Two-Photon-Absorption-Based OSNR Monitor for NRZ-PSK Transmission Systems

A two-photon absorption microcavity-based technique for monitoring in-band optical signal-to-noise ratio (OSNR) in nonreturn-to-zero phase-shift-keying systems is presented. Experiments using a 10-Gb/s differential phase-shift-keying system showed that accurate measurements (±1 dB) were possible for OSNRs in excess of 20 dB.