Patent Description:
This application relates to the optical communications field, and in particular, to a signal processing method and apparatus, and a coherent receiver.

Performance of a high-capacity optical communications system may deteriorate due to optical fiber attenuation, optical fiber chromatic dispersion, polarization mode chromatic dispersion, laser phase noise, optical fiber nonlinearity, or the like. A currently provided polarization multiplexing coherent receiver can effectively compensate for the foregoing deterioration factors in electrical domain during an electrical signal processing procedure.

During the electrical signal processing procedure of the existing polarization multiplexing coherent receiver, to implement the foregoing effective compensation in electrical domain, convolution of a time-domain signal and an inverse function of a channel response is implemented based on Fourier transform. Therefore, a fast Fourier transform (fast Fourier transform, FFT) module and an inverse fast Fourier transform (inverse fast Fourier transform, IFFT) module need to be introduced into a structure of the polarization multiplexing coherent receiver. However, the Fourier transform has high complexity and low precision. As a result, the electrical signal processing procedure is highly complex, and accuracy of a recovered signal is low. Therefore, how to improve performance of a polarization multiplexing coherent receiver in processing an electrical signal becomes an urgent problem to be resolved.

An optical signal processing method according to the state of the art is known from <CIT>.

This application provides a signal processing method and apparatus, and a coherent receiver, to improve signal processing performance.

According to a first aspect, a signal processing method is provided. The signal processing method may be performed by a coherent receiver, or may be performed by a chip or a circuit disposed in a coherent receiver. This is not limited in this application.

Further, if INTT and combination processing is first performed and then polarization compensation processing is performed, in the signal processing method provided in this application, phase recovery and decoding may be performed on m time-domain complex-number signals X and m time-domain complex-number signals Y that are obtained through polarization compensation, to obtain bit signals.

It should be understood that if the INTT and combination processing is first performed and then the polarization compensation processing is performed, the polarization compensation processing is performed based on a time-domain signal obtained through INTT processing. Specifically, a capability of resisting a loop delay can be enhanced by performing polarization compensation processing in time domain.

Alternatively, if polarization compensation processing is first performed and then INTT and combination processing is performed, in the signal processing method provided in this application, phase recovery and decoding may be performed on m time-domain complex-number signals X in a first polarization direction and m time-domain complex-number signals Y in a second polarization direction that are obtained through combination, to obtain bit signals, so as to implement signal recovery.

It should be understood that if the polarization compensation processing is first performed and then the INTT and combination processing is performed, the polarization compensation processing is performed based on a transform-domain signal. Specifically, polarization equalization impairment compensation is performed in transform domain, and multiplication is used to replace convolution, so that power consumption can be reduced.

In the signal processing method provided in this application, signals in two polarization directions are obtained through analog-to-digital conversion, and the signals in the two polarization directions are input to a receiver digital signal processing Rx DSP apparatus. During a processing procedure of the Rx DSP, number theoretic transform NTT and inverse number theoretic transform INTT processing is used to replace fast Fourier transform FFT and inverse fast Fourier transform IFFT processing, to avoid high complexity and low accuracy caused by the FFT and IFFT processing, thereby improving signal processing performance.

With reference to the first aspect, in some implementations of the first aspect, the performing at least number theoretic transform NTT processing on the P real-number signals to obtain P transform-domain first real-number signals includes: performing NTT processing on the P real-number signals to obtain the P transform-domain first real-number signals; or
performing digital back propagation DBP processing on the P real-number signals to obtain P time-domain tenth real-number signals, and separately performing NTT processing on the P time-domain tenth real-number signals to obtain the P transform-domain first real-number signals.

If the P real-number signals undergo DBP processing, a DBP module is used to implement nonlinear-effect compensation, to increase a signal transmission distance.

In the signal processing method provided in this application, the P transform-domain first real-number signals may be obtained by inputting the P real-number signals to an NTT module and performing NTT processing; or the P transform-domain first real-number signals may be obtained by first inputting the P real-number signals to the DBP module and performing DBP processing, and then performing NTT processing. Different manners of obtaining the P transform-domain first real-number signals are provided, so that a structural design of the Rx DSP apparatus is more flexible.

With reference to the first aspect, in some implementations of the first aspect, when the P real-number signals do not undergo DBP processing, chromatic dispersion compensation needs to be performed when the P transform-domain second real-number signals are obtained based on the P transform-domain first real-number signals. To be specific, the performing at least clock recovery on the P transform-domain first real-number signals to obtain P transform-domain second real-number signals includes: performing chromatic dispersion compensation on the P transform-domain first real-number signals to obtain P transform-domain third real-number signals; and performing clock recovery on the P transform-domain third real-number signals to obtain the P transform-domain second real-number signals.

Alternatively, when the P real-number signals undergo DBP processing, because the DBP module has a chromatic dispersion compensation function, no additional chromatic dispersion compensation needs to be performed when the P transform-domain second real-number signals are obtained based on the P transform-domain first real-number signals. To be specific, the performing at least clock recovery on the P transform-domain first real-number signals to obtain P transform-domain second real-number signals includes: performing chromatic dispersion compensation on the P transform-domain first real-number signals to obtain the P transform-domain second real-number signals.

With reference to the first aspect, in some implementations of the first aspect, the P real-number signals include an in-phase real-number signal Imx and a quadrature real-number signal Qmx in the first polarization direction, and an in-phase real-number signal Imy and a quadrature real-number signal Qmy in the second polarization direction. In the foregoing case in which additional chromatic dispersion compensation is required, a chromatic dispersion compensation process includes: performing NTT processing on a chromatic dispersion impulse response Ih(t) corresponding to an in-phase real-number signal and a chromatic dispersion impulse response Qh(t) corresponding to a quadrature real-number signal, to obtain a transform-domain chromatic dispersion equalization function Ih(w) corresponding to the in-phase real-number signal and a transform-domain chromatic dispersion equalization function Qh(w) corresponding to the quadrature real-number signal.

After Ih(w) and Qh(w) are obtained, <NUM>×m transform-domain third real-number signals that are in the P transform-domain third real-number signals and that are in the first polarization direction can be determined based on Ih(w), Qh(w), and an in-phase real-number signal and a quadrature real-number signal that are in the P transform-domain first real-number signals and that are in the first polarization direction, and <NUM>×m transform-domain third real-number signals that are in the P transform-domain third real-number signals and that are in the second polarization direction can be determined based on Ih(w), Qh(w), and an in-phase real-number signal and a quadrature real-number signal that are in the P transform-domain first real-number signals and that are in the second polarization direction, so as to complete chromatic dispersion compensation.

With reference to the first aspect, in some implementations of the first aspect, the transform-domain third real-number signals obtained through chromatic dispersion compensation and the transform-domain first real-number signals meet the following requirements: <MAT> <MAT> <MAT> and <MAT> where
Ix(w) represents an in-phase real-number signal that is in the transform-domain first real-number signals and that is in the first polarization direction, Qx(w) represents a quadrature real-number signal that is in the transform-domain first real-number signals and that is in the first polarization direction, Iy(w) represents an in-phase real-number signal that is in the transform-domain first real-number signals and that is in the second polarization direction, Qy(w) represents a quadrature real-number signal that is in the transform-domain first real-number signals and that is in the second polarization direction, I'x(w) represents an in-phase real-number signal that is in the transform-domain third real-number signals and that is in the first polarization direction, Q'x(w) represents a quadrature real-number signal that is in the transform-domain third real-number signals and that is in the first polarization direction, I'y(w) represents an in-phase real-number signal that is in the transform-domain third real-number signals and that is in the second polarization direction, and Q'y(w) represents a quadrature real-number signal that is in the transform-domain third real-number signals and that is in the second polarization direction.

Specifically, when m is equal to <NUM>, the determining <NUM>*m transform-domain third real-number signals that are in the P transform-domain third real-number signals and that are in the first polarization direction based on Ih(w), Qh(w), and an in-phase real-number signal and a quadrature real-number signal that are in the P transform-domain first real-number signals and that are in the first polarization direction includes: <MAT> where.

With reference to the first aspect, in some implementations of the first aspect, the DBP processing specifically includes: performing NTT processing on the P real-number signals to obtain P transform-domain fourth real-number signals; performing, in transform domain, chromatic dispersion compensation on the P transform-domain fourth real-number signals to obtain P transform-domain fifth real-number signals; performing INTT processing on the P transform-domain fifth real-number signals to obtain P time-domain ninth real-number signals; and performing nonlinear compensation on the P time-domain ninth real-number signals to obtain the P time-domain tenth real-number signals.

With reference to the first aspect, in some implementations of the first aspect, polarization compensation may be first performed and then INTT processing is performed, to obtain P time-domain seventh real-number signals.

Specifically, polarization compensation is performed on the P transform-domain second real-number signals to obtain P transform-domain sixth real-number signals; and INTT processing is performed on the P transform-domain sixth real-number signals to obtain the P time-domain seventh real-number signals. Equalization and depolarization are performed on <NUM>×m transform-domain second real-number signals that are in the P transform-domain second real-number signals and that are in the first polarization direction to obtain <NUM>×m transform-domain sixth real-number signals that are in the P transform-domain sixth real-number signals and that are in the first polarization direction. Equalization and depolarization are performed on <NUM>×m transform-domain second real-number signals that are in the P transform-domain second real-number signals and that are in the second polarization direction to obtain <NUM>×m transform-domain sixth real-number signals that are in the P transform-domain sixth real-number signals and that are in the second polarization direction.

Then, the P time-domain seventh real-number signals obtained through INTT processing are combined. <NUM>×m time-domain seventh real-number signals that are in the P time-domain seventh real-number signals and that are in the first polarization direction are combined into m time-domain complex-number signals X in the first polarization direction. <NUM>×m time-domain seventh real-number signals that are in the P time-domain seventh real-number signals and that are in the second polarization direction are combined into m time-domain complex-number signals Y in the second polarization direction.

