CN114137777B - Photon digital-to-analog conversion system based on pulse processing - Google Patents
Photon digital-to-analog conversion system based on pulse processing Download PDFInfo
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Abstract
The invention discloses a photon digital-to-analog conversion system based on pulse processing. The invention discloses a photon digital-to-analog conversion system based on pulse processing, which comprises a mode-locked laser and the like, wherein the mode-locked laser is connected with a first Mach-Zehnder modulator, the first code pattern generator is connected with the first Mach-Zehnder modulator, the first Mach-Zehnder modulator is connected with a spectrum shaper through a dispersion optical fiber, the spectrum shaper is connected with a second Mach-Zehnder modulator, the second code pattern generator is connected with the second Mach-Zehnder modulator, the second Mach-Zehnder modulator is connected with a photoelectric detector, and the photoelectric detector is connected with a low-pass filter. The invention has simple structure and easy realization; compared with the prior photon digital-to-analog converter, the digital signal of the invention is serial input and does not need any preprocessing; the weighted superposition of the digital signals can be realized only through one section of dispersion optical fiber, so that the system is greatly simplified and the integration is facilitated.
Description
Technical Field
The invention belongs to the technical field of optical communication signal processing, and particularly relates to a photon digital-to-analog conversion system based on pulse processing.
Background
The digital-to-analog converter can convert digital signals into required analog signals, is a key technology for numerous modern signal processing applications, and has wide application in the fields of arbitrary waveform generation, high-speed communication, sensor networks, broadband radars, electronic countermeasure and the like. However, electronic digital-to-analog converters are subject to high clock jitter and electromagnetic interference, severely affecting the rate and bandwidth of conversion. Photonic digital-to-analog converters have received increasing attention in recent years due to their strong immunity to electromagnetic interference, high speed and large bandwidth. The photon digital-to-analog converter not only provides a higher performance solution, but also has high compatibility with an optical communication network, and can be widely applied to various civil and military fields.
The photon digital-to-analog converter which has been proposed at present can be divided into a parallel mode and a serial mode according to the input mode of the digital signal. For parallel mode, digital-to-analog conversion is achieved in Yacoubias A, das P K. Digital-to-analog conversion using electrooptic modulators [ J ]. IEEE Photonics Technology Letters,2003,15 (1): 117-119. Multiple electro-optic modulators are used to achieve multi-channel intensity weighted summation; digital synthesis using a multi-Electrode Mach-Zehnder interferometer is proposed in Ehrlichman Y, amrani O, ruschin S.improved Digital-to-Analog Conversion Using Multi-electric Mach-Zehnder Interferometer [ J ]. Journal of Lightwave Technology,2009,26 (21): 3567-3575; coherent summation of optical phase modulated signals is used in level A, yang Y, lin J, et al, high speed integrated InP photonic digital-to-analog converter [ C ]// Indium Phosphide and Related Materials Conference Proceedings,2006International Conference on.IEEE,2006 to effect digital-to-analog conversion. The basic concept of these techniques is to weight the intensities of multiple optical carriers and add them according to an electrical digital signal, however, in practical applications, the system bit resolution is limited by the performance of the light source and the accuracy is limited by the multi-channel mismatch. For serial mode, weighted summation is performed by identifying the pattern of the input digital signal in T.Nishitani, et al, all-optical digital-to-analog conversion using pulse pattern recognition based on optical correlation processing, opt.express 13 (25) (2005) 10310-10315, respectively; the dispersive properties of the optical fibers are used in Peng Y, zhang H, zhang Y, yao M. Photonic Digital-to-Analog Converter Based on Summing of Serial Weighted Multiwavelength Pulses [ J ]. IEEE Photonics Technology Letters,2008,20 (24): 2135-2137. To achieve stretching and compression of the optical pulses and Digital-to-analog conversion. In the above scheme, the photon digital-to-analog converter of parallel input can achieve higher bit resolution by using more parallel channels, and the speed requirement of the optical device in each channel can be reduced. However, as the bit resolution increases, the number of channels and the complexity of the system increase, which increases the cost of the system and the difficulty of the synchronization operation. In contrast, the scheme of a serial input digital-to-analog converter is more compact and requires fewer optical devices. Therefore, how to realize a serial photon digital-to-analog conversion system which has simple structure, easy realization and high speed and high performance has important significance for the research of photon digital-to-analog conversion.
