Modulation instability in highly birefringent optical fibers: a coupled-mode analysis

The self- and cross-phase modulation instabilities (SPMI and XPMI) of the orthogonally polarized beams in high birefringent optical fibers are studied in detail by a coupled-mode theory in the frequency domain. This approach is mathematically identical to the perturbation method in the time domain, but lends itself to a clear insight of the physical process. It is noted that the phase-matching conditions are critical in the interactions between sideband components. By identifying these phase-matching conditions, possible patterns and the gains and positions of the peak gains of modulation instabilities may be well predicted by simple analytical expressions, which have been verified by the more rigorous full-wave solutions