With reference to the first aspect, in some implementations of the first aspect, INTT processing may be first performed and then polarization compensation is performed, to obtain a time-domain complex-number signal X and a time-domain complex-number signal Y that have undergone the polarization compensation.

Specifically, INTT processing is performed on the P transform-domain second real-number signals to obtain P time-domain eighth real-number signals. <NUM>×m time-domain eighth real-number signals that are in the P time-domain eighth real-number signals and that are in the first polarization direction are combined into m time-domain complex-number signals X in the first polarization direction. <NUM>×m time-domain eighth real-number signals that are in the P time-domain eighth real-number signals and that are in the second polarization direction are combined into m time-domain complex-number signals Y in the second polarization direction. Time-domain polarization compensation is performed on the m time-domain complex-number signals X in the first polarization direction and the m time-domain complex-number signals Y in the second polarization direction to obtain m time-domain complex-number signals X and m time-domain complex-number signals Y that have undergone the polarization compensation.

With reference to the first aspect, in some implementations of the first aspect, the P real-number signals include <NUM>×m real-number signals in m transmission modes. m may be a value equal to <NUM> or greater than <NUM>. P and m satisfy P=<NUM>×m. When m is equal to <NUM>, it may be understood as single-mode transmission; or when m is greater than <NUM>, it may be understood as multi-mode transmission.

According to a second aspect, a signal processing apparatus is provided, including a processor. The processor is coupled to a memory, and may be configured to execute an instruction in the memory, to implement the method in any one of the first aspect or the possible implementations of the first aspect.

Optionally, the apparatus further includes a communications interface, and the processor is coupled to the communications interface.

In an implementation, the apparatus is a digital signal processor. When the apparatus is a digital signal processor, the communications interface may be a transceiver or an input/output interface.

In another implementation, the apparatus is a chip configured in a digital signal processor. When the apparatus is a chip configured in a digital signal processor, the communications interface may be an input/output interface.

In another implementation, the apparatus is a chip or a chip system.

Optionally, the transceiver may be a transceiver circuit.

Optionally, the input/output interface may be an input/output circuit.

Specifically, the signal processing apparatus includes:.

With reference to the second aspect, in some implementations of the second aspect, the P input signals include P real-number signals, and that the first number theoretic transform NTT module is configured to perform NTT processing on P input signals to obtain P transform-domain first real-number signals includes: the first number theoretic transform NTT module is configured to perform number theoretic transform on the P real-number signals to obtain the P transform-domain first real-number signals.

For example, the P real-number signals include <NUM>×m real-number signals in m transmission modes. m may be a value equal to <NUM> or greater than <NUM>. P and m satisfy P=<NUM>×m. When m is equal to <NUM>, it may be understood as single-mode transmission; or when m is greater than <NUM>, it may be understood as multi-mode transmission.

With reference to the second aspect, in some implementations of the second aspect, the apparatus further includes a first chromatic dispersion compensation module, configured to perform chromatic dispersion compensation on the P transform-domain first real-number signals to obtain P transform-domain third real-number signals; and the clock recovery module is configured to perform clock recovery on the P transform-domain third real-number signals to obtain the P transform-domain second real-number signals.

With reference to the second aspect, in some implementations of the second aspect, that the first chromatic dispersion compensation module is configured to perform chromatic dispersion compensation on the P transform-domain first real-number signals to obtain P transform-domain third real-number signals includes:.

With reference to the second aspect, in some implementations of the second aspect, the transform-domain third real-number signals obtained through chromatic dispersion compensation and the transform-domain first real-number signals meet the following requirements: <MAT> <MAT> <MAT> and <MAT> where
Ix(w) represents an in-phase real-number signal that is in the transform-domain first real-number signals and that is in the first polarization direction, Qx(w) represents a quadrature real-number signal that is in the transform-domain first real-number signals and that is in the first polarization direction, Iy(w) represents an in-phase real-number signal that is in the transform-domain first real-number signals and that is in the second polarization direction, Qy(w) represents a quadrature real-number signal that is in the transform-domain first real-number signals and that is in the second polarization direction, I'x(w) represents an in-phase real-number signal that is in the transform-domain third real-number signals and that is in the first polarization direction, Q'x(w) represents a quadrature real-number signal that is in the transform-domain third real-number signals and that is in the first polarization direction, I'y(w) represents an in-phase real-number signal that is in the transform-domain third real-number signals and that is in the second polarization direction, and Q'y(w) represents a quadrature real-number signal that is in the transform-domain third real-number signals and that is in the second polarization direction.

With reference to the second aspect, in some implementations of the second aspect, the first chromatic dispersion compensation module includes a third NTT module, a combination module, and a multiplication module. The third NTT module is configured to perform NTT processing on a time-domain chromatic dispersion impulse response to obtain a chromatic dispersion equalization function, and perform NTT processing on the P transform-domain first real-number signals. The multiplication module is configured to multiply the chromatic dispersion equalization function by the P transform-domain first real-number signals obtained through NTT processing. The combination module is configured to combine signals obtained through processing by the multiplication module.

With reference to the second aspect, in some implementations of the second aspect, the P input signals include P time-domain tenth real-number signals; and the apparatus further includes a digital back propagation DBP module, configured to perform DBP processing on P digital signals to obtain the P time-domain tenth real-number signals.

When the apparatus includes the DBP module, the apparatus uses the DBP module to implement nonlinear-effect compensation on a basis of a linear impairment, to increase a signal transmission distance.

With reference to the second aspect, in some implementations of the second aspect, the DBP module sequentially includes:.

With reference to the second aspect, in some implementations of the second aspect, the clock recovery module is configured to perform clock recovery on the P transform-domain first real-number signals to obtain the P transform-domain second real-number signals.

With reference to the second aspect, in some implementations of the second aspect, the apparatus further includes:.

For example, the polarization compensation module includes a first butterfly filter and a second butterfly filter.

The first butterfly filter is configured to perform equalization and depolarization on <NUM>×m transform-domain second real-number signals that are in the P transform-domain second real-number signals and that are in the first polarization direction to obtain <NUM>×m transform-domain sixth real-number signals that are in the P transform-domain sixth real-number signals and that are in the first polarization direction.

The second butterfly filter is configured to perform equalization and depolarization on <NUM>×m transform-domain second real-number signals that are in the P transform-domain second real-number signals and that are in the second polarization direction to obtain <NUM>×m transform-domain sixth real-number signals that are in the P transform-domain sixth real-number signals and that are in the second polarization direction.

Specifically, during a signal processing procedure, when the apparatus first performs polarization compensation processing based on the polarization compensation module and then performs INTT processing based on the first INTT module, the polarization compensation processing is performed based on a transform-domain signal. Polarization equalization impairment compensation is performed in transform domain, and multiplication is used to replace convolution, so that power consumption can be reduced.

Alternatively, the apparatus further includes a combination module, where the first inverse number theoretic transform INTT module is configured to perform INTT processing on the P transform-domain second real-number signals to obtain P time-domain eighth real-number signals;.

For example, the polarization compensation module includes a third butterfly filter. The third butterfly filter is configured to perform time-domain polarization compensation on the m time-domain complex-number signals X in the first polarization direction and the m time-domain complex-number signals Y in the second polarization direction to obtain m time-domain complex-number signals X and m time-domain complex-number signals Y that have undergone the polarization compensation.

Specifically, during a signal processing procedure, when the apparatus first performs INTT processing based on the first INTT module and then performs polarization compensation processing based on the polarization compensation module, the polarization compensation processing is performed based on a time-domain signal obtained through INTT processing. A capability of resisting a loop delay can be enhanced by performing polarization compensation processing in time domain.

According to a third aspect, a coherent receiver is provided. The coherent receiver includes the signal processing apparatus in any one of the second aspect or the possible implementations of the second aspect.

Further, the coherent receiver further includes a polarization beam splitter, a frequency mixer, a photoelectric detector, and an analog-to-digital converter. The polarization beam splitter is configured to obtain signals in two polarization directions. The frequency mixer is configured to perform frequency mixing processing on signals in a same polarization direction. The photoelectric detector is configured to convert strength of an optical signal into strength of an electrical signal. The analog-to-digital converter is configured to perform analog-signal-to-digital-signal conversion on a signal.

According to a fourth aspect, a chip is provided. The chip includes a communications interface, a memory, and a processor. The memory is configured to store a computer program. The processor is configured to read and execute the computer program stored in the memory, so that the chip implements the signal processing method in any one of the first aspect or the possible implementations of the first aspect.

According to a fifth aspect, a signal processing apparatus is provided, including a processor and a communications interface. The processor is coupled to a memory. The processor may be configured to execute program code in the memory, to implement the signal processing method in any one of the first aspect or the possible implementations of the first aspect.

According to a sixth aspect, a computer-readable storage medium is provided. The computer-readable storage medium stores a computer program. When the computer program is executed by an apparatus, the apparatus is enabled to implement the signal processing method in any one of the first aspect or the possible implementations of the first aspect.

According to a seventh aspect, a computer program product including an instruction is provided. When the instruction is executed by a computer, the apparatus is enabled to implement the signal processing method in any one of the first aspect or the possible implementations of the first aspect.

The technical solutions in the embodiments of this application relate to improvement of a polarization multiplexing coherent receiver. The following first describes a conventional polarization multiplexing coherent receiver with reference to <FIG> and <FIG>. <FIG> and <FIG> are a schematic diagram of a single-mode polarization multiplexing coherent receiver.

It can be learned from <FIG> and <FIG> that a signal processing procedure of the single-mode polarization multiplexing coherent receiver includes the following steps.

An optical signal is split into signals x1 and y <NUM> through processing by a polarization beam splitter #<NUM> in a polarization beam splitter (Polarization beam splitter) <NUM>. x1 is sent to a frequency mixer #<NUM> in a frequency mixer (Hybrid) <NUM>, and y1 is sent to a frequency mixer #<NUM> in the frequency mixer <NUM>.

