CN115776336A - Photon dispersion equalization system of coherent optical communication based on MZI-MVM - Google Patents
Photon dispersion equalization system of coherent optical communication based on MZI-MVM Download PDFInfo
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Abstract
The invention belongs to the technical field of communication digital equalization, and particularly relates to a photon dispersion equalization system of coherent optical communication based on MZI-MVM. The photon dispersion equalization system of the present invention comprises: the system comprises a photon dispersion equalizer matrix design module, a coherent signal receiving module, an electric signal preprocessing module, an input signal transformation module, a signal processing module, a signal receiving module and an output signal synthesis module. The invention adopts the optical chip to compensate the chromatic dispersion in the long-distance optical fiber transmission system by using the tunable equipment, thereby effectively reducing the power consumption of chromatic dispersion balance; the same chip can be used for balancing the chromatic dispersion on a large number of different occasions; by adopting the scheme of reducing the number of taps designed by the photon dispersion equalizer, the performance of the dispersion equalization filter is improved by 60 percent under the condition that the number of taps is limited by the size of a device module, and the dispersion with the same length can be compensated by only 50 percent of the number of taps with a theoretical value, so that the limitation on the size of a hardware module is greatly improved, and the method has great application potential.
Description
Technical Field
The invention belongs to the technical field of communication digital equalization, and particularly relates to a photon signal equalization processing system.
Background
With increasing demand for bandwidth, optical fibers need to carry faster flows of information. Coherent transmission technology enables long-distance high-speed, large-capacity data transmission. In such coherent communication links, dispersion is one of the linear losses that must be compensated for. As the transmission distance increases and the transmission bandwidth becomes larger, the dispersion has a greater influence on the signal. In Digital Signal Processing (DSP), a Finite Impulse Response (FIR) filter in the time domain is usually used to compensate for the dispersion. The number of FIR taps required is proportional to the transmission distance and squared with the bandwidth. This results in high power consumption and high complexity of dispersion equalization in long-haul coherent optical communication systems. A dispersion equalizer employing a digital signal processing scheme typically accounts for more than 20% of the DSP's total power consumption and increases significantly as the fiber distance increases. Recently, optical Matrix-vector multiplication (MVM) has been designed to address the increasing demand for computational resources and capacity, with MVM based on Mach-Zehnder interferometers (MZIs) being considered one of the most promising solutions. As the operation is carried out based on coherent light, the MZI-MVM can use the phase to represent positive and negative, so that the system can carry out the operation containing positive and negative numbers more easily, and a simpler scheme is provided for the subsequent matrix design. Its matrix multiplication capabilities have proven to be more efficient and faster than electronic methods. In an MZI-based MVM, the linear transformation can be performed at the speed of light and detected at rates in excess of 100GHz, which makes it possible in many cases to achieve the same operational function with minimal power consumption. However, the current research on MZI-MVM has not considered its application in optical network systems and uses the optical chip method to perform dispersion compensation to reduce system power consumption.
Disclosure of Invention
The invention aims to provide a coherent optical communication photon dispersion equalization system based on MZI-MVM, so as to fully utilize the computing capability of the MVM, reduce the power consumption of the system and improve the performance of a dispersion equalization filter.
The coherent optical communication photon dispersion equalization system based on MZI-MVM comprises a scheme of processing data in a blocking mode, and a matrix with the size of M multiplied by M is converted into a matrix with the size of M on the premise of not reducing the operation speed and increasing the operation complexity 2 The filter of x 1 can maximize the operational capability of the matrix. In addition, the method also comprises a scheme for reducing the number of taps for designing the photon dispersion equalizer, and under the condition that the number of taps is limited by the size of a device module, the performance of the dispersion equalization filter is improved by 60 percent, and the dispersion with the same length can be compensated by only 50 percent of the number of taps with a theoretical value.
