Flat Power Response in a Polarization-Maintaining Coupler Based Nonlinear-Optical Loop Mirror (PMC-NOLM)

The nonlinear-optical loop mirror (NOLM) has been intensively investigated for the amplitude regeneration due to the power oscillatory mapping between the input and output waves. However, the noise-handling capability, i.e. the power plateau region is limited by the oscillatory nature, which becomes even worse when dealing with multiple levels. In the paper we review our novel NOLM regenerator scheme which is based on a polarization-maintaining coupler (PMC) instead of a conventional non-PM coupler (non-PMC). This modification brings the nonlinear polarization rotation effect into the NOLM unit, enabling significantly improving the regenerative range and the noise suppression efficiency. Compared to the conventional NOLM based on a non-PMC (non-PMC-NOLM), the proposed PMC-based NOLM (PMC-NOLM) offers an over 6dB flat power response, and consequently achieving 3.5dB Q-factor improvement in the regeneration experiment.