CN112684650B - A photonic analog-to-digital conversion method and system based on weighted modulation curve - Google Patents

Abstract

The invention relates to a photonic analog-to-digital conversion method and system based on a weighted modulation curve. By combining a phase-shifted optical quantization technology with a weighted multi-wavelength sampling pulse, the weighted modulation curve is used to realize the improvement of the quantization accuracy of a photonic analog-to-digital conversion system; The system utilizes a weighted multi-wavelength pulse source to generate weighted multi-wavelength sampling optical pulses, and modulates the RF analog signal onto the weighted multi-wavelength sampling optical pulses through a Mach-Zehnder modulator. The modulated signal is connected to the dispersive element to realize the time-domain walk-off of the multi-wavelength pulse, and then the photodetector performs photoelectric conversion and is connected to the comparator for threshold comparison, so as to realize the conversion of analog signal to digital signal; Compared with this scheme, the weighted modulation curve is used to realize the uniform quantization of the analog input signal, so as to improve the bit precision of the photonic analog-to-digital conversion system. At the same time, the system has a simple structure and is easy to implement.

Description

A method and system for photon analog-to-digital conversion based on weighted modulation curve

technical field

The invention belongs to the technical field of signal processing of optical communication, and in particular relates to a photonic analog-to-digital conversion method and system based on a weighted modulation curve.

Background technique

Analog-to-digital converter (Analog-to-digital Converter, ADC) as a bridge between the analog world and the digital world, ADC plays a vital role in electronic products, precision instrumentation and aviation communications. Over the past decade, electronic ADCs have made great strides in increasing sampling rates and resolutions. However, with the emergence of applications such as radar systems, real-time surveillance, and medical imaging that require both large bandwidth and high resolution, the performance of traditional electronic ADCs has reached its limits. Due to inherent electronic limitations such as RF delay, time jitter, and electromagnetic interference, traditional electronic ADCs cannot meet the large bandwidth and high precision requirements of existing signal processing systems. With the development of photonic devices and technologies, photonic ADCs can avoid the trade-off between energy efficiency and bandwidth of traditional electronic ADCs. First, photonic ADCs have the advantages of low loss, large bandwidth, and no electromagnetic interference compared to traditional electronic ADCs. Second, the sampled optical pulses generated by the mode-locked laser have the high-quality characteristics of high repetition rate and low time jitter, and their clock jitter is two quantities lower than electronic clock jitter, and the rate can reach more than 100GS/s. With the advantages of photonic technology, photonic analog-to-digital conversion technology has great development prospects in improving the performance of digital signal processing systems.

In 1979, Taylor first proposed a photonic ADC scheme based on a Mach-Zehnder modulator (MZM) array. In the scheme, the transfer function period of each modulator is different, so as to realize the quantization coding of different input signals. But the biggest disadvantage of this scheme is that the half-wave voltage of the modulator needs to be reduced by a multiple of 2. Due to the limitation of the manufacturing process, when the number of optical channels exceeds 4, it is difficult to realize the half-wave voltage of the modulator less than 1V. In order to avoid this problem, Stigwall proposed in 2005 to use the spatial MZ interference structure to realize the quantization coding of radio frequency signals. In this scheme, the phase modulator on one arm of the spatial interferometer modulates the analog signal and then spatially interferes with the optical signal of the other arm, and multiple photodetectors are integrated into a chip according to a certain spatial position to realize phase-shifted light quantization. However, the spatial light interference of the Stigwall scheme is easily affected by the environment, and the structure is complex, the insertion loss is large, and the technical implementation is difficult. In order to improve the stability of the system and better realize the phase-shifted optical quantization, the researchers proposed a series of coding quantization schemes, including the parallel MZM scheme; the photon quantization scheme using polarized light interference; the MZM scheme using unequal arm lengths; A quantization scheme for differential coding is implemented using a phase modulator and delay line interferometer. Phase-shifted optical quantization is the quantization and encoding of the input signal through different transfer functions with a constant phase difference. However, in the phase-shifted optical quantization technology, N optical channels can only achieve 2N quantization levels. When the number of optical channels is equal, the Taylor scheme can achieve uniform quantization of 2N quantization levels. Therefore, the low bit resolution of the system becomes the main limitation of the phase-shifted optical quantization scheme. In order to improve the bit accuracy of the photonic analog-to-digital conversion system, a scheme that uses multiple comparators to improve the bit accuracy of the system was proposed in 2009. In this scheme, a symmetric digital system (SNS) is used to connect multiple A comparator realizes the improvement of system bit accuracy. The number of comparators used in this scheme is large, which makes the system structure complex and is not conducive to integration. A cascade-based quantization scheme was proposed in 2014. In this scheme, the directional coupler array is used as the second-stage quantization, and the output power of the first-stage quantization is further quantized, thereby increasing the number of system quantization stages. However, the directional coupler array of this scheme needs special customization, and when the second-stage quantization bit resolution is increased, the inability to achieve uniform quantization leads to an increase in system quantization noise, thereby seriously reducing the system ENOB. In 2018, a quantization scheme using circuits to realize the linear combination of detection signals was proposed. This scheme uses logic circuits to linearly combine detection signals, equivalently to achieve the effect of increasing the number of channels. However, in this scheme, the bandwidth requirement of the logic electronic circuit is relatively large, and the system is complicated. In 2020, a serial flash quantization scheme is proposed, which uses dispersive elements to separate the pulses, thereby quantizing the input signal to obtain the serial output of the digital signal, thereby simplifying the system structure. However, this scheme can only work in the case of small signal modulation, and it is necessary to control the MZM bias at the quadrature point and the modulation depth is small to realize the linear intensity modulation of the input analog signal. Therefore, how to use a quantization scheme with a simple structure and easy implementation to improve the system bit accuracy is still a problem worthy of research.

