CN112684650B - Photon analog-to-digital conversion method and system based on weighted modulation curve - Google Patents
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Abstract
The invention relates to a photon analog-digital conversion method and a system based on a weighted modulation curve, wherein the quantization precision of a photon analog-digital conversion system is improved by utilizing the weighted modulation curve through combining a phase-shifting light quantization technology and weighted multi-wavelength sampling pulses; the system utilizes a weighted multi-wavelength pulse source to generate weighted multi-wavelength sampling light pulses, and radio frequency analog signals are modulated onto the weighted multi-wavelength sampling light pulses through a Mach-Zehnder modulator. The modulation signal is accessed into the dispersion element to realize the time domain walk-off of the multi-wavelength pulse, and then the photoelectric detector performs photoelectric conversion and is accessed into the comparator to perform threshold comparison, thereby realizing the conversion from the analog signal to the digital signal; compared with the traditional photon analog-to-digital conversion system, the scheme realizes uniform quantization of the analog input signal by using the weighting modulation curve, thereby realizing the improvement of the bit precision of the photon analog-to-digital conversion system, and simultaneously, the system has simple structure and is easy to realize.
Description
Technical Field
The invention belongs to the technical field of signal processing of optical communication, and particularly relates to a photon analog-to-digital conversion method and system based on a weighted modulation curve.
Background
Analog-to-digital converters (ADCs) serve as a bridge between the Analog world and the digital world, and ADCs play a vital role in electronic products, precision instruments and aeronautical communications. Over the past decade, electronic ADCs have made great advances in increasing sampling rates and resolution. However, with the advent of radar systems, real-time monitoring, and medical imaging applications that require both large bandwidth and high resolution, the performance of conventional electronic ADCs has reached a limit. Due to inherent electronic limitations such as radio frequency delay, time jitter, electromagnetic interference and the like, the conventional electronic ADC cannot meet the requirements of large bandwidth and high precision of the conventional signal processing system. With the development of photonic devices and technologies, photonic ADCs can avoid the disadvantage of a conventional electronic ADC that trades off energy efficiency and bandwidth. First, the photonic ADC has advantages of low loss, large bandwidth, and no electromagnetic interference, compared to the conventional electronic ADC. Secondly, the sampling light pulse generated by the mode-locked laser has the excellent characteristics of high repetition frequency and low time jitter, the clock jitter of the sampling light pulse is two quantities lower than the electronic clock jitter, and the speed can reach more than 100 GS/s. By virtue of the advantages of the photon technology, the photon analog-to-digital conversion technology has great development prospect in the aspect of improving the performance of a digital signal processing system.
In 1979, Taylor first proposed a photonic ADC scheme based on a mach-zehnder modulator (MZM) array. In the scheme, the transfer function periods of the modulators are different, so that quantization coding of different input signals is realized. But the biggest disadvantage of this solution is that the half-wave voltage of the modulator needs to be reduced by a factor of 2. Due to the limitation of the manufacturing process, when the number of optical channels exceeds 4, the half-wave voltage of the modulator is difficult to be realized, and is less than 1V. To avoid this problem Stigwall proposed in 2005 to implement quantization coding of the radio frequency signal using a spatial MZ interference structure. According to the scheme, a phase modulator on one arm of a spatial interferometer modulates an analog signal and then generates spatial interference with an optical signal on the other arm, and a plurality of optical detectors are integrated on one chip according to a certain spatial position to realize phase-shifting optical quantization. However, the Stigwall scheme is susceptible to environmental influences, and has a complex structure, large insertion loss and difficult technical