The photon dispersion equalization system for coherent optical communication based on MZI-MVM provided by the invention has the structure shown in figure 1, and comprises: the system comprises a photon dispersion equalizer matrix design module, a coherent signal receiving module, an electric signal preprocessing module, a photon dispersion equalizer input signal transformation module, a photon dispersion equalizer signal processing module, a photon dispersion equalizer signal receiving module and an output signal synthesis module. Wherein:
the photon dispersion equalizer matrix design module calculates the value of each matrix element in a pertinence manner according to the distance of dispersion to be equalized and the baud rate of a signal, and designs a photon matrix according to the value;
the coherent signal receiving module is configured to mix a received coherent signal with Local Oscillator (LO) light, and output a real part and an imaginary part of the coherent signal;
the electric signal preprocessing module is used for resampling and clock recovering the received electric signal according to actual requirements;
the input signal conversion module of the photon dispersion equalizer is used for carrying out serial-parallel conversion on the received electric signals and converting the electric signals into a size suitable for input of a dispersion matrix;
the photon dispersion equalizer signal processing module is used for processing the input optical signal on the basis of the equalizer matrix designed by the photon dispersion equalizer matrix design module to obtain the output optical signal subjected to dispersion equalization;
the photon dispersion equalizer signal receiving module is used for receiving the optical signal output by the photon dispersion equalizer matrix, and converting the optical signal into an electric signal through the coherent signal receiver array to output the electric signal so as to obtain a roughly processed electric signal subjected to photon dispersion equalization;
and the output signal synthesis module is used for sampling the signal output from the photon dispersion equalizer matrix and then carrying out serial-parallel conversion on the signal to change the signal into a required signal data stream so as to obtain a signal subjected to dispersion processing.
Further, the air conditioner is provided with a fan,
the photon dispersion equalizer matrix design module calculates the value of each matrix element in a pertinence manner according to the distance of dispersion to be equalized and the baud rate of a signal, and designs a photon matrix according to the value, wherein the photon dispersion equalizer matrix design module comprises two parts:
in a first section, dispersion equalizer tap coefficients are generated. Dispersion in long-distance high-baud-rate signals usually requires a large number of taps, and practical photonic devices are usually limited by design scale. Aiming at the difficulty, the invention provides a scheme for reducing the number of taps for designing a photon dispersion equalizer, which can improve the performance of a dispersion equalization filter under the condition that the number of taps is limited by the size of a device module. The tap parameters specifically used for dispersion equalization can be calculated by the following formula:
in the formula, T, D, z, and λ represent a sampling time, a dispersion constant, a propagation distance, and a center wavelength, respectively. j is an imaginary unit and n is a tap number. The tap values of the chromatic dispersion equalizer can be determined according to equation (1). But the problem varies when the maximum number of taps is fixed. The number of taps required by the formula may exceed the value that can be provided by a practical device, so the present invention uses a transformation method from frequency domain filtering to time domain convolution. When the transmission distance becomes larger than the number of taps available for the available MZI-MVM, a filter with a longer number of taps is generated and then clipped to a feasible range.
And a second part, mapping the parameters of the dispersion equalization filter into a matrix, wherein the specific mapping method comprises the following steps:
where λ is the tap of the dispersion filter, distributed in the matrix in the order shown above. And calculating the parameters of each phase shifter in the required MZI-MVM matrix according to the parameters, and applying a response electric signal to the matrix to complete the design of the photonic dispersion equalizer matrix.
The coherent signal receiving module is used for detecting the coherent signal by an Integrated Coherent Receiver (ICR) after the coherent signal is mixed with the emitted LO light; the relative phase difference of the four output ports is respectively 0 degrees, 90 degrees, 180 degrees and 270 degrees; the photocurrents obtained by the four ports are respectively as follows:
wherein, P S ,P LO Representing the optical power, k, of the signal and LO, respectively S1 And k S2 Respectively representing the component intensities, k, of the I and Q paths of the signal light L1 And k L2 Respectively representing the component intensity of an LO optical path I and a LO optical path Q; phi shape sig ，ф L0 Respectively representing the phases of the signal light and the local oscillator light; the photocurrent direct-current components obtained by the ports of 0 degrees and 180 degrees and the ports of 90 degrees and 270 degrees through the balanced detector are respectively equal, so that two coherent signals can be obtained through respective subtraction, and the two signals respectively correspond to an I path and a Q path of the received coherent signals. This process can be formulated as:
the electric signal preprocessing module is used for resampling and clock recovery of the received electric signal, specifically, resampling the electric signal to twice the sampling rate, then carrying out clock recovery on the electric signal, recovering the sampling point to the maximum power position, and utilizing the signal-to-noise ratio of the signal to the maximum.
