Research On Phase And Amplitude Regeneration Technology For Advanced Modulator Signals

Phase sensitive amplifier (PSA) possessing the unique phase selection, hign gain,low noise figure (0 dB in theroy), fast speed and broad bandwith characteristics, can be used as a regenerator to regenerate optical signals with advanced modulation format, and remedy the phase insensitive defect of phase insensitive amplifier (PIA).However, PSA deteriorates amplitude characteristics during the phase squeezing because it converts part of phase noise into amplitude noise. Furthermore, due to Gordon-Mollenauer effect4, the amplitude noise converts into the phase noise in turn during transmission, degrading signal quality. This thesis is the research on solving the above problems. A modified Mach-Zehnder Interferometer phase sensitive amplifier (MMZI-PSA) has been proposed to achieve amplitude and phase regeneration of signals simultaneously. The main results of this thesis are as follows:Firstly, the thesis presents a theoretical derivation on four-wave mixing (FWM)effects. The principle and mechanism is analyzed for FWM effect and phase mismatch. From the above theories, the major factors of FWM efficiency are obtained,such as the spectrum intervals, the length and working wavelength of the fiber,dispersion and attenuation coefficient, etc. And five methods are discussed to impove the effective of FWM. Selecting appropriate spectrum intervals and fiber length,working in zero dispersion wavelengths, compensating by self-phase modulation(SPM) and cascading FWM are all optional.Secondly, this thesis presents a study on phase sensitive amplified technology based on FWM. A theoretical derivation of phase sensitive amplified technology based on FWM is discussed by means of electronmagnetic fields. Combined with the simulation using Matlab, the problems and development bottleneck of the exsiting PSA are presented. Then, the thesis proposes a novel phase sensitive amplified technology to solve the problem of introducing amplified noises when regenerating phase, achieving phase and amplitude regeneration, simutanously. Finally, a modified Mach-Zehnder interferometer phase sensitive amplier (MMZI-PSA) is proposed, and has been verified from the perspective of the theory and Matlab simulation.Finally, this thesis presents a simulation on MMZI-PSA to verify its feasibility and system regeneration performances. The traditional four-wave mixing phase sensitive amplifier (FWM-PSA) is used as contrast experiment to better demonstrate the regeneration performances of MMZI-PSA. The constellation, bit error rate (BER)and error vector magnitude (EVM) of regenerated QPSK signals are discussed in different noise level. In the low noise level, the BER of MMZI-PSA has ameliorated to 44%, and the EVM of MMZI-PSA has ameliorated to 10%, compared to FWM-PSA on the condition of 13dB OSNR. In the high noise level, the BER and EVM of MMZI-PSA have ameliorated to 48% and 16%, respectively. Regardless of constellation, BER or EVM, MMZI-PSA exhibts better performances than FWM-PSA.MMZI-PSA effectively overcomes performance deficiencies of FWM-PSA, which introduces amplitude noise during phase regeneration process. Although both schemes have similar phase regeneration characteristics, an obvious difference in amplitude characteristics is observed that MMZI-PSA well reduces phase-to-amplitude noise conversion.In conclusion, the above results provide a new idea to the reseach and application for all optical phase sensitive amplified technology. It plays an import role to promote all optical networks moving towards faster speed, higher capacity.