Disclosure of Invention
The invention aims to provide a photon digital-to-analog conversion system based on pulse processing by widening and cutting optical pulses according to the existing photon digital-to-analog conversion technology.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the photon digital-to-analog conversion system based on pulse processing comprises a mode-locked laser, a first Mach-Zehnder modulator, a first code pattern generator, a dispersion optical fiber, a spectrum shaper, a second Mach-Zehnder modulator, a second code pattern generator, a photoelectric detector and a low-pass filter; the mode-locked laser is connected with a first Mach-Zehnder modulator, the first code pattern generator is connected with the first Mach-Zehnder modulator, the first Mach-Zehnder modulator is connected with the spectrum shaper through the dispersion optical fiber, the spectrum shaper is connected with a second Mach-Zehnder modulator, the second code pattern generator is connected with the second Mach-Zehnder modulator, the second Mach-Zehnder modulator is connected with the photoelectric detector, and the photoelectric detector is connected with the low-pass filter.
The photon digital-to-analog conversion system based on pulse processing comprises the following steps:
s1, generating an optical pulse sequence by a mode-locked laser and transmitting the optical pulse sequence to a first Mach-Zehnder modulator;
s2, a first code pattern generator generates a digital signal and sends the digital signal to a first Mach-Zehnder modulator intensity modulation optical pulse sequence;
s3, the output signal of the first Mach-Zehnder modulator is transmitted through a dispersion optical fiber and then enters a spectrum shaper, so that the broadening and mutual overlapping of optical pulses are realized;
s4, adjusting the spectrum of the optical pulse sequence by the spectrum shaper, so that different wavelength bands of the optical pulse have different optical powers, and enabling the optical pulse sequence subjected to spectrum adjustment to enter a second Mach-Zehnder modulator;
s5, the second code pattern generator generates a periodical rectangular pulse signal and sends the periodical rectangular pulse signal to the second Mach-Zehnder modulator, and the intensity modulation optical pulse sequence is used for cutting the optical pulse;
s6, the output signal of the second Mach-Zehnder modulator enters a photoelectric detector to be converted into an electric signal;
s7, the electric signals output by the photoelectric detector are subjected to smoothing processing through a low-pass filter, and corresponding analog signals are obtained.
Further, the resolution of the digital-to-analog conversion method and system is N.
Further, the period of the optical pulse sequence generated by the mode-locked laser is T 0 The repetition frequency is f 0 =1/T 0 。
Further, the first pattern generator generates a digital signal having a rate f 1 =f 0 。
Further, the spectrum shaper adjusts the spectrum of the light pulse into N wavelength bands, and the spectrum width of each wavelength band is delta lambda, which satisfies the following conditionsAnd the ratio of the powers of the N wavelength bands is: 2 0 :2 1 :…:2 N-1 。
Further, the rate f of the rectangular pulse signal generated by the second pattern generator 2 =f 0 and/N, duty cycle d=1/N.
Further, the photoelectric converter functions to convert the weighted superimposed optical signal into an electrical signal.
The invention takes the output optical pulse sequence of the mode-locked laser as a carrier, and the digital signal output by the first code pattern generator intensity modulates the optical carrier through the first Mach-Zehnder modulator. After the modulated optical pulse train passes through a section of dispersive medium, the pulses are stretched and adjacent optical pulses overlap each other. The spectrum of the light pulses is adjusted by a spectrum shaper so that different wavelength bands of each pulse have different optical powers. The optical pulse sequence processed by the spectrum shaper is sent to a second Mach-Zehnder modulator, and the rectangular pulse signal generated by the second code pattern generator carries out intensity modulation on the optical pulse sequence, so that the stretched pulse is cut, and the cut signal is the result of the superposition of the weighted intensities of the digital signals. Finally, the optical signal is converted into an electric signal through a photoelectric detector, and then the electric signal is obtained through low-pass filtering.
The beneficial effects of the invention are as follows:
compared with the existing photon digital-analog converter, the digital signal is serial input, no pretreatment is needed, the weighted superposition of the digital signal can be realized only through one section of dispersion optical fiber, the system is greatly simplified, and the integration is facilitated. In addition, the technical scheme of the invention fully utilizes the advantage of large bandwidth of photonics, greatly improves the conversion precision and conversion rate of the system, and provides important guiding significance for the practical application of high-speed high-precision analog-digital conversion.
Drawings
FIG. 1 is a schematic diagram of a photon digital-to-analog conversion system based on pulse processing according to a preferred embodiment;
fig. 2 (a) shows a schematic diagram of a pulse sequence output by a first mach-zehnder modulator in a photon-to-digital conversion system based on pulse processing, and fig. 2 (b) shows a schematic diagram of a signal output by a spectrum shaper and a rectangular pulse signal generated by a pattern generator in a photon-to-digital conversion system based on pulse processing.
