Simulation of 40 Gbps WDM systems using single mode fiber

40 Gbps WDM systems have been studied by numerical simulation to optimize their performance. Standard single mode fiber is assumed, and the most popular modulation format, NRZ, is used for the study. These assumptions are valid when existing WDM systems are required to upgrade their performance to 40 Gbps. It is shown that the standard single mode fiber can transmit optical signals over 480 km (BER < 10/sup -15/) by optimizing optical and electrical filter characteristics at the receiver and by compensation of dispersion. In addition, when the system performance is mainly limited by ASE noise of EDFAs, it is found that flattop-shaped optical filter at the receiver gives a better result than Gaussian-shaped filter unless the insertion loss of the optical filter is larger than 5dB.