Local oscillator light (for example, generated by a local laser (local laser) or a transmitter) is split into signals x2 and y2 through processing by a polarization beam splitter #<NUM> in the polarization beam splitter <NUM>. x2 is sent to the frequency mixer #<NUM> in the frequency mixer <NUM>, and y2 is sent to the frequency mixer #<NUM> in the frequency mixer <NUM>.

It should be noted that an optical signal or the local oscillator light has two polarization modes: transverse electric (transverse electric, TE) and transverse magnetic (transverse magnetic, TM), which may also be referred to as a polarization state X and a polarization state Y, or may also be referred to as a polarization direction X and a polarization direction Y.

The polarization state X and the polarization state Y are orthogonal to each other. To be specific, after undergoing polarization rotation, a light beam in a single polarization state (a polarization state Y) becomes a light beam in a polarization state X. It should be noted that X and Y herein are not an x-axis and a y-axis in a narrow sense, but are two orthogonal directions in a broad sense, for example, a horizontal +<NUM>° direction and a vertical -<NUM>° direction.

The frequency mixer #<NUM> and the frequency mixer #<NUM> output four signals. The four signals are used as input of a photoelectric detector (Photodiode) <NUM>, and are separately input to a photoelectric detector #<NUM> to a photoelectric detector #<NUM>. The photoelectric detector is configured to convert strength of an optical signal into strength of an electrical signal.

An output signal of the photoelectric detector #<NUM> is a signal Ix, an output signal of the photoelectric detector #<NUM> is a signal Qx, an output signal of the photoelectric detector #<NUM> is a signal Iy, and an output signal of the photoelectric detector #<NUM> is a signal Qy.

Ix, Qx, Iy, and Qy are converted by an analog-to-digital converter #<NUM> to an analog-to-digital converter #<NUM> in an analog-to-digital converter (analog-to-digital converter, ADC) <NUM> respectively, and digital signals Ix, Qx, Iy, and Qy obtained through analog-to-digital conversion are output. Ix and Qx are combined by a combination module #<NUM> in a combination module <NUM> to obtain a complex-number signal X. Iy and Qy are combined by a combination module #<NUM> in the combination module <NUM> to obtain a complex-number signal Y. For example, the combination module in this application may also be referred to as an adder.

The complex-number signal X is input to an FFT module #<NUM> in an FFT module <NUM>, and is processed by the FFT module #<NUM> to obtain a frequency-domain signal X that has undergone fast Fourier transform. The complex-number signal Y is input to an FFT module #<NUM> in the FFT module <NUM>, and is processed by the FFT module #<NUM> to obtain a frequency-domain signal Y that has undergone fast Fourier transform.

The frequency-domain signal X is input to a chromatic dispersion compensation module #<NUM> in a chromatic dispersion compensation (Chromatic dispersion compensation, CDC) module <NUM>, and chromatic dispersion compensation is performed in frequency domain to obtain a frequency-domain signal X that has undergone the frequency-domain dispersion compensation. The frequency-domain signal Y is input to a chromatic dispersion compensation module #<NUM> in the chromatic dispersion compensation module <NUM>, and chromatic dispersion compensation is performed in frequency domain to obtain a frequency-domain signal Y that has undergone the frequency-domain chromatic dispersion compensation.

The frequency-domain signal X obtained through frequency-domain chromatic dispersion compensation is input to a clock recovery module #<NUM> in a clock recovery module <NUM>, and clock recovery is performed to obtain a frequency-domain signal X that has undergone the clock recovery. The frequency-domain signal Y obtained through frequency-domain chromatic dispersion compensation is input to a clock recovery module #<NUM> in the clock recovery module <NUM>, and clock recovery is performed to obtain a frequency-domain signal Y that has undergone the clock recovery.

The frequency-domain signal X obtained through clock recovery is input to an IFFT module #<NUM> in an IFFT module <NUM>, and is processed by the IFFT module #<NUM> to obtain a time-domain signal X that has undergone inverse fast Fourier transform. The frequency domain signal Y obtained through clock recovery is input to an IFFT module #<NUM> in the IFFT module <NUM>, and is processed by the IFFT module #<NUM> to obtain a time-domain signal Y that has undergone inverse fast Fourier transform.

Both the time-domain signal X and the time-domain signal Y are input to a polarization compensation module <NUM>. Optionally, the polarization compensation module includes <NUM>×<NUM> butterfly filters, and performs polarization demultiplexing and impairment equalization to obtain a time-domain signal X and a time-domain signal Y that have undergone polarization compensation. Specifically, as shown in <FIG> and <FIG>, the polarization compensation module <NUM> further includes a coefficient update module <NUM>. The coefficient update module <NUM> is configured to update a coefficient of a filter included in the polarization compensation module <NUM>.

The complex-number signal X obtained through polarization compensation is sequentially sent to a phase recovery module #<NUM> in a phase recovery (phase recovery) module <NUM> and a decoding module #<NUM> in a decoding (decoder) module <NUM> to obtain a bit signal. The complex-number signal Y obtained through polarization compensation is sequentially sent to a phase recovery module #<NUM> in the phase recovery module <NUM> and a decoding module #<NUM> in the decoding module <NUM> to obtain a bit signal.

It should be noted that, because the FFT module <NUM> and the IFFT module <NUM> are introduced into the current signal processing procedure of the coherent receiver, the following cases may occur:.

This embodiment of this application mainly relates to improvement of a processing procedure after the ADC. Therefore, for ease of description, the processing procedure after the ADC is collectively referred to as a receiver digital signal processing (Receiver Digital Signal Processing, Rx DSP) procedure, for example, an Rx DSP signal processing procedure included in a large dashed-line box in <FIG> and <FIG>.

For ease of understanding, several basic concepts in this application are briefly described.

A transmission mode, that is, an HE<NUM> mode, for an optical signal in a single-mode optical fiber includes two sub-modes: HEx<NUM> and HEy<NUM>. The two sub-modes are independent of each other, and their polarization directions are orthogonal to each other. The two sub-modes present different forms in a transmission process: linear polarization, elliptical polarization, and circular polarization, but always remain orthogonal. X-polarization and Y-polarization in this application are two orthogonal polarization states in a multiplexing single-mode optical fiber.

Compared with the single-mode optical fiber, a multi-mode optical fiber can transmit signals in a plurality of modes. Currently, an LPpq mode is commonly used. Values of p and q represent different mode field characteristics of an LP mode.

Both NTT processing and FFT processing in this application belong to transformation for implementing fast convolution. The FFT processing is complex-number transformation whose core is K=exp(jα). exp(jα) is a complex number and has a truncation error in storage. In addition, multiplication complexity of the complex number is quite high. NTT transformation is transformation that is defined in a finite field and whose core is K (K is an integer). Usually, K is <NUM>. Therefore, a transformation matrix has no truncation error. On a binary computer, both multiplication and division of <NUM> can be implemented through shifting, so that multiplication can be avoided and power consumption can be reduced.

In addition, the INTT processing is an inverse process of the NTT processing, and IFFT is an inverse process of the FFT processing. Details are not described in this application.

A time-domain signal in the embodiments of this application is a signal that is input to an Rx DSP process through analog-to-digital conversion. A signal obtained by performing FFT processing on the time-domain signal is referred to as a frequency-domain signal, and a signal obtained through NTT processing is referred to as a transform-domain signal.

In addition, a time-domain signal is obtained by performing IFFT processing on the frequency-domain signal, and a time-domain signal is obtained by performing INTT processing on the transform-domain signal.

To be specific, the time-domain signal in this application may be understood as a signal at a time granularity, and may change as time changes; the frequency-domain signal may be understood as a frequency-domain representation into which a time-domain signal is converted through transformation from time domain to frequency domain; and likewise, the transform-domain signal may be understood as a transform-domain representation into which a time-domain signal is converted through transformation from time domain to transform domain. During a process of transformation from time domain to transform domain, a time-domain signal is usually segmented, then a part is superposed at a beginning and an end, and then the signal is sent to an NTT/INTT transformation module. For example, a segment of time-domain data includes <NUM> points. A time-domain signal is first divided into <NUM> points, then <NUM> points are superposed at a beginning and an end, and then the <NUM> points are sent to the NTT/INTT transformation module. <NUM>, <NUM>, and <NUM> herein are merely examples. A specific superposition proportion and a specific quantity of points in a segment are not limited in this application. A quantity of points of data transformation is an array length during the data transformation. Generally, a larger quantity of points contributes to better transformation performance.

Quadrature amplitude modulation is widely used in modern coherent communications. The quadrature amplitude modulation is a modulation scheme in which amplitude modulation is performed on two orthogonal carriers. The two carriers are usually sine waves with a phase difference of <NUM>°, and therefore are referred to as orthogonal carriers. The real part of a complex-number signal is referred to as a codirectional component, and the imaginary part of the signal is referred to as a quadrature component.

It should be noted that both a real part and an imaginary part of a complex-number signal (for example, X=a+bj) are real numbers (for example, both a and b are real numbers). Therefore, in this application, the codirectional component is referred to as an in-phase real-number signal, and the quadrature component is referred to as a quadrature real-number signal.

It can be learned from the foregoing descriptions that introducing the FFT module and the IFFT module into an electrical signal processing procedure of the coherent receiver may increase complexity of the signal processing procedure. To resolve a problem in the existing electrical signal processing procedure of the coherent receiver and reduce power consumption of an algorithm, the embodiments of this application provide a signal processing method and apparatus, in which an electrical signal is processed without introducing the FFT module or the IFFT module, thereby improving performance of the polarization multiplexing coherent receiver in processing an electrical signal and reducing complexity.

