Optical Signal Filtering Using Phase-Sensitive Amplification and De-Amplification

Abstract

We utilize for the first time, to the best of our knowledge, the amplification and de-amplification properties of a fiber-based optical phase-sensitive amplifier (PSA) to implement a flexible, multiple notch filter with optical power extinction ratio given by the internal amplifier gain squared. Our PSA-based filter is completely realized in the optical domain, permitting further downstream optical signal processing, if desired. Direct detection leads to an additional gain-squared enhancement, resulting in electrical filter extinction that is a biquadratic function of the PSA gain. This suggests that the PSAs with even modest optical gains can be used to realize filters with extremely large electrical extinction ratios or notch depths. We characterize filter performance using bit error rates, and demonstrate highly effective isolation of a signal-of-interest from neighboring interferers. Finally, we measure filter extinctions of 20 and 40 dB in the optical and electrical domains, respectively.