In view of the above problems, it is necessary to improve it.

SUMMARY OF THE INVENTION

Aiming at the defects of the existing photonic analog-to-digital conversion technology, the present invention proposes a photonic analog-to-digital conversion method and system based on a weighted modulation curve. The coding and quantization of the input signal is realized, the bit precision of the photonic analog-to-digital conversion system is greatly improved, and the system structure is simple and easy to implement.

In order to achieve the above purpose, the technical solution adopted in the present invention is: a photon analog-to-digital conversion method based on a weighted modulation curve, comprising the following steps:

S1. The weighted multi-wavelength sampling optical pulse sent by the weighted multi-wavelength pulse source is divided into N parallel multi-wavelength sampling optical pulses through the optical beam splitter;

S2. The N parallel multi-wavelength sampling optical pulses modulate the analog radio frequency signals in the first Mach-Zehnder modulator, the second Mach-Zehnder modulator, and the Nth Mach-Zehnder modulator, respectively, and output N-way modulated signal;

S3. The first Mach-Zehnder modulator, the second Mach-Zehnder modulator, and the Nth Mach-Zehnder modulator output N optical modulation signals and connect them to the first dispersion element, the second dispersion element, and the Nth dispersion element. Dispersion element to obtain N channels of time-domain separated modulated pulse signals;

S4. The N-channel modulated signals are respectively input into the photoelectric converter for photoelectric conversion and then connected to the corresponding comparator. By comparing with the preset comparator judgment threshold, when the input voltage is greater than the threshold, the judgment output is "1", otherwise the output is "0", thereby converting the analog signal to a digital signal.

As a preferred solution of the present invention, the total number of wavelengths of the weighted multi-wavelength sampling optical pulses emitted by the weighted multi-wavelength pulse source is M (M≥3), and the pulse power of the i-th wavelength is normalized P _i (i=1 ,2,...,M) is expressed as:

As a preferred solution of the present invention, in the step S2, the analog radio frequency signal is generated by a signal generator and input to the first Mach-Zehnder modulator, the second Mach-Zehnder modulator and the Nth (Nth) synchronously. ≥3) In the Mach-Zehnder modulator, the peak-to-peak value of the analog RF signal is V _π (2NM-M+1)/(2NM).

