CN115242312A - Photon compression sensing system and method for generating frequency multiplication bipolar code based on time delay - Google Patents

Abstract

The invention belongs to the technical field of optical communication, and in particular relates to a photonic compressed sensing system and method for generating frequency-doubling bipolar codes 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 optocoupler, a sparse signal generator, a third electro-optical modulator, a WDM, a balanced a photodetector, a sampler and a digital signal processing module; the two output ports of the continuous wave light source are respectively connected with the first electro-optical modulator and the second electro-optical modulator; the second electro-optical modulator is connected with the optical coupler after passing through the optical delay line ; The optical coupler is connected with the third electro-optical modulator, the wave decomposition multiplexer, the balanced photodetector, the sampler and the digital signal processing module in turn. The invention has the characteristics of effectively reducing the rate of the PRBS required by the system, breaking through the limitation of the system bandwidth by the rate of the PRBS, and improving the reconstruction performance of the signal at the same time.

Description

Photon Compressive Sensing System and Method Based on Time Delay to Generate Frequency Doubled Bipolar Codes

technical field

The invention belongs to the technical field of optical communication, and in particular relates to a photonic compressed sensing system and method for generating frequency-doubling bipolar codes based on time delay.

Background technique

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

In the existing literature abroad, Valley et al. first proposed a photonic compressed sensing scheme. They used a pulsed laser source and a spatial light modulator to realize the mixing of sparse RF signals and pseudo-random sequences in the optical domain. At the same time, it has been proposed that optical mixing is achieved using a continuous wave light source and an electro-optic modulator. In addition, it has been proposed to combine photonic compressed sensing with photonic time-stretching techniques to further reduce the sampling rate for capturing UWB signals. Since then, there are compressed sensing schemes for realizing low-pass filtering in the optical domain, and photonic multi-channel schemes based on modulated broadband converters.

However, since the PRBS rate required for random mixing is 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. Besides, the optical link has the characteristics of intensity modulation-direct detection, so the PRBS mixed with sparse signal is usually unipolar, which affects the signal recovery performance in the compressed sensing system.

Therefore, a photonic compressed sensing system and method based on time delay to generate frequency-doubling bipolar codes, which can effectively reduce the rate of 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, are designed. becomes very important.

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

SUMMARY OF THE INVENTION

The present invention is to overcome in the prior art, since the PRBS rate required for random mixing is greater than or equal to the Nyquist rate of the sparse radio frequency signal, and the optical link has the characteristics of intensity modulation and direct detection, plus the sparse signal The mixed PRBS is usually unipolar, which leads to the problem of affecting the signal recovery performance in the compressed sensing system. It provides a rate that can effectively reduce the PRBS required by the system, breaks through the limitation of the PRBS rate on the system bandwidth, and at the same time A photonic compressed sensing system and method for generating frequency-doubling bipolar codes based on time delay to improve signal reconstruction performance.

In order to achieve the above-mentioned purpose of the invention, the present invention adopts the following technical solutions:

Photonic compressive sensing system based on time delay to generate frequency doubled bipolar codes, including continuous wave light source, programmable pulse generator, first electro-optical modulator, second electro-optical modulator, optical delay line, optical coupler, sparse signal generation device, a third electro-optical modulator, a wavelength 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 with 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 a modulator; the optical coupler is connected with the third electro-optic modulator, the WDM, 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.

Preferably, the pseudo-random signal generated by the programmable pulse generator is modulated on two optical signals of different wavelengths generated by the continuous wave light source through the first electro-optical modulator and the second electro-optical modulator, wherein one optical signal is The time delay is generated by the optical delay line; the two modulated optical signals are synthesized by an optical coupler.

Preferably, the sparse signal generated by the sparse signal generator passes through the third electro-optical modulator, and at the same time completes the frequency mixing with the two channels of pseudo-random signals, and then separates the two channels of optical signals through the WDM, and sends them to the balanced photodetector The device completes the photoelectric conversion, and obtains the difference of the two optical signals at the same time, and generates a new frequency-doubling bipolar pseudo-random code.

