Abstract: To obtain an optimumdispersionmanagement (DM) scheme for 40 Gb/s long-haul multi-period postcompensation systems, compensation lengthswere studied by simulation. The results showthatthe pulse width is inerratic alongthe longfiber, the optimumlength for a long-haul multi-period system is shorterthan the maximum compressed compensation length for a single-period system, and the optimum length is lengthened as an increase in the peak power of the pulses.