的表达式为：As a preferred solution of the present invention, the initial phases of the N modulated signals output by the first Mach-Zehnder modulator, the second Mach-Zehnder modulator and the Nth Mach-Zehnder modulator

The expression is:

As a preferred solution of the present invention, the initial phases of the N modulated signals of the first Mach-Zehnder modulator, the second Mach-Zehnder modulator and the Nth Mach-Zehnder modulator are respectively determined by the first The current power supply, the second DC power supply and the Nth DC power supply provide bias voltages for control, so that the bias voltage V _bj of the N modulators is expressed as:

的表达式为：As a preferred solution of the present invention, in the step S2, the optical signal intensities output by the first Mach-Zehnder modulator, the second Mach-Zehnder modulator and the Nth Mach-Zehnder modulator

The expression is:

代表输入模拟信号引入的相移。in,

Represents the phase shift introduced by the input analog signal.

As a preferred solution of the present invention, in the step S3, the first dispersion element, the second dispersion element and the Nth dispersion element cause the input N multi-wavelength overlapping modulated pulses to walk away due to the group velocity dispersion effect. , the multi-wavelength pulses are separated in the time domain and do not overlap with the next periodic pulse.

As a preferred solution of the present invention, in the step S4, the threshold of the comparator is set to 1/2 of the maximum power of the input pulse, and the electrical signal after photoelectric conversion is compared with the threshold of the comparator. When the input voltage is greater than the threshold The decision output is "1", otherwise the output is "0", thereby converting the analog signal into a digital signal.

A photonic analog-to-digital conversion system based on a weighted modulation curve, comprising a weighted multi-wavelength pulse source, an optical beam splitter, a first Mach-Zehnder modulator, a second Mach-Zehnder modulator, and an Nth Mach-Zehnder modulator device, signal generator, first DC power supply, second DC power supply, Nth DC power supply, first dispersion element, second dispersion element, Nth dispersion element, first photodetector, second photodetector, N photodetectors, first comparators, second comparators and Nth comparators; the weighted multi-wavelength pulse source is used to emit multi-wavelength sampling light pulses, and the signal generator is used to generate analog radio frequency signals and synchronously input them to In the first Mach-Zehnder modulator, the second Mach-Zehnder modulator, and the Nth Mach-Zehnder modulator, the first DC power supply, the second DC power supply, and the Nth DC power supply are respectively used for the A Mach-Zehnder modulator, a second Mach-Zehnder modulator, and an Nth Mach-Zehnder modulator provide bias voltages; the multi-wavelength sampling optical pulse is divided into N sampling pulses through an optical beam splitter, and the N channels of sampled optical pulses respectively enter the first Mach-Zehnder modulator, the second Mach-Zehnder modulator and the Nth Mach-Zehnder modulator to modulate the analog radio frequency signal at the same time, and output N channels of modulated signals; After the modulated signal passes through the first dispersive element, the second dispersive element and the Nth dispersive element, respectively, a modulated pulse signal with non-overlapping time domain is obtained, and the modulated signal separated in the time domain is respectively input to the first photodetector, the second The second photodetector and the Nth photodetector realize photoelectric conversion to obtain electrical signals, and the electrical signals are respectively input to the first comparator, the second comparator and the Nth comparator to compare with the threshold to complete the analog signal to digital signal. conversion.

The beneficial effects of the present invention are: compared with the prior art, a photonic analog-to-digital conversion method and system based on a weighted modulation curve proposed by the present invention, by combining the phase-shifted optical quantization technology with the weighted multi-wavelength sampling pulse, uses The weighted modulation curve realizes the coding and quantization of the input signal, which greatly improves the bit precision of the photonic analog-to-digital conversion system, and the system structure is simple and easy to implement.

Description of drawings

1 is a schematic structural diagram of Embodiment 1 of a photonic analog-to-digital conversion system and method based on a weighted modulation curve of the present invention;

2 is a schematic diagram of a modulation curve of the first embodiment of the photonic analog-to-digital conversion system and method based on a weighted modulation curve of the present invention;

Reference signs in the figure: weighted multi-wavelength pulse source 1, optical beam splitter 2, first Mach-Zehnder modulator 3, second Mach-Zehnder modulator 4, third Mach-Zehnder modulator 5, signal Generator 6, first DC power source 7, second DC power source 8, third DC power source 9, first dispersive element 10, second dispersive element 11, third dispersive element 12, first photodetector 13, second Photodetector 14 , third photodetector 15 , first comparator 16 , second comparator 17 , third comparator 18 .

