Research On Quantization And Encoding Method In All-optical Analog-to-Digital Conversion Based On Soliton Self-Frequency Shift

All-optical analog-to-digital conversion is the method of processing signals using light as a carrier,which can solve an electronic bottleneck,and is now widely concerned.According to different quantization methods,all-optical analog-to-digital conversion is divided into three categories:amplitude quantization,phase quantization,and frequency quantization.Amplitude quantization has the characteristics of simple principle and mature system,so it is used more.With the development of nonlinear optics,the all-optical analog-to-digital conversion method using optical nonlinear effects has been proposed.The frequency quantization in analog-to-digital conversion system represented by the self-frequency shift of soliton has become one of the research hotspots.Compared with amplitude quantization and phase quantization,it has higher frequency band utilization and better all-optical coding performance.In order to further optimize the existing soliton self-frequency shift quantization and coding scheme for improving the performance of the all-optical analog-to-digital conversion system,the following research works are carried out:1.In order to improve the coding accuracy in all-optical analog-to-digital conversion,a novel directional coupler and the all-optical encoder are designed.Symmetrical and asymmetrical waveguide structures are used in the directional coupler to control the phase of the optical signal during transmission in the waveguide,which can achieve directional coupling over a wide range of wavelengths.The relationship between waveguide size,signal wavelength and coupling ratio is given by numerical calculation.The encoder based on the directional coupler is designed and applied to the all-optical analog-to-digital conversion system by soliton self-frequency shift.The simulation results show that the coupling coefficient fluctuation is reduced by 79.6%in the wavelength range of 100 nm,and the maximum reduction of the intensity error is 24.3%.The total length of the encoder is less than 100?m.2.The new scheme of all-optical quantization based on soliton self-frequency shift effect and coding is proposed.The scheme performs cascaded quantization of frequency and amplitude,and the new coding method is designed to achieve analog-to-digital conversion.This scheme can improve the effective quantization resolution of the existing all-optical quantization system based on the soliton self-frequency shifting by 1.5 bits.The quantized transfer function of the system is obtained by simulation.The integral nonlinearity error and differential nonlinear error are within±0.5LSB.The effects of noise,error and quantization error on the system performance are analyzed.