Preferably, the sampler and the digital signal processing module are used to complete the process of low-pass filtering, down-sampling and signal recovery.

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.

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

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

The present invention also provides a photon compressed sensing method for generating frequency-doubling bipolar codes based on time delay, comprising the following steps;

S1, setting the wavelengths of the two paths of optical carrier signals emitted by the continuous wave light source to be consistent with the center wavelength of the WDM;

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

S3, the two modulated optical signals in step S2 are synthesized by an optical coupler to synthesize one optical signal, and the third electro-optic modulator modulates the input sparse signal to mix the pseudo-random signal and the sparse signal;

S4, the mixed signal passes through the wavelength decomposition multiplexer to separate the two mixed optical signals of different wavelengths, and then converts the optical signal into an electrical signal through a balanced photodetector, and simultaneously subtracts the two mixed optical signals , to obtain a new frequency-doubling bipolar PRBS;

S5, using a sampler and a digital signal processing module to complete the process of low-pass filtering, down-sampling and signal recovery.

Compared with the prior art, the present invention has the beneficial effects that the present invention utilizes an optical delay line and a balanced photodetector to generate a PRBS with frequency doubling and zero-average characteristics, which effectively reduces the rate of the PRBS required by the system and breaks through the PRBS rate Limiting system bandwidth while improving signal reconstruction performance.

Description of drawings

Fig. 1 is a kind of principle block diagram of the photonic compressed sensing system of frequency-doubling bipolar code generation based on time delay in the present invention;

Fig. 2 is a kind of contrasting schematic diagram of the new frequency-doubling bipolar PRBS and the original PRBS that the photonic compressed sensing system that generates frequency-doubling bipolar codes based on time delay in the present invention produces;

Fig. 3 is a kind of simulation result diagram of the photonic compressed sensing system of frequency-doubling bipolar code generation based on time delay in the present invention;

FIG. 4 is another simulation result diagram of the photonic compressed sensing system for generating frequency-doubling bipolar codes based on time delay in the present invention.

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

Detailed ways

In order to describe the embodiments of the present invention more clearly, the following will describe specific embodiments of the present invention with reference to the accompanying drawings. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative efforts, and obtain other implementations.

Example:

As shown in Fig. 1, a photonic compressed sensing system based on time delay to generate frequency-doubling bipolar codes, includes a continuous wave light source 1, a programmable pulse generator 2, a first electro-optical modulator 3, a second electro-optical modulator 4, a light source delay line 5, optical coupler 6, sparse signal generator 7, third electro-optical modulator 8, wave decomposition multiplexer 9, balanced photodetector 10, sampler 11 and digital signal processing module 12; the continuous wave light source The two output ports are respectively connected with the first electro-optical modulator and the second electro-optical modulator; the first electro-optical modulator is connected with the coupler; the second electro-optical modulator is connected with 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 and the third electro-optical modulator, wave decomposition multiplexer, balanced photodetector, sampler, digital signal processing The modules are connected in sequence; the sparse signal generator is connected to the third electro-optic modulator.

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 time of the pseudo-random signal, and N can be any positive integer. Optical couplers can be replaced with wavelength division multiplexers. The digital signal processing module is specifically a computer, which processes the collected data in the matlab program to complete the process of low-pass filtering (integration and accumulation), downsampling and signal recovery in compressed sensing.

The pseudo-random signal generated by the programmable pulse generator is modulated on two optical signals of different wavelengths generated by the continuous wave light source through the first electro-optical modulator and the second electro-optical modulator, and one of the optical signals is generated by an optical delay line. Time delay; two modulated optical signals are combined into one through an optocoupler. The sparse signal generated by the sparse signal generator passes through the third electro-optical modulator, and at the same time completes the frequency mixing with the two channels of pseudo-random signals, and then separates the two channels of optical signals through the wave decomposition multiplexer, and sends it to the balanced photodetector to complete the photoelectric Conversion, at the same time, the difference between the two optical signals is obtained, and a new frequency-doubling bipolar pseudo-random code is generated. The sampler and digital signal processing module are used to complete low-pass filtering, down-sampling and signal recovery processes.

