一种基于Φ-OTDR长距离海缆振动探测关键技术研究

Key Technology of Long-Distance Submarine Cable Vibration Detection Based on Φ-OTDR

振动可以作为探测外部冲击破坏的指标参数,远海范围的海缆安全防护对低成本、长距离、高信噪比的海缆振动探测提出了更高的要求。通过对相位敏感光时域反射计(Φ-OTDR)的长距离海缆振动探测进行分析探讨,得出在50 km以上的长距离海缆探测的主要问题是末端的探测脉冲存在巨大的传输损耗,长距离海缆末端探测信号容易湮没在噪声中。对比以Φ-OTDR作为探测设备的直接探测方案、外差相干探测方案、双向拉曼探测方案以及末端振动信号降噪方案,在结合双向拉曼放大技术以及外差检测技术上,提出一种末端振动探测的降噪方法,以此来解决长距离海缆末端振动探测的问题。经过实验验证该方案实现的振动探测距离达120 km,探测光纤末端的信噪比得到有效提升。

Vibration can be used as an index parameter for monitoring external shock damage.The safety protection of submarine cables in the far sea puts forward higher requirements on the vibration monitoring of submarine cables with low cost,long distance and high signal-to-noise ratio.Through the analysis and discussion of the long-distance submarine cable vibration detection based on phase-sensitive optical time domain reflectometry(Φ-OTDR),it is concluded that the main problem in the long-distance submarine cable detection above 50 km is that the detection pulse at the end has a huge transmission loss,and the detection signal at the end of the long-distance submarine cable is drowned easily in noise.Comparing the direct detection scheme,the heterodyne coherent detection scheme,the bidirectional Raman detection scheme and the terminal vibration signal noise reduction scheme that uses the Φ-OTDR as the detection device,combined with bidirectional Raman amplification technology and heterodyne coherent detection technology,a noise reduction method for end vibration detection is proposed to solve the problem of vibration detection at the end of long-distance submarine cables.It has been verified by experiments that the vibration monitoring distance achieved by this solution is up to 120 km,and the signal-to-noise ratio of the detection fiber end is effectively improved.