Soliton optical phase control by use of is-line filters

We address the problem of soliton phase jitter caused by fiber amplifier no ise in a communication channel. An analytical expression for phase jitter i s derived by use of perturbation theory. In the absence of filters the vari ance of the phase is found to be proportional to the cube of the propagatio n distance, but it increases only linearly if in-line filters are used. We verify with simulations that in-line filters maintain the phase jitter at a level that is tolerable for transoceanic links. (C) 1999 Optical Society o f America.