CN114422035B - Optical Fiber Nonlinear Damage Compensation Method and System in Coherent Optical Communication System - Google Patents
Optical Fiber Nonlinear Damage Compensation Method and System in Coherent Optical Communication System Download PDFInfo
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- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/25—Arrangements specific to fibre transmission
- H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
- H04B10/2513—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to chromatic dispersion
- H04B10/2525—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to chromatic dispersion using dispersion-compensating fibres
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
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- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
- H04B10/61—Coherent receivers
- H04B10/616—Details of the electronic signal processing in coherent optical receivers
- H04B10/6165—Estimation of the phase of the received optical signal, phase error estimation or phase error correction
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Abstract
The application provides a method and a system for compensating nonlinear damage of an optical fiber in a coherent optical communication system, comprising the following steps: and a noise obtaining step: obtaining perturbation noise by reducing perturbation terms and multiplying calculation; and a damage compensation step: the perturbation noise is processed to compensate for nonlinear impairments in the fibre channel. The application can be used at the transmitting end based on the transmitting symbol and at the receiving end based on the receiving symbol, and can obviously reduce the implementation complexity while effectively compensating the nonlinear damage of the optical fiber.
Description
Technical Field
The application relates to the technical field of optical fiber nonlinear damage compensation in a coherent optical communication system, in particular to an optical fiber nonlinear damage compensation method and system in a coherent optical communication system. And more particularly, to a method for compensating nonlinear damage of a low-complexity optical fiber in a coherent optical communication system.
Background
As a basis for modern communication systems, coherent optical communication systems have assumed communication traffic of 95% or more of the global communication system. The application of the novel modulation technology and the advanced forward error correction coding technology (Forward Error Correction, abbreviated as FEC) enables the existing coherent optical communication system to further approach the linear shannon limit. Currently, fiber nonlinear impairments are one of the important factors limiting further increases in channel capacity.
The existing method for compensating the nonlinear damage of the optical fiber mainly comprises Digital Back-propagation (DBP for short), and the method is based on a step Fourier method and has higher algorithm precision. But high-precision compensation precision requires a large number of fast fourier transforms (english full name Fast Fourier Transform, FFT for short) and inverse fast fourier transforms (english full name Inverse Fast Fourier Transform, IFFT for short), which results in very high implementation complexity. In addition, a perturbation nonlinear compensation (Perturbative Nonlinearity Compensation, PNC) method based on a first-order perturbation theory is also an effective method for compensating nonlinear damage of the optical fiber. The scheme directly carries out nonlinear compensation on the signals in the time domain, thereby avoiding FFT and IFFT operation required by time-frequency domain conversion of the signals, and having lower complexity compared with DBP algorithm.
The chinese patent publication No. CN111385029a discloses a method and apparatus for compensating nonlinear damage of an optical fiber, in which the apparatus for signaling includes: the device comprises a data coding module, a first transformation module, an inverse normalization module, a waveform modulation module and a multiplexer. The apparatus for signal reception includes: the device comprises a demultiplexer, a demodulation module, a normalization module, a second transformation module and a nonlinear compensation module.
With respect to the related art in the above, the inventors consider that as the baud rate becomes larger and the transmission distance becomes longer, the memory effect between symbols introduced by dispersion becomes longer, which also leads to an increase in the complexity of PNC. This places higher demands on the design of low complexity implementations of PNC algorithms from the hardware implementation of the algorithms in the actual chip.
Disclosure of Invention
Aiming at the defects in the prior art, the application aims to provide a method and a system for compensating nonlinear damage of an optical fiber in a coherent optical communication system.
The application provides a method for compensating nonlinear damage of an optical fiber in a coherent optical communication system, which comprises the following steps:
and a noise obtaining step: obtaining perturbation noise by reducing perturbation terms and multiplying calculation;
and a damage compensation step: the perturbation noise is processed to compensate for nonlinear impairments in the fibre channel.
Preferably, the step of acquiring noise includes the steps of:
step S1: combining the calculation of the same perturbation terms based on the symmetry of the perturbation coefficients to obtain a combined perturbation noise calculation formula;
step S2: based on the combined perturbation noise calculation formula, the product result of two symbols is shared when the perturbation noise of the adjacent symbols is calculated, and the multiplication quantity is reduced; simultaneously degrading the third symbol into QPSK symbol to obtain a degraded symbol;
multiplying the product result of two symbols by the degraded symbol, wherein the multiplication operation is replaced by logic operation, so as to obtain a three-symbol product term;
step S3: firstly, the perturbation coefficients are quantized, then, the three-symbol product items with the same perturbation coefficients are summed, and the sum result is multiplied with the corresponding quantized perturbation coefficients to obtain multiplied perturbation items; and finally, summing the multiplied perturbation terms to obtain perturbation noise.