The following describes in detail the signal processing method and apparatus provided in the embodiments of this application with reference to the accompanying drawings. The signal processing method provided in the embodiments of this application may be used by a polarization multiplexing coherent receiver to process an electrical signal in a single-mode or multi-mode transmission scenario.

<FIG> is a schematic diagram of an Rx DSP architecture according to an embodiment of this application. The Rx DSP architecture <NUM> includes:
a first NTT module <NUM>, a first chromatic dispersion compensation module <NUM>, a clock recovery module <NUM>, a first polarization compensation module <NUM>, a first INTT module <NUM>, a combination module <NUM>, a phase recovery module <NUM>, and a decoding module <NUM>.

The first NTT module includes an NTT module #<NUM>, an NTT module #<NUM>, an NTT module #<NUM>, and an NTT module #<NUM>. Signals I<NUM>x, Q<NUM>x, I<NUM>y, and Q<NUM>y are input to the NTT module #<NUM>, the NTT module #<NUM>, the NTT module #<NUM>, and the NTT module #<NUM> respectively.

Optionally, the signals I<NUM>x, Q<NUM>x, I<NUM>y, and Q<NUM>y are real-number signals obtained through conversion by an ADC.

The NTT module #<NUM>, the NTT module #<NUM>, the NTT module #<NUM>, and the NTT module #<NUM> perform NTT processing on I<NUM>x, Q<NUM>x, I<NUM>y, and Q<NUM>y respectively, and output transform-domain first real-number signals Ix_1, Qx_1, Iy_1, and Qy_1 to the first chromatic dispersion compensation module <NUM>.

The first chromatic dispersion compensation module <NUM> includes a chromatic dispersion compensation module #<NUM> and a chromatic dispersion compensation module #<NUM>. Ix_1 and Qx_1 are input to the chromatic dispersion compensation module #<NUM>, and chromatic dispersion compensation is performed to obtain transform-domain third real-number signals Ix_3 and Qx_3. Iy_1 and Qy_1 are input to the chromatic dispersion compensation module #<NUM>, and chromatic dispersion compensation is performed to obtain transform-domain third real-number signals Iy _3 and Qy_3.

The clock recovery module <NUM> includes a clock recovery module #<NUM> and a clock recovery module #<NUM>. Ix_3 and Qx_3 are input to the clock recovery module #<NUM>, and clock recovery is performed to obtain transform-domain second real-number signals Ix_2 and Qx_2. Iy_3 and Qy_3 are input to the clock recovery module #<NUM>, and clock recovery is performed to obtain transform-domain second real-number signals Iy_2 and Qy_2.

The second real-number signals Ix_2, Qx_2, Iy_2, and Qy_2 are input to the first polarization compensation module <NUM>, and polarization demultiplexing and impairment equalization are performed to obtain transform-domain sixth real-number signals Ix_5, Qx_5, Iy_5, and Qy_5. Optionally, the first polarization compensation module <NUM> further includes a coefficient update module <NUM>. The coefficient update module <NUM> is configured to update a coefficient of a filter included in the first polarization compensation module <NUM>.

The first INTT module <NUM> includes an INTT module #<NUM>, an INTT module #<NUM>, an INTT module #<NUM>, and an INTT module #<NUM>. Signals Ix_5, Qx_5, Iy_5, and Qy_5 are input to the INTT module #<NUM>, the INTT module #<NUM>, the INTT module #<NUM>, and the INTT module #<NUM> respectively.

The INTT module #<NUM>, the INTT module #<NUM>, the INTT module #<NUM>, and the INTT module #<NUM> perform INTT processing on Ix_5, Qx_5, Iy_5, and Qy_5 respectively, and output time-domain seventh real-number signals Ix_6, Qx_6, Iy_6, and Qy_6 to the combination module <NUM>.

The combination module <NUM> includes a combination module #<NUM> and a combination module #<NUM>. Ix_6 and Qx _6 are input to the combination module #<NUM>, and are combined to obtain a time-domain complex-number signal X. Iy_6 and Qy_6 are input to the combination module #<NUM>, and are combined to obtain a time-domain complex-number signal Y.

The phase recovery module <NUM> includes a phase recovery module #<NUM> and a phase recovery module #<NUM>. The decoding module <NUM> includes a decoding module #<NUM> and a decoding module #<NUM>. The time-domain complex-number signal X is sequentially input to the phase recovery module #<NUM> and the decoding module #<NUM> to obtain a recovered bit signal. The time-domain complex-number signal Y is sequentially input to the phase recovery module #<NUM> and the decoding module #<NUM> to obtain a recovered bit signal.

The Rx DSP architecture <NUM> shown in <FIG> may be referred to as a full-transform-domain Rx DSP architecture. The full-transform-domain Rx DSP architecture not only performs chromatic dispersion compensation based on NTT/INTT, but also performs polarization compensation based on NTT/INTT, that is, performs chromatic dispersion compensation and polarization compensation in transform domain. Specifically, polarization equalization impairment compensation is performed in transform domain, and multiplication is used to replace convolution, so that power consumption can be further reduced. In addition, a quantity (size) of transformation points can be increased, so that an impairment is effectively equalized and performance is improved.

<FIG> is a schematic diagram of another Rx DSP architecture according to an embodiment of this application. The Rx DSP architecture <NUM> includes:
a first NTT module <NUM>, a first chromatic dispersion compensation module <NUM>, a clock recovery module <NUM>, a second polarization compensation module <NUM>, a coefficient update module <NUM>, a first INTT module <NUM>, a combination module <NUM>, a phase recovery module <NUM>, and a decoding module <NUM>.

Modules before clock recovery in the architecture <NUM> are the same as those in the architecture <NUM>. A difference lies in that a signal output by the clock recovery module <NUM> is first processed by the INTT module <NUM> and combined by the combination module <NUM>, and then input to the second polarization compensation module <NUM>. A process before the clock recovery is not described again.

The first INTT module <NUM> includes an INTT module #<NUM>, an INTT module #<NUM>, an INTT module #<NUM>, and an INTT module #<NUM>. Second real-number signals Ix_2, Qx_2, Iy_2, and Qy_2 are input to the INTT module #<NUM>, the INTT module #<NUM>, the INTT module #<NUM>, and the INTT module #<NUM> respectively.

The INTT module #<NUM>, the INTT module #<NUM>, the INTT module #<NUM>, and the INTT module #<NUM> perform INTT processing on Ix_2, Qx_2, Iy_2, and Qy_2 respectively, and output time-domain eighth real-number signals Ix_7, Qx_7, Iy_7, and Qy_7 to the combination module <NUM>.

The combination module <NUM> includes a combination module #<NUM> and a combination module #<NUM>. Ix_7 and Qx _7 are input to the combination module #<NUM>, and are combined to obtain a time-domain complex-number signal X. Iy_7 and Qy_7 are input to the combination module #<NUM>, and are combined to obtain a time-domain complex-number signal Y.

The time-domain complex-number signal X and the time-domain complex-number signal Y are input to the second polarization compensation module <NUM>, and polarization demultiplexing and impairment equalization are performed to obtain a time-domain complex-number signal X and a time-domain complex-number signal Y that have undergone polarization compensation. The second polarization compensation module <NUM> further includes a coefficient update module <NUM>. The coefficient update module <NUM> is configured to update a coefficient of a filter included in the second polarization compensation module <NUM>.

The phase recovery module <NUM> includes a phase recovery module #<NUM> and a phase recovery module #<NUM>. The decoding module <NUM> includes a decoding module #<NUM> and a decoding module #<NUM>. The time-domain complex-number signal X obtained through polarization compensation is sequentially input to the phase recovery module #<NUM> and the decoding module #<NUM> to obtain a recovered bit signal. The time-domain complex-number signal Y obtained through polarization compensation is sequentially input to the phase recovery module #<NUM> and the decoding module #<NUM> to obtain a recovered bit signal.

The Rx DSP architecture <NUM> shown in <FIG> may be referred to as an Rx DSP architecture combining time domain and transform domain. In the Rx DSP architecture combining time domain and transform domain, chromatic dispersion compensation is performed based on NTT/INTT, and polarization compensation is still performed in time domain, that is, chromatic dispersion compensation is performed in transform domain but polarization compensation is performed in time domain. Specifically, a chromatic dispersion compensation module with quite high power consumption implements compensation in transform domain, so that overall power consumption can be effectively reduced, and a polarization equalization module is left in time domain to perform compensation, so that a capability of the equalization module in resisting a loop delay is enhanced.

<FIG> is a schematic structural diagram of a chromatic dispersion compensation module <NUM>. The chromatic dispersion compensation module <NUM> may be applied to the architecture shown in <FIG> and <FIG>. The chromatic dispersion compensation module includes an FFT module <NUM>, an FFT module <NUM>, a combination module <NUM>, a combination module <NUM>, and a multiplication module <NUM>.

Signals are transmitted in an optical fiber. Impact of chromatic dispersion of the optical fiber on the signals may be described as an impulse response. In time-domain chromatic dispersion equalization, a finite impulse response (finite impulse response, FIR) is used for compensation. An FIR coefficient is as follows: <MAT>. β<NUM> indicates a chromatic dispersion coefficient of an optical fiber, z indicates a transmission distance of a signal in the optical fiber, j indicates an imaginary number, and t indicates time. Because a signal in a polarization direction x and a signal in a polarization direction y undergo a same chromatic dispersion impairment, a same function h(t) is used during equalization.

In the FFT-based chromatic dispersion compensation module in the signal processing procedure shown in <FIG> and <FIG>, input of the chromatic dispersion compensation module is a frequency-domain complex-number signal X (ω).

For example, Ih(t) and Qh(t) are time-domain chromatic dispersion impulse responses, Ih(t) and Qh(t) are combined by the combination module <NUM> into a complex-number impulse response H(t), H(t) is input to the FFT module <NUM> to obtain a frequency-domain equalization function H(ω), and H(ω) and X(ω) are input to the multiplication module <NUM>, and are multiplied to obtain output of the chromatic dispersion compensation module: Xοut(ω)=H(ω).

