serial-to-parallel conversion, QAM mapping, subcarrier mapping, i.e., signal modulation, IFFT, CP adding, and parallel-to-serial conversion on the second path of digital signal X2, and output a first real signal I2 and a first imaginary signal Q2, where the frequencies of I2 and Q2 fall into the high-frequency 1/3 portion of the bandwidth of the optical communication system, and Q2 is hilbert transform of I2. The adder 221 may receive the first real signal I1 and the second real signal I2, add them to obtain a first operation signal I1+ I2, and input the first operation signal I1+ I2 to the DAC 231. The subtractor 222 may receive the first imaginary signal Q1 and the second imaginary signal Q2, subtract them to obtain second operation signals Q1-Q2, and input the second operation signals Q1-Q2 to the DAC 232. The DAC231 performs digital-to-analog conversion on the first operation signal I1+ I2 to obtain a first analog signal Y1, and the DAC 232 performs digital-to-analog conversion on the second operation signals Q1-Q2 to obtain a first analog signal Y2. The first radio frequency port RF1 of the single-bias electro-optic modulator 240 receives Y1 or amplified Y1 and the second radio frequency port RF2 receives Y2 or amplified Y2, while the optical input port EI of the single-bias electro-optic modulator 240 receives a continuous optical signal Ein that may be generated by the laser 260. The signals input by the optical input port Ein, the first RF port RF1 and the second RF port RF2 are subjected to electro-optical modulation by a dc bias voltage, so that a single-sideband modulated signal Eout of an optical domain can be obtained, wherein two sidebands of a spectrum of the Eout respectively carry data of X1 and X2, and the Eout is Ein (I1+ Q1+ I2-Q2).

In the embodiment of the present invention, as shown in fig. 7, the output I1 and I2 can be further processed by the subtractor 222 to output the first operation signals I1-I2, and at the same time, the output Q1 and Q2 can be processed by the adder 221 to output the second operation signal Q1+ Q2. At this time, I1-I2 are used as the input of the DAC231, and are subjected to digital-to-analog conversion to obtain a first analog signal Y1, and Q1+ Q2 are used as the input of the DAC 232, and are subjected to digital-to-analog conversion to obtain a second analog signal Y2.

In the embodiment of the present invention, I1+ I2 may also be used as the input of DAC 232, and in this case, Q1-Q2 may be used as the input of DAC 231; similarly, I1-I2 may also be used as the input of DAC 232, in this case, Q1+ Q2 may be used as the input of DAC231, and the input of DAC is not limited in the embodiment of the present invention.

It should be understood that, in the embodiment of the present invention, the DAC231 and the DAC 232 may be the same DAC that can process at least two signals simultaneously, or may be different DACs. In this embodiment of the present invention, the DSP 211 and the DSP 212 may be the same DSP or different DSPs, and the specific implementation form of the DSP is not limited in this embodiment of the present invention.

It should also be understood that in the embodiments of the present invention, the laser is used to generate Ein only for illustration, and the embodiments of the present invention do not limit the source and specific form of Ein.

Optionally, in this embodiment of the present invention, the first digital signal X1 and the second digital signal X2 are PRBS digital signals.

Specifically, when X1 is PRBS1 and X2 is PRBS2, the input of DSP 211 is PRBS1 and the input of DSP 212 is PRBS 1. In other words, the two signals to be processed by the device are PRBS1 and PRBS 2.

Optionally, in the embodiment of the present invention, the modulation method of the first real signal I1, the first imaginary signal Q1, the second real signal I2, and the second imaginary signal Q2 is DMT modulation or CAP modulation. It should be understood that the modulation scheme may also include other modulation schemes.

It should be understood that, in the embodiment of the present invention, QAM mapping is to implement frequency band compression of a signal, subcarrier mapping is to modulate a signal to implement spectrum shifting of a signal, and specifically, to process information of a signal to load on a subcarrier to make the signal become a form suitable for channel transmission. The method for carrying information in the modulation process comprises the following steps: polarization direction, amplitude, frequency, phase, etc., and these factors or combinations thereof are often referred to as modulation schemes. The embodiment of the present invention only exemplifies modulation schemes including DMT modulation and CAP modulation, and the modulation scheme is not limited in the embodiment of the present invention.