Preferably, in step S1, according to the first order disturbance theory, the nonlinear damage of the optical fiber in the channel is expressed as:
wherein p is 0 Representing signal power, A i,x A signal representing x-polarization; a is that i,y A signal representing y polarization; c (C) m,n Representing nonlinear perturbation coefficients, m and n being indexes relative to the current symbol; c (C) m,n The calculation is as follows:
wherein γ represents the fiber nonlinear coefficient; beta 2 Representing the group velocity dispersion coefficient of the optical fiber; t represents the pulse width; τ represents a symbol interval; l represents a transmission distance; j represents an imaginary unit; e (E) 1 (. Cndot.) represents an exponential integral function.
Preferably, in step S1, a perturbation coefficient C is obtained according to the formulas (2 a) and (2 b) m,n Satisfy relation C m,n ＝C n,m The method comprises the steps of carrying out a first treatment on the surface of the According to C m,n ＝C n,m The calculation perturbation term is reduced, and the nonlinear damage of the optical fiber is obtained again by the following steps:
wherein C is n,m Representing the perturbation coefficients after the exchange of m and n.
Preferably, in said step S2, a k+n A k+m Is present in the computation of the perturbation noise of a plurality of symbols, temporarily reserved and reused for A k+n A k+m And the number of multiplication computations is reduced.
Preferably, in said step S2, for a k+n A k+m With after degradationMultiplication of (a) will->And degrading into QPSK symbols, and replacing the multiplication operation with logic operation to finally obtain a three-symbol product term.
Preferably, in the damage compensation step, the sign generated by the digital modulation of the transmitting end is subtracted by the perturbation noise to perform pre-compensation of the nonlinear damage of the optical fiber.
Preferably, in the impairment compensation step, the perturbation noise is subtracted from the received symbol obtained after the carrier phase recovery at the receiving end, so as to compensate for the nonlinear impairment of the optical fiber.
The application provides a coherent optical fiber communication transmitting end optical fiber nonlinear damage compensation system, which comprises the following modules:
and a digital modulation module: for mapping a bit sequence to be transmitted into quadrature amplitude modulation symbols;
and the optical fiber nonlinear damage compensation module is used for: subtracting the perturbation noise from the quadrature amplitude modulation symbol to compensate nonlinear damage of the quadrature amplitude modulation symbol in the optical fiber channel, thereby obtaining the quadrature amplitude modulation symbol after the damage is compensated;
pulse forming module: forming the root raised cosine pulse of the quadrature amplitude modulation symbol after the compensation damage to generate a digital signal;
DAC module: converting the digital signal into an analog signal.
The application provides a coherent optical fiber communication receiving end optical fiber nonlinear damage compensation system, which comprises the following modules:
ADC module: converting the analog signal into a digital signal;
dispersion compensation module: compensating for chromatic dispersion accumulated in the digital signal during optical fiber transmission;
and the frequency offset compensation module is used for: obtaining the frequency offset of the digital signal after compensating the chromatic dispersion and compensating;
and the self-adaptive equalization module is used for: equalizing the digital signal after compensating the frequency offset by using a minimum mean square error equalizer to obtain a receiving symbol;
carrier phase recovery module: tracking the phase noise of the received symbol and performing phase recovery on the received symbol;
and the optical fiber nonlinear damage compensation module is used for: subtracting perturbation noise from the received symbol obtained after phase recovery, and compensating nonlinear damage in the fiber channel to obtain a received symbol after compensating damage;
digital demodulation module: the received symbols after the compensation impairments are demapped to a bit sequence.
Compared with the prior art, the application has the following beneficial effects:
1. the application relates to a compensating fiber nonlinear damage with ultra-low complexity based on a first-order disturbance theory, which relates to the field of coherent optical communication application and has the capability of compensating fiber nonlinear damage;
2. the application utilizes the symmetry of perturbation coefficients to reduce perturbation items needing to be calculated; the multiplication calculation is reduced by sharing the product result by a plurality of symbols; the multiplication is replaced by a logic operation by a partial degradation method of degrading one symbol into a QPSK symbol;
3. the application is easy to realize, convenient to use and low in realization complexity, and can overcome the defects of the prior art.