implementation. In order to improve the stability of a system and better realize phase-shifting light quantization, researchers provide a series of coding quantization schemes, wherein the coding quantization schemes comprise a parallel MZM scheme; adopting a photon quantization scheme of polarized light interference; adopting an MZM scheme with unequal arm length; a phase modulator and delay line interferometer are used to implement quantization schemes for differential encoding, etc. Phase-shifted optical quantization is the quantization coding of an input signal by different transfer functions with constant phase difference. However, the phase-shift quantization technique can only realize 2N quantization levels for N optical channels, and the Taylor scheme can realize uniform quantization of 2N quantization levels for the same number of optical channels. The low system bit resolution becomes a major limitation of phase-shifted quantization schemes. In order to improve the bit precision of a photonic analog-to-digital conversion system, a scheme for improving the bit precision of the system by using a plurality of comparators is proposed in 2009, wherein a symmetric digital system (SNS) is used to connect a plurality of comparators behind each modulator to improve the bit precision of the system. The number of comparators used in the scheme is large, so that the system structure is complex and is not beneficial to integration. A cascade-based quantization scheme was proposed in 2014. The scheme utilizes the directional coupler array as a second-stage quantization, and further quantizes the output power of the first-stage quantization so as to increase the quantization level number of the system. 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 results in increased system quantization noise, resulting in a severe reduction of system ENOB. In 2018, a quantization scheme for realizing linear combination of detection signals by using a circuit is provided, and the scheme equivalently realizes the effect of increasing the number of channels by linearly combining the detection signals by using a logic circuit. However, the bandwidth requirement for the logic electronics in this solution is large and the system is complex. In 2020, a serial flash quantization scheme is proposed, in which pulses are separated by using a dispersion element, so that an input signal is quantized to obtain serial output of a digital signal, thereby simplifying the system structure. However, this scheme can only work in small signal modulation, and it is necessary to control the MZM bias at the quadrature point and the modulation depth is small to achieve 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 bit precision of the system still remains a considerable problem to be researched.
In view of the above problems, it is necessary to improve them.
Disclosure of Invention
The invention provides a photon analog-digital conversion method and a system based on a weighted modulation curve aiming at the defects of the existing photon analog-digital conversion technology.
In order to achieve the above purposes, the technical scheme adopted by the invention is as follows: a photon analog-to-digital conversion method based on a weighted modulation curve comprises the following steps:
s1, dividing a weighted multi-wavelength sampling optical pulse emitted by a weighted multi-wavelength pulse source into N paths of parallel multi-wavelength sampling optical pulses through an optical beam splitter;
s2, the N paths of parallel multi-wavelength sampling light pulses respectively modulate analog radio frequency signals in a first Mach-Zehnder modulator, a second Mach-Zehnder modulator and an Nth Mach-Zehnder modulator and output N paths of modulation signals;
s3, outputting N paths of optical modulation signals by the first Mach-Zehnder modulator, the second Mach-Zehnder modulator and the Nth Mach-Zehnder modulator, and accessing the optical modulation signals into the first dispersion element, the second dispersion element and the Nth dispersion element to obtain N paths of modulated pulse signals with separated time domains;
and S4, the N paths of modulated signals are respectively input into the photoelectric converter to be subjected to photoelectric conversion, then the signals are connected into corresponding comparators, the signals are compared with preset comparator judgment threshold values, when the input voltage is greater than the threshold values, the judgment output is '1', otherwise, the judgment output is '0', and therefore the analog signals are converted into digital signals.
