Dark solitons in periodically amplified fiber transmission systems with stepwise-varying dispersion

We examine the dark soliton propagation in periodically amplified fiber transmission systems with stepwise-varying dispersion. The stepwise-varying dispersion in fibers is shown to be more effective for extending the amplifier spacing or reducing required amplifier numbers in the high-bit-rate dark soliton transmission system than in the corresponding bright soliton transmission system. The origin of the difference is discussed.