Improvement of NRZ signal transmission through phase modulation

Dispersion maps are required for successful nonreturn to zero (NRZ) transmission, as they allow signals to avoid the deleterious effects of four-wave mixing while still experiencing an average dispersion that is nearly zero. In wavelength-division multiplexed (WDM) systems, only one channel can be perfectly compensated in a short dispersion map; the others are compensated at the end of the transmission and thus experience a long effective dispersion map. Therefore, finding ways to minimize the distortion is of critical importance. Here, we will show that phase modulation greatly diminishes the signal distortion at high powers and with long maps, which in turn can be used by the system designers to improve the system performance by operating with higher powers