Carrier to Noise Ratio Improvement by Brillouin Amplification for 64-QAM Coherent Communications

The limits of narrowband Brillouin gain improving the carrier to noise ratio (CNR) of spectral lines in coherent communications is evaluated. Extrapolation from experiments with 48 Gb/s 64-QAM signals predict allowing an input CNR as low as ≈19 dB/0.1 nm for minimal bit-error-rate degradation.