In the embodiment of the present invention, as shown in fig. 8, the Eout is output through the optical output port and transmitted through one or more segments of optical fibers to reach the optical receiver 250, and the implementation form of the optical receiver 250 may be the optical receiver 130 shown in fig. 1, or may be different from the implementation form of the optical receiver 130. For example, the optical receiver 250 may include a Photodiode (PD), an analog-to-digital converter (ADC), a DSP, and the like. Specifically, as shown in fig. 3, after the Eout is beaten by a PD, the SSBI may fall within the low frequency 1/3 guard band, I1 may fall within the medium frequency 1/3 bandwidth, and I2 may fall within the high frequency 1/3 bandwidth. In fig. 3, the sum of the signal AI and the signal a2 is I1, and the sum of the signal BI and the signal B2 is I2. After the PD converts the optical signal into an Analog electrical signal, the Analog-to-digital converter (ADC) converts the Analog electrical signal into a digital signal, and finally the DSP performs a series of processing on the digital signal, such as serial-to-parallel conversion, CP removal, FFT, subcarrier mapping, QAM mapping, and parallel-to-serial conversion, to obtain the first path of digital signal X1 and the second path of digital signal X2.

It should be understood that the Eout may be amplified by the erbium-doped fiber amplifier after being output through the optical output port, and then transmitted, and the embodiment of the present invention does not limit the transmission form. .

It should also be understood that the optical receiver 250 may further include an amplifying circuit, and the embodiment of the present invention is not limited to the specific configuration form of the optical receiver.

Therefore, the real part and the imaginary part of the two paths of digital signals are respectively subjected to arithmetic operation, and the operated result is used as two paths of input of the single-bias electro-optical modulator, so that the two side bands of the spectrum of the obtained single-side band modulation signal respectively bear the data of the two paths of digital signals, the two paths of digital signals are not required to be respectively modulated by the double-bias electro-optical modulator, and the cost can be saved.

In addition, the above processing of the embodiment of the invention is performed on the two paths of digital signals at the same time, and only the part of the low frequency 1/3 in the obtained single sideband modulation signal is not used for transmitting data and is used as a guard band for accommodating the SSBI, so that the spectrum resource of 2/3 can be utilized, and the signal performance is improved and the good utilization rate of the system resource is achieved.

In the embodiment of the present invention, optionally, the single-bias electro-optical modulator 240 is a quadrature IQ modulator, wherein the first RF port RF1 is an I port of the IQ modulator and the second RF port RF2 is a Q port of the IQ modulator, or the first RF port RF1 is a Q port of the IQ modulator and the second RF port RF2 is an I port of the IQ modulator, the plurality of dc bias ports bias includes a first bias port bias1 corresponding to the I port, a second bias port bias2 corresponding to the Q port, and a third bias port bias3, wherein the dc bias of the first bias port bias1 is set at 0.75 pi, the dc bias of the second bias port bias2 is set at 0.75 pi, and the dc bias of the third bias port bias3 is set at 0.5 pi.

Fig. 9 shows a schematic block diagram of an IQ-modulator 241 according to an embodiment of the present invention. Specifically, referring to fig. 9, in the embodiment of the present invention, after a carrier input Ein of the IQ Modulator 241 passes through an Optical Coupler (OC) OC1, two signals with a power ratio of 1:1 are generated and respectively used as inputs of an Intensity Modulator (IM) IM1 and an IM 12. The input of the I port of the IM1 is I1+ I2, the input of the Q port of the IM2 is Q1-Q2, and the bias voltages of the bias1 and the bias2 are adjusted to be 0.75 pi. For example, assume a half-wave voltage V of the IQ-modulator 241_πWhen the input voltages of bias1 and bias2 are both 3V at 4V, bias1 and bias2 are both biased at 0.75 pi. At this time, the output of the IM1 includes the signal I1+ I2, as shown in (a) of fig. 10; the output of the IM2 includes signals Q1-Q2, as shown in FIG. 10 (b). By adjusting the dc bias voltage input to bias3, bias3 is biased at 0.5 pi, so that the output of IM2 passes through a Phase Shifter (PS) inside IQ modulator 241, which produces a 0.5 pi Phase shift, and the output of PS includes signals I1-I2, as shown in fig. 10 (c). Thus, the two signals output via the IM1 and PS output are single sideband modulated Eout via the OC2 as shown in fig. 5.

