Nonlinear optical loop mirror with an optical bias controller for achieving full-swing operation of gate switching

Cross-phase modulation between counterpropagating lights degrades the extinction ratio of nonlinear optical-loop-mirror (NOLM) switches. To suppress such effect, we propose an NOLM with an optical-bias controller that can give a proper amount of optical bias between lights propagating through an NOLM in opposite directions. Implementing such optical bias controller in a conventional NOLM composed of a polarization-maintaining fiber, we demonstrate, for the first time, wavelength conversion of a nonreturn-to-zero signal under the full-swing condition with the maximum extinction ratio.