Research On Some Key Issues In Ultra-low Noise Optical Fiber Amplifier Based On Phase Sensitive Parametric Amplification

Nowadays,a new round of technological revolution and industrial transformation led by artificial intelligence is in the ascendant.Driven by new technologies and concepts such as edge computing,Internet of Things,mobile Internet and brain science,the amount of business data has shown explosive growth,and the transmission rate,transmission bandwidth and transmission distance of optical fiber communication system have been put forward.As one of the key devices in the optical fiber communication system,all-optical amplifier is also facing the severe challenges of higher gain,wider bandwidth,lower noise and smaller flatness.With the breakthroughs in the manufacturing of non-linear gain materials and high-performance laser technology,optical fiber parametric amplifier(FOPA)provides a solution for all-optical amplification in future optical fiber communications.The gain of one FOPA can be flexibly designed,providing flat broadband and high gain signal amplification over communication band,moreover the noise performance is more prominent.Especially when FOPA works in phase-sensitive mode,the noise figure(NF)can approach 0 dB and realize ultra-low noise all-optical amplification.In addition,FOPA has the characteristics of ultra-fast response,wavelength conversion,all-optical sampling,3R regeneration and phase compression.Therefore,as an ultra-low noise all-optical amplifier,FOPA has attracted a lot of attention at home and abroad.In this dissertation,the gain and noise performance of phase-insensitive(PI)and phase-sensitive(PS)FOPAs are studied theoretically and experimentally.The gain equalization scheme of cascaded PS-FOPAs,low-noise transmission scheme of optical orthogonal frequency division multiplexing(OFDM)signals and multi-cascaded FOPAs are studied.Broadband gain flattening optimization scheme to meet the amplification requirements of high-speed,large-capacity,long-distance optical fiber communication systems.The main research work and innovations of this paper are as follows:1.Research on cascaded PS-FOPA gain equalization scheme based on dispersion component fiberBased on the gain theory of cascaded PS-FOPA,a parametric gain equalization scheme is proposed,and the equalization effect is verified by 10-channel WDM signal.The results show that this scheme can effectively suppress the difference of output optical power of cascaded PS-FOPA amplified WDM signals,and reduce the optical power difference about 14dB between WDM signals after equalization,so that all channel signals can achieve error-free transmission.This scheme can improve the compatibility between PS-FOPA and WDM system.2.Research on OFDM signal low noise transmission scheme based on cascaded PS-FOPABased on the theoretical study of PI-FOPA noise performance,three different noise characteristics,namely amplified quantum noise,pump transfer noise and Raman extra noise,are simulated and experimentally studied.Based on the theoretical and experimental study of cascaded PS-FOPA noise performance,a low noise transmission scheme for OFDM signal with black subcarrier interpolation is proposed.The phase sensitive parametric amplification cascaded structure can effectively suppress the influence of pump transfer noise by on-line amplification of black subcarrier interpolation OFDM signals.The results show that the OFDM signal has better lower noise transmission characteristics and longer distance in parametric amplification link.3.Research on optimizing scheme for gain flatness of multi-stage cascaded PI-FOPABased on the study of differential evolution algorithm,a multi-stage cascaded PI-FOPA wideband gain flattening optimization scheme is proposed.The wide-band flattening optimization of PI-FOPA parametric gain spectrum is realized by constructing a multi-stage cascade PI-FOPA mathematical model and improved differential evolution algorithm.After optimizing the four stage of HNLF gain medium,the gain spectrum with 400 nm gain bandwidth,20 dB average gain and less than 0.5 dB gain fluctuation is obtained.4.Research on optimizing scheme of gain flatness for multi-stage cascaded PS-FOPABased on PI-FOPA broadband gain flatness optimization scheme,a multi-stage cascade PS-FOPA broadband gain flatness optimization scheme is proposed.The wide-band flattening optimization of PS-FOPA parametric gain spectrum is realized by using the mathematical model of multi-cascade PS-FOPA and the improved differential evolution algorithm,and the parameters of HNLF is obtained.The PS-FOPA gain spectra with 225 nm gain bandwidth,10.9 dB average parametric gain and gain fluctuation less than 0.4 dB are obtained by four-stage gain medium optimization.