Fig. 10 (a), 10 (b), 10 (c), and 5 show only that the output signal includes a signal component, and are not specific expressions of the output signal. It should be understood that in the embodiment of the present invention, only I1+ I2 is used as the input of the I port, and Q1-Q2 are used as the input of the Q port, which is described as a specific embodiment of the present invention. In the embodiment of the present invention, the input of the I port may also be I1-I2, and the input of the Q port may also be Q1+ Q2, which is not described herein again to avoid repetition.

In the embodiment of the present invention, optionally, the single-bias electro-optic modulator 240 is a parallel dual-electrode mach-zehnder modulator DD-MZM, wherein the first RF port RF1 is an upper arm RF input port of the DD-MZM and the second RF port RF2 is a lower arm RF input port of the DD-MZM, or the first RF port RF1 is a lower arm RF input port of the DD-MZM and the second RF port RF2 is an upper arm RF input port of the DD-MZM, the plurality of dc bias ports bias includes a first bias port bias1 corresponding to the upper arm RF input port and a second bias port bias2 corresponding to the lower arm RF input port, wherein the first bias port bias is grounded, and the dc bias of the second bias port bias is set at 0.25 pi.

Specifically, in the embodiment of the present invention, as shown in fig. 11, Ein is inputted as a continuous optical carrier signal to DD-MZM242, Y1 and Y2 are inputted as two RF inputs of DD-MZM242, and a dc voltage V1 and V2 are applied to two bias ports bias1 and bias2 of the DD-MZM respectively through RF1 and RF2, and one bias port is grounded, and a dc bias voltage of the other bias port is set to 0.25 pi, so that a single sideband modulation signal Eout of an optical domain can be obtained.

It should be understood that, since the operation principle of the DD-MZM modulator is similar to that of the IQ modulator, the details are not repeated herein to avoid redundancy.

It should also be understood that, in the embodiments of the present invention, only the single-bias electro-optical modulator is described as an IQ modulator and a DD-MZM modulator, and the present invention does not limit the specific form of the single-bias electro-optical modulator.

Therefore, in the apparatus for processing signals in the optical communication system according to the embodiment of the present invention, the real part and the imaginary part of the two digital signals are respectively subjected to arithmetic operation, and the result after the arithmetic operation is used as two inputs of a single-bias electro-optical modulator, so that the two side bands of the spectrum of the obtained single-sideband modulation signal respectively carry data of the two digital signals, and thus, the two digital signals do not need to be respectively modulated by using a double-bias electro-optical modulator, which can save the cost.

The apparatus for processing a signal in an optical communication system according to an embodiment of the present invention is described in detail above with reference to fig. 1 to 11, and a method for processing a signal in an optical communication system according to an embodiment of the present invention is described below with reference to fig. 12.

Fig. 12 shows a schematic flow chart of a method 300 of processing signals in an optical communication system according to an embodiment of the present invention. The optical communication system is used for processing a first path of digital signal and a second path of digital signal, and the first path of digital signal and the second path of digital signal are two paths of digital signals transmitted by the optical communication system.

310, performing digital signal processing on the first path of digital signal to output a first real signal and a first imaginary signal, and performing digital signal processing on the second path of digital signal to output a second real signal and a second imaginary signal, wherein the frequencies of the first real signal and the first imaginary signal fall into an intermediate frequency X/2 part of the bandwidth of the optical communication system, the frequencies of the second real signal and the second imaginary signal fall into a high frequency X/2 part of the bandwidth of the optical communication system, wherein 1/2 is not less than X is not less than 2/3, the first imaginary signal is a hilbert transform of the first real signal, and the second imaginary signal is a hilbert transform of the second real signal;