FIG. 3 (a) shows simulation results of the output of a photon digital-to-analog conversion system based on pulse processing for a sawtooth signal; fig. 3 (b) shows the output simulation result for the cosine signal.
The method comprises the following steps of 1, locking a mode laser; 2. a first Mach-Zehnder modulator; 3. a first pattern generator, 4. A dispersive optical fiber; 5. a spectrum shaper; 6. a second Mach-Zehnder modulator; 7. a second pattern generator; 8. a photodetector; 9. a low pass filter.
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention. It should be noted that the following embodiments and features in the embodiments may be combined with each other without conflict.
The invention provides a photon digital-to-analog conversion system based on pulse processing by widening and cutting optical pulses according to the existing photon digital-to-analog conversion technology. After the modulated optical pulse train passes through a section of dispersive medium, the pulses are stretched and adjacent optical pulses overlap each other. The spectrum of the light pulses is adjusted by a spectrum shaper so that different wavelength bands of each pulse have different optical powers. The optical pulse sequence processed by the spectrum shaper is sent to a second Mach-Zehnder modulator, the rectangular pulse signal generated by the second code pattern generator carries out intensity modulation on the optical pulse sequence, the cutting of the stretched pulse is realized, the signal obtained by cutting is the result of the superposition of the weighted intensity of the digital signal, and finally the optical signal is converted into the electric signal, and the electric signal can be obtained by low-pass filtering.
Examples:
the embodiment provides a high-speed photon digital-to-analog conversion system based on pulse processing, which comprises the following specific steps:
as shown in fig. 1, a 4-bit photon digital-to-analog conversion system is taken as an example.
In step S1, the mode-locked laser 1 generates an optical pulse train and sends it to the first mach-zehnder modulator 2;
the mode-locked laser 1 is connected to a first mach-zehnder modulator 2.
Period T of the optical pulse train generated by the mode-locked laser 1 0 =100 ps, repetition frequency f 0 =10GHz。
In step S2, the first pattern generator 3 generates a digital signal and sends the digital signal to the first mach-zehnder modulator 2;
the first pattern generator 3 is connected to the first mach-zehnder modulator 2.
The digital signal rate f generated by the first pattern generator 3 1 =10Gbit/s。
In step S3, the output signal of the first mach-zehnder modulator 2 is transmitted through the dispersive optical fiber 4 and then enters the optical spectrum shaper 5;
the signal output from the first mach-zehnder modulator 2 is coupled to a spectrum shaper 5 via a dispersive optical fiber 4.
In step S4, the spectrum shaper 5 adjusts the spectrum of the optical pulse sequence, and the optical pulse sequence after the spectrum adjustment enters the second mach-zehnder modulator 6;
the optical spectrum shaper 5 is connected with the second Mach-Zehnder modulator 6;
the spectrum shaper 5 divides the spectrum of the light pulse into n=4 wavelength bands, the spectral width Δλ=7.5 nm of each wavelength band, and the ratio of the powers of the 4 wavelength bands satisfies: 2 0 :2 1 :2 2 :2 3 。
In step S5, the second pattern generator 7 generates a periodic rectangular pulse signal and sends the periodic rectangular pulse signal to the second mach-zehnder modulator 6;
the second code pattern generator 7 is connected with the second Mach-Zehnder modulator 6;
the rate f of the periodic rectangular pulse train generated by the second pattern generator 7 2 =2.5 Gbit/s, duty cycle d=0.25.
In step S6, the output signal of the second mach-zehnder modulator 6 enters the photodetector 8 to be converted into an electrical signal;
in step S7, the electrical signal output from the photodetector 8 is smoothed by the low-pass filter 9 to obtain a corresponding analog signal.
Fig. 2 (a) shows an output pulse signal of the first mach-zehnder modulator, where the optical pulse is preserved when the modulated digital signal is "1", and blocked when the modulated digital signal is "0". Fig. 2 (b) shows the signals output by the spectrum shaper, realizing that each pulse consists of signals in four wavelength bands, the power of each short wavelength signal being different. The broken line represents a rectangular pulse signal generated by the pattern generator for cutting the stretched pulse signal.