As a preferable scheme of the invention, the total number of the wavelengths of the weighted multi-wavelength sampling optical pulses emitted by the weighted multi-wavelength pulse source is M (M is more than or equal to 3), and the pulse power normalization P of the ith wavelengthi(i ═ 1, 2.., M) is expressed as:
in a preferred embodiment of the present invention, in step S2, the analog RF signal is generated by the signal generator and is synchronously inputted to the first Mach-Zehnder modulator, the second Mach-Zehnder modulator, and the Nth Mach-Zehnder modulator (N.gtoreq.3), and the analog RF signal has a peak-to-peak value Vπ(2NM-M+1)/(2NM)。
In a preferred embodiment of the present invention, the first mach-zehnder modulator, the second mach-zehnder modulator, and the nth mach-zehnder modulator output N-channel modulation signals each having an initial phase
The expression of (a) is:
in a preferred embodiment of the present invention, the initial phases of the N-channel modulation signals of the first mach-zehnder modulator, the second mach-zehnder modulator, and the nth mach-zehnder modulator are controlled by providing bias voltages from the first direct-current power supply, the second direct-current power supply, and the nth direct-current power supply, respectively, such that N modulator bias voltages V are setbjThe expression is as follows:
in a preferred embodiment of the present invention, in step S2, the intensities of the optical signals output from the first mach-zehnder modulator, the second mach-zehnder modulator, and the nth mach-zehnder modulator
The expression of (a) is:
wherein,
representing the phase shift introduced by the input analog signal.
In a preferred embodiment of the present invention, in step S3, the first dispersive element, the second dispersive element, and the nth dispersive element separate the input N multi-wavelength superposition modulated pulses by group velocity dispersion effect, and the multi-wavelength pulses are separated in the time domain and do not overlap with the next periodic pulse.
In a preferred embodiment of the present invention, in step S4, the comparator threshold is set to 1/2 of the maximum power of the input pulse, the photoelectrically converted electrical signal is compared with the comparator threshold, and when the input voltage is greater than the threshold, the output is determined to be "1", otherwise, the output is "0", thereby converting the analog signal into a digital signal.
A photon analog-to-digital conversion system based on a weighted modulation curve comprises a weighted multi-wavelength pulse source, an optical beam splitter, a first Mach-Zehnder modulator, a second Mach-Zehnder modulator, an Nth Mach-Zehnder modulator, a signal generator, a first direct-current power supply, a second direct-current power supply, an Nth direct-current power supply, a first dispersive element, a second dispersive element, an Nth dispersive element, a first photoelectric detector, a second photoelectric detector, an Nth photoelectric detector, a first comparator, a second comparator and an Nth comparator; the weighted multi-wavelength pulse source is used for emitting multi-wavelength sampling light pulses, the signal generator is used for generating analog radio frequency signals and synchronously inputting the analog radio frequency signals into the first Mach-Zehnder modulator, the second Mach-Zehnder modulator and the Nth Mach-Zehnder modulator, and the first direct current power supply, the second direct current power supply and the Nth direct current power supply are respectively used for providing bias voltages for the first Mach-Zehnder modulator, the second Mach-Zehnder modulator and the Nth Mach-Zehnder modulator; the multi-wavelength sampling optical pulse is divided into N paths of sampling pulses through an optical splitter, the N paths of sampling optical pulses respectively enter a first Mach-Zehnder modulator, a second Mach-Zehnder modulator and an Nth Mach-Zehnder modulator to simultaneously modulate the analog radio frequency signal, and N paths of modulation signals are output; the N paths of modulated signals respectively pass through a first dispersive element, a second dispersive element and an Nth dispersive element to obtain modulated pulse signals of which the time domains are not overlapped, the modulated signals of which the time domains are separated are respectively input into a first photoelectric detector, a second photoelectric detector and an Nth photoelectric detector to realize photoelectric conversion to obtain electric signals, and the electric signals are respectively input into a first comparator, a second comparator and an Nth comparator to be compared with a threshold value to finish the conversion from analog signals to digital signals.
The invention has the beneficial effects that: compared with the prior art, the photon analog-to-digital conversion method and system based on the weighting modulation curve, which are provided by the invention, realize the coding quantization of the input signal by utilizing the weighting modulation curve through combining the phase-shifting light quantization technology and the weighting multi-wavelength sampling pulse, greatly improve the bit precision of the photon analog-to-digital conversion system, and have simple system structure and easy realization.
