A Novel High-Performance OSNR Measurement Technique Based on the Polynomial Fitting Function of Signals

A novel in-band optical signal-to-noise ratio (OSNR) measurement technique based on a polynomial fitting function with a high performance is proposed and experimentally demonstrated. By introducing a polynomial function to fit the normalized autocorrelation function of the signal, the OSNR can be measured without the requirement for any prior knowledge of the signals. The OSNR measurement range from 0 to 26 dB with error less than ±0.5 dB is realized for 4-channel 32-Gbaud PDM-QPSK signals separated by 37.5-GHz channel intervals, and the upper limit of the measurement range is enlarged from 22 (without polynomial fitting function) to 26 dB, which is a significant improvement, especially for advanced modulation formats. Further experimental investigations also demonstrate that the OSNR measurement technique is robust to the bandwidth of the filter, bit rate of signal, input optical power, and chromatic dispersion. In addition, the simulation results show that the technique may be potentially compatible with different modulation formats.