Photon compressed sensing system and method based on time delay to generate frequency-doubled bipolar code

Abstract

The present invention belongs to the field of optical communication technology, and specifically relates to a photon compressed sensing system and method for generating a frequency-multiplied bipolar code based on time delay. The system includes a continuous wave light source, a programmable pulse generator, a first electro-optical modulator, a second electro-optical modulator, an optical delay line, an optical coupler, a sparse signal generator, a third electro-optical modulator, a wave decomposition multiplexer, a balanced photodetector, a sampler and a digital signal processing module; the two output ports of the continuous wave light source are respectively connected to the first electro-optical modulator and the second electro-optical modulator; the second electro-optical modulator is connected to the optical coupler after passing through the optical delay line; the optical coupler is connected to the third electro-optical modulator, the wave decomposition multiplexer, the balanced photodetector, the sampler, and the digital signal processing module in sequence. The present invention has the characteristics of being able to effectively reduce the rate of the PRBS required by the system, break through the limitation of the PRBS rate on the system bandwidth, and improve the reconstruction performance of the signal.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical communications, and in particular relates to a photon compressed sensing system and method for generating frequency-doubled bipolar codes based on time delay. Background Art

[0002] At present, compressed sensing has aroused widespread research interest due to its application prospects in broadband signal acquisition. Compressed sensing provides a method to effectively reduce the sampling rate to capture sparse signals, and its implementation process usually includes a measurement process and a reconstruction process. In the measurement process, the sparse signal of interest is linearly mapped into several data points. Using these measured data points, an optimization method can be used to reconstruct the sparse signal in the reconstruction process. These processes specifically involve mixing, low-pass filtering and downsampling of the sparse signal with a PRBS (pseudo-random binary sequence signal). Due to the large bandwidth advantage of photonic technology and devices, photonic compressed sensing is considered to be a potential solution for the digital reception of ultra-wideband sparse signals. So far, many photonic compressed sensing schemes have been reported.

[0003] In the existing foreign literature, Valley et al. first proposed a scheme for photon compressed sensing. They used a pulsed laser source and a spatial light modulator to achieve mixing of sparse RF signals and pseudo-random sequences in the optical domain. At the same time, some people proposed that optical mixing is achieved using a continuous wave light source and an electro-optical modulator. In addition, some people proposed combining photon compressed sensing with photon time stretching technology to further reduce the sampling rate of capturing ultra-wideband signals. Since then, there have been compressed sensing schemes that implement low-pass filtering in the optical domain, photon multi-channel schemes based on modulated broadband converters, and so on.

[0004] However, since the PRBS rate required for random mixing must be greater than or equal to the Nyquist rate of the sparse RF signal, it is a great challenge for the electronic devices that generate PRBS in high-frequency application scenarios. In addition, the optical link has the characteristics of intensity modulation-direct detection, so the PRBS mixed with the sparse signal is usually unipolar, which affects the signal recovery performance in the compressed sensing system.

[0005] Therefore, it is very important to design a photon compressed sensing system and method based on time delay to generate frequency-doubled bipolar codes, which can effectively reduce the PRBS rate required by the system, break through the limitation of PRBS rate on system bandwidth, and improve the reconstruction performance of the signal.

[0006] For example, the Chinese patent document with application number CN202111332890.2 describes a broadband frequency measurement system and method based on microwave photon filtering and compressed sensing technology. A multi-wavelength light source is used to provide an optical carrier, and the broadband signal to be measured is modulated on the optical carrier through a first Mach-Zehnder modulator, and then enters the second Mach-Zehnder modulator to modulate the random sequence on the optical signal. After group velocity dispersion is introduced through a dispersive optical fiber, the optical signal is divided into two paths through a first optical coupler, one path leads to a first optical attenuator and a first photodetector, and the other path leads to a first tunable optical delay line and is divided into two paths again by a second optical coupler, one path leads to a second optical attenuator and a second photodetector, and the other path leads to a second tunable optical delay line, a third optical attenuator and a third photodetector. After photoelectric conversion in the first photodetector, the second photodetector and the third photodetector, signals with different delays in multiple channels are accumulated and finally enter the electronic analog-to-digital converter and the digital signal processing module. Although it can reduce the number of tunable laser sources required, lower the system cost, and greatly reduce the requirements for the wavelength tuning range of the laser source and the tuning range of the tunable optical delay line, the performance of the low-pass filter has been improved, and the number of delay line channels can also be adjusted according to the compression rate, thereby enhancing the reconfigurability of the system, its disadvantage is that it will still affect the signal recovery performance in the compressed sensing system. Summary of the invention