In the input signal conversion module of the photon dispersion equalizer, the received electrical signals are subjected to serial-parallel conversion and converted into the size suitable for the input of a dispersion matrix, namely, the electrical signals are subjected to serial-parallel conversion and then input from each input port of the matrix; this process is actually a block process on the input signal, specifically, for an M × M matrix, the input data stream is first converted into the following form:
where x (n) is the received data stream, which is a sequence of length n. In the actual use process, the electric signals are loaded on the optical carrier in sequence, and the optical carrier loaded with the signals is input to the matrix input port through the delayer in a certain delay sequence.
In the signal processing module of the photon dispersion equalizer, the input optical signal is processed, specifically, matrix operation is performed in an optical domain, and the following matrix operation operations are performed:
and obtaining the output optical signal after dispersion equalization.
The output signal synthesis module samples the signal output from the photon dispersion equalizer matrix, performs serial-to-parallel conversion on the sampled signal, and converts the sampled signal into a required signal data stream to obtain a signal subjected to dispersion processing, specifically, the data of the output signal is processed according to a certain rule to obtain a signal which is subjected to dispersion equalization and has no dispersion damage; the whole operation process is expressed by a block matrix as follows:
accumulating the values on the diagonal of the obtained diagonal matrix to obtain the final output vector, wherein each X is i Represents a row vector:
X i ＝[x(i),x(i+1),x(i+2),…,x(i+M 2 -1)]， (7)。
the coherent optical communication photon dispersion equalization system based on MZI-MVM provided by the invention has the working flow that:
firstly, in a photonic dispersion equalizer matrix design module part, designing a photonic dispersion equalizer matrix according to the transmission distance of the baud rate of a signal needing to be compensated in an actual system;
receiving the transmitted optical signal through a coherent signal receiving module to obtain a sampled electric signal;
thirdly, the electric signal preprocessing module is used for carrying out resampling and clock recovery on the received electric signals, and the signal-to-noise ratio of the signals is utilized to the maximum extent;
preprocessing the signals, and inputting the processed optical signals from each input port of the photon dispersion equalizer matrix;
(V) processing the signal by a photon dispersion equalizer matrix to obtain an original signal output by the matrix;
sixthly, the photon dispersion equalizer signal receiving module receives the optical signal output by the photon dispersion equalizer matrix through the coherent signal receiver array and converts the optical signal into an electric signal to be output, and the roughly processed electric signal subjected to photon dispersion equalization is obtained;
and (seventhly), the output signal synthesis module processes the output data according to a certain rule to obtain a signal which is not subjected to dispersion damage after dispersion equalization.
The invention has the following advantages:
the invention provides a brand-new dispersion balancing scheme, and an optical chip is adopted to compensate dispersion in a long-distance optical fiber transmission system by utilizing tunable equipment. Compared with the traditional DSP scheme, the method can effectively reduce the power consumption of dispersion equalization. Owing to the mode of using the optical chip to carry out dispersion equalization, the same chip can be used for the dispersion equalization in a large number of different occasions, and the method has a wide application range. By using the scheme of reducing the number of taps for designing the photon dispersion equalizer, the performance of the dispersion equalization filter can be improved by 60 percent under the condition that the number of taps is limited by the size of a device module, and the dispersion with the same length can be compensated by only 50 percent of the number of taps with a theoretical value. The limitation on the size of a hardware module is greatly promoted, and the method has great application potential.