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FIG. 1 is a schematic structural diagram of a first embodiment of a system and method for photon analog-to-digital conversion based on a weighted modulation curve according to the present invention;
FIG. 2 is a schematic diagram of a modulation curve of a first embodiment of the weighted modulation curve-based photon analog-to-digital conversion system and method of the present invention;
reference numbers in the figures: the optical fiber multi-wavelength pulse source comprises a weighted multi-wavelength pulse source 1, an optical beam splitter 2, a first Mach-Zehnder modulator 3, a second Mach-Zehnder modulator 4, a third Mach-Zehnder modulator 5, a signal generator 6, a first direct current power supply 7, a second direct current power supply 8, a third direct current power supply 9, a first dispersion element 10, a second dispersion element 11, a third dispersion element 12, a first photoelectric detector 13, a second photoelectric detector 14, a third photoelectric detector 15, a first comparator 16, a second comparator 17 and a third comparator 18.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
The first embodiment is as follows:
as shown in fig. 1, the photon analog-to-digital conversion system based on a weighted modulation curve provided by the present invention includes a weighted multi-wavelength pulse source 1, an optical splitter 2, a first mach-zehnder modulator 3, a second mach-zehnder modulator 4, a third mach-zehnder modulator 5, a signal generator 6, a first dc power supply 7, a second dc power supply 8, a third dc power supply 9, a first dispersive element 10, a second dispersive 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; the weighted multi-wavelength pulse source 1 is used for emitting multi-wavelength sampling light pulses, the signal generator 6 is used for generating analog radio frequency signals and synchronously inputting the analog radio frequency signals into the first Mach-Zehnder modulator 3, the second Mach-Zehnder modulator 4 and the third Mach-Zehnder modulator 5, and the first direct current power supply 7, the second direct current power supply 8 and the third direct current power supply 9 are respectively used for providing bias voltages for the first Mach-Zehnder modulator 3, the second Mach-Zehnder modulator 4 and the third Mach-Zehnder modulator 5; the multi-wavelength sampling light pulse is divided into three sampling pulses through the optical beam splitter 2, the three sampling light pulses respectively enter the first Mach-Zehnder modulator 3, the second Mach-Zehnder modulator 4 and the third Mach-Zehnder modulator 5 to simultaneously modulate the analog radio frequency signal, and three modulation signals are output; the three paths of modulation signals respectively pass through a first dispersive element 10, a second dispersive element 11 and a third dispersive element 12 to obtain modulated pulse signals with non-overlapping time domains, the modulated signals with the separated time domains are respectively input into a first photoelectric detector 13, a second photoelectric detector 14 and a third photoelectric detector 15 to realize photoelectric conversion to obtain electric signals, and the electric signals are respectively input into a first comparator 16, a second comparator 17 and a third comparator 18 to be compared with threshold values to finish conversion from analog signals to digital signals.
According to the photon analog-digital conversion method and system based on the weighting modulation curve, the phase-shifting light quantization technology is combined with the weighting multi-wavelength sampling pulse, the weighting modulation curve is used for realizing coding quantization of an input signal, the bit precision of the photon analog-digital conversion system is greatly improved, and meanwhile, the system is simple in structure and easy to realize.
Specifically, this example provides a photon analog-to-digital conversion method based on a weighted modulation curve, which specifically includes:
as shown in fig. 1, a 4-bit photon analog-to-digital conversion system is taken as an example.
S1, dividing weighted multi-wavelength sampling optical pulses emitted by a weighted multi-wavelength pulse source into three parallel multi-wavelength sampling optical pulses through an optical beam splitter;
s2, the three paths of parallel multi-wavelength sampling light pulses respectively modulate analog radio frequency signals in a first Mach-Zehnder modulator, a second Mach-Zehnder modulator and a third Mach-Zehnder modulator and output three paths of modulation signals;
s3, the first Mach-Zehnder modulator, the second Mach-Zehnder modulator and the third Mach-Zehnder modulator output three paths of optical modulation signals to be accessed into the first dispersive element, the second dispersive element and the third dispersive element, and three paths of modulated pulse signals with separated time domains are obtained;
and S4, inputting each signal of the three paths of modulated signals into a photoelectric converter respectively, performing photoelectric conversion, then accessing a corresponding comparator, comparing the signal with a preset comparator judgment threshold value, judging that the output is 1 when the input voltage is greater than the threshold value, and otherwise, outputting the output is 0, so that the analog signals are converted into digital signals.
