Nonlinear optical effects suppression methods in WDM systems with EDFAs: A review

This paper presents a review of novel methods that have been proposed by many authors for nonlinear optical effects suppression in WDM systems. Among the major nonlinear optical effects in WDM systems include nonlinear crosstalk, cross-phase modulation (XPM) and four wave mixing (FWM). These nonlinearities will degrade the performance of WDM systems particularly at bit rates higher than 2.5 Gbit/s. There are many nonlinear optical effects suppression methods that have been proposed since a decade ago. Generally, nonlinear optical effects suppression can be achieved by using chirped fibre Bragg gratings, laser oscillations, unconventional modulation formats and unequally spaced channel allocation by using various types of algorithms. These suppression methods were compared against the complexity and effectiveness in the application of present WDM systems.