Nonlinear phase shift scanning method for the optimal design of Raman transmission systems

In this paper, an efficient algorithm for the search of optimum design parameters and corresponding transmission quality factor (Q) for a Raman amplified transmission system is presented. Taking the nonlinear phase shift (NPS) as the first-order key design parameter for the determination of the remaining secondary system parameters, and solving the nonlinear Schroumldinger equation (NLSE) as a function of NPS to obtain the optimum (Q) factor, the multiparameter, time-consuming fiber Raman amplifier (FRA) system design process can be reduced to a highly efficient and precise semianalytic one-dimensional optimization problem. As an application example for the suggested optimization algorithm, the authors show the design process for the determination of the system design parameters (input powers to single mode fiber (SMF), dispersion-compensating fiber (DCF), distributed Raman gain, and forward Raman pumping ratio) for a single channel 10-Gb/s 2000-km transmission link. In addition, for the first time within the author's knowledge, they assess the requirements of pump relative intensity noise (RIN), as a function of the pumping direction/span-length changes, to study the shift in the optimum design parameters. Results show a Q-factor improvement for the system more than 1.16 dB/4.89 dB at a 100-km/200-km span length with their design method, when compared to previous optimization method. Discussion on the application to dense wavelength division multiplexing (DWDM) system is also presented