Fig. 1 is a schematic structural diagram of a photon analog-to-digital conversion method based on a weighted modulation curve, which includes a weighted multi-wavelength pulse source 1, an optical splitter 2, a first mach-zehnder modulator 3, a second mach-zehnder modulator 4, a third mach-zehnder modulator 5, a signal generator 6, a first dc power source 7, a second dc power source 8, a third dc power source 9, a first dispersive element 10, a second dispersive 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 multiwavelength sampled optical pulse emitted by the weighted multiwavelength pulse source is split into three parallel multiwavelength sampled optical pulses by the optical splitter;
the weighted multi-wavelength pulse source 1 is connected with a first Mach-Zehnder modulator 3, a second Mach-Zehnder modulator 4 and a third Mach-Zehnder modulator 5 through an optical beam splitter 2.
The total wavelength of weighted multi-wavelength sampling optical pulses emitted by a weighted multi-wavelength pulse source 1 is 3, and the pulse power normalization P of the ith wavelengthi(i ═ 1,2,3) is represented by:
in step S2, the three parallel multi-wavelength sampling optical pulses respectively modulate analog radio frequency signals in the first mach-zehnder modulator, the second mach-zehnder modulator, and the third mach-zehnder modulator, and output three modulation signals;
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 first dc power supply 7, the second dc power supply 8, and the third dc power supply 9 are connected to the first mach-zehnder modulator 3, the second mach-zehnder modulator 4, and the third mach-zehnder modulator 5, respectively.
The analog radio frequency signal generated by the signal generator 6 is synchronously inputted 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 8Vπ(iii)/9; initial phases of three modulation signals output from the first Mach-Zehnder modulator 3, the second Mach-Zehnder modulator 4 and the third Mach-Zehnder modulator 5
The expression of (a) is:
first Mach-The initial phases of the three modulation signals output by the Zehnder modulators 3, the second Mach-Zehnder modulators 4 and the third Mach-Zehnder modulators 5 are respectively controlled by bias voltages provided by the first direct current power supply 7, the second direct current power supply 8 and the third direct current power supply 9, so that the bias voltages V of the three modulators are controlledbjThe expression is as follows:
the intensities of optical signals output from the first Mach-Zehnder modulator 3, the second Mach-Zehnder modulator 4, and the third Mach-Zehnder modulator 5
The expression of (a) is:
wherein,
representing 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 paths of optical modulation signals to access the first dispersive element, the second dispersive element, and the third dispersive element, and obtain three paths of time-domain separated modulated pulse signals;
the first mach-zehnder modulator 3, the second mach-zehnder modulator 4, and the third mach-zehnder modulator 5 are connected to the first dispersive element 10, the second dispersive element 11, and the third dispersive element 12, respectively.
The first dispersion element 10, the second dispersion element 11 and the third dispersion element 12 separate the input three multi-wavelength overlapped modulated pulses 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.
In step S4, each of the three modulated signals is input into a photoelectric converter for photoelectric conversion, and then is connected to a corresponding comparator, and the three modulated signals are compared with a preset comparator decision threshold, where the decision output is "1" when the input voltage is greater than the threshold, and the output is "0" otherwise, so as to convert the analog signal into a digital signal.
The first comparator 16, the second comparator 17, and the third comparator 18 are connected to the first dispersing element 10, the second dispersing element 11, and the third dispersing element 12 through the first photodetector 13, the second photodetector 14, and the third photodetector 15.
