WDM in long-haul transmission systems

Summary form only given, as follows. The transmission capacity of long-haul light-wave systems is experiencing the second "order-of-magnitude" increase within the past 6 years. The introduction of single channel EDFA based systems gave the first large capacity increase, and WDM is giving the next. The tutorial reviews the important issues regarding the use of wavelength division multiplexing in long-haul lightwave systems. Large transmission capacity enhancements have resulted from an increased understanding of the effects that can limit the performance of WDM systems. Important strides have been made in areas of dispersion management, gain equalization, and modulation formats which have made possible the demonstration of large data transmission capacity.