Data-Aided OSNR Estimation Using Low-Bandwidth Coherent Receivers

We propose an optical signal-to-noise ratio (OSNR) estimation technique using low-bandwidth coherent receivers and Golay training sequences (TSs) for coherent optical systems with data-aided channel estimation. The same TSs used for channel estimation in a coherent optical system are also used for OSNR estimation using low speed receivers. The technique is based on analyzing the spectral property of the TSs within the receivers' bandwidths and thus can be adopted for receivers with low bandwidths and for the distributed optical monitoring purpose. The technique is demonstrated to have an accuracy of 1 dB for 40-Gb/s polarization-multiplexed quadrature phase shift keying and 16-quadrature amplitude modulation coherent single-carrier optical systems at up to 1000-km transmission.