Polarization-independent all-optical AND-gate using randomly birefringent fiber in a nonlinear optical loop mirror

摘要

Polarization independence is a critical issue for all-optical logic gates if they are to be implemented in future high-speed data transmission networks. Here we present a method to make the nonlinear optical loop mirror (NOLM) fully insensitive to polarization changes in any of the two input signals by having a fiber with random birefringence, i.e., a fiber with moderate polarization-mode dispersion (PMD). The basic idea is to make the wavelength difference between the signal and control pulses large enough so the polarization states, when evolving through the fiber, will be different for the two signals as a result of PMD in the fibre.