320, performing a first operation on the first real signal and the second real signal output by the signal processing module to obtain a first operation signal, and performing a second operation on the first imaginary signal and the second imaginary signal output by the signal processing module to obtain a second operation signal, wherein the first operation is an addition operation and the second operation is a subtraction operation, or the first operation is a subtraction operation and the second operation is an addition operation;

330, performing digital-to-analog conversion on the first operation signal to obtain a first analog signal, and performing digital-to-analog conversion on the second operation signal to obtain a second analog signal;

340, performing single-sideband modulation by using a single-bias electro-optical modulator, wherein the single-bias electro-optical modulator is configured to receive the first analog signal or the amplified signal of the first analog signal, and the second analog signal or the amplified signal of the second analog signal, perform electro-optical modulation to obtain a single-sideband modulation signal in an optical domain, and output the single-sideband modulation signal to the optical fiber link via the single-bias electro-optical modulator, where two sidebands of a spectrum of the single-sideband modulation signal respectively carry data of the first path of digital signal and the second path of digital signal.

The embodiment of the invention provides a method for processing signals in an optical communication system, which is characterized in that the real parts and the imaginary parts of two paths of digital signals are respectively subjected to arithmetic operation, and the operated result is used as two paths of input of a single-bias electro-optical modulator, so that the two side bands of the spectrum of the obtained single-side band modulation signal respectively bear the data of the two paths of digital signals, and the two paths of digital signals are not required to be respectively modulated by using a double-bias electro-optical modulator, so that the cost can be saved.

The steps of the method 300 may refer to the operations of the corresponding modules and/or devices of the apparatus 100 in fig. 1, and are not repeated herein to avoid repetition.

It should be understood that the term "and/or" herein is merely one type of association relationship that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.

It should be understood that, in various embodiments of the present invention, the sequence numbers of the above-mentioned processes do not mean the execution sequence, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

Those of ordinary skill in the art will appreciate that the elements and algorithm steps of the examples described in connection with the embodiments disclosed herein may be embodied in electronic hardware, computer software, or combinations of both, and that the components and steps of the examples have been described in a functional general in the foregoing description for the purpose of illustrating clearly the interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.

In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may also be an electric, mechanical or other form of connection.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment of the present invention.

In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.

The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention essentially or partially contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product stored in a storage medium and including instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.

While the invention has been described with reference to specific embodiments, the invention is not limited thereto, and various equivalent modifications and substitutions can be easily made by those skilled in the art within the technical scope of the invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. An apparatus for processing signals in an optical communication system, wherein the optical communication system is configured to process a first path of digital signals and a second path of digital signals, the apparatus comprising:

a signal processing module, configured to perform digital signal processing on the first path of digital signal to output a first real signal and a first imaginary signal, and perform digital signal processing on the second path of digital signal to output a second real signal and a second imaginary signal, where frequencies of the first real signal and the first imaginary signal fall into an intermediate-frequency X/2 part of a bandwidth of the optical communication system, frequencies of the second real signal and the second imaginary signal fall into a high-frequency X/2 part of the bandwidth of the optical communication system, where 1/2 is not less than X2/3, the first imaginary signal is a hilbert transform of the first real signal, and the second imaginary signal is a hilbert transform of the second real signal;

an operation module, configured to perform a first operation on the first real signal and the second real signal output by the signal processing module to obtain a first operation signal, and perform a second operation on the first imaginary signal and the second imaginary signal output by the signal processing module to obtain a second operation signal, where the first operation is an addition operation and the second operation is a subtraction operation, or the first operation is a subtraction operation and the second operation is an addition operation;

the digital-to-analog conversion module is used for performing digital-to-analog conversion on the first operation signal to obtain a first analog signal, and performing digital-to-analog conversion on the second operation signal to obtain a second analog signal;

the single-bias electro-optical modulator is used for receiving the first analog signal or the amplified signal of the first analog signal and the amplified signal of the second analog signal or the amplified signal of the second analog signal, and performing electro-optical modulation to obtain a single-sideband modulation signal of an optical domain, wherein two sidebands of a spectrum of the single-sideband modulation signal respectively bear data of the first path of digital signal and the second path of digital signal;

2/3, wherein the frequencies of the first real signal and the first imaginary signal fall within the intermediate frequency 1/3 portion of the bandwidth of the optical communication system, and the frequencies of the second real signal and the second imaginary signal fall within the high frequency 1/3 portion of the bandwidth of the optical communication system.

