Low-complexity optical arbitrary waveform measurement system and method based on single-ended PD array

Abstract

The invention discloses a low-complexity optical arbitrary waveform measurement system and method based on a single-ended PD array, and the system comprises a to-be-measured signal transmitting end, a local oscillation optical frequency comb end, a signal receiver array, and a receiving end digital signal processing DSP. The receiver array comprises a mixer array, a photoelectric detector array, and an analog-to-digital converter array. A traditional coherent optical receiver array adopts a 2 * 4 90-degree optical mixer to output four paths of frequency mixing signals with the phase difference of 90 degrees, the four paths of frequency mixing signals are detected through four photoelectric detectors (PD) to obtain light current in-phase and orthogonal components, digital signal processing is carried out subsequently, and broadband signal reconstruction is completed. In the system, a 2 * 2 90-degree optical mixer is used for replacing a 90-degree mixer in a traditional coherent optical receiver to obtain two paths of frequency mixing signals, and the two paths of frequency mixing signals enter two single-end photoelectric detectors PD to be detected to obtain photocurrent in-phase and orthogonal components; according to the invention, the complexity of the device in the traditional optical arbitrary waveform measurement system can be well reduced, and the system composition is simplified.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technology, and more specifically, to a low-complexity optical arbitrary waveform measurement system and method based on a single-ended PD array. Background Art

[0002] With the rapid increase of multimedia services and the development of the communications industry, the requirements for communication rates are getting higher and higher, which brings tremendous pressure and challenges to the existing fiber-optic communication network. The surge in traffic has driven fiber-optic communications to continuously upgrade and evolve in five dimensions: ultra-high speed, ultra-large capacity, ultra-long distance, ultra-wide flexibility, and ultra-intelligent, and coherent optical communications have emerged. Coherent optical communication systems that support high-order modulation formats have higher transmission rates and longer transmission distances due to their higher spectral efficiency SE and receiver sensitivity. They are not only used in long-distance and metropolitan area networks, but also in short-distance networks including data center interconnection. They are the future development direction of fiber-optic communications. With the increasing bandwidth utilization and wider signal bandwidth, measuring and monitoring the development of high-speed and high-bandwidth optical signals has become a key technology to ensure the reliability of fiber-optic communication networks. By using parallelized reception to increase the measurement bandwidth of optical channels, spectrum slicing optical arbitrary waveform measurement technology can improve the broadband optical signal measurement capabilities of single and multiple optical channels without increasing the electronic bandwidth. The inherent bandwidth scalability of these technologies and their ability to continuously receive full-field waveforms enable communication systems to support flexible bandwidth allocation and modulation format independence. Optical arbitrary waveform measurement technology solutions are one of the hot research directions at the receiving end of communication systems.

[0003] For optical arbitrary waveform measurement technology, optical frequency comb technology plays a multifaceted role in optical arbitrary waveform measurement, and it is very attractive to use the scalability advantages of optical frequency comb at the receiving end. Regarding free-running optical frequency combs, spectrum slicing signal processing has been proven to be a viable solution for broadband coherent detection. Spectral slicing detection supported by optical frequency combs represents a very powerful method that allows the complete reconstruction of arbitrary optical waveforms over an accessible bandwidth beyond the range of electronic signal processing. In optical communication systems, it is important to note that optical arbitrary waveform measurement schemes provide obvious advantages for applications with coherent reception of broadband data signals. The achievable measurement bandwidth of the system increases linearly by using more spectrum slices. Specifically, the system measurement bandwidth is further expanded by increasing the number of coherent optical receivers at the receiving end of the system.

