Research On All-Optical Processing Technology Of Multi-Level Phase-Modulated Signals

All-optical signal processing technology is the future direction of the evolution of the optical fiber communication network,and capable of overcoming the speed limitation of electronics since the signals are directly operated in the optical domain.Four-wave mixing(FWM)is widely used in all-optical signal processing devices such as optical parametric amplifier,all-optical regenerator and optical logic gate.According to the analytic solution of FWM parametric process under pump depletion,the performance of all-optical regeneration and phase arithmetic operation for multi-level phase-modulated signals in highly-nonlinear fibers(HNLFs)are analyzed by using the Matlab programming method.The main contents and innovations are listed as follows:1.The analytic solutions to the coupled-mode equations for degenerate and non-degenerate FWM under pump depletion are deduced in detail.The output phase and power of the guided optical waves are expressed by the first and third kind elliptic integrals,as well as the Jacobian elliptic functions.The corresponding calculation commands are presented in Matlab functions and the validity of the analytic solutions are shown by comparison with the numerical results given by the Runge-Kutta method.2.The 8PSK regenerator based on phase-sensitive amplifier(PSA)is designed by analyzing the requirement for multi-level phase regeneration based on degenerate FWM and the dependence of phase transfer curves on initial pump phase and power.It is shown that the phase transfer curve of the PSA can be controlled by adjusting the initial pump phase to match with the multi-level phase of the input signal.The phase fluctuation can be suppressed by optimizing the fiber length or pump power,in which the optimized initial pump power is inversely proportional to the fiber length approximately.The performance of the PSA-based 8PSK regenerator is simulated by the OptiSystem software.The phase fluctuation suppression ratio is up to 4.62 for the normalized input phase fluctuation of 0.1(the standard deviation of the input noise is 0.1?? 4 rad),and the symbol error rate without forward error correction can be reduced by two orders of magnitude.3.A phase calculator of the hybrid arithmetic functions(2A B?-?,2B A?-?)of phase-modulated signals is designed based on the phase-insensitive amplifier(PIA)and the principle of optical phase inter-modulation in degenerate FWM.The hybrid arithmetic functions of doubling and subtraction(2A-B,2B-A)for two quaternary signals,A and B,are realized and the influence of input amplitude noise on the hybrid arithmetic calculator is analyzed.It is shown that the calculator has an optical noise figure or optical signal-to-noise ratio(OSNR)degradation of about 6.6 dB and the input OSNR should be more than about 25 dB for a symbol-error rate(SER)of 10-3,corresponding to the error vector magnitude(EVM)of 22%.