Unified analysis of modulational instability induced by cross-phase modulation in optical fibers

Cross-phase modulation in an optical fiber can lead to various types of modulational instability, such as polarization instability in a highly birefringent fiber and two-pump optical parametric amplification. We present unified analyses of such instabilities and clarify the general mechanisms behind them. By solving the generalized eigenvalue equation, we indicate the explicit conditions of inducing modulational instability. The eigenvector is also calculated, which allows us to explain underlying physics of instabilities using a phasor diagram. As a result, all types of cross-phase modulation-induced modulational instability are classified into three types in terms of their mechanisms. (C) 2003 Optical Society of America.