2. The apparatus of claim 1, wherein the single-bias electro-optic modulator comprises an optical input port for inputting a continuous optical signal, an optical output port for inputting the first analog signal or an amplified signal of the first analog signal, a first radio frequency port for inputting the second analog signal or an amplified signal of the second analog signal, a second radio frequency port for inputting a DC bias voltage, and a plurality of DC bias ports for outputting the single-sideband modulated signal.

3. The apparatus of claim 2, wherein the single-bias electro-optic modulator is a quadrature-IQ modulator, wherein the first RF port is an I-port of the IQ modulator and the second RF port is a Q-port of the IQ modulator, or wherein the first RF port is a Q-port of the IQ modulator and the second RF port is an I-port of the IQ modulator, and wherein the plurality of DC bias ports comprises a first bias port corresponding to the I-port, a second bias port corresponding to the Q-port, and a third bias port, wherein the DC bias of the first bias port is set at 0.75 pi, the DC bias of the second bias port is set at 0.75 pi, and the DC bias of the third bias port is set at 0.5 pi.

4. The apparatus of claim 2, wherein the single-bias electro-optic modulator is a parallel two-electrode mach-zehnder modulator DD-MZM, wherein the first rf port is an upper arm rf input port of the DD-MZM and the second rf port is a lower arm rf input port of the DD-MZM, or the first rf port is a lower arm rf input port of the DD-MZM and the second rf port is an upper arm rf input port of the DD-MZM, and wherein the plurality of dc bias ports comprises a first bias port corresponding to the upper arm rf input port and a second bias port corresponding to the lower arm rf input port, wherein the first bias port is grounded and a dc bias voltage of the second bias port is set at 0.25 pi.

5. The apparatus according to any one of claims 1 to 4, wherein the signal processing module, the arithmetic module and the digital-to-analog conversion module are implemented by a Digital Signal Processor (DSP).

6. The apparatus according to any one of claims 1 to 4, wherein the first path of digital signal and the second path of digital signal are Pseudo Random Binary Sequence (PRBS) digital signals.

7. A method for processing a signal in an optical communication system, wherein the optical communication system is configured to process a first path of digital signal and a second path of digital signal, and the method comprises:

performing digital signal processing on the first path of digital signal to output a first real signal and a first imaginary signal, and performing digital signal processing on the second path of digital signal to output a second real signal and a second imaginary signal, wherein the frequencies of the first real signal and the first imaginary signal fall into an intermediate frequency (X/2) part of the bandwidth of the optical communication system, the frequencies of the second real signal and the second imaginary signal fall into a high frequency (X/2) part of the bandwidth of the optical communication system, wherein X is greater than or equal to 1/2 and less than or equal to 2/3, the first imaginary signal is a Hilbert transform of the first real signal, and the second imaginary signal is a Hilbert transform of the second real signal;

performing a first operation on the first real signal and the second real signal output by the signal processing module to obtain a first operation signal, and performing a second operation on the first imaginary signal and the second imaginary signal output by the signal processing module to obtain a second operation signal, wherein the first operation is an addition operation and the second operation is a subtraction operation, or the first operation is a subtraction operation and the second operation is an addition operation;

performing digital-to-analog conversion on the first operation signal to obtain a first analog signal, and performing digital-to-analog conversion on the second operation signal to obtain a second analog signal;

performing single-sideband modulation by using a single-bias electro-optical modulator, wherein the single-bias electro-optical modulator is used for receiving the first analog signal or the amplified signal of the first analog signal and the amplified signal of the second analog signal or the amplified signal of the second analog signal, and performing electro-optical modulation to obtain a single-sideband modulation signal of an optical domain, and two side bands of a spectrum of the single-sideband modulation signal respectively bear data of the first path of digital signal and the second path of digital signal;

8. The method of claim 7, wherein the single-bias electro-optic modulator comprises an optical input port for inputting a continuous optical signal, an optical output port for inputting the first analog signal or an amplified signal of the first analog signal, a first radio frequency port for inputting the second analog signal or an amplified signal of the second analog signal, a second radio frequency port for inputting a DC bias voltage, and a plurality of DC bias ports for outputting the single-sideband modulated signal.

