Abstract

The third-order nonlinearity in optical fibers is the cause of the related phenomena of self-phase modulation (SPM), four-wave mixing (FWM), and cross-phase modulation (XPM). The FWM generation efficiency in a single fiber segment depends on the propagation constant mismatch Δβ between the participating waves.¹ A common technique to reduce FWM in WDM networks is to use high-dispersion fibers, but a drawback is that high dispersion in turn leads to pulse shape distortion. Hence the need arises to compensate for this high dispersion. Means have been introduced to do so, including: localized dispersion compensation (DC) by placing a dispersion compensator after each segment;² alternating dispersion (AD), i.e. reversing the sign of the dispersion coefficient in consecutive fiber segments;³ phase conjugation (PC) between two consecutive segments.^4,5 Here we show that by broadening the approach to FWM reduction, to encompass all the tools listed above, one can find a combination which can in principle completely cancel all third-order nonlinear effects in a two-segment link. We first present the proof for FWM, and then discuss its extension to XPM and SPM.

© 1995 Optical Society of America