Drawings
Other features, objects and advantages of the present application will become more apparent upon reading of the detailed description of non-limiting embodiments, given with reference to the accompanying drawings in which:
FIG. 1 is a flow chart of the method for compensating nonlinear damage of optical fiber applied to coherent optical fiber communication;
FIG. 2 is a schematic diagram of a system for compensating nonlinear damage of an optical fiber when the application is applied to a transmitting end of coherent optical fiber communication;
FIG. 3 is a schematic diagram of a nonlinear fiber damage compensation system when the application is applied to a receiving end of coherent fiber communication;
FIG. 4 is a schematic diagram of the performance of the present application after compensating for nonlinear impairments of an optical fiber in a coherent optical fiber transmission simulation system.
Detailed Description
The present application will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the present application, but are not intended to limit the application in any way. It should be noted that variations and modifications could be made by those skilled in the art without departing from the inventive concept. These are all within the scope of the present application.
The embodiment of the application discloses a low-complexity optical fiber nonlinear damage compensation method in a coherent optical communication system, which comprises the following steps as shown in fig. 1: and a noise obtaining step: the perturbation noise is obtained by reducing perturbation terms and multiplying calculations. The step of obtaining noise comprises the steps of: step S1: and combining the calculation of the same perturbation terms based on the symmetry of the perturbation coefficients to obtain a combined perturbation noise calculation formula.
The perturbation coefficient is C m,n Can be obtained by calculation according to the formula (2 a) and the formula (2 b). The perturbation term refers to the formula (1 a) and the formula (1 b) These items.
Step S1 comprises the steps of: step S1.1: the nonlinear damage of the optical fiber can be seen as being caused by the mutual collision between optical solitons. Three signals at any moment collide with each other due to the nonlinear effect of the optical fibers so as to generate different levels of perturbation noise at different positions, and the influence degree of the different perturbation noise is determined by the magnitude of the perturbation coefficient. When these three signals meet certain conditions, the generated perturbation noise is a main source of nonlinear damage to the optical fiber. According to the first order disturbance theory, the nonlinear impairment of the fiber within the channel is expressed as:
wherein Deltau k,x Representing the nonlinear noise of the optical fiber corresponding to the kth symbol of the x polarization; deltau k,y Representing the nonlinear noise of the optical fiber corresponding to the kth symbol of y polarization; p is p 0 Representing signal power; a is that i,x The ith symbol representing x polarization, i including k+n, k+m, and k+m+n; a is that i,y An ith symbol representing y polarization;a conjugate symbol representing the ith symbol of x polarization; />Representing the conjugate of the ith symbol of y polarization. A is that k+n,x 、A k+m,x The k+n symbol and the k+m symbol of the x polarization are represented, respectively. A is that k+n,y 、A k+m,y K+n symbols each representing y polarizationAnd the k+m symbol. />Representing the conjugate of the symbol. The two polarizations are x-polarization and y-polarization. C (C) m,n Representing nonlinear perturbation coefficients, m and n being indexes relative to the current symbol; c (C) m,n The calculation is as follows:
wherein γ represents the fiber nonlinear coefficient; beta 2 Representing the group velocity dispersion coefficient of the optical fiber; t represents the pulse width; τ represents a symbol interval; l represents a transmission distance; j represents an imaginary unit; e (E) 1 (. Cndot.) represents an exponential integral function.
Step S1.2: obtaining perturbation coefficient C according to the formulas (2 a) and (2 b) m,n Satisfy relation C m,n ＝C n,m The method comprises the steps of carrying out a first treatment on the surface of the According to C m,n ＝C n,m And (5) reducing the calculation perturbation term and obtaining the calculation of the nonlinear damage of the optical fiber again. Specifically, m and n can be exchanged according to the formulas (2 a) and (2 b) without changing the perturbation coefficient C m,n Depending on the nature, the finishing formulas (2 a) and (2 b) may reduce the perturbation terms that need to be calculated. From the formulae (2 a) and (2 b), it can be found that the perturbation coefficient C m,n Satisfy relation C m,n ＝C n,m Therefore, we can reduce the need to calculate perturbation terms, and retrieve the nonlinear damage of the fiber as follows:
wherein C is n,m Representing the perturbation coefficients after the exchange of m and n.