[0004] Although the optical arbitrary waveform measurement technology of slice coherent detection has more advantages in receiving high-bandwidth signals, it still faces some inherent key technical challenges. On the one hand, it is reflected in reducing the complexity of the system, which affects the practical application of the optical arbitrary waveform measurement system in future optical communication systems. In the optical arbitrary waveform measurement system, the traditional coherent receiver at the receiving end is composed of multiple devices such as 2×4 optical 90° mixers, photodetectors, and analog-to-digital converters. The more parallel coherent optical receivers there are, the more underlying devices are required, the greater the cost, and the higher the complexity. To a certain extent, it limits the development of coherent receivers for optical arbitrary waveform measurement towards integration. Therefore, for high-bandwidth signal reception, it is very meaningful to study low-complexity optical arbitrary waveform measurement systems without increasing the complexity and loss of the system framework. Summary of the invention

[0005] In order to solve the problem of high complexity of the receiving end in the existing optical arbitrary waveform measurement system, the present invention proposes a low-complexity optical arbitrary waveform measurement system based on a single-ended PD array.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A low-complexity optical arbitrary waveform measurement system based on a single-ended PD array comprises a laser source, a fiber coupler, a signal generating module, an adjustable optical filter array, an optical frequency comb generating module, a parallel receiver array, and a digital signal processing module; the laser source is connected to the fiber coupler, the fiber coupler is respectively connected to the signal generating module and the optical frequency comb generating module, after the signal generating module and the adjustable optical filter array are connected in sequence, the output of the adjustable optical filter array and the output of the optical frequency comb generating module are input to the parallel receiver array together, and the output of the parallel receiver array is input to the digital signal processing module;

[0008] The signal generation module includes an arbitrary waveform generator, an IQ modulator, and an optical amplifier EDFA;

[0009] The optical frequency comb generation module includes an MZM modulator and a wavelength selective switch WSS;

[0010] The parallel receiver array includes a 2×2 optical mixer array, a single-ended PD array, and an analog-to-digital converter array which are connected in sequence.

[0011] The optical frequency comb generation module is generated by electro-optical modulation. The central wavelength of the optical frequency comb is 1548nm-1550nm, and the frequency interval of the optical frequency comb is 24GHz-26GHz. The frequency interval of the optical frequency comb is adjustable, and the frequency interval of the optical frequency comb is determined by the bandwidth of the signal to be measured and the number of receivers.

[0012] Preferably, the parallel receiver array comprises four columns of parallel receivers.

[0013] At the same time, the present invention also provides a low-complexity optical arbitrary waveform measurement method based on a single-ended PD array. The method is based on the above-mentioned low-complexity optical arbitrary waveform measurement method based on a single-ended PD array, and comprises the following steps:

[0014] S1. Obtaining an optical signal through the laser source, and dividing the optical signal into an optical path one and an optical path two through the optical fiber coupler;

[0015] S2. The optical signal of optical path 1 is sequentially input into the signal generating module and the tunable optical filter array to obtain four spectral slices E of different signal frequency bands. S,1 、E S,2 、E S,3 、E S,4 The optical signal of the optical path 2 is input into the optical frequency comb generation module to obtain four parallel local oscillator signals E L,1 、E L,2 、E L,3 、E L,4 ; Where S represents the signal light, L represents the local oscillator light signal; Spectral slice E S,1 With the local oscillator signal E L,1 Correspondingly, when the numerical subscripts of the slice signal and the intrinsic signal are the same, the two correspond one to one;

[0016] S3. The parallel receiver array receives four spectrum slices and four parallel local oscillator signals; the 2×2 optical mixer array mixes different spectrum slice signals with corresponding local oscillator signals to obtain two mixing output signals E of each of the four parallel receivers. 1,1 、E 1,2 ; E 2,1 、E 2,2 ; E 3,1 、E 3,2 ; E 4,1 、E 4,2 ; E S,i represents the slice signal corresponding to the i-th receiver, E L,i represents the local oscillator signal corresponding to the i-th receiver, E i,1 represents the first mixer output of the i-th receiver, E i,2 represents the second mixer output of the i-th receiver, i represents the number of parallel receivers, and the range of i is 1-4;

[0017] The mixing operation is as follows:

[0018]

[0019] The single-ended PD array performs beat frequency synthesis on the mixed output signal to synthesize an intermediate frequency signal, down-converts the high-frequency optical modulation signal to be received into an intermediate frequency signal with a lower frequency, and the single-ended PD array outputs a photocurrent I i,1 ,I i,2 , I S,i =|E S,i | 2 , I L,i =|E L,i | 2 ;

[0020]

[0021] Among them, I S,i ,I L,i are the photocurrents of the slice signal light and the local oscillator light corresponding to the i-th receiver, is the phase difference between the chip signal and the local oscillator signal of the i-th receiver, δ = π / 2;

[0022] The photocurrent I is output through each receiver. i,1 ,I i,2 , calculate the in-phase signal component I of each slice signal I,i , orthogonal signal component I Q,i , and finally obtain the baseband signal I of each slice signal i,s ,

[0023]

[0024] I i,S =I I,i +j*I Q,i (5) Where α = I S,i +I L,i , α is the self-frequency noise additionally introduced by the i-th receiver;

[0025] S4. Send the baseband signals obtained from different signal frequency bands of each receiver to the analog-to-digital converter array for analog-to-digital conversion, and the digital signal processing module processes the digital signals after the analog-to-digital conversion to finally achieve signal waveform measurement. The specific steps of the digital signal processing module processing the digital signals after the analog-to-digital conversion include:

[0026] S41. The baseband signals obtained by the four parallel receivers are moved left and right accordingly to the original positions of the sliced ​​spectrum;

[0027] S42. Perform channel response inverse compensation on the moved slice spectrum signal, and realize signal splicing through a sliding window algorithm on the compensated slice signal;

[0028] S43. Normalize the amplitude of the spliced ​​signal, estimate and compensate for the I / Q quadrature imbalance, and correct the sampling clock deviation to synchronize the clock signals at the transmitter and receiver;

[0029] S44. Equalize the channel using an equalization algorithm;

[0030] S45. Using a square root raised cosine filter to implement the matched filtering function, downsampling the matched filtered signal;

[0031] S46. Calculate the bit error rate of the reconstructed signal through the downsampled signal to evaluate the performance of the received signal.

[0032] After adopting the above scheme, the beneficial effects of the present invention are as follows: compared with the traditional coherent optical receiver, the present invention reduces the number of photodetectors, and the number of single-channel photodetectors is reduced from 4 to 2. In the optical arbitrary waveform measurement system using four-channel parallel reception, 8 photodetectors are reduced, the system receiving end structure is simplified, and a considerable signal reconstruction function is achieved through fewer devices, which effectively reduces the system cost and complexity, and is more conducive to system integration and miniaturization. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the structure of a low-complexity optical arbitrary waveform measurement system based on a single-ended PD array of the present invention;

[0034] Figure 2 This is a schematic diagram of the single-ended PD principle;

[0035] Figure 3 is a schematic diagram of the principle of the optical arbitrary waveform measurement system;

[0036] Figure 4 This is the signal spectrum diagram after the transmission loss compensation of the four-way slice signal in the simulation;

[0037] Figure 5 It is the spliced ​​signal spectrum diagram obtained by sliding window splicing of four-way slice signals in the simulation in the digital signal processing module;

[0038] Figure 6 The signal constellation diagram for the spliced ​​signal in the simulation that is successfully demodulated through the digital signal processing module. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with the accompanying drawings. It should be understood that the embodiments are only intended to explain the present invention but not to limit it.