<FIG> is a schematic structural diagram of a chromatic dispersion compensation module <NUM> according to an embodiment of this application. The chromatic dispersion compensation module <NUM> may be applied to the RX DSP architectures <NUM> and <NUM>. The chromatic dispersion compensation module includes an NTT module <NUM>, an NTT module <NUM>, an NTT module <NUM>, an NTT module <NUM>, a combination module <NUM>, a combination module <NUM>, a multiplication module <NUM>, a multiplication module <NUM>, a multiplication module <NUM>, and a multiplication module <NUM>.

In the signal processing procedures shown in <FIG> and <FIG>, the NTT-based chromatic dispersion compensation module separately performs chromatic dispersion compensation on a signal in a polarization direction x and a signal in a polarization direction y. A chromatic dispersion compensation process (as shown in <FIG>) is described by using chromatic dispersion compensation in the polarization direction x as an example.

For example, a chromatic dispersion impulse response h(t) in the polarization direction x is split into Ih(t) and Qh(t), where <MAT>, and <MAT>.

Ih(t) and Qh(t) are input to the NTT module <NUM> and the NTT module <NUM> respectively, and are transformed to obtain chromatic dispersion equalization functions Ih(w) and Qh(w) in NTT transform domain. A codirectional signal Ix(t) and a quadrature signal Qx(t) in the polarization direction x are input to the NTT module <NUM> and the NTT module <NUM> respectively, and are transformed to obtain transform-domain signals Ix(w) and Qx(w).

It can be learned from <FIG> that a result obtained by inputting the transform-domain codirectional signal Ix(w) and the codirectional component Ih(w) of the equalization function to the multiplication module <NUM> and performing multiplication, and a result obtained by inputting the transform-domain quadrature signal Qx(w) and the quadrature component Qh(w) of the equalization function to the multiplication module <NUM> and performing multiplication are combined by the combination module <NUM> as follows: Ix_out(w)=Ix(w)·Ih(w)-Qx(w)·Qh(w).

A result obtained by inputting Qx(w) and Ih(w) to the multiplication module <NUM> and performing multiplication, and a result obtained by inputting Ix(w) and Qh(w) to the multiplication module <NUM> and performing multiplication are combined by the combination module <NUM> as follows: Qx_out(w)=Qx(w)·Ih(w)-Ix(w)·Qh(w).

Likewise, when chromatic dispersion compensation is performed in the polarization direction y, a codirectional signal Iy(t) and a quadrature signal Qy(t) in the polarization direction y are input to NTT modules, and are transformed to obtain transform-domain signals Iy(w) and Qy(w) respectively. A chromatic dispersion compensation process in the polarization direction y may be described by using the following formulas: <MAT> and <MAT>.

In an actual operation, the equalization function H(ω) in Fourier transform domain in <FIG> and the chromatic dispersion equalization functions Ih(w) and Qh(w) in number theoretic transform domain in <FIG> need to be calculated only once and stored in a memory, and may be repeatedly invoked for different input signals.

For example, one NTT transformation and one FFT transformation are used as examples to explain a difference between the two types of transformations:.

Transformation matrices of both FFT and NTT may be represented as follows: <MAT>.

A difference lies in a transformation core <MAT> of FFT. A transformation core α of NTT is a power of <NUM>. Usually, α is <NUM> (or may be <MAT> or another value, which is not limited in this application). For example, α = <NUM>. Each element in a transformation matrix is still a power of <NUM>, and multiplication by <NUM> or a power of <NUM> in a binary operation may be performed through bit shifting.

Correspondingly, for example, the core α = <NUM>. A transformation matrix H of NTT and a transformation matrix H-<NUM> of INTT are respectively as follows: <MAT> <MAT>.

Internal working processes of the clock recovery module #<NUM> and the clock recovery module #<NUM> are similar to that in <FIG>, and only the chromatic dispersion equalization functions Ih(w) and Qh(w) need to be replaced with functions for equalizing clock delays. A delay caused by a clock is expressed as h(t) = exp(-<NUM>πft<NUM>) by using a time-domain finite impulse response. In the clock recovery module, Ih(w) and Qh(w) may be replaced with NTT transformation of cos(<NUM>πft<NUM>).

<FIG> is a schematic diagram of still another Rx DSP architecture according to an embodiment of this application. The Rx DSP architecture <NUM> includes:
a digital back propagation (digital back propagation, DBP) module <NUM>, a first NTT module <NUM>, a clock recovery module <NUM>, a first polarization compensation module <NUM>, a first INTT module <NUM>, a combination module <NUM>, a phase recovery module <NUM>, and a decoding module <NUM>.

An architecture after the first polarization compensation module <NUM> in the Rx DSP architecture <NUM> is the same as that in the Rx DSP architecture <NUM>. A difference lies in that a signal undergoes DBP processing before polarization compensation. Because the DBP module <NUM> has a chromatic dispersion compensation function, a process after the DBP module may not require the chromatic dispersion compensation module <NUM>.

Signals I<NUM>x, Q<NUM>x, I<NUM>y, and Q<NUM>y are input to the DBP module <NUM>, DBP processing is performed, and time-domain tenth real-number signals Ix_4, Qx_4, Iy_4, and Qy_4 are output to the first NTT module <NUM>.

The first NTT module <NUM> includes an NTT module #<NUM>, an NTT module #<NUM>, an NTT module #<NUM>, and an NTT module #<NUM>. Ix_4, Qx_4, Iy_4, and Qy_4 are input to the NTT module #<NUM>, the NTT module #<NUM>, the NTT module #<NUM>, and the NTT module #<NUM> respectively.

The NTT module #<NUM>, the NTT module #<NUM>, the NTT module #<NUM>, and the NTT module #<NUM> perform NTT processing on Ix_4, Qx_4, Iy_4, and Qy_4 respectively, and output transform-domain first real-number signals Ix_1, Qx_1, Iy_1, and Qy_1 to the clock recovery module <NUM>.

The clock recovery module <NUM> includes a clock recovery module #<NUM> and a clock recovery module #<NUM>. Ix_1 and Qx_1 are input to the clock recovery module #<NUM>, and clock recovery is performed to obtain transform-domain second real-number signals Ix_2 and Qx_2. Iy_1 and Qy_1 are input to the clock recovery module #<NUM>, and clock recovery is performed to obtain transform-domain second real-number signals Iy_2 and Qy_2.

For a process after the clock recovery module <NUM>, refer to the embodiment shown in <FIG>.

The Rx DSP architecture <NUM> shown in <FIG> may be referred to as a full-transform-domain Rx DSP architecture in which DBP is added. A difference from the full-transform-domain Rx DSP architecture shown in <FIG> lies in that the DBP module is added. It should be understood that in the full-transform-domain Rx DSP architecture shown in <FIG>, only a linear impairment of an optical fiber is compensated for, for example, chromatic dispersion compensation. In the full-transform-domain Rx DSP architecture in which the DBP module is added, the DBP module is used to implement nonlinear-effect compensation on a basis of a linear impairment, to increase a signal transmission distance.

<FIG> is a schematic diagram of still another Rx DSP architecture according to an embodiment of this application. The Rx DSP architecture <NUM> includes:
a DBP module <NUM>, a first NTT module <NUM>, a clock recovery module <NUM>, a second polarization compensation module <NUM>, a coefficient update module <NUM>, a first INTT module <NUM>, a combination module <NUM>, a phase recovery module <NUM>, and a decoding module <NUM>.

An architecture after the second polarization compensation module <NUM> in the Rx DSP architecture <NUM> is the same as that in the Rx DSP architecture <NUM>. An architecture before the second polarization compensation module <NUM> is the same as that in the Rx DSP architecture <NUM>. To be specific, a received signal obtained through conversion by an ADC first undergoes DBP processing. For a process before the DBP processing and clock recovery, refer to the embodiment shown in <FIG>. For a process after the clock recovery module <NUM>, refer to the embodiment shown in <FIG>.

The Rx DSP architecture <NUM> shown in <FIG> may be referred to as an Rx DSP architecture combining time domain and transform domain in which DBP is added. A difference from the Rx DSP architecture combining time domain and transform domain shown in <FIG> lies in that the DBP module is added. It should be understood that in the Rx DSP architecture combining time domain and transform domain shown in <FIG>, only a linear impairment of an optical fiber is compensated for, for example, chromatic dispersion compensation. In the Rx DSP architecture combining time domain and transform domain in which the DBP module is added, the DBP module is used to implement nonlinear-effect compensation on a basis of a linear impairment, to increase a signal transmission distance.

<FIG> is a schematic structural diagram of a DBP module according to an embodiment of this application. The DBP module <NUM> includes:
a second NTT module <NUM>, a second chromatic dispersion compensation module <NUM>, a second INTT module <NUM>, and a nonlinear compensation module <NUM>, where a structure of the second chromatic dispersion compensation module <NUM> is shown in <FIG>, and is not described in detail herein.

It can be learned from the structural diagram of the DBP module shown in <FIG> that the performing DBP processing on I<NUM>x, Q<NUM>x, I<NUM>y, and Q<NUM>y to obtain the real-number signals Ix_4, Qx_4, Iy_4, and Qy_4 shown in <FIG> and <FIG> specifically includes the following steps.

The second NTT module <NUM> includes an NTT module #<NUM>, an NTT module #<NUM>, an NTT module #<NUM>, and an NTT module #<NUM>. I<NUM>x, Q<NUM>x, I<NUM>y, and Q<NUM>y are input to the NTT module #<NUM>, the NTT module #<NUM>, the NTT module #<NUM>, and the NTT module #<NUM> respectively.