The threshold values of the first comparator 16, the second comparator 17 and the third comparator 18 are all set to be one-half of the maximum power of the input pulse, the photoelectrically converted electrical signal is compared with the threshold value of the comparator, when the input voltage is greater than the threshold value, the output is judged to be '1', otherwise, the output is '0', and thus the analog signal is converted into the digital signal.
Fig. 2 is a schematic diagram of a modulation curve. The figure shows transfer function curves and quantized coding results corresponding to three mach-zehnder modulators, with a weighted multi-wavelength pulse having a total number of three wavelengths as a sampling pulse. The abscissa thereof represents the amount of phase shift introduced by the input analog signal, and the ordinate represents the normalized output of the optical signal intensity; weighting the power ratio P of multiple wavelength pulses to achieve uniform quantization1:P2:P31:0.7451:0.6087, 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 decision is completed, a digital signal converted from an analog signal is obtained, as shown in the lower part of fig. 2. The output has 16 code words in total, so the bit precision of the photon ADC system is 4 bits. The total quantization technique which can be realized by using weighted multi-wavelength pulses with the total number of wavelengths M as a sampling source and inputting the weighted multi-wavelength pulses into N modulators is L2 NM-M +1, and the bit resolution which can be realized by a photon analog-to-digital conversion system is B log2(2NM-M+1)。
According to the photon analog-digital conversion method and system based on the weighting modulation curve, the phase-shifting quantization technology and the weighting multi-wavelength sampling pulse are combined, the weighting modulation curve is used for realizing coding quantization of input signals, the bit precision of the photon analog-digital conversion system is greatly improved, and meanwhile, the system is simple in structure and easy to realize.
The previous description of the disclosed embodiments is provided to enable 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 generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention; thus, the present invention is not intended 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 figures are used more here: weighted multi-wavelength pulse source 1, optical splitter 2, first mach-zehnder modulator 3, second mach-zehnder modulator 4, third mach-zehnder modulator 5, signal generator 6, first direct current power supply 7, second direct current power supply 8, third direct current power supply 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, etc., without excluding the possibility of using other terms. These terms are used merely to more conveniently describe and explain the nature of the present invention; they are to be construed as being without limitation to any additional limitations that may be imposed by the spirit of the present invention.
Claims (9)
1. A photon analog-to-digital conversion method based on a weighted modulation curve is characterized in that: the method comprises the following steps:
s1, dividing a weighted multi-wavelength sampling optical pulse emitted by a weighted multi-wavelength pulse source into N paths of parallel multi-wavelength sampling optical pulses through an optical beam splitter;
s2, the N paths of parallel multi-wavelength sampling light pulses respectively modulate analog radio frequency signals in a first Mach-Zehnder modulator, a second Mach-Zehnder modulator and an Nth Mach-Zehnder modulator, and N paths of modulation signals are output, wherein N is more than or equal to 3;
s3, outputting N paths of optical modulation signals by the first Mach-Zehnder modulator, the second Mach-Zehnder modulator and the Nth Mach-Zehnder modulator, and accessing the optical modulation signals into the first dispersion element, the second dispersion element and the Nth dispersion element to obtain N paths of modulated pulse signals with separated time domains;
and S4, the N paths of modulated signals are respectively input into the photoelectric converter to be subjected to photoelectric conversion, then the signals are connected into corresponding comparators, the signals are compared with preset comparator judgment threshold values, when the input voltage is greater than the threshold values, the judgment output is '1', otherwise, the judgment output is '0', and therefore the analog signals are converted into digital signals.
