The limits of narrowband Brillouin gain for improving the carrier to noise ratio (CNR) of spectral lines is evaluated for 64-QAM communications. Calculations of the change in CNR for practical gain, noise, and bandwidth parameters indicate the maximum obtainable CNR enhancement factor and output CNR as being ≈25 dB and ≈40∼43 dB/0.1 nm, respectively, limited by the narrowness of the Brillouin gain bandwidth and Brillouin amplifier noise, respectively. These limits determined from the relative power suppression of out of band noise contained within a 10 GHz channel bandwidth are relevant to spectral line amplification either before data modulation at the transmitter, or for a local oscillator (LO) at the receiver for coherent detection. A calibration measurement of the bit error rate (BER) of a 48 Gb/s 64-QAM signal versus CNR of a LO loaded with ASE noise is used to extrapolate the BER from the calculated CNR for Brillouin gain. The results predict the BER being minimally degraded for an input CNR of ≈>20 dB/0.1 nm and falling below the hard decision FEC limit for an input CNR as low as ≈0 dB/0.1 nm. The estimates are found consistent with 64-QAM signal experiments of pilot tone carrier recovery by Brillouin gain for both single channel and WDM cases. The insight aids the design and estimation of achievable performance improvement for applying Brillouin amplifiers to coherent communications.

中文翻译：

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通过布里渊放大提高光通信的载噪比

针对 64-QAM 通信评估了用于改善频谱线的载噪比 (CNR) 的窄带布里渊增益的限制。实际增益、噪声和带宽参数的 CNR 变化计算表明，受布里渊增益窄度限制，可获得的最大 CNR 增强因子和输出 CNR 分别为 ≈25 dB 和 ≈40∼43 dB/0.1 nm带宽和布里渊放大器噪声。这些由 10 GHz 信道带宽内包含的带外噪声的相对功率抑制确定的限制与发射机进行数据调制之前的谱线放大有关，或者与接收机处的本地振荡器 (LO) 进行相干检测有关。48 Gb/s 64-QAM 信号的误码率 (BER) 与加载有 ASE 噪声的 LO 的 CNR 的校准测量用于从计算的 CNR 外推 BER 以获得布里渊增益。结果预测，对于 ≈>20 dB/0.1 nm 的输入 CNR，BER 降级最低，并且对于低至 ≈0 dB/0.1 nm 的输入 CNR，BER 会低于硬判决 FEC 限制。发现这些估计与单信道和 WDM 情况下通过布里渊增益进行的导频载波恢复的 64-QAM 信号实验一致。该见解有助于设计和估计可实现的性能改进，以将布里渊放大器应用于相干通信。1 nm 并低于输入 CNR 低至 ≈0 dB/0.1 nm 的硬判决 FEC 限制。发现这些估计与单信道和 WDM 情况下通过布里渊增益进行的导频载波恢复的 64-QAM 信号实验一致。该见解有助于设计和估计可实现的性能改进，以将布里渊放大器应用于相干通信。1 nm 并低于输入 CNR 低至 ≈0 dB/0.1 nm 的硬判决 FEC 限制。发现这些估计与单信道和 WDM 情况下通过布里渊增益进行的导频载波恢复的 64-QAM 信号实验一致。该见解有助于设计和估计可实现的性能改进，以将布里渊放大器应用于相干通信。