Fig. 3 (a) shows the simulation result of the output of the photon digital-to-analog conversion system for the sawtooth wave signal based on the pulse processing. The abscissa thereof represents time and the ordinate thereof represents signal amplitude. The solid line represents the output electrical signal of the photodetector, i.e., the pulse signal without low-pass filtering, and the broken line represents the saw-tooth wave signal output by low-pass filtering, with a frequency of 156.25MHz. The simulation results are very close to the ideal waveform. Fig. 3 (b) shows the output simulation result for the cosine signal. In accordance with fig. 3 (a), the abscissa indicates time, the ordinate indicates signal amplitude, the solid line indicates an output electric signal of the photodetector, i.e., a pulse signal which is not low-pass filtered, and the broken line indicates a cosine signal which is output by low-pass filtering, and the frequency thereof is 156.25MHz. The simulation results are very close to the ideal waveform.
Compared with the prior art, the photon digital-to-analog conversion system based on pulse processing has the following beneficial effects:
compared with the existing photon digital-to-analog converter, the digital signal is serially input, no pretreatment is needed, the weighted superposition of the digital signal can be realized only through one section of dispersion optical fiber, the system is greatly simplified, and the integration is facilitated. In addition, the technical scheme of the invention fully utilizes the advantage of large bandwidth of photonics, greatly improves the conversion precision and conversion rate of the system, and provides important guiding significance for the practical application of high-speed and high-precision analog-digital conversion.
Note that the above is only a preferred embodiment of the present invention and the technical principle applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, while the invention has been described in connection with the above embodiments, the invention is not limited to the embodiments, but may be embodied in many other equivalent forms without departing from the spirit or scope of the invention, which is set forth in the following claims.
Claims (7)
1. The photon digital-to-analog conversion system based on pulse processing is characterized by comprising a mode-locked laser, a first Mach-Zehnder modulator, a first code pattern generator, a dispersion optical fiber, a spectrum shaper, a second Mach-Zehnder modulator, a second code pattern generator, a photoelectric detector and a low-pass filter; the mode-locked laser is connected with a first Mach-Zehnder modulator, the first code pattern generator is connected with the first Mach-Zehnder modulator, the first Mach-Zehnder modulator is connected with the spectrum shaper through the dispersion optical fiber, the spectrum shaper is connected with a second Mach-Zehnder modulator, the second code pattern generator is connected with the second Mach-Zehnder modulator, the second Mach-Zehnder modulator is connected with the photoelectric detector, and the photoelectric detector is connected with the low-pass filter; the mode-locked laser generates an optical pulse sequence and sends the optical pulse sequence to the first Mach-Zehnder modulator; the first code pattern generator generates a digital signal and sends the digital signal to the first Mach-Zehnder modulator for intensity modulating the optical pulse sequence; the output signal of the first Mach-Zehnder modulator enters a spectrum shaper after being transmitted by a dispersion optical fiber, so that the broadening and mutual overlapping of optical pulses are realized; the spectrum shaper adjusts the spectrum of the optical pulse sequence to enable different wavelength bands of the optical pulse to have different optical powers, and the optical pulse sequence subjected to spectrum adjustment enters the second Mach-Zehnder modulator; the second code generator generates a periodic rectangular pulse signal and sends the periodic rectangular pulse signal to the second Mach-Zehnder modulator, and the intensity modulation optical pulse sequence is used for realizing the cutting of the optical pulse; the output signal of the second Mach-Zehnder modulator enters a photoelectric detector to be converted into an electric signal; the electric signal output by the photoelectric detector is processed by a low-pass filter in a smoothing way to obtain a corresponding analog signal.
2. The pulse-based photonic digital-to-analog conversion system of claim 1, wherein the photonic digital-to-analog conversion system has a bit resolution of N.
3. The pulse-based photonic digital-to-analog conversion system of claim 2 wherein said mode-locked laser produces a sequence of optical pulses with period T 0 The repetition frequency is f 0 =1/T 0 。
4. A photonic digital-to-analog conversion system based on pulse processing according to claim 3 and wherein said first pattern generator generates a digital signal having a rate f 1 =f 0 。
6. The pulse-based photonic digital-to-analog conversion system of claim 5 wherein said spectral shaper adjusts the spectrum of the optical pulse to N wavelength bands, each wavelength band having a spectral width Δλ that satisfiesAnd the ratio of the powers of the N wavelength bands is: 2 0 :2 1 :…:2 N-1 。
7. The digital-to-analog conversion system based on pulse processing according to claim 3 or 4, wherein the rate f of the rectangular pulse signal generated by the second pattern generator 2 =f 0 and/N, duty cycle d=1/N.
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