[0040] like Figure 1As shown, a low-complexity optical arbitrary waveform measurement system based on a single-ended PD array includes a laser source, a fiber coupler, a signal generating module, an adjustable optical filter array, an optical frequency comb generating module, a parallel receiver array, and a digital signal processing module; the laser source is connected to the fiber coupler, the fiber coupler is respectively connected to the signal generating module and the optical frequency comb generating module, after the signal generating module and the adjustable optical filter array are connected in sequence, the output of the adjustable optical filter array and the output of the optical frequency comb generating module are input to the parallel receiver array together, and the output of the parallel receiver array is input to the digital signal processing module;

[0041] The signal generation module includes an arbitrary waveform generator, an IQ modulator, and an optical amplifier EDFA;

[0042] The optical frequency comb generation module includes an MZM modulator and a wavelength selective switch WSS;

[0043] The parallel receiver array includes a 2×2 optical mixer array, a single-ended PD array, and an analog-to-digital converter array which are connected in sequence.

[0044] The optical frequency comb generation module is generated by electro-optical modulation. The central wavelength of the optical frequency comb is 1548nm-1550nm, and the frequency interval of the optical frequency comb is 24GHz-26GHz. The frequency interval of the optical frequency comb is adjustable, and the frequency interval of the optical frequency comb is determined by the bandwidth of the signal to be measured and the number of receivers. The parallel receiver array includes four parallel columns of receivers.

[0045] Based on this system, the method of the present invention is as follows:

[0046] S1. Obtain an optical signal through the laser source, and divide the optical signal into optical path 1 and optical path 2 through the optical fiber coupler. After the output optical signal of the laser source passes through the optical fiber coupler, the optical signal is divided into two beams according to a 50 / 50 splitting ratio, and enters the signal generation module and the optical frequency comb generation module respectively.

[0047] S2. The optical signal of optical path 1 is sequentially input into the signal generating module and the tunable optical filter array to obtain four spectral slices E of different signal frequency bands. S,1 、E S,2 、E S,3 、E S,4 The optical signal of the optical path 2 is input into the optical frequency comb generation module to obtain four parallel local oscillator signals E L,1 、E L,2 、E L,3 、E L,4 ; Where S represents the signal light, L represents the local oscillator light signal; Spectral slice E S,1 With the local oscillator signal E L,1Correspondingly, when the digital subscripts of the slicing signal and the intrinsic signal are the same, the two correspond one to one; in the signal generation module, the arbitrary waveform generator is used as a signal source to generate an electrical signal, the electrical signal to be tested is loaded to the RF input of the IQ modulator, and the DC bias port is loaded with a DC voltage. The electrical signal to be tested is modulated onto the optical signal, and any QAM optical modulation signal can be modulated to generate, followed by an optical amplifier EDF to amplify the optical modulation signal. The adjustable optical filter array is used for spectral slicing. The optical modulation signal amplified by the optical amplifier EDFA is spectrally sliced ​​by adjusting the adjustable passband position of the optical filter to filter out different signal frequency bands of the optical modulation signal.

[0048] In the optical frequency comb generation module, a DC voltage is loaded on the RF input port of the MZM modulator, and through amplitude phase modulation, an optical frequency comb with equal frequency interval and flatness is finally generated. The optical frequency comb is separated and balanced through the wavelength selection switch WSS as the local oscillator signal of each receiver; the corresponding local oscillator signal for coherent reception of different spectral slices is determined by the wavelength selection switch. The optical frequency comb generation module is generated by electro-optical modulation. The central wavelength of the optical frequency comb is 1550nm, and the frequency interval of the optical frequency comb is 26GHz. The frequency interval is adjustable, and the frequency interval of the optical frequency comb is determined by the bandwidth of the signal to be measured and the number of receivers.