The NTT module #<NUM>, the NTT module #<NUM>, the NTT module #<NUM>, and the NTT module #<NUM> perform NTT processing on I<NUM>x, Q<NUM>x, I<NUM>y, and Q<NUM>y respectively, and output fourth real-number signals Ix_4', Qx_4', Iy_4', and Qy_4' to the second chromatic dispersion compensation module <NUM>.

The second chromatic dispersion compensation module <NUM> includes a chromatic dispersion compensation module #<NUM> and a chromatic dispersion compensation module #<NUM>. Ix_4' and Qx_4' are input to the chromatic dispersion compensation module #<NUM>, and chromatic dispersion compensation is performed in transform domain to obtain transform-domain fifth real-number signals Ix_4" and Qx_4". Iy_4' and Qy_4' are input to the chromatic dispersion compensation module #<NUM>, and chromatic dispersion compensation is performed in transform domain to obtain transform-domain fifth real-number signals Iy_4" and Qy_4".

The second INTT module <NUM> includes an INTT module #<NUM>, an INTT module #<NUM>, an INTT module #<NUM>, and an INTT module #<NUM>. Ix_4", Qx_4", Iy_4", and Qy_4" are input to the INTT module #<NUM>, the INTT module #<NUM>, the INTT module #<NUM>, and the INTT module #<NUM> respectively.

The INTT module #<NUM>, the INTT module #<NUM>, the INTT module #<NUM>, and the INTT module #<NUM> perform INTT processing on Ix_4", Qx_4", Iy_4", and Qy_4" respectively, and output time-domain ninth real-number signals Ix_4‴, Qx_4‴, Iy_4‴, and Qy_4‴ to the nonlinear compensation module <NUM>.

The nonlinear compensation module <NUM> includes a nonlinear compensation module #<NUM> and a nonlinear compensation module #<NUM>. Ix_4' and Qx_4' are input to the nonlinear compensation module #<NUM>, and nonlinear compensation is performed to obtain Ix_4 and Qx_4. Iy_4' and Qy_4' are input to the nonlinear compensation module #<NUM>, and nonlinear compensation is performed to obtain Iy_4 and Qy_4.

It should be noted that the foregoing processing procedure in the DBP module needs to be repeated for Ns times. To ensure performance, when a span of a link increases, a quantity Ns of DBP iterations also needs to be increased. Different DBP solutions are not limited herein. Depending on different power consumption required by scenarios, Ns may be set to be equal to a total span of a link, or single-step DBP may be set. In the DBP module in this embodiment of this application, no FFT module or IFFT module is used; instead, the NTT module and the INTT module are used. In this way, during a signal processing procedure of the DBP module, repeated Ns transformations do not cause error accumulation.

<FIG> is a schematic structural diagram of a first polarization compensation module <NUM> according to an embodiment of this application. <FIG> is a schematic structural diagram of a second polarization compensation module <NUM> according to an embodiment of this application.

It can be learned from <FIG> that the first polarization compensation module <NUM> in this embodiment of this application includes a butterfly filter <NUM> and a butterfly filter <NUM>. The butterfly filter <NUM> includes a filter <NUM>, a filter <NUM>, a filter <NUM>, a filter <NUM>, an adder <NUM>, and an adder <NUM>. The butterfly filter <NUM> includes a filter <NUM>, a filter <NUM>, a filter <NUM>, a filter <NUM>, an adder <NUM>, and an adder <NUM>.

Output of the filter <NUM>, output of the filter <NUM>, output of the filter <NUM>, and output of the filter <NUM> are negative. The foregoing four signals are input to the adder <NUM> to obtain a signal Ix_5 that has undergone chromatic dispersion compensation. The output of the filter <NUM>, the output of the filter <NUM>, the output of the filter <NUM>, and the output of the filter <NUM> are input to the adder <NUM> to obtain a signal Qx_5 that has undergone chromatic dispersion compensation. Output of the filter <NUM>, output of the filter <NUM>, output of the filter <NUM>, and output of the filter <NUM> are negative. The foregoing four signals are input to the adder <NUM> to obtain a signal Iy_5 that has undergone chromatic dispersion compensation. The output of the filter <NUM>, the output of the filter <NUM>, the output of the filter <NUM>, and the output of the filter <NUM> are output to the adder <NUM> to obtain a signal Qy_5 that has undergone chromatic dispersion compensation.

A clock recovery module outputs four signals. The four signals Ix_2, Qx_2, Iy_2, and Qy_2 are input to a polarization compensation module. The polarization compensation module includes two butterfly filters. One butterfly filter represents a <NUM>×<NUM> two-input, two-output system. Two complex-number signals are input, and two complex-number signals are output. Because real-number signals are processed in NTT transformation, a polarization equalization part is a <NUM>×<NUM> four-input, four-output system.

The first butterfly filter <NUM> is for equalization and depolarization of I-path signals (including an x-polarization I-path signal Ix_2 and a y-polarization I-path signal Iy_2), and a transformation matrix is <MAT>. The second butterfly filter <NUM> is for Q-path signals (including an x-polarization Q-path signal Qx_2 and a y-polarization Q-path signal Qy_2), and a transformation matrix is <MAT>.

The polarization compensation module outputs four real-number signals: Ix_5, Qx_5, Iy_5, and Qy_5. A process of performing polarization compensation by the first polarization compensation module <NUM> is described with reference to <FIG>.

Input signals of the first polarization compensation module <NUM> are four real-number signals: Ix_2, Qx_2, Iy_2, and Qy_2, which are a codirectional signal Ix_2 in a polarization direction x, a quadrature signal Qx_2 in the polarization direction x, a codirectional signal Iy_2 in a polarization direction y, and a quadrature signal Qy_2 in the polarization direction y, respectively.

Specifically, a multiplication result of Ix_2 and Ihxx is input to the adder <NUM>, a negative value of a multiplication result of Qx_2 and Qhxx is input to the adder <NUM>, a multiplication result of Iy_2 and Ihxy is input to the adder <NUM>, a negative value of a multiplication result of Qy_2 and Qhxy is input to the adder <NUM>, and the adder <NUM> outputs a codirectional signal Ix_5 that is in the polarization direction x and that is obtained through polarization compensation.

A multiplication result of Ix_2 and Qhxx is input to the adder <NUM>, a negative value of a multiplication result of Qx_2 and Ihxx is input to the adder <NUM>, a multiplication result of Iy_2 and Qhxy is input to the adder <NUM>, a multiplication result of Qy_2 and Ihxy is input to the adder <NUM>, and the adder <NUM> outputs a quadrature signal Qx_5 that is in the polarization direction x and that is obtained through polarization compensation.

A multiplication result of Ix_2 and Ihyx is input to the adder <NUM>, a negative value of a multiplication result of Qx_2 and Qhyx is input to the adder <NUM>, a multiplication result of Iy_2 and Ihyy is input to the adder <NUM>, a negative value of a multiplication result of Qy_2 and Qhyy is input to the adder <NUM>, and the adder <NUM> outputs a codirectional signal Iy_5 that is in the polarization direction y and that is obtained through polarization compensation.

A multiplication result of Ix_2 and Qhyx is input to the adder <NUM>, a multiplication result of Qx_2 and Ihyx is input to the adder <NUM>, a multiplication result of Iy_2 and Qhyy is input to the adder <NUM>, a multiplication result of Qy_2 and Ihyy is input to the adder <NUM>, and the adder <NUM> outputs a quadrature signal Qy_5 that is in the polarization direction y and that is obtained through polarization compensation.

A process in which the output Ix_5, Qx_5, Iy_5, and Qy_5 of the first polarization compensation module <NUM> interact with an equalization matrix and the input signals Ix_2, Qx_2, Iy_2, and Qy_2 is described by using the following formula: <MAT>.

For example, the first polarization compensation module <NUM> further includes a coefficient update module <NUM> (not shown in the figure). The coefficient update module <NUM> is configured to update a coefficient of a filter included in the first polarization compensation module <NUM>. In this embodiment of this application, manners of updating equalization coefficient matrices <MAT> and <MAT> of a polarization compensation module include a blind update, an update with training, an update without decision feedback, an update with decision feedback, and the like. A manner of updating a coefficient of the polarization compensation module is not limited in this embodiment of this application.

It can be learned from <FIG> that the second polarization compensation module <NUM> in this embodiment of this application includes <NUM>×<NUM> butterfly filters, and the butterfly filters include a filter <NUM>, a filter <NUM>, a filter <NUM>, a fourth filter <NUM>, an adder <NUM>, and an adder <NUM>.

Functions of the second polarization compensation module <NUM> include channel optical fiber effects such as equalization compensation (equalization compensation), a differential group delay (differential group delay, DGD), and residual chromatic dispersion. An optical fiber effect may be described by using a <NUM>×<NUM> impairment matrix. An inverse matrix of the impairment matrix may be obtained by using different algorithms. Tap coefficients of a time-domain butterfly filter <NUM> are hxx, hxy, hyx, and hyy. X and Y signals are convolved with the tap coefficient matrices hxx, hxy, hyx, and hyy to obtain signals Xout and Yout that have undergone polarization impairment compensation. Common algorithms for calculating a tap coefficient matrix include a constant modulus algorithm (constant modulus algorithm, CMA), a least mean square (Least Mean Square, LMS), and various modified versions of the LMS or other forms such as a data-aided LMS.

The combination module <NUM> outputs a complex-number signal X in a polarization direction X, and the complex-number signal X is input to the filter <NUM> and the filter <NUM>. The combination module <NUM> outputs a complex-number signal Y in a polarization direction Y, and the complex-number signal Y is input to the filter <NUM> and the filter <NUM>. The filter <NUM> and the filter <NUM> provide output to the adder <NUM>. The filter <NUM> and the filter <NUM> provide output to the adder <NUM>.

hxx, hxy, hyx, and hyy in <FIG> represent coefficients of the filter <NUM>, the filter <NUM>, the filter <NUM>, and the filter <NUM> respectively.