[0007] The present invention aims to overcome the problem in the prior art that the PRBS rate required for random mixing must be greater than or equal to the Nyquist rate of the sparse radio frequency signal, the optical link has the characteristics of intensity modulation-direct detection, and the PRBS mixed with the sparse signal is usually unipolar, which affects the signal recovery performance in the compressed sensing system. The present invention provides a photonic compressed sensing system and method based on time delay to generate frequency-doubled bipolar codes, which can effectively reduce the rate of the PRBS required by the system, break through the limitation of the PRBS rate on the system bandwidth, and improve the reconstruction performance of the signal.

[0008] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0009] A photon compressed sensing system for generating frequency-doubled bipolar codes based on time delay comprises a continuous wave light source, a programmable pulse generator, a first electro-optical modulator, a second electro-optical modulator, an optical delay line, an optical coupler, a sparse signal generator, a third electro-optical modulator, a wavelength division multiplexer, a balanced photodetector, a sampler and a digital signal processing module; the two output ports of the continuous wave light source are respectively connected to the first electro-optical modulator and the second electro-optical modulator; the first electro-optical modulator is connected to the coupler; the second electro-optical modulator is connected to the optical coupler after passing through the optical delay line; the programmable pulse generator is connected to the first electro-optical modulator and the second electro-optical modulator; the optical coupler is connected to the third electro-optical modulator, the wavelength division multiplexer, the balanced photodetector, the sampler and the digital signal processing module in sequence; the sparse signal generator is connected to the third electro-optical modulator.

[0010] Preferably, the pseudo-random signal generated by the programmable pulse generator is modulated on two optical signals of different wavelengths generated by a continuous wave light source through a first electro-optical modulator and a second electro-optical modulator, respectively, one of the optical signals being time delayed by an optical delay line; and the two modulated optical signals are combined into one through an optical coupler.

[0011] Preferably, the sparse signal generated by the sparse signal generator passes through a third electro-optical modulator to simultaneously complete mixing with two pseudo-random signals, then passes through a wavelength division multiplexer to separate the two optical signals, and is sent to a balanced photodetector to complete photoelectric conversion, while obtaining the difference between the two optical signals to generate a new frequency-doubled bipolar pseudo-random code.

[0012] Preferably, the sampler and digital signal processing module are used to complete low-pass filtering, downsampling and signal recovery processes.

[0013] Preferably, the continuous wave light source is a light source with two output ends or a continuous wave light source with two single output ends.

[0014] Preferably, the time delay generated by the optical delay line is (2N+1) / 2 bit times of the pseudo-random signal, where N can be any positive integer.

[0015] Preferably, the optical coupler is replaced by a wavelength division multiplexer.

[0016] The present invention also provides a photon compressed sensing method for generating a frequency-doubled bipolar code based on time delay, comprising the following steps:

[0017] S1, setting the wavelengths of the two optical carrier signals emitted by the continuous wave light source to be consistent with the central wavelength of the wavelength division multiplexer;

[0018] S2, the pseudo-random signal generated by the programmable pulse generator is modulated on two optical signals through the first electro-optical modulator and the second electro-optical modulator, one of which is delayed by the optical delay line, and the delay time is set to (2N+1) / 2 bit periods of the pseudo-random signal by adjusting the optical delay line, where N is an arbitrary positive integer;

[0019] S3, the two optical signals modulated in step S2 are combined into one optical signal through an optical coupler, and the third electro-optical modulator modulates the input sparse signal to mix the pseudo-random signal with the sparse signal;

[0020] S4, the mixed signal passes through a wavelength division multiplexer to separate the two mixed optical signals of different wavelengths, and then the optical signal is converted into an electrical signal through a balanced photodetector, and the two mixed optical signals are subtracted to obtain a new frequency-doubled bipolar PRBS;

[0021] S5, using the sampler and digital signal processing module to complete the low-pass filtering, downsampling and signal recovery process.

