Simulation of RIN transfer in coherent optical communication links with distributed Raman amplification

It is well known that degradation of an information signal during its propagation along the optical fiber communication link affects the achievable bit rate. In practice, any real transmission link introduces signal distortions that can be either recoverable (e.g., dispersive broadening) or not fully removable (e.g., noise). The sources of such unremovable distortions leading to loss of information are: amplified spontaneous emission (ASE), double Rayleigh scattering (DRS), RIN (relative intensity noise) transfer and other effects. Knowledge of noise properties of the distributed Raman amplifiers (DRAs) are important for Raman-based communication systems [1]. RIN transfer from pump to signal in DRAs has studied both numerically [2] and analytically [3] as a main factor limiting telecom applications of such amplifiers. However, the most common analytical and numerical models are based on balance (average-power) equations and do not describe evolution of phase modulated signals along the fiber under influence of dispersive and nonlinear effects.