Importance of prechirping in constant-dispersion fiber links with a large amplifier spacing

We use the variational method to find the optimum launch conditions that ca n sustain path-averaged solitons in a periodically amplified, constant-disp ersion, optical communication system even when amplifier spacing is compara ble to or larger than the dispersion length. We determine the amount of pre chirping and the initial peak power required and show that both the pulse w idth and the chirp recover their initial values at each amplifier. The prec hirped solitons are different from the standard solitons in constant disper sion since their width and chirp are allowed to vary over each amplifier se ction. This feature results in an interesting regime in which amplifier spa cing can exceed the dispersion length. Numerical solutions of the nonlinear Schrodinger equation show that the use of prechirped solitons improves sta bility in comparison with guiding-center solitons in constant-dispersion fi ber links. (C) 2000 Optical Society of America [S0740-3224(00)00904-8] OCIS codes: 060.2330, 060.4510, 060.5530.