The present invention also provides a photon compressed sensing method for generating frequency-doubling bipolar codes based on time delay, comprising the following steps;

S1, setting the wavelengths of the two paths of optical carrier signals emitted by the continuous wave light source to be consistent with the center wavelength of the WDM;

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

S3, the two modulated optical signals in step S2 are synthesized by an optical coupler to synthesize one optical signal, and the third electro-optic modulator modulates the input sparse signal to mix the pseudo-random signal and the sparse signal;

S4, the mixed signal passes through the wavelength decomposition multiplexer to separate the two mixed optical signals of different wavelengths, and then converts the optical signal into an electrical signal through a balanced photodetector, and simultaneously subtracts the two mixed optical signals , to obtain a new frequency-doubling bipolar PRBS;

S5, using a sampler and a digital signal processing module to complete the process of low-pass filtering, down-sampling and signal recovery.

The specific working principle of the photon compressed sensing system based on the time delay to generate the frequency-doubling bipolar code involved in the present invention is as follows:

The system uses a random demodulator model to measure compressed sensing, and its measurement process can be expressed as y=Φx=DHRx=DHRWθ, where x represents the sparse signal, Φ represents the M×N measurement matrix, and y represents the M×1 measurement As a result, R is a pseudo-random binary sequence, H is a low-pass filter matrix, D is a downsampling matrix, W is an N×N Fourier orthonormal basis, and θ is an N×1 vector representing x in the frequency domain. Sparse coefficient, the compression ratio of compressed sensing can be expressed by R _CS =N/M, and the recovery process from y to x is a problem of solving convex optimization. When the matrix product ΦW satisfies the constrained isometric condition, a recovery algorithm can be used to obtain a unique and correct solution by solving a minimum l ₁ norm reconstruction problem:

其中P表示光功率，

表示平衡光电探测器的响应度，平衡光电探测器的输出为Assuming that the spectrum of the continuous wave light source is relatively flat, and the modulation depth of the two electro-optical modulators used to modulate the PRBS is large, the modulation coefficient of the electro-optical modulator for modulating the sparse signal is α, so the mixed signal obtained by adding the channel can be expressed as r(t)·[1+αx(t)], the mixed signal of the drop channel can be expressed as r(t-τ)·[1+αx(t)], where x(t) represents the sparse signal, r( t) represents the PRBS produced by the programmable pulse generator, and τ represents the time delay produced by the optical delay line. After passing through the balanced photodetector, the two photocurrents are

where P is the optical power,

represents the responsivity of the balanced photodetector, and the output of the balanced photodetector is

在之后的压缩感知测量过程中减掉它，可以得到混频信号Among them, r'(t)=r(t)-r(t-τ) represents the new multiplied PRBS obtained by subtracting the two PRBSs. Since the generated r(t) is an alternating sequence of 0 and 1, r '(t) is a sequence alternating between 0 and ±1, with a zero mean characteristic. In order to remove the DC component in the signal, the sequence can be recorded during the calibration process before the measurement

Subtracting it during subsequent compressive sensing measurements yields the mixed signal

Thus, the mixed product of the sparse signal x(t) and a new frequency-doubling bipolar code r'(t) is obtained, which reduces the rate of the required PRBS under the condition that the required system bandwidth is determined. The new PRBS also has a zero mean property, which improves the recovery performance of compressed sensing systems.

In the simulation verification of the system shown in Figure 1, the system is compared with the basic compressed sensing system based on the random demodulator model. The parameters of the simulation 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, 1.7GHz, and the compression ratio is 20. The compressive sensing reconstruction algorithm l1-ls developed by Koh and Kim is used to recover the input sparse signal. Figure 2 (a) is the original PRBS, and Figure 2 (b) is the new PRBS generated after passing through the system. It can be seen that its frequency is twice the original and has zero mean characteristics. The recovered spectrum is shown in (a) in Figure 3, the sparse signal is well recovered and there is no DC component, while (b) in Figure 3 shows the basic compressed sensing based on the random demodulator model The recovery result of the system, it is obvious that the signal has not been recovered.