Detailed ways

The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "installed", "connected" and "connected" should be understood in a broad sense, unless otherwise expressly specified and limited, for example, it may be a fixed connection or a detachable connection Connection, or integral connection; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be internal communication between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in specific situations.

Example 1:

As shown in FIG. 1, a photonic analog-to-digital conversion system based on a weighted modulation curve proposed by the present invention includes a weighted multi-wavelength pulse source 1, an optical beam splitter 2, a first Mach-Zehnder modulator 3, a second Mach -Zehnder modulator 4, third Mach-Zehnder modulator 5, signal generator 6, first DC power supply 7, second DC power supply 8, third DC power supply 9, first dispersive element 10, second dispersion element 11, third dispersive element 12, first photodetector 13, second photodetector 14, third photodetector 15, first comparator 16, second comparator 17, and third comparator 18; the The weighted multi-wavelength pulse source 1 is used for sending out multi-wavelength sampling optical pulses, and the signal generator 6 is used for generating an analog radio frequency signal and synchronously inputting it to the first Mach-Zehnder modulator 3 and the second Mach-Zehnder modulator 4 and the third Mach-Zehnder modulator 5, the first DC power supply 7, the second DC power supply 8 and the third DC power supply 9 are respectively used for the first Mach-Zehnder modulator 3, the second Mach-Zehnder The Zehnder modulator 4 and the third Mach-Zehnder modulator 5 provide bias voltages; the multi-wavelength sampling optical pulses are divided into three sampling pulses by the optical beam splitter 2, and the three sampling optical pulses enter the first sampling pulse respectively. The Mach-Zehnder modulator 3, the second Mach-Zehnder modulator 4 and the third Mach-Zehnder modulator 5 simultaneously modulate the analog radio frequency signal to output three modulated signals; A dispersive element 10, a second dispersive element 11 and a third dispersive element 12 obtain modulated pulse signals with non-overlapping time domains, and the modulated signals separated in time domains are respectively input to the first photodetector 13 and the second photoelectric detector. Photoelectric conversion is achieved in the detector 14 and the third photodetector 15 to obtain electrical signals, which are respectively input to the first comparator 16, the second comparator 17 and the third comparator 18 for comparison with the threshold to complete the analog signal conversion to digital signals.

A photonic analog-to-digital conversion method and system based on a weighted modulation curve proposed by the present invention, by combining the phase-shifted optical quantization technology with the weighted multi-wavelength sampling pulse, the weighted modulation curve is used to realize the coding and quantization of the input signal, which greatly improves the The bit precision of the photonic analog-to-digital conversion system is improved, and the system structure is simple and easy to implement.

Specifically, this example provides a photon analog-to-digital conversion method based on a weighted modulation curve, as follows:

As shown in Figure 1, a 4-bit photonic analog-to-digital conversion system is taken as an example.

S1. The weighted multi-wavelength sampling optical pulse sent by the weighted multi-wavelength pulse source is divided into three parallel multi-wavelength sampling optical pulses through the optical beam splitter;

S2. The three parallel multi-wavelength sampling optical pulses modulate the analog radio frequency signals in the first Mach-Zehnder modulator, the second Mach-Zehnder modulator, and the third Mach-Zehnder modulator, respectively, and output Three-way modulation signal;

S3. The first Mach-Zehnder modulator, the second Mach-Zehnder modulator and the third Mach-Zehnder modulator output three-way optical modulation signals and connect to the first dispersion element, the second dispersion element and the third Dispersive element to obtain three modulated pulse signals separated in time domain;

S4. Each signal of the three modulated signals is respectively input into the photoelectric converter for photoelectric conversion and then connected to the corresponding comparator. By comparing with the preset comparator judgment threshold, when the input voltage is greater than the threshold The decision output is "1", otherwise the output is "0", thereby converting the analog signal into a digital signal.

Figure 1 shows a schematic structural diagram of a photonic analog-to-digital conversion method based on a weighted modulation curve, including a weighted multi-wavelength pulse source 1, an optical beam splitter 2, a first Mach-Zehnder modulator 3, a second Mach-Zehnder modulator 3, and a second Mach-Zehnder modulator. Del modulator 4, third Mach-Zehnder modulator 5, signal generator 6, first DC power supply 7, second DC power supply 8, third DC power supply 9, first dispersion element 10, second dispersion element 11 , a third dispersive element 12 , a first photodetector 13 , a second photodetector 14 , a third photodetector 15 , a first comparator 16 , a second comparator 17 , and a third comparator 18 .