2. The method of claim 1, wherein the modulation curve is weighted according to the following equation: the total wavelength of the weighted multi-wavelength sampling optical pulse emitted by the weighted multi-wavelength pulse source is M which is not less than 3, and the pulse power normalization P of the ith wavelengthi(i ═ 1, 2.. times, M), expressed as:
3. the method of claim 1, wherein the modulation curve is weighted according to the following equation: in step S2, the analog rf signal is generated by the signal generator and is synchronously input to the first mach-zehnder modulator, the second mach-zehnder modulator, and the nth mach-zehnder modulator, N is greater than or equal to 3, and the peak-to-peak value of the analog rf signal is Vπ(2NM-M+1)/(2NM)。
4. The method of claim 3, wherein the modulation curve is weighted according to the following equation: the initial phase of N-path modulation signals output by the first Mach-Zehnder modulator, the second Mach-Zehnder modulator and the Nth Mach-Zehnder modulator
The expression of (a) is:
5. the method of claim 4, wherein the modulation curve is weighted according to the following equation: the initial phases of N modulation signals of the first Mach-Zehnder modulator, the second Mach-Zehnder modulator and the Nth Mach-Zehnder modulator are respectively controlled by providing bias voltages by the first direct-current power supply, the second direct-current power supply and the Nth direct-current power supply so as to enable the N modulator bias voltages V to be controlledbjThe expression is as follows:
6. the method of claim 1, wherein the modulation curve is weighted according to the following equation: in the step S2, the intensity of the optical signal output from the first Mach-Zehnder modulator, the second Mach-Zehnder modulator, and the Nth Mach-Zehnder modulator
The expression of (a) is:
wherein,
representing the phase shift introduced by the input analog signal.
7. The method of claim 1, wherein the modulation curve is weighted according to the following equation: in step S3, the first dispersive element, the second dispersive element, and the nth dispersive element separate the input N multi-wavelength overlapped modulated pulses 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. The method of claim 1, wherein the modulation curve is weighted according to the following equation: in step S4, the comparator determines that the threshold is set to 1/2 of the maximum power of the input pulse, compares the photoelectrically converted electrical signal with the comparator threshold, determines that the output is "1" when the input voltage is greater than the threshold, and otherwise outputs "0", thereby converting the analog signal into a digital signal.
9. A photon analog-to-digital conversion system based on a weighted modulation curve is characterized by comprising a weighted multi-wavelength pulse source (1), an optical beam splitter (2), a first Mach-Zehnder modulator (3), a second Mach-Zehnder modulator (4), an Nth Mach-Zehnder modulator (5), a signal generator (6), a first direct-current power supply (7), a second direct-current power supply (8), an Nth direct-current power supply (9), a first dispersion element (10), a second dispersion element (11), an Nth dispersion element (12), a first photoelectric detector (13), a second photoelectric detector (14), an Nth photoelectric 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, the signal generator (6) is used for generating analog radio frequency signals and synchronously inputting the analog radio frequency signals into the first Mach-Zehnder modulator (3), the second Mach-Zehnder modulator (4) and the Nth Mach-Zehnder modulator (5), and the first direct current power supply (7), the second direct current power supply (8) and the Nth direct current power supply (9) are respectively used for providing bias voltages for the first Mach-Zehnder modulator (3), the second Mach-Zehnder modulator (4) and the Nth Mach-Zehnder modulator (5); the multi-wavelength sampling optical pulse is divided into N paths of sampling pulses through an optical beam splitter (2), the N paths of sampling optical pulses respectively enter a first Mach-Zehnder modulator (3), a second Mach-Zehnder modulator (4) and an Nth Mach-Zehnder modulator (5) to simultaneously modulate analog radio frequency signals, and N paths of modulation signals are output; the N paths of modulation signals respectively pass through a first dispersion element (10), a second dispersion element (11) and an Nth dispersion element (12) to obtain modulated pulse signals with separated time domains, the modulated signals with the separated time domains are respectively input into a first photoelectric detector (13), a second photoelectric detector (14) and an Nth photoelectric detector (15) to realize photoelectric conversion to obtain electric signals, and the electric signals are respectively input into a first comparator (16), a second comparator (17) and an Nth comparator (18) to be compared with a threshold value to finish conversion from analog signals to digital signals; n is more than or equal to 3.
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