Single-mode optical fibers are really bimodal because of the presence of birefringence. A constant birefringence will cause a pulse which originally consists of two polarizations to break up, due to the different group velocities of the two polarizations. Menyuk1 has shown that this pulse breakup can be avoided by making use of the fiber nonlinearity; the two fractional pulses in the two polarizations shift each other's central frequency just enough to eliminate any initial difference in group velocity. As a result of this, the original pulse, consisting of both polarizations, is self-trapped in the time domain.
© 1991 Optical Society of AmericaPDF Article