In step S1, the weighted multi-wavelength sampling optical pulse sent by the weighted multi-wavelength pulse source is divided into three parallel multi-wavelength sampling optical pulses through the optical beam splitter;

The weighted multi-wavelength pulse source 1 is connected with the first Mach-Zehnder modulator 3 , the second Mach-Zehnder modulator 4 , and the third Mach-Zehnder modulator 5 through an optical beam splitter 2 .

The total number of wavelengths of the weighted multi-wavelength sampling optical pulses emitted by the weighted multi-wavelength pulse source 1 is 3, and the normalized P _i (i=1, 2, 3) of the pulse power of the i-th wavelength is expressed as:

In step S2, the three parallel multi-wavelength sampling optical pulses are respectively performed on the analog radio frequency signals in the first Mach-Zehnder modulator, the second Mach-Zehnder modulator, and the third Mach-Zehnder modulator. Modulation, output three-way modulation signal;

The signal generator 6 is connected with the first Mach-Zehnder modulator 3, the second Mach-Zehnder modulator 4, and the third Mach-Zehnder modulator 5; The three DC power sources 9 are respectively connected to the first Mach-Zehnder modulator 3 , the second Mach-Zehnder modulator 4 , and the third Mach-Zehnder modulator 5 .

的表达式为：The analog radio frequency signal generated by the signal generator 6 is synchronously input into the first Mach-Zehnder modulator 3, the second Mach-Zehnder modulator 4 and the third Mach-Zehnder modulator 5, and the peak-to-peak value of the analog radio frequency signal is is 8V _π /9; the initial phase of the three-way modulation signal output by the first Mach-Zehnder modulator 3, the second Mach-Zehnder modulator 4 and the third Mach-Zehnder modulator 5

The expression is:

The initial phases of the three modulated signals output by the first Mach-Zehnder modulator 3, the second Mach-Zehnder modulator 4 and the third Mach-Zehnder modulator 5 are respectively supplied by the first DC power supply 7 and the second DC power supply. 8 and the third DC power supply 9 provide bias voltages for control, so that the three modulator bias voltages V _bj are expressed as:

的表达式为：The optical signal intensity output by the first Mach-Zehnder modulator 3, the second Mach-Zehnder modulator 4 and the third Mach-Zehnder modulator 5

The expression is:

代表输入模拟信号引入的相移。in,

Represents the phase shift introduced by the input analog signal.

In step S3, the first Mach-Zehnder modulator, the second Mach-Zehnder modulator, and the third Mach-Zehnder modulator output three-way optical modulation signals, which are connected to the first dispersion element, the second dispersion element, and the third dispersion element. Three dispersive elements to obtain three modulated pulse signals separated in time domain;

The first Mach-Zehnder modulator 3 , the second Mach-Zehnder modulator 4 , and the third Mach-Zehnder modulator 5 are respectively connected to the first dispersion element 10 , the second dispersion element 11 and the third dispersion element 12 .

The first dispersive element 10, the second dispersive element 11 and the third dispersive element 12 cause the input three-way multi-wavelength overlapping modulated pulses to walk away due to the group velocity dispersion effect, and the multi-wavelength pulses are separated in the time domain and are separated from the next cycle. The pulses do not overlap.

In step S4, each signal of the three modulated signals is respectively input into the photoelectric converter for photoelectric conversion and then connected to the corresponding comparator. By comparing with the preset comparator judgment threshold, when the input voltage is greater than the threshold When the judgment output is "1", otherwise the output is "0", thereby converting the analog signal into a digital signal.

The first comparator 16 , the second comparator 17 and the third comparator 18 communicate with the first dispersive element 10 and the second dispersive element 11 through the first photodetector 13 , the second photodetector 14 and the third photodetector 15 and the third dispersive element 12 is connected.

The thresholds of the first comparator 16, the second comparator 17 and the third comparator 18 are all set to one-half of the maximum power of the input pulse, and the photoelectrically converted electrical signal is compared with the comparator threshold. When the input voltage is greater than When the threshold is determined, the output is "1", otherwise the output is "0", thereby converting the analog signal into a digital signal.