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

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

The above is only a detailed description of the preferred embodiments and principles of the present invention. For those of ordinary skill in the art, according to the ideas provided by the present invention, there will be changes in the specific implementation, and these changes should also be It is regarded as the protection scope of the present invention.

Claims (8)

1. the photon compressed sensing system of frequency-doubling bipolar code is produced based on time delay, it is characterized in that, comprise continuous wave light source, programmable pulse generator, the first electro-optical modulator, the second electro-optical modulator, optical delay line, optical a 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 connected with the second electro-optical modulator; the first electro-optical modulator is connected with the coupler; the second electro-optical modulator is connected with the optical coupler after passing through the optical delay line; the programmable pulse generator is connected to the first electro-optical a modulator and a second electro-optical modulator; the optical coupler is connected to the third electro-optical modulator, a wavelength division multiplexer, a balanced photodetector, a sampler, and a digital signal processing module in sequence; the sparse signal generator is connected to The third electro-optic modulator. 2. the photon compressive sensing system of generating frequency-doubling bipolar codes based on time delay according to claim 1, is characterized in that, the pseudorandom signal that described programmable pulse generator produces passes through the first electro-optical modulator and the first electro-optical modulator respectively. Two electro-optic modulators are modulated on two optical signals of different wavelengths generated by a continuous wave light source, one of which is delayed by an optical delay line; the two modulated optical signals are combined by an optical coupler. 3. the photon compressive sensing system based on time delay generation frequency doubled bipolar code according to claim 2, is characterized in that, the sparse signal that sparse signal generator produces passes through the 3rd electro-optical modulator, completes with two-way pseudo simultaneously. The random signal is mixed, and then the two optical signals are separated by the wave decomposition multiplexer, and sent to the balanced photodetector to complete the photoelectric conversion. At the same time, the difference between the two optical signals is obtained, and a new frequency doubled bipolar pseudo random code. 4. the photon compressive sensing system of generating frequency-doubling bipolar code based on time delay according to claim 3, is characterized in that, described sampler and digital signal processing module are used to complete low-pass filtering, down-sampling and signal recovery process. 5. The photon compressed sensing system for generating frequency-doubling bipolar codes based on time delay according to claim 1, wherein the continuous wave light source is a light source with two output ends or a continuous wave with two single output ends light source. 6. The photonic compressed sensing system for generating frequency-doubling bipolar codes based on time delay according to claim 1, wherein the time delay generated by the optical delay line is (2N+1)/2 pseudo-random signals The bit time of , N can be any positive integer. 7 . The photonic compressed sensing system for generating frequency-doubling bipolar codes based on time delay according to claim 1 , wherein the optical coupler is replaced by a wavelength division multiplexer. 8 . 8. produce the photon compressive sensing method of frequency doubled bipolar code based on time delay, produce the photon compressed sensing system of frequency doubled bipolar code based on time delay according to claim 1, it is characterized in that, comprise the steps; S1, setting the wavelengths of the two paths of optical carrier signals emitted by the continuous wave light source to be consistent with the center wavelength of the WDM; S2, the pseudo-random signal generated by the programmable pulse generator is modulated on the two optical signals through the first electro-optical modulator and the second electro-optical modulator respectively, and one of the modulated optical signals is delayed by the optical delay line, and by adjusting Optical delay line, let the delay time be set to (2N+1)/2 bit periods of pseudo-random signals, where N is any positive integer; S3, the two modulated optical signals in step S2 are combined with one signal through an optical coupler, and the third electro-optic modulator modulates the input sparse signal to mix the pseudo-random signal and the sparse signal; S4, the mixed signal passes through the wavelength decomposition multiplexer to separate the two mixed optical signals of different wavelengths, and then converts the optical signal into an electrical signal through a balanced photodetector, and simultaneously subtracts the two mixed optical signals , to obtain a new frequency-doubling bipolar PRBS; S5, using a sampler and a digital signal processing module to complete the process of low-pass filtering, down-sampling and signal recovery.

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