Four-wave mixing induced Q-factor variations in WDM systems

Summary form only given.Four-wave mixing (FWM) is a major limiting factor on system performance for wavelength division multiplexing (WDM) systems in low-dispersion fiber. Extensive work on FWM has been done in the last decade. Now estimating FWM crosstalk in a short piece of fiber with a couple of channels is not a difficult task. However, for multiple-span dense WDM systems, accurately predicating FWM induced system performance penalty is still not trivial. The first issue comes from the variations of FWM power due to some random factors, such as the non-uniform dispersion-profile in fiber, intensity-induced phase-match effects, and polarization state fluctuations of channel signals induced by polarization-mode dispersion (PMD) in the fiber link. The second issue arises from the random characteristics of the interference between the FWM signals and channel signals, which depends on the phase coherency of FWM crosstalk, the variations of polarization slate of FWM signals and the non-Gaussian characteristics of FWM crosstalk. The problems related to the second issue seem more serious than that in the first one since their variations are more difficult to measure and thus more unpredictable. In this paper, we experimentally investigate the significance of these problems.