Figure 2 is a schematic diagram of the modulation curve. The figure shows the weighted multi-wavelength pulses with a total of three wavelengths as the sampling pulses, the corresponding transfer function curves of the three Mach-Zehnder modulators, and the quantized coding results. The abscissa represents the phase shift introduced by the input analog signal, and the ordinate represents the normalized output of the optical signal intensity; in order to achieve uniform quantization, the power ratio of the weighted multi-wavelength pulses P ₁ :P ₂ :P ₃ is 1:0.7451 : 0.6087, the normalized thresholds of the comparators are all set to 0.5. When the signal strength is greater than the threshold, the comparator outputs "1"; when the signal is less than the threshold, the comparator outputs "0". After the judgment is completed, the digital signal converted from the analog signal is obtained, as shown in the lower part of Figure 2. The output has a total of 16 code words, so the bit accuracy of the photonic ADC system is 4 bits. That is, using weighted multi-wavelength pulses with a total number of M wavelengths as the sampling source, the total quantization technology that can be input into N modulators is L=2NM-M+1, and the achievable bit resolution of the photonic analog-to-digital conversion system is B=log ₂ (2NM-M+1).

A photonic analog-to-digital conversion method and system based on a weighted modulation curve proposed in this example, by combining phase-shifted optical quantization technology and weighted multi-wavelength sampling pulses, the weighted modulation curve is used to realize the encoding and quantization of the input signal, which greatly improves the photonic performance. The bit precision of the analog-to-digital conversion system, and the system structure is simple and easy to implement.

The above description of the disclosed embodiments enables any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention; thus , the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Although the reference numerals in the figure are used more in this paper: weighted multi-wavelength pulse source 1, optical beam splitter 2, first Mach-Zehnder modulator 3, second Mach-Zehnder modulator 4, third Mach-Zehnder modulator Zehnder modulator 5, signal generator 6, first DC power source 7, second DC power source 8, third DC power source 9, first dispersive element 10, second dispersive element 11, third dispersive element 12, first The terms photodetector 13, second photodetector 14, third photodetector 15, first comparator 16, second comparator 17, third comparator 18, etc., do not exclude the possibility of using other terms. These terms are used only to more conveniently describe and explain the essence of the present invention; it is contrary to the spirit of the present invention to interpret them as any kind of additional limitation.

Claims (9)

1. a photon analog-to-digital conversion method based on a weighted modulation curve, is characterized in that: comprise the following steps: S1. The weighted multi-wavelength sampling optical pulse sent by the weighted multi-wavelength pulse source is divided into N parallel multi-wavelength sampling optical pulses through the optical beam splitter; S2. The N parallel multi-wavelength sampling optical pulses modulate the analog radio frequency signals in the first Mach-Zehnder modulator, the second Mach-Zehnder modulator, and the Nth Mach-Zehnder modulator, respectively, and output N modulated signals, N≥3; S3. The first Mach-Zehnder modulator, the second Mach-Zehnder modulator, and the Nth Mach-Zehnder modulator output N optical modulation signals and connect them to the first dispersion element, the second dispersion element, and the Nth dispersion element. Dispersion element to obtain N channels of time-domain separated modulated pulse signals; S4. The N-channel modulated signals are respectively input into the photoelectric converter for photoelectric conversion and then connected to the corresponding comparator. By comparing with the preset comparator judgment threshold, when the input voltage is greater than the threshold, the judgment output is "1", otherwise the output is "0", thereby converting the analog signal to a digital signal. 2. a kind of photon analog-to-digital conversion method based on weighted modulation curve according to claim 1 is characterized in that: the total number of wavelengths of the weighted multi-wavelength sampling optical pulses sent by the weighted multi-wavelength pulse source is M, and M≥3, The pulse power of the i-th wavelength is normalized P _i , (i=1,2,...,M), expressed as:

3. a kind of photon analog-to-digital conversion method based on weighted modulation curve according to claim 1, is characterized in that: in described step S2, the analog radio frequency signal is produced by the signal generator and input to the first Mach-Zeng synchronously In the Del modulator, the second Mach-Zehnder modulator and the Nth Mach-Zehnder modulator, N≥3, the peak-to-peak value of the analog radio frequency signal is V _π (2NM-M+1)/(2NM). 4. A photon analog-to-digital conversion method based on a weighted modulation curve according to claim 3, characterized in that: the first Mach-Zehnder modulator, the second Mach-Zehnder modulator and the Nth Mach-Zehnder modulator The initial phase of the N-channel modulated signal output by the Zehnder modulator

The expression is:

5. A photonic analog-to-digital conversion method based on a weighted modulation curve according to claim 4, characterized in that: the first Mach-Zehnder modulator, the second Mach-Zehnder modulator and the Nth Mach-Zehnder modulator The initial phases of the N-channel modulation signals of the Zehnder modulator are controlled by the bias voltages provided by the first DC power supply, the second DC power supply, and the Nth DC power supply, respectively, so that the bias voltages V _bj of the N modulators are expressed as :

6 . The photonic analog-to-digital conversion method based on a weighted modulation curve according to claim 1 , wherein: in the step S2 , the first Mach-Zehnder modulator and the second Mach-Zehnder modulation and the optical signal intensity output by the Nth Mach-Zehnder modulator

The expression is:

in,

Represents the phase shift introduced by the input analog signal. 7 . The photonic analog-to-digital conversion method based on a weighted modulation curve according to claim 1 , wherein in the step S3 , the first dispersion element, the second dispersion element and the Nth dispersion element make the input The N-way multi-wavelength overlapping modulated pulses walk away due to the group velocity dispersion effect, and the multi-wavelength pulses are separated in the time domain and do not overlap with the next periodic pulse. 8. a kind of photon analog-to-digital conversion method based on weighted modulation curve according to claim 1, is characterized in that: in described step S4, described comparator judgment threshold is set as 1/2 of the maximum power of input pulse, Comparing the electrical signal after photoelectric conversion with the threshold of the comparator, when the input voltage is greater than the threshold, the judgment output is "1", otherwise the output is "0", thereby converting the analog signal into a digital signal. 9. A photonic analog-to-digital conversion system based on a weighted modulation curve, characterized in that it comprises a weighted multi-wavelength pulse source (1), an optical beam splitter (2), a first Mach-Zehnder modulator (3), a first Mach-Zehnder modulator (3), a Two Mach-Zehnder modulators (4), Nth Mach-Zehnder modulators (5), signal generators (6), first DC power supply (7), second DC power supply (8), Nth DC power supply Power supply (9), first dispersion element (10), second dispersion element (11), Nth dispersion element (12), first photodetector (13), second photodetector (14), Nth photoelectric a detector (15), a first comparator (16), a second comparator (17) and an Nth comparator (18); the weighted multi-wavelength pulse source (1) is used for emitting multi-wavelength sampling light pulses, so The signal generator (6) is used to generate an analog radio frequency signal and synchronously input it to the first Mach-Zehnder modulator (3), the second Mach-Zehnder modulator (4) and the Nth Mach-Zehnder modulator ( 5), the first DC power supply (7), the second DC power supply (8), and the Nth DC power supply (9) are respectively used for the first Mach-Zehnder modulator (3), the second Mach-Zehnder modulator (3), and the second Mach-Zehnder modulator (3). The Zehnder modulator (4) and the Nth Mach-Zehnder modulator (5) provide a bias voltage; the multi-wavelength sampling optical pulse is divided into N sampling pulses by the optical beam splitter (2), and the N sampling pulses are divided into N sampling pulses. The optical pulses respectively enter the first Mach-Zehnder modulator (3), the second Mach-Zehnder modulator (4) and the Nth Mach-Zehnder modulator (5) to modulate the analog radio frequency signal at the same time, and output N channels Modulated signal; the N-channel modulated signals respectively pass through the first dispersion element (10), the second dispersion element (11) and the Nth dispersion element (12) to obtain time-domain separated modulated pulse signals, the time-domain separation The modulated signals are respectively input to the first photodetector (13), the second photodetector (14), and the Nth photodetector (15) to achieve photoelectric conversion to obtain electrical signals, which are respectively input to the first photodetector (14) and the Nth photodetector (15). The comparator (16), the second comparator (17) and the Nth comparator (18) compare with the threshold to complete the conversion of the analog signal to the digital signal; N≥3.

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