Research On All-Optical Quantization Based On Fiber Nonlinear Effect

Analog-to-digital conversion plays an important role in signal processing and communication systems.Analog-to-digital converters with large analog bandwidths,high sampling rates,and high quantization resolution have always been the goals pursued by people.Analog-to-digital conversion is composed of sampling,quantization,and encoding,sampling and quantization mainly determine the performance of the analog-to-digital converter.In the traditional electrical analog-to-digital conversion,it is difficult to improve its performance due to the mutual limitation of the sampling rate and quantization resolution.All-optical analog-to-digital conversion can not only avoid the bottleneck of the rate of electronic devices,but also resolve the contradiction between the sampling rate and the quantization resolution,so it has caused concern.At present,optical sampling can achieve a rate of more than 100 GS/s.In order to make full use of high-speed optical sampling,the problem of optical quantization needs to be solved urgently.All-optical quantization based on nonlinear effects such as self-phase modulation,cross-phase modulation,and four-wave mixing is expected to achieve higher quantization resolution and miniaturization of devices,so it has important research significance.This thesis has carried out a study on all-optical quantization based on optical nonlinear effects.Slicing the supercontinuum and soliton self-frequency shift are used to achieve all-optical quantization.The specific research work is as follows:1.Based on the quantization principle by slicing supercontinuum,this thesis designs an all-optical quantization scheme that slices supercontinuum generated in highly nonlinear fibers with normal dispersion.The optical quantization is achieved by mapping the input power of pulses to different high-level quantities.The process of generating supercontinuum in an optical fiber is simulated using a nonlinear Schrodinger equation.The width of the supercontinuum is approximately proportional to the input power of the pulse.The wavelength division multiplexing device is used to slice the supercontinuum.The feasibility of the scheme is proved by simulation.The all-optical quantization experiment platform is built,and a 3-bit all-optical quantizer is implemented.Its differential nonlinear error and integral nonlinear error are 0.29 LSB and 0.36 LSB,respectively,which further proves the effectiveness of the scheme.2.Based on the quantization principle by using the soliton self-frequency shift,this thesis designs an all-optical quantization scheme that utilizes soliton self-frequency shift generated in a highly nonlinear fiber with anomalous dispersion.The all-optical quantization is obtained by mapping the pulse input power to the self-frequency shift amount.An all-optical quantization experiment platform is set up to achieve quantization resolution of 2.74 bits.The nonlinear Schrodinger equation is used to simulate the process of generating soliton self-frequency shift in the fiber,and the quantization resolution of 1.7 bits is achieved.Finally,cascading single-mode fibers and highly nonlinear fibers compresses the spectrum for increasing the quantization resolution to 5.6 bits.