Research On The Phase-encoded Optical Sampling Based On Optical Frequency Multiplication Method Using Mach-zehnder Modulator

The technology of optical analog-to-digital conversion(OADC)is the most promising technology to realize high-speed analog signal digitization and break through the bottleneck of traditional ADC electronic.The OADC technology is also the most competitive in terms of conversion speed,conversion accuracy,security,and anti-interference.It is of great significance to modern communication system.Since the scheme of optical phase coded analog-to-digital conversion was proposed by Taylor in1975,scientists all over the world have been studied it more than 40 years.Many new schemes and methods of the OADC have been presented;however,the research work is still an important challenge of the whole world.Whether it's critical components,key technologies or overall architecture,there has been no breakthrough.On the basis of understanding the research trends at home and abroad,a new scheme of analog to digital conversion is studied and proposed,which solves the mutually exclusion between the sampling frequency and the quantization precision of Taylor's optical ADC schemes.Firstly,the Taylor's scheme and its improved schemes are studied.The research results show that these schemes have failed to break the mutual restriction between sampling rate and quantization precision,and results of high work voltage.To solve these problems,a scheme of analog-to-digital conversion based on optical frequency multiplication is proposed in this paper.The scheme uses nonlinear modulation of M-Z modulator to generate harmonic of modulation signal,and extracts specific harmonic to form phase coded array.Then our proposed scheme solves the shortcomings of the Taylor's optical ADC scheme,which is originated from sampling rate and quantization accuracy are both limited by the modulation electrode and transit time increasing by 2the power of n bits,and thus simplified the front-end circuit system of the analog to digital conversion system.Secondly,the generation and acquisition method of frequency multiplication harmonic signal for the optical frequency conversion scheme is studied.Many techniques generation 1,2,4 and 8 multiplication frequency signals without filters aretheoretically analyzed and studied.A 16 multiplication frequency signal generation scheme for a dual parallel M-Z modulator followed a one modulating arm M-Z modulator is proposed and verified by simulation experimentsThirdly,combining OptiSystem with MATLAB,the frequency multiplication signal generation simulation system and the optical analog to digital conversion system based on the frequency multiplication method are set up.The system can support the analog to digital conversion of RF signal with bandwidth of 19 GHz,the effective digit is 5 bits,and the quantization grade is extended to 32.The highest sampling rate is 304Gs/s.Simulation results show that the proposed scheme based on optical frequency conversion module is feasible.