Drawings
Fig. 1 is a block diagram of a photonic dispersion equalization system for MZI-MVM-based coherent optical communication according to the present invention.
Fig. 2 shows the design of the fixed tap number dispersion filter according to the present invention.
Fig. 3 shows the design structure of the photonic dispersion equalizer chip of the present invention.
Figure 4 is a result demonstration of a fixed tap dispersion filter design in accordance with the present invention.
Fig. 5 is a simulation result of the final photon dispersion equalization chip of the present invention.
Reference numbers in the figures: 101 is a photonic dispersion equalizer matrix design module, 102 is a coherent signal receiving module, 103 is an electrical signal preprocessing module, 104 is a photonic dispersion equalizer input signal transformation module, 105 is a photonic dispersion equalizer signal processing module, 106 is a photonic dispersion equalizer signal receiving module, and 107 is an output signal synthesis module.
Detailed Description
The invention will be further elucidated with reference to the drawings and examples.
The invention provides MZI-MVM-based coherent optical communication photon dispersion equalizationThe system makes full use of the computing capability of MVM, and converts the matrix with the size of M multiplied by M into the matrix with the size of M multiplied by M on the premise of not reducing the computing speed and increasing the computing complexity by carrying out block processing on data 2 Filter of x 1. In addition, the system provides a scheme for reducing the number of taps for designing the photon dispersion equalizer, so that the performance of the dispersion equalization filter can be improved by 60 percent under the condition that the number of taps is limited by the size of a device module, and the dispersion with the same length can be compensated by only 50 percent of the number of taps with a theoretical value. The dispersion balance with low power consumption and high performance can be realized.
The block diagram of the coherent optical communication photonic dispersion equalization system based on MZI-MVM provided by the present invention is shown in fig. 1, and the system comprises a photonic dispersion equalizer matrix design module 101, a coherent signal receiving module 102, an electrical signal preprocessing module 103, a photonic dispersion equalizer input signal transformation module 104, a photonic dispersion equalizer signal processing module 105, a photonic dispersion equalizer signal receiving module 106, and an output signal synthesis module 107. Wherein:
the photonic dispersion equalizer matrix design module 101 is responsible for designing parameters of a photonic dispersion equalizer matrix according to the transmission distance of the baud rate of a signal needing to be compensated in the practice system;
the coherent signal receiving module 102 can receive the transmitted optical signal and sample the optical signal to obtain an electrical signal;
the electric signal preprocessing module 103 performs resampling and clock recovery operations on the received electric signal;
the input signal transformation module 104 of the photon dispersion equalizer preprocesses the signal, and the processed optical signal is input from each input port of the photon dispersion equalizer matrix in sequence after fixed time delay;
the signal processing module 105 of the photon dispersion equalizer is responsible for carrying out matrix operation on the input optical signal and obtaining an original signal output by a matrix after processing;
the photon dispersion equalizer signal receiving module 106 receives the optical signal output by the photon dispersion equalizer matrix through the coherent signal receiver array and converts the optical signal into an electrical signal to be output, so as to obtain a roughly processed electrical signal subjected to photon dispersion equalization;
the output signal synthesizing module 107 is configured to process the output data according to a certain rule to obtain a signal that has not been dispersion-damaged after being subjected to dispersion equalization.
The invention provides an optical fiber wireless integrated self-adaptive sensing communication integrated system, which comprises the following specific steps:
the method comprises the following steps: through the photonic dispersion equalizer matrix design module 101, the photonic dispersion equalizer matrix is designed according to the transmission distance of the baud rate of the signal to be compensated in the training system.
