分布式拉曼放大对布里渊时域分析的负面影响

Negative Effects of Distributed Raman Amplification on Long Distance Brillouin Optical Time-Domain Analyzer

为研究拉曼抽运源相对强度噪声（RIN）和布里渊慢光对基于分布式拉曼放大（DRA）的远距离布里渊时域分析仪（BOTDA）的负面影响，分别采用解析法和数值法分析了传感光纤中拉曼抽运光、布里渊抽运光和探测光相互作用的振幅耦合模型。对拉曼抽运源RIN传递的研究表明：RIN强度每增加1dB，检测信号信噪比（SNR）降低约1dB；当RIN值小于-135dB时，其影响可忽略不计。对布里渊慢光的研究结果表明：分布式拉曼放大补偿光波线性衰减的同时，增加了由布里渊慢光延迟导致的光学时域反射定位误差。该定位误差使不同扫描频率获取的检测信号时间迹上同一时刻点对应不同的传感光纤空间位置，影响了布里渊谱的三维重构及其布里渊频移的准确提取。

To investigate the negative effects of the relative intensity noise （RIN） of the Raman pump and the Brillouin slow light on the long-distance Brillouin optical time-domain analyzer （BOTDA） assisted by distributed Raman amplification （DRA）, the coupled amplitude equations describing the interactions between the Raman pump, Brillouin pump and Brillouin probe have been solved. Results of RIN transmission of the Raman pump show that 1 dB increase in the RIN of the Raman pump leads to about 1 dB decrement in the signal-to-noise ratio （SNR） of the received electrical signal. This undesirable effect can be ignored when the RIN value of the Raman pump is down to -135 dB. Furthermore, results of Brillouin slow light show that compensating the linear loss of the waves in the sensing fiber by DRA results in an increase of position locating error （PLR） induced by Brillouin slow light effect. It＇s also shown that, at the same time, point in the detected signal traces obtained at different sweeping frequencies corresponds to different spatial locations on account of PLR. The errors will have a significant negative effect on the reconstruction of the 3D Brillouin spectrum and the accurate extracting of the Brillouin frequency shift of the sensing fiber.