基于拉曼放大的零差布里渊光时域反射技术

Homodyne Brillouin Optical Time-Domain Reflectometry Based on Raman Amplification

提出一种基于拉曼放大的零差布里渊光时域反射技术，在长距离分布式光纤传感中实现对温度和应变的快速单端测量。该方法通过拉曼放大提高多峰布里渊峰值功率，实现布里渊拍频峰功率的提升，可有效提高传感系统的信噪比（SNR）和传感距离。通过解拉曼放大的耦合方程，得到同向、反向以及双向拉曼增益，并从理论上导出了前端拉曼抽运系统的布里渊拍频峰的峰值功率分布。以50km的大有效面积光纤为例，在抽运功率为800mW的前端拉曼抽运下，仿真得到2个拍频峰的最低信噪比位于光纤初始端，分别约为26．4dB和21．5dB。光纤末端处2个拍频峰的信噪比分别为70．9dB和46．8dB。结果表明，所提出的方法在不降低测量精度和测量速度的情况下，可使光纤传感的动态范围提高11倍。

A homodyne Brillouin optical time-domain reflectometry （BOTDR） based on Raman amplification is proposed to achieve the fast and single-end measurement of temperature and strain in long-range distributed optical sensors. In this method, Raman amplification can be used to enhance multi-Brillouin peaks power in order to improve the power of the Brillouin beat peaks, which can effectively improve the signal-to-noise ratio （$NR） and sensing distance of the sensing system. ＂l＇he co-Raman gain, counter-Raman gain and bidirectional-Raman gain are achieved by solving the coupled equation of the Raman amplification and the power distribution of Brillouin beat peak in front-end Raman pumped system is derived. Take a 50 km large effective area fiber （LEAF） as an example, when the front-end Raman pump power is 800 mW, the lowest SNRs of two Brillouin beat peaks appear at the front end of the LEAF and they are respectively 26.4 dB and 21.5 dB. The SNRs in the rear end of the LEAF are 70.9 dB and 46.8 dB, respectively. The results show that by using the proposed method, the optical fiber sensing dynamic range can be increased by 11 times without degrading the measurement accuracy and speed.