[0022] Compared with the prior art, the present invention has the following beneficial effects: the present invention utilizes an optical delay line and a balanced photodetector to generate a frequency-doubled PRBS with a zero-mean characteristic, thereby effectively reducing the rate of the PRBS required by the system, breaking through the limitation of the PRBS rate on the system bandwidth, and improving the signal reconstruction performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A principle block diagram of a photon compression sensing system for generating frequency-doubled bipolar codes based on time delay in the present invention;

[0024] Figure 2 A schematic diagram for comparing a new frequency-doubled bipolar PRBS generated by the photon compressed sensing system for generating frequency-doubled bipolar codes based on time delay in the present invention with the original PRBS;

[0025] Figure 3 A simulation result diagram of a photon compression sensing system for generating frequency-doubled bipolar codes based on time delay in the present invention;

[0026] Figure 4 This is another simulation result diagram of the photon compressed sensing system that generates frequency-doubled bipolar codes based on time delay in the present invention.

[0027] In the figure: continuous wave light source 1, programmable pulse generator 2, first electro-optic modulator 3, second electro-optic modulator 4, optical delay line 5, optical coupler 6, sparse signal generator 7, third electro-optic modulator 8, wavelength division multiplexer 9, balanced photodetector 10, sampler 11, digital signal processing module 12. DETAILED DESCRIPTION

[0028] In order to more clearly illustrate the embodiments of the present invention, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other accompanying drawings and other implementation methods can be obtained based on these accompanying drawings without creative work.

[0029] Example:

[0030] like Figure 1 The photon compressed sensing system for generating frequency-doubled bipolar codes based on time delay shown in the figure comprises a continuous wave light source 1, a programmable pulse generator 2, a first electro-optical modulator 3, a second electro-optical modulator 4, an optical delay line 5, an optical coupler 6, a sparse signal generator 7, a third electro-optical modulator 8, a wavelength division multiplexer 9, a balanced photodetector 10, a sampler 11 and a digital signal processing module 12; the two output ports of the continuous wave light source are respectively connected to the first electro-optical modulator and the second electro-optical modulator; the first electro-optical modulator is connected to the coupler; the second electro-optical modulator is connected to the optical coupler after passing through the optical delay line; the programmable pulse generator is connected to the first electro-optical modulator and the second electro-optical modulator; the optical coupler is connected to the third electro-optical modulator, the wavelength division multiplexer, the balanced photodetector, the sampler, and the digital signal processing module in sequence; the sparse signal generator is connected to the third electro-optical modulator.

[0031] Wherein, the continuous wave light source is a light source with two output ends or a continuous wave light source with two single output ends. The time delay generated by the optical delay line is (2N+1) / 2 bit times of the pseudo-random signal, and N can be any positive integer. The optical coupler can be replaced by a wavelength division multiplexer. The digital signal processing module is specifically a computer, which processes the collected data in a matlab program to complete the low-pass filtering (integral accumulation), downsampling and signal recovery process in compressed sensing.

[0032] The pseudo-random signal generated by the programmable pulse generator is modulated on two optical signals of different wavelengths generated by a continuous wave light source through the first electro-optical modulator and the second electro-optical modulator, one of which is delayed by a time delay through an optical delay line; the two modulated optical signals are combined into one through an optical coupler. The sparse signal generated by the sparse signal generator is mixed with the two pseudo-random signals through the third electro-optical modulator, and then the two optical signals are separated by a wavelength division multiplexer and sent to a balanced photodetector to complete the photoelectric conversion, and the difference between the two optical signals is obtained to generate a new frequency-doubled bipolar pseudo-random code. The sampler and digital signal processing module are used to complete the low-pass filtering, downsampling and signal recovery process.

[0033] The present invention also provides a photon compressed sensing method for generating a frequency-doubled bipolar code based on time delay, comprising the following steps:

[0034] S1, setting the wavelengths of the two optical carrier signals emitted by the continuous wave light source to be consistent with the central wavelength of the wavelength division multiplexer;

[0035] S2, the pseudo-random signal generated by the programmable pulse generator is modulated on two optical signals through the first electro-optical modulator and the second electro-optical modulator, one of which is delayed by the optical delay line, and the delay time is set to (2N+1) / 2 bit periods of the pseudo-random signal by adjusting the optical delay line, where N is an arbitrary positive integer;

[0036] S3, the two optical signals modulated in step S2 are combined into one optical signal through an optical coupler, and the third electro-optical modulator modulates the input sparse signal to mix the pseudo-random signal with the sparse signal;

[0037] S4, the mixed signal passes through a wavelength division multiplexer to separate the two mixed optical signals of different wavelengths, and then the optical signal is converted into an electrical signal through a balanced photodetector, and the two mixed optical signals are subtracted to obtain a new frequency-doubled bipolar PRBS;

[0038] S5, using the sampler and digital signal processing module to complete the low-pass filtering, downsampling and signal recovery process.