Step S2: based on the combined perturbation noise calculation formula, the product result of two symbols is shared when the perturbation noise of the adjacent symbols is calculated, and the multiplication quantity is reduced; simultaneously degrading the third symbol into QPSK symbol to obtain a degraded symbol; multiplying the product result of two symbols by the degenerated symbol, and the multiplication operation is replaced by a logic operation, so as to obtain a three-symbol product term. I.e. the temporally adjacent symbols share the product result of two symbols, thereby reducing the number of multiplications. While degrading the third symbol to a quadrature phase shift keying (Quadrature Phase Shift Keying, QPSK) signal, the multiplication operation can be replaced by a replacement simple logic operation.
Fig. 1 shows a flow chart of the optical fiber nonlinear damage compensation method applied to coherent optical fiber communication.
Step S2 includes the steps of: step S2.1: a is that k+n A k+m Is present in the computation of the perturbation noise of a plurality of symbols, temporarily reserved and reused for A k+n A k+m And the number of multiplication computations is reduced. As shown in FIG. 1, consider A k+ n A k+m Which are present in the computation of the perturbation noise for a plurality of symbols, so that the result can be temporarily retained and reused, whereby the number of multiplication computations can be reduced.
Step S2.2: for A k+n A k+m With after degradationMultiplication of (a) will->And degrading into QPSK symbols, and replacing the multiplication operation with logic operation to finally obtain a three-symbol product term. I.e. for A k+n A k+m And->Multiplication of (a) will->The degradation into QPSK symbols, the multiplication can be replaced by a logical operation, and the result of the three-symbol product is finally obtained.
Step S3: firstly, the perturbation coefficients are quantized, then, the three-symbol product items with the same perturbation coefficients are summed, and the sum result is multiplied with the corresponding quantized perturbation coefficients to obtain multiplied perturbation items; and finally, summing the multiplied perturbation terms to obtain perturbation noise. Firstly, the perturbation coefficients are quantized, then the three-symbol product items with the same perturbation coefficients are summed, the summation result is multiplied with the corresponding perturbation coefficients, and finally, all the perturbation items are summed to obtain the perturbation noise. Specifically, the perturbation coefficient can be obtained through training in advance or calculation, in order to reduce implementation complexity, the perturbation coefficient is quantized according to needs, and a plurality of quantized three-symbol products may correspond to the same perturbation coefficient. It should be noted that the choice of quantization step requires consideration of a compromise in complexity and performance. And carrying out summation operation on the three-symbol products corresponding to the same perturbation coefficient, multiplying the summation result with the corresponding perturbation coefficient, and adding all the product results to obtain the final perturbation noise.
And a damage compensation step: the perturbation noise is processed to compensate for nonlinear impairments in the fibre channel. And subtracting perturbation noise from a symbol generated by digital modulation of a transmitting end to pre-compensate nonlinear damage of the optical fiber. And subtracting the perturbation noise from the received symbol obtained after the carrier phase of the receiving end is recovered, and compensating the nonlinear damage of the optical fiber. For the system of the compensation at the transmitting end, the sign generated by the digital modulation at the transmitting end is subtracted by the perturbation noise, so that the pre-compensation of the nonlinear damage of the optical fiber is realized. And for a system compensated at a receiving end, the received symbol obtained after carrier phase recovery is subtracted by the perturbation noise, so that the compensation of nonlinear damage of the optical fiber is realized.
The application discloses an ultralow-complexity compensation optical fiber nonlinear damage based on a first-order disturbance theory, which is applied to optical fiber nonlinear damage compensation of a coherent optical communication system and relates to the field of optical fiber communication application. Reducing perturbation items to be calculated by combining coefficients; reducing the number of multiplication operations by sharing the product result of two symbols; the multiplication operation is converted into a logical operation by a half-degenerate method. The application can be used at the transmitting end based on the transmitting symbol and at the receiving end based on the receiving symbol, and can obviously reduce the implementation complexity while effectively compensating the nonlinear damage of the optical fiber.
The embodiment of the application also discloses a system for compensating the nonlinear damage of the optical fiber of the coherent optical fiber communication transmitting end, and the structure of the system for compensating the nonlinear damage of the optical fiber when the application is applied to the transmitting end is shown in figure 2, and the system comprises the following modules: and a digital modulation module: for mapping the bit sequence to be transmitted into quadrature amplitude modulation symbols. For mapping the bit sequence to be transmitted into quadrature amplitude modulation symbols.
And the optical fiber nonlinear damage compensation module is used for: and subtracting the perturbation noise from the quadrature amplitude modulation symbol to compensate nonlinear damage of the quadrature amplitude modulation symbol in the optical fiber channel, thereby obtaining the quadrature amplitude modulation symbol after the damage is compensated. For compensating for nonlinear impairments in the fibre channel.