The photonic dispersion equalizer matrix design module comprises two steps. The first step is the chromatic dispersion equalizer tap coefficient generation. Dispersion in long-distance high-baud-rate signals usually requires a large number of taps, and practical photonic devices are usually limited by design scale. Aiming at the difficulty, the invention provides a scheme for reducing the number of taps for designing the photon dispersion equalizer, and the performance of the dispersion equalization filter can be improved under the condition that the number of taps is limited by the size of a device module. The tap parameters for dispersion equalization can be calculated by the following formula:
in the formula, T, D, z, and λ represent sampling time, dispersion constant, propagation distance, and center wavelength, respectively. j is an imaginary unit and n is a tap number. The tap values of the chromatic dispersion equalizer are practically fixed according to the formula. But the problem varies when the maximum number of taps is fixed. The number of taps required by the formula may exceed the value provided by the actual device, so the invention provides a method for transforming from frequency domain filtering to time domain convolution. As shown in fig. 2, when the transmission distance becomes larger than the number of taps available for the available MZI-MVM, a filter with a longer number of taps is generated and then clipped to a feasible range. In the examples, a dispersion constant of 17X 10 was chosen -6 ps/(nm. Km), sampling time 15.6ns, transmissionThe propagation distance is 1000km, the center wavelength is 1550nm, a filter with 280 taps is generated, and the most central 256 points are selected as generated taps.
The second step is to map the parameters of the dispersion equalization filter into a matrix, and the specific mapping method is as follows:
where λ is the tap of the dispersion filter, distributed in the matrix in the order shown above. And calculating the parameters of each phase shifter in the required MZI-MVM matrix according to the parameters, and applying a response electric signal to the matrix, thereby finishing the design and deployment of the photonic dispersion equalizer matrix.
In this process, since MZI-MVM can only perform real number operations, the input signal and the filter taps are both complex in the dispersion equalization of coherent signals. Therefore, the present invention designs the structure shown in fig. 3 to perform complex number operation. The input complex signal is first divided into imaginary and real parts and then fed to the photon dispersion equalizer array formed by the real and imaginary parts calculation instead of the filter taps. And finally, accumulating the received signals and outputting the accumulated signals. In an embodiment, a matrix of size 16 × 16 is generated.
Step two: the coherent signal receiving module 102 receives the transmitted optical signal to obtain a sampled electrical signal.
The signal in the coherent signal receiving module is mixed with the emitted LO light and then detected by an Integrated Coherent Receiver (ICR).
In the embodiment, the electric signal with the baud rate of 25 gbaud is obtained by sampling the optical signal through the step.
Step three: the received electrical signal is resampled and clock recovered by the electrical signal preprocessing module 103, so that the signal-to-noise ratio of the signal is maximally utilized.
In this step, the electrical signal preprocessing module may perform operations of resampling and clock recovery on the received electrical signal, perform clock recovery on the signal after resampling the signal to twice the sampling rate, recover the sampling point to the maximum power point, and may maximize the signal-to-noise ratio of the signal.
Clock recovery algorithms are a common requirement of communication systems, and a Gardner feedback time domain clock recovery algorithm is adopted, and the algorithm adopts a feedback clock synchronization structure, and estimates the phase of a retimed digital clock source by calculating a timing error. The estimation of the timing error can track the adopted frequency jitter of the signal for dynamic clock recovery.
Step four: the signal is preprocessed by the input signal transformation module 104 of the photon dispersion equalizer, and then the processed optical signal is input from each input port of the photon dispersion equalizer matrix.
This process is actually a block processing of the input signal. For an M × M matrix, the input data stream is first converted to the form:
where x (n) is the received data stream, which is a sequence of length n. In the actual use process, the electrical signals are loaded on the optical carrier in sequence, and the optical carrier loaded with the signals is input to the matrix input port through the delayer in a certain delay sequence. In the embodiment, a 16 × 16 matrix module is used to process signals, and after the original signals are modulated on optical signals, the optical signals are divided into 16 paths, and the signals are sequentially delayed by 15.6ns and input from 16 input ports. I.e. each port's signal is 15.6ns slower than the signal of the last adjacent port. Then at the initial moment the signals of the 16 ports are x (1) to (16) in turn, at the next moment the signals of the 16 ports are x (2) to x (17) in turn, and so on.
Step five: the signals are processed by a photon dispersion equalizer matrix to obtain original signals output by the matrix.