[0039] The specific working principle of the photon compressed sensing system based on time delay to generate frequency-doubled bipolar code according to the present invention is as follows:

[0040] The system uses a random demodulator model to perform compressed sensing measurements. The measurement process can be expressed as y=Φx=DHRx=DHRWθ, where x represents a sparse signal, Φ represents an M×N measurement matrix, y represents an M×1 measurement result, R represents a pseudo-random binary sequence, H represents a low-pass filter matrix, D represents a downsampling matrix, W is an N×N Fourier orthogonal basis, and θ is an N×1 vector representing the sparse coefficient of x in the frequency domain. The compression rate of compressed sensing can be expressed as R CS =N / M means that the recovery process from y to x is a convex optimization problem. When the matrix product ΦW satisfies the constraint isometry condition, a recovery algorithm can be used to obtain a unique and correct solution by solving a minimum l1 norm reconstruction problem:

[0041]

[0042] Assuming that the spectrum of the continuous wave light source is relatively flat, and the modulation depth of the two electro-optic modulators used to modulate the PRBS is large, the modulation coefficient of the electro-optic modulator modulating the sparse signal is α, so the mixed signal obtained by the upper channel can be expressed as r(t)·[1+αx(t)], and the mixed signal of the lower channel can be expressed as r(t-τ)·[1+αx(t)], where x(t) represents the sparse signal, r(t) represents the PRBS generated by the programmable pulse generator, and τ represents the time delay generated by the optical delay line. After passing through the balanced photodetector, the two photocurrents are Where P represents the optical power, represents the responsivity of the balanced photodetector. The output of the balanced photodetector is

[0043]

[0044] Among them, r'(t) = r(t)-r(t-τ) represents the new frequency-doubled PRBS obtained by subtracting the two PRBS. Since the generated r(t) is a sequence alternating between 0 and 1, r'(t) is a sequence alternating between 0 and ±1, which has a zero mean characteristic. In order to remove the DC component in the signal, the sequence can be recorded during the calibration process before measurement. Subtract it in the subsequent compressed sensing measurement process to obtain the mixed signal

[0045]

[0046] Thus, a mixed product of a sparse signal x(t) and a new frequency-doubled bipolar code r'(t) is obtained. Under the condition that the required system bandwidth is determined, the rate of the required PRBS is reduced, and since the new PRBS also has a zero-mean characteristic, the recovery performance of the compressed sensing system is improved.

[0047] exist Figure 1 In the simulation verification of the system shown, the system is compared with the basic compressed sensing system based on the random demodulator model. The simulation parameters are set as follows: the frequency of the PRBS is 4.8GHz, the length is 500bits, the delay time of the optical delay line is 12.5 bit periods, the frequency of the sparse signal is 1.2GHz and 1.7GHz, and the compression ratio is 20. The compressed sensing reconstruction algorithm l1-ls developed by Koh and Kim is used to recover the input sparse signal. Figure 2 Figure (a) is the original PRBS. Figure 2 Figure (b) shows the new PRBS generated after passing through the system. It can be seen that its frequency is twice the original one and has a zero mean characteristic. The recovered spectrum is shown in Figure 3 As shown in Figure (a), the sparse signal is well restored and there is no DC component. Figure 3Figure (b) shows the recovery result of the basic compressed sensing system based on the random demodulator model. It is obvious that the signal is not recovered.

[0048] The above process verifies that the system of the present invention effectively improves the signal recovery performance and the compression ratio of the system.

[0049] In order to further verify the improvement of the system bandwidth by the system of the present invention, the simulation parameters are reset as follows: the frequency of the PRBS is 4.8 GHz, the length is 1000 bits, the delay time of the optical delay line is 12.5 bit periods, the frequency of the sparse signal is 2.7 GHz and 3.4 GHz, and the compression ratio is 10. The recovered spectrum is as follows: Figure 4 As shown, it can be seen that the frequency is greater than f PRBS / 2 signal still obtains a good recovery result, which verifies that the system of the present invention effectively improves the system bandwidth.