Pulse forming module: and forming the root raised cosine pulse of the quadrature amplitude modulation symbol after the compensation damage to generate a digital signal. For shaping the root raised cosine pulse of the symbol to produce a signal.
DAC module: converting the digital signal into an analog signal. The DAC is used to convert a digital signal to an analog signal. DAC English is called Digital-to-Analog Converter, chinese translation is Digital Analog Converter.
The embodiment of the application also discloses a system for compensating the nonlinear damage of the optical fiber at the receiving end of the coherent optical fiber communication, and the structure of the system for compensating the nonlinear damage of the optical fiber when the application is applied to the receiving end is shown in a figure 3, and the system comprises the following modules: ADC module: the analog signal is converted into a digital signal. The ADC is used to convert an analog signal into a digital signal. ADC English is called Analog-to-Digital Converter, chinese translation is Analog-to-digital converter.
Dispersion compensation module: compensating for the accumulated dispersion of the digital signal during fiber transmission. For compensating for accumulated dispersion of the fiber during transmission.
And the frequency offset compensation module is used for: and obtaining and compensating the frequency offset of the digital signal after the dispersion compensation. For estimating the frequency offset of the signal and compensating.
And the self-adaptive equalization module is used for: and using a minimum mean square error equalizer to equalize the digital signal after compensating the frequency offset to obtain a received symbol. For minimum mean square error equalizer pair signal equalization.
Carrier phase recovery module: the phase noise of the received symbols is tracked and the received symbols are phase recovered. For tracking the phase noise of the symbol and for phase recovering the symbol.
And the optical fiber nonlinear damage compensation module is used for: and subtracting the perturbation noise from the received symbol obtained after phase recovery, compensating nonlinear damage in the fiber channel, and obtaining the received symbol after compensating damage. For compensating for nonlinear impairments in the fibre channel.
Digital demodulation module: the received symbols after the compensation impairments are demapped to a bit sequence. For demapping the symbols into a bit sequence.
The optical fiber nonlinear compensation scheme provided by the application can be used for compensating at the transmitting end and also can be used for compensating at the receiving end.
The embodiment of the application also provides performance of the designed algorithm after compensating the nonlinear damage of the optical fiber in the single-channel coherent optical fiber transmission simulation system, and as shown in fig. 4, the algorithm shows that the modulation format is a dual-polarized 16-ary quadrature amplitude modulation (16 QAM,16 quadrature amplitude modulation) signal, the Baud rate is 70Gbaud, G is unit Ji, baud is unit Baud, and the roll-off coefficient is 0.02. The transmission optical fiber is a standard single-mode optical fiber, 25 spans are transmitted by signals, the optical fiber length of each span is 80km, and km is a unit kilometer. As can be seen from fig. 4, with the proposed scheme, the transmission performance can be significantly improved. SNR English is called signal-to-noise ratio, chinese translation is signal-to-noise ratio.
Those skilled in the art will appreciate that the application provides a system and its individual devices, modules, units, etc. that can be implemented entirely by logic programming of method steps, in addition to being implemented as pure computer readable program code, in the form of logic gates, switches, application specific integrated circuits, programmable logic controllers, embedded microcontrollers, etc. Therefore, the system and various devices, modules and units thereof provided by the application can be regarded as a hardware component, and the devices, modules and units for realizing various functions included in the system can also be regarded as structures in the hardware component; means, modules, and units for implementing the various functions may also be considered as either software modules for implementing the methods or structures within hardware components.
The foregoing describes specific embodiments of the present application. It is to be understood that the application is not limited to the particular embodiments described above, and that various changes or modifications may be made by those skilled in the art within the scope of the appended claims without affecting the spirit of the application. The embodiments of the application and the features of the embodiments may be combined with each other arbitrarily without conflict.