The signal processing module of the photon dispersion equalizer can process the input optical signal on the basis of the parameters designed by the matrix design module of the photon dispersion equalizer, in the embodiment, the matrix operation is specifically performed in the optical domain, and the following matrix operation is performed:
and obtaining the output optical signal after dispersion equalization.
Step six: and the photon dispersion equalizer signal receiving module receives the optical signal output by the photon dispersion equalizer matrix through the coherent signal receiver array and converts the optical signal into an electric signal to be output, so as to obtain a roughly processed electric signal subjected to photon dispersion equalization.
Step seven: the output signal synthesis module needs to process the output data according to a certain rule to obtain a signal without dispersion damage after dispersion equalization.
In the invention, the output signal synthesis module needs to process the output data according to a certain rule to obtain a signal which is not subjected to dispersion damage after dispersion equalization. The whole operation process is expressed by a block matrix as follows:
and accumulating the values on the diagonal line of the obtained diagonal matrix to obtain the final output vector. Wherein each X i Represents a row vector:
X i ＝[x(i),x(i+1),x(i+2),…,x(i+M 2 -1)]
in the embodiment, according to the description of the above blocking matrix, the final accumulation process should be to add the value output by the matrix output port 1 at a certain time t to the value output by the matrix output port 2 at a time t +16, the value output by the matrix output port 3 at a time t +32, and the value output by the matrix output port M up to a time t +240, so as to obtain the final result of outputting the data after passing through the cd equalizer at a time t + 128. The time required for this process is the same as the delay required for the equivalent 16 tap filter to operate. And therefore such matrix blocking operations have no impact on the latency and speed of data processing.
The implementation method of the coherent optical communication photon dispersion equalization technology based on the MZI-MVM is finished.
The verification steps and the verification results of the coherent optical communication photon dispersion equalization system based on MZI-MVM in the optical fiber transmission experiment system are described next.
In this example, referring to fig. 1, the experimental framework of the coherent optical communication system includes a photonic dispersion equalizer matrix design module 101, a coherent signal receiving module 102, an electrical signal preprocessing module 103, a photonic dispersion equalizer input signal transformation module 104, a photonic dispersion equalizer signal processing module 105, a photonic dispersion equalizer signal receiving module 106, and an output signal synthesis module 107.
Fig. 4 illustrates the feasibility of the dispersion filter design. The optical signal was transmitted over a distance of 1000km in the experiment. Here, normalized Mean Square Error (NMSE) between a waveform after perfect dispersion equalization and a waveform after a filter with a fixed number of taps is used as a standard. As the proportion of the number of additional taps initially produced increases, the NMSE can decrease rapidly by about 60%. Therefore, the performance of the dispersion filter under the condition that the number of taps is limited can be effectively improved by the scheme.
Fig. 5 shows the case where photon calculation modules of different sizes were used in simulation experiments to deal with dispersion in different lengths of fiber. We have numerically studied the performance of NMSE versus different distances. Here exemplified by two matrices, 8 x 8 and 16 x 16, respectively. As the distance increases, NMSE initially goes around 0 and then slowly increases until the NMSE exceeds a threshold that prevents the signal from being demodulated. For a signal with a bandwidth of 25 gbaud, the maximum dispersion transmission distance that can be handled by each matrix is 400 and 1500 km, where only 50% and 53% of the theoretical number of taps are used. Referring to this result, numerical studies confirmed that large-scale MZI-MVMs can be used for photonic CDEs up to several thousand kilometers in distance.
In summary, the invention provides a coherent optical communication photonic dispersion equalization scheme based on MZI-MVM, which can compensate dispersion in a long-distance optical fiber transmission system by using tunable equipment in an optical chip manner. Compared with the traditional DSP scheme, the method can effectively reduce the power consumption of dispersion equalization. The invention benefits from the mode of adopting the optical chip to carry out dispersion equalization, can deal with the dispersion equalization in a large number of different occasions by using the same chip, has wider application range and has larger commercial value.