[0049] S3. The parallel receiver array receives four spectrum slices and four parallel local oscillator signals; the 2×2 optical mixer array mixes different spectrum slice signals with corresponding local oscillator signals to obtain two mixing output signals E of each of the four parallel receivers. 1,1 、E 1,2 ; E 2,1 、E 2,2 ; E 3,1 、E 3,2 ; E 4,1 、E 4,2 ; E S,i represents the slice signal corresponding to the i-th receiver, E L,i represents the local oscillator signal corresponding to the i-th receiver, E i,1 represents the first mixer output of the i-th receiver, E i,2Represents the second mixing output of the i-th receiver, i represents the number of parallel receivers, and the range of i is 1-4. The parallel receiver array is used to receive different spectral slices and corresponding local oscillator signals. The 2×2 optical mixer array mixes the different spectral slice signals with the corresponding local oscillator signals. The photodetector array beats the output signals obtained after mixing to synthesize intermediate frequency signals, thereby down-converting the high-frequency optical modulation signal to be received to a lower-frequency intermediate frequency signal. The analog-to-digital converter array performs analog-to-digital conversion on the electrical signal output from the photodetector array and converts it into a digital signal. Specifically, the 2×2 90° optical mixer array and photodetector array included in the parallel receiver array mix the corresponding slice signals through the 90° optical mixer, and the single-ended PD array beats the mixed signals to synthesize the intermediate frequency signals corresponding to each slice signal. Figure 2 This is a schematic diagram of the single-ended PD principle. The sliced ​​signal is mixed with the local oscillator optical frequency comb signal to generate two mixed outputs.

[0050] The mixing operation is as follows:

[0051]

[0052] The single-ended PD array performs beat frequency synthesis on the mixed output signal to synthesize an intermediate frequency signal, down-converts the high-frequency optical modulation signal to be received into an intermediate frequency signal with a lower frequency, and the single-ended PD array outputs a photocurrent I i,1 ,I i,2 , I S,i =|E S,i | 2 , I L,i =|E L,i | 2 ;

[0053]

[0054] Among them, I S,i ,I L,i are the photocurrents of the slice signal light and the local oscillator light corresponding to the i-th receiver, is the phase difference between the chip signal and the local oscillator signal of the i-th receiver, δ = π / 2;

[0055] The photocurrent I is output through each receiver. i,1 ,I i,2 , calculate the in-phase signal component I of each slice signal I,i , orthogonal signal component I Q,i , and finally obtain the baseband signal I of each slice signal i,S ,

[0056]

[0057] Ii,S =I I,i +j*I Q,i (5) Where α = I S,i +I L,i , α is the self-frequency noise additionally introduced by the i-th receiver;

[0058] S4. Send the baseband signals obtained from different signal frequency bands of each receiver to the analog-to-digital converter array for analog-to-digital conversion. The digital signal processing module (DSP) processes the digital signal after analog-to-digital conversion to achieve reconstruction of the signal to be measured. The digital signal processing includes slicing signal movement, amplitude and phase compensation, signal splicing, normalization, DC removal, IQ orthogonalization, clock synchronization, channel equalization, matched filtering, downsampling, and BER calculation, and finally realizes signal waveform measurement. The specific steps of the digital signal processing module processing the digital signal after analog-to-digital conversion include:

[0059] S41. The baseband signals obtained by the four parallel receivers are moved left and right accordingly to the original positions of the sliced ​​spectrum;

[0060] S42. Perform channel response inverse compensation on the moved slice spectrum signal, and realize signal splicing through a sliding window algorithm on the compensated slice signal;

[0061] S43. Normalize the amplitude of the spliced ​​signal, estimate and compensate for the I / Q quadrature imbalance, and correct the sampling clock deviation to synchronize the clock signals at the transmitter and receiver;

[0062] S44. Equalize the channel using an equalization algorithm;

[0063] S45. Using a square root raised cosine filter to implement the matched filtering function, downsampling the matched filtered signal;

[0064] S46. Calculate the bit error rate of the reconstructed signal through the downsampled signal to evaluate the performance of the received signal.

