Power Profile Optimization in Phase-Modulated Systems in Presence of Nonlinear Phase Noise

In optical fiber transmission systems using inline amplifiers, the interaction of signal and amplifier noise through the Kerr effect leads to nonlinear (NL) phase noise that impairs detection of phase-modulated signals. We study the minimization of the total phase noise variance (linear, NL, and receiver) by using a power profile along the link that is linear (on a decibel scale) with distance. For DPSK systems with direct detection, a total variance reduction of 65% can be achieved by designing the transmitted power to be about 8 dB higher than the received power in typical terrestrial links. In addition, for a given transmitted power and received power, the optimal power profile along the link is numerically determined