It should be noted that although <FIG> and <FIG> are used as examples to describe the butterfly filters in this application, the butterfly filters shown in <FIG> and <FIG> are merely examples, and do not constitute any limitation on the protection scope of this application. The butterfly filters in the embodiments of this application should be understood in a broad sense, and a filter or a filter combination that can implement a deconvolution function may be referred to as a butterfly filter.

The Rx DSP provided in this embodiment of this application may be further applied to a multi-mode transmission scenario. For example, the Rx DSP is applied to m transmission modes. In this case, the Rx DSP receives P real-number signals.

<FIG> is a schematic diagram of an Rx DSP architecture in a multi-mode transmission scenario according to an embodiment of this application. The Rx DSP architecture <NUM> includes:
a first NTT module <NUM>, a first chromatic dispersion compensation module <NUM>, a clock recovery module <NUM>, a first polarization compensation module <NUM>, a first INTT module <NUM>, a combination module <NUM>, a phase recovery module <NUM>, and a decoding module <NUM>.

P real-number signals are input to the first NTT module <NUM>. The first NTT module separately performs NTT processing on the P real-number signals, and outputs P transform-domain first real-number signals to the first chromatic dispersion compensation module <NUM>.

Optionally, the P real-number signals are real-number signals obtained through conversion by an ADC. The P real-number signals include <NUM>×m real-number signals in m transmission modes.

The first chromatic dispersion compensation module <NUM> separately performs chromatic dispersion compensation on the P transform-domain first real-number signals, and outputs P transform-domain third real-number signals to the clock recovery module <NUM>.

The clock recovery module <NUM> separately performs clock recovery on the P transform-domain third real-number signals, and outputs P transform-domain second real-number signals to the first polarization compensation module <NUM>.

The first polarization compensation module <NUM> performs polarization compensation processing on the P transform-domain second real-number signals, and outputs P transform-domain sixth real-number signals to the first INTT module <NUM>.

The first INTT module <NUM> separately performs INTT processing on the P transform-domain sixth real-number signals, and outputs P time-domain seventh real-number signals to the combination module <NUM>.

The combination module <NUM> combines the P time-domain seventh real-number signals, and outputs m complex-number signals X and m complex-number signals Y to the phase recovery module <NUM> and the decoding module <NUM>.

The phase recovery module <NUM> and the decoding module <NUM> perform phase recovery and decoding processing on the m complex-number signals X and the m complex-number signals Y to obtain recovered bit signals.

<FIG> is a schematic diagram of an Rx DSP architecture in another multi-mode transmission scenario according to an embodiment of this application. The Rx DSP architecture <NUM> includes:
a first NTT module <NUM>, a first chromatic dispersion compensation module <NUM>, a clock recovery module <NUM>, a second polarization compensation module <NUM>, a first INTT module <NUM>, a combination module <NUM>, a phase recovery module <NUM>, and a decoding module <NUM>.

Modules before clock recovery in the architecture <NUM> are the same as those in the architecture <NUM>. A difference lies in that a signal output by the clock recovery module is first processed by the INTT module and combined by the combination module, and then input to the second polarization compensation module <NUM>. A process before the clock recovery is not described again.

The first INTT module <NUM> separately performs INTT processing on the P transform-domain second real-number signals, and outputs P time-domain eighth real-number signals to the combination module <NUM>. The combination module <NUM> combines the P time-domain eighth real-number signals, and outputs m complex-number signals X and m complex-number signals Y to the second polarization compensation module <NUM>.

The second polarization compensation module <NUM> performs polarization compensation processing on the m complex-number signals X and the m complex-number signals Y, and outputs m time-domain complex-number signals X and m time-domain complex-number signals Y obtained through polarization compensation to the phase recovery module <NUM> and the decoding module <NUM>. The second polarization compensation module <NUM> further includes a coefficient update module <NUM> (not shown in the figure). The coefficient update module <NUM> is configured to update a coefficient of a filter included in the second polarization compensation module <NUM>.

<FIG> is a schematic diagram of an Rx DSP architecture in still another multi-mode transmission scenario according to an embodiment of this application. The Rx DSP architecture <NUM> includes:
a DBP module <NUM>, a first NTT module <NUM>, a clock recovery module <NUM>, a first polarization compensation module <NUM>, a first INTT module <NUM>, a combination module <NUM>, a phase recovery module <NUM>, and a decoding module <NUM>.

P real-number signals are input to the DBP module <NUM>, DBP processing is performed, and P time-domain tenth real-number signals are output to the first NTT module <NUM>.

The first NTT module <NUM> separately performs NTT processing on the P time-domain tenth real-number signals, and outputs P transform-domain first real-number signals to the clock recovery module <NUM>.

The clock recovery module <NUM> separately performs clock recovery processing on the P transform-domain first real-number signals, and outputs P transform-domain second real-number signals to the first polarization compensation module <NUM>.

<FIG> is a schematic diagram of an Rx DSP architecture in still another multi-mode transmission scenario according to an embodiment of this application. The Rx DSP architecture <NUM> includes:
a DBP module <NUM>, a first NTT module <NUM>, a clock recovery module <NUM>, a second polarization compensation module <NUM>, a first INTT module <NUM>, a combination module <NUM>, a phase recovery module <NUM>, and a decoding module <NUM>.

For example, the DBP module <NUM> shown in <FIG> and <FIG> is shown in <FIG> is a schematic structural diagram of another DBP module according to an embodiment of this application. The DBP module <NUM> includes:
a second NTT module <NUM>, a second chromatic dispersion compensation module <NUM>, a second INTT module <NUM>, and a nonlinear compensation module <NUM>.

That P real-number signals are input to the DBP module <NUM>, and DBP processing is performed to obtain P time-domain tenth real-number signals specifically includes the following steps.

The P real-number signals are respectively input to P second NTT modules <NUM>, NTT processing is performed, and P transform-domain fourth real-number signals are output to the second chromatic dispersion compensation module <NUM>.

The second chromatic dispersion compensation module <NUM> performs chromatic dispersion compensation processing on the P transform-domain fourth real-number signals, and outputs P transform-domain fifth real-number signals to the second INTT module <NUM>.

The second INTT module <NUM> performs INTT processing on the P transform-domain fifth real-number signals, and outputs P time-domain ninth real-number signals to the nonlinear compensation module <NUM>.

The nonlinear compensation module <NUM> performs nonlinear compensation on the P time-domain ninth real-number signals to obtain the P time-domain tenth real-number signals.

Specifically, compared with performing signal processing by using the FFT module and the IFFT module, performing signal processing by using the NTT module and the INTT module has the following advantages.

When signal processing is performed based on the FFT module and the IFFT module, during a signal transmission process, power consumption of merely chromatic dispersion compensation accounts for half of total power consumption of Rx DSP, and complexity of N-point FFT is proportional to Nlog2N multiplications. Depending on different data bit widths of operations, complexity of a multiplication is equal to several times to dozens of times of that of an addition.

However, complexity of signal processing performed based on the NTT module and the INTT module is proportional to 2Nlog2N additions. Depending on different data bit widths and different quantities N of transformation points, complexity of signal processing performed based on the NTT module and the INTT module is reduced to different degrees. For example, if a quantity of transformation points is <NUM>, power consumption of NTT is reduced to approximately <NUM>/<NUM> of that of FFT.

(<NUM>) When signal processing is performed based on the NTT module and the INTT module, a transformation matrix has no truncation error or fixed-point penalty.

When signal processing is performed based on the FFT module and the IFFT module, because a transformation core of FFT is an exponential function, a truncation error cannot be accurately expressed on a binary computer. In addition, a bit width of a transformation matrix is not fixed, causing a fixed-point penalty.

However, in signal processing performed based on the NTT module and the INTT module, because a transformation core of NTT is an integer and the transformation core is usually <NUM> or a power of <NUM>, the transformation core can be accurately expressed in a memory. In addition, a bit width of a transformation matrix is fixed, without a fixed-point penalty.

(<NUM>) When signal processing is performed based on the NTT module and the INTT module, no error accumulates.

A truncation error and a fixed-point penalty in a single FFT or IFFT transformation repeatedly accumulate during DBP propagation. As a result, a final result error is larger.

However, there is no truncation error or fixed-point penalty in a single NTT or INTT transformation. Therefore, repeated Ns transformations do not cause error accumulation.

(<NUM>) When signal processing is performed based on the NTT module and the INTT module, storage can be reduced.

A transformation core of NTT is <NUM>, and a transformation matrix includes <NUM> or a power of <NUM>. In a binary system, a number is multiplied by a power of <NUM> only through shifting. Therefore, no huge transformation matrix needs to be stored in a DSP process, and only the transformation core needs to be stored.

<FIG> is a schematic flowchart of a signal processing method according to an embodiment of this application. The following steps S1010 to S1050 are included.

For example, the P real-number signals include real-number signals that are in two polarization directions and that correspond to each of m modes. When m is equal to <NUM>, it indicates single-mode transmission; or when m is greater than <NUM>, it indicates multi-mode transmission. m and P are positive integers.

Obtain P transform-domain first real-number signals.

At least NTT processing is performed on the P real-number signals to obtain the P transform-domain first real-number signals. The following two possible implementations are included.

Implementation <NUM>: Perform NTT processing on the P real-number signals to obtain the P transform-domain first real-number signals.

Implementation <NUM>: Sequentially perform DBP processing and NTT processing on the P real-number signals to obtain the P transform-domain first real-number signals.

In the implementation <NUM>, DBP processing is first performed on the P real-number signals to obtain P time-domain tenth real-number signals, and then NTT processing is performed on the P time-domain tenth real-number signals to obtain the P transform-domain first real-number signals.

The performing NTT processing on the P real-number signals in the implementation <NUM>, and the performing NTT processing on the P time-domain tenth real-number signals that are obtained by performing DBP processing on the P real-number signals in the implementation <NUM> may be collectively referred to as performing NTT processing on P input signals. In other words, in this embodiment of this application, the P input signals include the P real-number signals, or the P time-domain tenth real-number signals that are obtained by performing DBP processing on the P real-number signals.