[0065] A low-complexity optical arbitrary waveform measurement system based on a single-ended PD array was built on Matlab. The 100GBd16QAM Nyquist single-carrier signal was numerically simulated. The broadband optical signal was generated by modulating the optical carrier with an IQ modulator. The driving signal was generated by an arbitrary waveform generator AWG. The optical modulated signal was amplified by EDFA. A root raised cosine RRC pulse shaping filter with a roll-off factor of 0.01 was used to generate a single-channel 100GBd 16QAM signal. The transmission was carried out in a back-to-back situation. First, the optical modulated signal amplified by EDFA passed through the optical filter array to realize the broadband signal slicing operation at the transmitting end. The sliced ​​signals corresponded to different frequency bands of the optical signal to be measured, and there was partial overlap between adjacent sliced ​​signals. The optical signal emitted by the continuous laser passed through a 50 / 50 optical coupler, and the other part of the output optical signal was modulated by MZM to generate an optical frequency comb. Then, WSS selected 4 specific sub-optical combs as the input local oscillators of the local oscillator input end.

[0066] After the four-channel slice signal and the corresponding optical frequency comb are mixed by a 2×2 90° optical mixer array and a single-ended PD array, the baseband signal of the four-channel slice signal is obtained at the receiving end. The slice signal is moved to the original position. After each slice signal is transmitted through the channel, there is amplitude and phase loss. For each slice signal, the baseband transfer function of each slice signal is used to compensate for the signal loss. For the compensated slice signal, the adjacent slice signal sliding window method is used to complete the signal splicing. The spliced ​​signal is consistent with the transmitter signal before the signal to be measured enters the receiver array. The slice signal passes through the DSP processing flow of the optical arbitrary waveform measurement system. The traditional DSP processing flow includes: DC removal, IQ orthogonalization, clock synchronization, signal equalization, matched filtering, downsampling, QAM demodulation, calculation of signal BER, EVM, SNR, and finally evaluation of signal reconstruction performance to complete signal reception reconstruction.

[0067] Figure 3 It is a schematic diagram of the principle of the present invention; the signal to be measured is divided into slice signals of different frequency bands, which are received through the corresponding local oscillator light combs.

[0068] Figure 4 This is the signal spectrum diagram after the transmission loss of the four-way slice signal is compensated in the simulation; there is a 4GHz spectrum overlap between adjacent slice signals.

[0069] Figure 5 The overlapping frequency parts of adjacent slice signals are processed by the digital signal processing module in the simulation to obtain the spliced ​​signal spectrum diagram by sliding window splicing. The spliced ​​signal is consistent with the transmitting end signal before the signal to be tested enters the receiver array.

[0070] Figure 6To successfully complete the demodulated signal constellation diagram through the digital signal processing module in the simulation, the system performance is evaluated, the requirements of communication transmission are met, and successful reconstruction is achieved.

[0071] Parts of the present invention that are not described in detail belong to common knowledge among those skilled in the art.

[0072] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A low-complexity optical arbitrary waveform measurement system based on a single-ended PD array, characterized in that: It includes a laser source, a fiber coupler, a signal generating module, an adjustable optical filter array, an optical frequency comb generating module, a parallel receiver array, and a digital signal processing module; the laser source is connected to the fiber coupler, the fiber coupler is respectively connected to the signal generating module and the optical frequency comb generating module, after the signal generating module and the adjustable optical filter array are connected in sequence, the output of the adjustable optical filter array and the output of the optical frequency comb generating module are input to the parallel receiver array together, and the output of the parallel receiver array is input to the digital signal processing module; The signal generation module includes an arbitrary waveform generator, an IQ modulator, and an optical amplifier EDFA; The optical frequency comb generation module includes an MZM modulator and a wavelength selective switch WSS; The parallel receiver array includes a 2×2 optical mixer array, a single-ended PD array, and an analog-to-digital converter array which are connected in sequence.

2. The low-complexity optical arbitrary waveform measurement system based on a single-ended PD array according to claim 1, characterized in that: The optical frequency comb generation module is generated by electro-optical modulation. The central wavelength of the optical frequency comb is 1548nm-1550nm, and the frequency interval of the optical frequency comb is 24GHz-26GHz.