9. The method of claim 8, wherein the single-bias electro-optic modulator is a quadrature IQ modulator,

the first radio frequency port is an I port of the IQ modulator and the second radio frequency port is a Q port of the IQ modulator, or the first radio frequency port is a Q port of the IQ modulator and the second radio frequency port is an I port of the IQ modulator, and the plurality of dc bias ports include a first bias port corresponding to the I port, a second bias port corresponding to the Q port, and a third bias port, wherein a dc bias of the first bias port is set at 0.75 pi, a dc bias of the second bias port is set at 0.75 pi, and a dc bias of the third bias port is set at 0.5 pi.

10. The method of claim 8, wherein the single-bias electro-optic modulator is a parallel two-electrode Mach-Zehnder modulator DD-MZM,

the first rf port is an upper arm rf input port of the DD-MZM and the second rf port is a lower arm rf input port of the DD-MZM, or the first rf port is a lower arm rf input port of the DD-MZM and the second rf port is an upper arm rf input port of the DD-MZM, and the plurality of dc bias ports include a first bias port corresponding to the upper arm rf input port and a second bias port corresponding to the lower arm rf input port, where the first bias port is grounded and a dc bias of the second bias port is set at 0.25 pi.

11. An optical communication system, wherein the optical communication system is configured to process a first path of digital signals and a second path of digital signals, the optical communication system includes a transmitter, a receiver, and an optical fiber link connected between the transmitter and the receiver, the transmitter includes a signal processing module, an arithmetic module, a digital-to-analog conversion module, and a single-bias electro-optical modulator, the receiver includes a photodiode, an amplifier, and a signal recovery module,

the signal processing module is configured to perform digital signal processing on the first path of digital signal to output a first real signal and a first imaginary signal, and perform digital signal processing on the second path of digital signal to output a second real signal and a second imaginary signal, where frequencies of the first real signal and the first imaginary signal fall into an intermediate-frequency X/2 part of a bandwidth of the optical communication system, frequencies of the second real signal and the second imaginary signal fall into a high-frequency X/2 part of the bandwidth of the optical communication system, where 1/2 is not less than X2/3, the first imaginary signal is a hilbert transform of the first real signal, and the second imaginary signal is a hilbert transform of the second real signal;

the operation module is configured to perform a first operation on the first real number signal and the second real number signal output by the signal processing module to obtain a first operation signal, and perform a second operation on the first imaginary number signal and the second imaginary number signal output by the signal processing module to obtain a second operation signal, where the first operation is an addition operation and the second operation is a subtraction operation, or the first operation is a subtraction operation and the second operation is an addition operation;

the single-bias electro-optical modulator is configured to receive the first analog signal or an amplified signal of the first analog signal and the second analog signal or an amplified signal of the second analog signal, perform electro-optical modulation to obtain a single-sideband modulation signal of an optical domain, and output the single-sideband modulation signal to an optical fiber link through the single-bias electro-optical modulator, where two sidebands of a spectrum of the single-sideband modulation signal respectively carry data of the first path of digital signal and the second path of digital signal;

the photodiode receives the single-sideband modulation signal from the optical fiber link and performs photoelectric conversion processing on the single-sideband modulation signal to obtain a beat frequency signal, wherein an intermediate frequency X/2 part of the bandwidth of the beat frequency signal bears data of the first path of digital signal, a high frequency X/2 part of the bandwidth of the beat frequency signal bears data of the second path of digital signal, and a low frequency 1-X part of the bandwidth of the beat frequency signal is used as a guard band of beat frequency interference SSBI of the signal and the signal;

the amplifier is used for amplifying the beat frequency signal to obtain an amplified beat frequency signal;

the signal recovery module is used for recovering the amplified beat frequency signal to obtain data of the first path of digital signal and the second path of digital signal;

12. The optical communication system of claim 11, wherein the optical communication system is a short-range optical communication system.