Analysis of mode partition noise in laser transmission systems

Abstract

Mode partition noise can be the dominant limitation on a system error rate for single-mode-fiber laser transmission systems. The distribution of power among the longitudinal modes of the laser fluctuates and, as a consequence of chromatic dispersion in the fiber, causes an amplitude fluctuation of the signal at the decision circuit in the receiver. The effect is in essence a pulse-delay fluctuation, and the error rate cannot be reduced by increasing the received signal power. We derive a simple formula describing this mode partition noise, give useful design relations, and verify the analysis by comparison with system experiments.