For ease of understanding, a process of performing DBP processing on the P real-number signals to obtain the P time-domain tenth real-number signals is briefly described with reference to <FIG> is a schematic flowchart of DBP processing according to an embodiment of this application. The following steps S1021 to S1024 are included.

Obtain P transform-domain fourth real-number signals.

NTT processing is performed on P real-number signals to obtain the P transform-domain fourth real-number signals.

Obtain P transform-domain fifth real-number signals.

Chromatic dispersion compensation is performed on the P transform-domain fourth real-number signals in transform domain to obtain the P transform-domain fifth real-number signals.

Obtain P time-domain ninth real-number signals.

INTT processing is performed on the P transform-domain fifth real-number signals to obtain the P time-domain ninth real-number signals.

Obtain P time-domain tenth real-number signals.

Nonlinear compensation is performed on the P time-domain ninth real-number signals to obtain the P time-domain tenth real-number signals.

Obtain P transform-domain second real-number signals.

At least clock recovery processing is performed on the P transform-domain first real-number signals to obtain the P transform-domain second real-number signals. Corresponding to the two possibilities in step S1020, the following two possible implementations are included.

Implementation <NUM>: This corresponds to the implementation <NUM> in step S1020. A processing procedure includes the following steps.

First, perform chromatic dispersion compensation on the P transform-domain first real-number signals to obtain P transform-domain third real-number signals.

Then, separately perform clock recovery on the P transform-domain third real-number signals to obtain the P transform-domain second real-number signals.

The performing chromatic dispersion compensation on the P transform-domain first real-number signals to obtain P transform-domain third real-number signals specifically includes the following steps:.

First, determine a chromatic dispersion impulse response Ih(t) corresponding to an in-phase real-number signal and a chromatic dispersion impulse response Qh(t) corresponding to a quadrature real-number signal, and perform NTT to obtain a transform-domain chromatic dispersion equalization function Ih(w) corresponding to the in-phase real-number signal and a transform-domain chromatic dispersion equalization function Qh(w) corresponding to the quadrature real-number signal.

Then, determine <NUM>×m transform-domain third real-number signals that are in the P transform-domain third real-number signals and that are in a first polarization direction based on Ih(w), Qh(w), and an in-phase real-number signal and a quadrature real-number signal that are in the P transform-domain first real-number signals and that are in the first polarization direction, and determine <NUM>×m transform-domain third real-number signals that are in the P transform-domain third real-number signals and that are in a second polarization direction based on Ih(w), Qh(w), and an in-phase real-number signal and a quadrature real-number signal that are in the P transform-domain first real-number signals and that are in the second polarization direction.

Specifically, the transform-domain third real-number signals obtained through chromatic dispersion compensation and the transform-domain first real-number signals that have not undergone chromatic dispersion compensation meet the following requirements: <MAT> <MAT> <MAT> and <MAT> where
Ix(w) represents an in-phase real-number signal that is in the transform-domain first real-number signals and that is in the first polarization direction, Qx(w) represents a quadrature real-number signal that is in the transform-domain first real-number signals and that is in the first polarization direction, Iy(w) represents an in-phase real-number signal that is in the transform-domain first real-number signals and that is in the second polarization direction, Qy(w) represents a quadrature real-number signal that is in the transform-domain first real-number signals and that is in the second polarization direction, I'x(w) represents an in-phase real-number signal that is in the transform-domain third real-number signals and that is in the first polarization direction, Q'x(w) represents a quadrature real-number signal that is in the transform-domain third real-number signals and that is in the first polarization direction, I'y(w) represents an in-phase real-number signal that is in the transform-domain third real-number signals and that is in the second polarization direction, and Q'y(w) represents a quadrature real-number signal that is in the transform-domain third real-number signals and that is in the second polarization direction.

This corresponds to the implementation <NUM> in step S1020. A processing procedure includes the following step:
Separately perform clock recovery on the P transform-domain first real-number signals to obtain the P transform-domain second real-number signals.

Obtain time-domain complex-number signals.

At least polarization compensation processing and INTT processing are performed on the P transform-domain second real-number signals to obtain m time-domain complex-number signals X and m time-domain complex-number signals Y. The following two possible implementations are included.

Implementation <NUM>: Sequentially perform polarization compensation processing, INTT processing, and combination processing on the P transform-domain second real-number signals to obtain the m time-domain complex-number signals X and the m time-domain complex-number signals Y. <FIG> is a schematic flowchart of obtaining a time-domain complex-number signal according to an embodiment of this application. The following steps S1041 to S1043 are included.

Obtain P transform-domain sixth real-number signals.

Polarization compensation is performed on P transform-domain second real-number signals to obtain the P transform-domain sixth real-number signals.

Obtain P time-domain seventh real-number signals.

INTT processing is separately performed on the P transform-domain sixth real-number signals to obtain the P time-domain seventh real-number signals.

Perform combination to obtain m complex-number signals X and m complex-number signals Y.

Every two of <NUM>×m time-domain seventh real-number signals that are in the P time-domain seventh real-number signals and that are in a first polarization direction are combined to obtain the m time-domain complex-number signals X in the first polarization direction.

Every two of <NUM>×m time-domain seventh real-number signals that are in the P time-domain seventh real-number signals and that are in a second polarization direction are combined to obtain the m time-domain complex-number signals Y in the second polarization direction.

Implementation <NUM>: Sequentially perform INTT processing, combination processing, and polarization compensation processing on the P transform-domain second real-number signals. <FIG> is another schematic flowchart of obtaining a time-domain complex-number signal according to an embodiment of this application. The following steps S1044 to S1046 are included.

Obtain P time-domain eighth real-number signals.

INTT processing is performed on P transform-domain second real-number signals to obtain the P time-domain eighth real-number signals.

Obtain m complex-number signals X and m complex-number signals Y.

Every two of <NUM>×m time-domain eighth real-number signals that are in the P time-domain eighth real-number signals and that are in a first polarization direction are combined to obtain the m time-domain complex-number signals X in the first polarization direction.

Every two of <NUM>×m time-domain eighth real-number signals that are in the P time-domain eighth real-number signals and that are in a second polarization direction are combined to obtain the m time-domain complex-number signals Y in the second polarization direction.

Obtain m complex-number signals X and m complex-number signals Y that have undergone polarization compensation.

Polarization compensation is performed on the m time-domain complex-number signals X in the first polarization direction and the m time-domain complex-number signals Y in the second polarization direction to obtain the m time-domain complex-number signals X and the m time-domain complex-number signals Y that have undergone the polarization compensation.

To obtain the recovered bit signals, phase recovery and decoding need to be performed on the time-domain complex-number signals obtained in S1040.

First, phase recovery is performed on the m time-domain complex-number signals X and the m time-domain complex-number signals Y to obtain m time-domain complex-number signals X and m time-domain complex-number signals Y that have undergone the phase recovery.

Then, the m time-domain complex-number signals X and the m time-domain complex-number signals Y that are obtained through phase recovery are decoded to obtain m time-domain complex-number signals X and m time-domain complex-number signals Y that have been decoded.

It should be noted that how to perform phase recovery and decoding on the time-domain complex-number signals is not limited in this embodiment of this application. Refer to a current process of performing phase recovery and decoding on an electrical signal by a polarization multiplexing coherent receiver.

An embodiment of this application further provides a coherent receiver, including a polarization beam splitter, a frequency mixer, a photoelectric detector, an analog-to-digital converter, and the Rx DSP shown in <FIG>, <FIG>, <FIG>, or <FIG>. The polarization beam splitter, the frequency mixer, the photoelectric detector, and the analog-to-digital converter are similar to those shown in <FIG> and <FIG>.

An embodiment of this application further provides a chip. <FIG> is a schematic diagram of a chip <NUM> according to this application. The chip <NUM> includes a processor <NUM>, a memory <NUM>, and a communications interface <NUM>. The processor <NUM> is coupled to the memory <NUM>. The memory <NUM> is configured to store a computer program or an instruction and/or data. The processor <NUM> is configured to execute the computer program or the instruction and/or the data stored in the memory <NUM>, so that the method in the foregoing method embodiment is performed.

In a possible implementation, the chip shown in <FIG> may be a signal processing apparatus including a processor <NUM> and a communications interface <NUM>. The processor <NUM> is coupled to a memory by using the communications interface <NUM>, and the processor <NUM> is configured to perform the method in the foregoing method embodiment.

It should be understood that the foregoing embodiments are merely examples for describing the signal processing procedure provided in this application, and do not constitute any limitation on the protection scope of this application. Other simple variations of the Rx DSP architecture all fall within the protection scope of this application. A difference between the Rx DSP architecture in this application and an existing Rx DSP architecture lies in that an FFT module and an IFFT module are not used for signal processing, but an NTT module and an INTT module are used.

It should be further understood that, in the embodiments of this application, unless otherwise specified or in case of a logical conflict, terms and/or descriptions in different embodiments may be consistent and may be mutually referenced. Technical features in different embodiments may be combined based on an internal logical relationship of the technical features to form a new embodiment.

Claim 1:
A signal processing method, wherein the method comprises:
obtaining P real-number signals;
performing at least number theoretic transform NTT processing on the P real-number signals to obtain P transform-domain first real-number signals;
performing at least clock recovery on the P transform-domain first real-number signals to obtain P transform-domain second real-number signals;
performing at least polarization compensation and inverse number theoretic transform INTT processing on the P transform-domain second real-number signals to obtain m time-domain complex-number signals X and m time-domain complex-number signals Y; and
performing phase recovery and decoding on the m time-domain complex-number signals X and the m time-domain complex-number signals Y to obtain bit signals, wherein
m and P are positive integers.