Claims (3)
1. The method for compensating the nonlinear damage of the optical fiber in the coherent optical communication system is characterized by comprising the following steps:
and a noise obtaining step: obtaining perturbation noise by reducing perturbation terms and multiplying calculation;
and a damage compensation step: processing the perturbation noise to compensate nonlinear damage in the optical fiber channel;
the step of obtaining noise comprises the following steps:
step S1: combining the calculation of the same perturbation terms based on the symmetry of the perturbation coefficients to obtain a combined perturbation noise calculation formula;
step S2: based on the combined perturbation noise calculation formula, the product result of two symbols is shared when the perturbation noise of the adjacent symbols is calculated, and the multiplication quantity is reduced; simultaneously degrading the third symbol into QPSK symbol to obtain a degraded symbol;
multiplying the product result of two symbols by the degraded symbol, wherein the multiplication operation is replaced by logic operation, so as to obtain a three-symbol product term;
step S3: firstly, the perturbation coefficients are quantized, then, the three-symbol product items with the same perturbation coefficients are summed, and the sum result is multiplied with the corresponding quantized perturbation coefficients to obtain multiplied perturbation items; finally, summing the multiplied perturbation items to obtain perturbation noise;
in step S1, according to the first order disturbance theory, for a bi-polarized signal, the nonlinear impairment of the fiber in the channel is expressed as:
wherein Deltau k，x Representing the nonlinear noise of the optical fiber corresponding to the kth symbol of the x polarization; deltau k，y Representing the nonlinear noise of the optical fiber corresponding to the kth symbol of y polarization; p is p 0 Representing signal power; a is that i，x The ith symbol representing x polarization, i including k+n, k+m, and k+m+n; a is that i，y An ith symbol representing y polarization;a conjugate symbol representing the ith symbol of x polarization; />A conjugate symbol representing the ith symbol of y polarization; c (C) m，n Representing nonlinear perturbation coefficients, m and n being indexes relative to the current symbol; c (C) m，n The calculation is as follows:
wherein γ represents the fiber nonlinear coefficient; beta 2 Representing the group velocity dispersion coefficient of the optical fiber; t represents the pulse width; τ represents a symbol interval; l represents a transmission distance; j represents an imaginary unit; e (E) 1 (. Cndot.) represents an exponential integral function;
in step S1, a perturbation coefficient C is obtained according to the formulas (2 a) and (2 b) m，n Satisfy relation C m，n ＝C n，m The method comprises the steps of carrying out a first treatment on the surface of the According to C m，n ＝C n，m The calculation perturbation term is reduced, and the nonlinear damage of the optical fiber is obtained again by the following steps:
wherein C is n，m Representing perturbation coefficients after m and n are exchanged;
in said step S2, A k+n A k+m Is present in the computation of the perturbation noise of a plurality of symbols, temporarily reserved and reused for A k+n A k+m Reducing the number of multiplication computations;
for A k+n A k+m With after degradationMultiplication of (a) will->Degradation into QPSK symbol, multiplication is replaced by logic operation, and three-symbol product term is finally obtained;
in the damage compensation step, the sign generated by digital modulation of a transmitting end is subtracted by perturbation noise to perform pre-compensation of nonlinear damage of the optical fiber;
and subtracting the perturbation noise from the received symbol obtained after the carrier phase of the receiving end is recovered, and compensating the nonlinear damage of the optical fiber.
2. The optical fiber nonlinear damage compensation system of the coherent optical fiber communication transmitting end is characterized by comprising the following modules:
and a digital modulation module: for mapping a bit sequence to be transmitted into quadrature amplitude modulation symbols;
and the optical fiber nonlinear damage compensation module is used for: subtracting the perturbation noise from the quadrature amplitude modulation symbol to compensate nonlinear damage of the quadrature amplitude modulation symbol in the optical fiber channel, thereby obtaining the quadrature amplitude modulation symbol after the damage is compensated;
pulse forming module: forming the root raised cosine pulse of the quadrature amplitude modulation symbol after the compensation damage to generate a digital signal;
DAC module: converting the digital signal into an analog signal.
3. The optical fiber nonlinear damage compensation system of the coherent optical fiber communication receiving end is characterized by comprising the following modules:
ADC module: converting the analog signal into a digital signal;
dispersion compensation module: compensating for chromatic dispersion accumulated in the digital signal during optical fiber transmission;
and the frequency offset compensation module is used for: obtaining the frequency offset of the digital signal after compensating the chromatic dispersion and compensating;
and the self-adaptive equalization module is used for: equalizing the digital signal after compensating the frequency offset by using a minimum mean square error equalizer to obtain a receiving symbol;
carrier phase recovery module: tracking the phase noise of the received symbol and performing phase recovery on the received symbol;
and the optical fiber nonlinear damage compensation module is used for: subtracting perturbation noise from the received symbol obtained after phase recovery, and compensating nonlinear damage in the fiber channel to obtain a received symbol after compensating damage;
digital demodulation module: the received symbols after the compensation impairments are demapped to a bit sequence.
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| 诸葛群碧 ; 钟雪颖 ; 蔡萌 ; 刘晓敏 ; 刘蕾.光纤通信数字孪生系统架构及关键技术研究.信息通信技术与政策.2021,全文. * |
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