Research On Spectral Properties Of Four-wave Mixing Based On Nonlinear Effect In Few-mode Fiber

With the communication capacity of single-mode fiber approaching the nonlinear Shannon limit,it is urgent to develop new techniques.Space-division multiplexing based on few-mode fibers(FMFs)has attracted much attention because it can utilize the space dimension in fibers to increase the communication capacity.However,in fiber communication systems,the influence of nonlinear effect should be taken into consideration.We study the nonlinear effect of FMF,especially explore the joint spectral function of inter-modal four-wave mixing(IM-FWM)theoretically and experimentally.The main content of this thesis includes three major parts:1.The parameters and characteristics of the FMF are simulated by Comsol.We calculate the dispersion,the group velocity and the effective mode area of the FMF and study the phase matching condition of IM-FWM accordingly.2.The effective nonlinear coefficients of the FMF are measured experimentally.By comparing the spectral broadening of the pulse fields induced by self-phase modulation and cross-phase modulation respectively,we obtain the intra-modal effective nonlinear coefficient of LP₁₁ mode and the inter-modal effective nonlinear coefficient between LP₀₁ and LP₁₁ modes.The experimental results are in good agreement with the theoretical predictions of the multi-mode Manakov equations.3.Spectral properties of IM-FWM is studied theoretically and experimentally.First,we calculate the joint spectral function and analyze its relationship to pump bandwidth.Based on the theoretical analysis,we experimentally measure the IM-FWM gain spectral for different pump bandwidths.The experimental results show that uncorrelated IM-FWM gain can be achieved when pump bandwidth is 1.34 nm,which is consistent with the theoretical analysis.