Optimal input Gaussian pulse width for transmission in dispersive nonlinear fibers

Using the variational method, we derive simple, closed-form algebraic expre ssions that approximate the optimal input rms pulse width and the correspon ding minimum output rms width for Gaussian pulses subject to both dispersiv e and nonlinear effects in single-mode fibers. We present results in both n umerical and analytical forms and confirm them by the split-step Fourier nu merical method. Our results cover both normal and anomalous dispersion in f ibers with gain and loss. For the case of normal dispersion we show that bo th the optimal input and output widths are asymptotically linearly dependen t on distance and dependent on the square roots of the dispersion coefficie nt and the transmitted power. (C) 1999 Optical Society of America [S0740-32 24(99)02407-8].