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.