Compared with the traditional design scheme of the dispersion filter, the scheme for reducing the number of the taps for designing the photon dispersion equalizer, provided by the invention, can improve the performance of the dispersion equalizer filter by 60% under the condition that the number of the taps is limited by the size of a device module, and can compensate the dispersion with the same length by only needing 50% of the number of the taps with the theoretical value. The limitation on the size of a hardware module is greatly promoted, and the method has great application potential.
The division of each step in this embodiment is only for clarity of description, and implementation may be combined into one step or split some steps into multiple steps, and all that is included in the same logical relationship is within the scope of the present patent.
It will be understood by those of ordinary skill in the art that the foregoing embodiments are specific examples for carrying out the invention, and that various changes in form and details may be made therein without departing from the spirit and scope of the invention in practice.
Claims (8)
1. A photon dispersion equalization system for coherent optical communication based on MZI-MVM, comprising: the system comprises a photon dispersion equalizer matrix design module, a coherent signal receiving module, an electric signal preprocessing module, a photon dispersion equalizer input signal transformation module, a photon dispersion equalizer signal processing module, a photon dispersion equalizer signal receiving module and an output signal synthesis module; wherein:
the photon dispersion equalizer matrix design module calculates the value of each matrix element in a pertinence manner according to the distance of dispersion to be equalized and the baud rate of a signal, and designs a photon matrix according to the value;
the coherent signal receiving module is used for mixing the received coherent signal with local oscillator Light (LO) and outputting a real part and an imaginary part of the coherent signal;
the electric signal preprocessing module is used for resampling and clock recovery of the received electric signal according to actual requirements;
the input signal conversion module of the photon dispersion equalizer is used for carrying out serial-parallel conversion on the received electric signals and converting the electric signals into a size suitable for input of a dispersion matrix;
the photon dispersion equalizer signal processing module is used for processing the input optical signal on the basis of the equalizer matrix designed by the photon dispersion equalizer matrix design module to obtain the output optical signal subjected to dispersion equalization;
the photon dispersion equalizer signal receiving module is used for receiving the optical signal output by the photon dispersion equalizer matrix, and converting the optical signal into an electric signal through the coherent signal receiver array to output the electric signal so as to obtain a roughly processed electric signal subjected to photon dispersion equalization;
and the output signal synthesis module is used for sampling the signal output from the photon dispersion equalizer matrix and then carrying out serial-parallel conversion on the signal to change the signal into a required signal data stream so as to obtain a signal subjected to dispersion processing.
2. The system of claim 1, wherein in the photonic dispersion equalizer matrix design module, the photonic dispersion equalizer matrix design module calculates the value of each matrix element in a targeted manner according to the distance of the dispersion to be equalized and the baud rate of the signal, and designs the photonic matrix according to the calculated value, and the photonic matrix comprises two parts:
the first part is to generate tap coefficients of the chromatic dispersion equalizer, specifically adopt a scheme of reducing the number of taps of the photonic chromatic dispersion equalizer, and calculate tap parameters for chromatic dispersion equalization by the following formula:
in the formula, T, D, z and lambda respectively represent sampling time, a dispersion constant, a propagation distance and a central wavelength j as an imaginary number unit, n is a tap serial number, and when the maximum number of taps is fixed, the number of taps required by the formula possibly exceeds the value provided by an actual device, so that a conversion method from frequency domain filtering to time domain convolution is adopted; when the transmission distance becomes larger than the number of available taps of the available MZI-MVM, a filter with a longer number of taps is generated and then reduced to a feasible range;
and a second part, mapping the parameters of the dispersion equalization filter into a matrix, wherein the specific mapping method comprises the following steps:
where λ is the tap of the dispersion filter, distributed in the matrix in the order shown above; and calculating the parameters of each phase shifter in the required MZI-MVM matrix according to the parameters, and applying a response electric signal to the matrix, namely completing the design of the photonic dispersion equalizer matrix.