[0050] The above description is only a detailed description of the preferred embodiments and principles of the present invention. For ordinary technicians in this field, according to the ideas provided by the present invention, there will be changes in the specific implementation methods, and these changes should also be regarded as the protection scope of the present invention.

Claims

1. A photon compressed sensing method based on time delay to generate frequency-doubled bipolar codes, characterized in that: A photon compression sensing system for generating a frequency-doubled bipolar code based on time delay, the photon compression sensing system for generating a frequency-doubled bipolar code based on time delay comprising a continuous wave light source, a programmable pulse generator, a first electro-optic modulator, a second electro-optic modulator, an optical delay line, an optical coupler, a sparse signal generator, a third electro-optic modulator, a wavelength division multiplexer, a balanced photodetector, a sampler and a digital signal processing module; The two output ports of the continuous wave light source are respectively connected to the first electro-optic modulator and the second electro-optic modulator; the first electro-optic modulator is connected to the coupler; the second electro-optic modulator is connected to the optical coupler after passing through the optical delay line; the programmable pulse generator is connected to the first electro-optic modulator and the second electro-optic modulator; the optical coupler is connected to the third electro-optic modulator, the wavelength division multiplexer, the balanced photodetector, the sampler, and the digital signal processing module in sequence; the sparse signal generator is connected to the third electro-optic modulator; The photon compressed sensing method for generating frequency-doubled bipolar codes based on time delay comprises the following steps: S1, setting the wavelengths of the two optical carrier signals emitted by the continuous wave light source to be consistent with the central wavelength of the wavelength division multiplexer; S2, the pseudo-random signal generated by the programmable pulse generator is modulated on two optical signals through the first electro-optical modulator and the second electro-optical modulator, one of which is delayed by the optical delay line, and the delay time is set to (2N+1) / 2 bit periods of the pseudo-random signal by adjusting the optical delay line, where N is an arbitrary positive integer; S3, the two optical signals modulated in step S2 are combined into one signal through an optical coupler, and the third electro-optical modulator modulates the input sparse signal to mix the pseudo-random signal with the sparse signal; S4, the mixed signal passes through a wavelength division multiplexer to separate the two mixed optical signals of different wavelengths, and then the optical signal is converted into an electrical signal through a balanced photodetector, and the two mixed optical signals are subtracted to obtain a new frequency-doubled bipolar PRBS; S5, using the sampler and digital signal processing module to complete the low-pass filtering, downsampling and signal recovery process.

2. The photon compressed sensing method based on time delay to generate frequency-doubled bipolar code according to claim 1, characterized in that: The pseudo-random signal generated by the programmable pulse generator is modulated on two optical signals of different wavelengths generated by a continuous wave light source through a first electro-optical modulator and a second electro-optical modulator, one of which is delayed by an optical delay line; the two modulated optical signals are combined into one through an optical coupler.

3. The photon compressed sensing method based on time delay to generate frequency-doubled bipolar code according to claim 2, characterized in that: The sparse signal generated by the sparse signal generator passes through the third electro-optical modulator to simultaneously complete mixing with two pseudo-random signals, and then passes through the wavelength division multiplexer to separate the two optical signals and send them to the balanced photodetector to complete the photoelectric conversion. At the same time, the difference between the two optical signals is obtained to generate a new frequency-doubled bipolar pseudo-random code.

4. The photon compressed sensing method based on time delay to generate frequency-doubled bipolar code according to claim 3, characterized in that: The sampler and digital signal processing module are used to complete the low-pass filtering, down-sampling and signal recovery processes.

5. The photon compressed sensing method based on time delay to generate frequency-doubled bipolar code according to claim 1, characterized in that: The continuous wave light source is a light source with two output ends or a continuous wave light source with two single output ends.

6. The photon compressed sensing method based on time delay to generate frequency-doubled bipolar code according to claim 1, characterized in that: The time delay generated by the optical delay line is (2N+1) / 2 bit times of the pseudo-random signal, where N can be any positive integer.

7. The photon compressed sensing method based on time delay to generate frequency-doubled bipolar code according to claim 1, characterized in that: The optical coupler is replaced by a wavelength division multiplexer.

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