3. The low-complexity optical arbitrary waveform measurement system based on a single-ended PD array according to claim 1, characterized in that: The parallel receiver array includes four columns of parallel receivers.

4. A low-complexity optical arbitrary waveform measurement method based on a single-ended PD array, characterized in that: The method is based on the low-complexity optical arbitrary waveform measurement method based on a single-ended PD array described in claims 1-3, and comprises the following steps: S1. Obtaining an optical signal through the laser source, and dividing the optical signal into an optical path one and an optical path two through the optical fiber coupler; S2. The optical signal of optical path 1 is sequentially input into the signal generating module and the tunable optical filter array to obtain four spectral slices E of different signal frequency bands. S,1 、E S,2 、E S,3 、E S,4 The optical signal of the optical path 2 is input into the optical frequency comb generation module to obtain four parallel local oscillator signals E L,1 、E L,2 、E L,3 、E L,4 ; Where S represents the signal light, L represents the local oscillator light signal; Spectral slice E S,1 With the local oscillator signal E L,1 Correspondingly, when the numerical subscripts of the slice signal and the intrinsic signal are the same, the two correspond one to one; S3. The parallel receiver array receives four spectrum slices and four parallel local oscillator signals; the 2×2 optical mixer array mixes different spectrum slice signals with corresponding local oscillator signals to obtain two mixing output signals E of each of the four parallel receivers. 1,1 、E 1,2 ; E 2,1 、E 2,2 ; E 3,1 、E 3,2 ; E 4,1 、E 4,2 ; E S,i represents the slice signal corresponding to the i-th receiver, E L,i represents the local oscillator signal corresponding to the i-th receiver, E i,1 represents the first mixer output of the i-th receiver, E i,2 represents the second mixer output of the i-th receiver, i represents the number of parallel receivers, and the range of i is 1-4; The mixing operation is as follows: The single-ended PD array performs beat frequency synthesis on the mixed output signal to synthesize an intermediate frequency signal, down-converts the high-frequency optical modulation signal to be received into an intermediate frequency signal with a lower frequency, and the single-ended PD array outputs a photocurrent I i,1 ,I i,2 , I S,i =|E S,i | 2 , I L,i =|E L,i | 2 ; Among them, I S,i ,I L,i are the photocurrents of the slice signal light and the local oscillator light corresponding to the i-th receiver, is the phase difference between the chip signal and the local oscillator signal of the i-th receiver, δ = π / 2; The photocurrent I is output through each receiver. i,1 ,I i,2 , calculate the in-phase signal component I of each slice signal I,i , orthogonal signal component I Q,i , and finally obtain the baseband signal I of each slice signal i,S , I i,S =I I,i +j*I Q,i (5) Where α = I S,i +I L,i , α is the self-frequency noise additionally introduced by the i-th receiver; S4. The baseband signals obtained from different signal frequency bands of each receiver are sent to the analog-to-digital converter array for analog-to-digital conversion. The digital signal processing module processes the digital signals after the analog-to-digital conversion, and finally realizes the signal waveform measurement.

5. The low-complexity optical arbitrary waveform measurement method based on a single-ended PD array according to claim 4, characterized in that: The specific steps of the digital signal processing module processing the digital signal after analog-to-digital conversion include: S41. The baseband signals obtained by the four parallel receivers are moved left and right accordingly to the original positions of the sliced ​​spectrum; S42. Perform channel response inverse compensation on the moved slice spectrum signal, and realize signal splicing through a sliding window algorithm on the compensated slice signal; S43. Normalize the amplitude of the spliced ​​signal, estimate and compensate for the I / Q quadrature imbalance, and correct the sampling clock deviation to synchronize the clock signals at the transmitter and receiver; S44. Equalize the channel using an equalization algorithm; S45. Using a square root raised cosine filter to implement the matched filtering function, downsampling the matched filtered signal; S46. Calculate the bit error rate of the reconstructed signal through the downsampled signal to evaluate the performance of the received signal.

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