3. The system of claim 2, wherein the coherent signal reception module mixes the coherent signal with the transmitted LO light and detects the mixed signal by an Integrated Coherent Receiver (ICR), so that the relative phase difference of the four output ports is 0 °, 90 °, 180 °, 270 °; the photocurrents obtained by the four ports are respectively as follows:
wherein, P S ,P LO Representing the optical power, k, of the signal and LO, respectively S1 And k S2 Respectively representing the component intensities, k, of the I and Q paths of the signal light L1 And k L2 Respectively representing the component intensity of an LO light I path and an LO light Q path; phi shape sig ，ф L0 Respectively representing the phases of the signal light and the local oscillator light; the photocurrent direct-current components obtained by the ports of 0 degree, 180 degrees, 90 degrees and 270 degrees through the balanced detector are respectively equal, so that two coherent signals are obtained through respective subtraction, and the two signals respectively correspond to an I path and a Q path of the received coherent signals; this process is formulated as:
4. the system of claim 3, wherein in the electrical signal preprocessing module, the electrical signal is resampled and recovered with a clock, and then recovered with a clock, and the sampling point is recovered at the maximum power, so as to maximize the signal-to-noise ratio of the signal.
5. The system of claim 4, wherein the photonic dispersion equalizer is input to the signal conversion module, and the photonic dispersion equalizer performs serial-to-parallel conversion on the received electrical signal to convert the received electrical signal to a size suitable for input of the dispersion matrix, that is, performs serial-to-parallel conversion on the electrical signal and inputs the electrical signal from each input port of the matrix; this process is actually a block process on the input signal, specifically, for an M × M matrix, the input data stream is first converted into the following form:
wherein x (n) is a received data stream, and is a sequence with the length of n; in the using process, the electric signals are loaded on the optical carrier waves in sequence, and the optical carrier waves loaded with the signals are input to the matrix input port through the delayer in a certain delay sequence.
6. The system of claim 5, wherein the photonic dispersion equalizer signal processing module performs processing on the input optical signal, specifically performs matrix operation in the optical domain, and the matrix operation is as follows:
and obtaining the output optical signal after dispersion equalization.
7. The MZI-MVM-based photonic dispersion equalization system for coherent optical communication according to claim 6, wherein in the output signal synthesis module, the signal output from the photonic dispersion equalizer matrix is sampled and then converted from serial to parallel, and then converted into a required signal data stream, so as to obtain a signal after dispersion processing, specifically, the data of the output signal is processed according to a certain rule, so as to obtain a signal without dispersion damage after dispersion equalization; the whole operation process is expressed by a block matrix as follows:
accumulating the values on the diagonal of the diagonal matrix to obtain the final output vector, wherein each X is i Represents a row vector:
X i ＝[x(i),x(i+1),x(i+2),…,x(i+M 2 -1)]， (7)。
8. the system for photon dispersion equalization for MZI-MVM based coherent optical communications according to any of claims 1 to 7, wherein the workflow is as follows:
designing a photonic dispersion equalizer matrix according to the transmission distance of the baud rate of a signal needing to be compensated in an actual system in a photonic dispersion equalizer matrix design module part;
receiving the transmitted optical signal through a coherent signal receiving module to obtain a sampled electric signal;
thirdly, an electric signal preprocessing module is used for carrying out resampling and clock recovery on the received electric signals, and the signal-to-noise ratio of the signals is utilized to the maximum extent;
preprocessing the signals, and inputting the processed optical signals from each input port of the photon dispersion equalizer matrix;
processing the signal by a photon dispersion equalizer matrix to obtain an original signal output by the matrix;
sixthly, the photon dispersion equalizer signal receiving module receives the optical signal output by the photon dispersion equalizer matrix through the coherent signal receiver array and converts the optical signal into an electric signal to be output, and the roughly processed electric signal subjected to photon dispersion equalization is obtained;
and (seventhly), the output signal synthesis module processes the output data according to a certain rule to obtain the signal which is not subjected to dispersion damage after dispersion equalization.
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