基于BOTDR的光纤复合海底电缆应变/温度监测

Strain and Temperature Monitoring of 110 kV Optical Fiber Composite Submarine Power Cable Based on Brillouin Optical Time Domain Reflectometer

高压光纤复合海底电缆结构复杂、敷设环境特殊,日常巡检和状态检测实现难度大,利用分布式光纤应变和温度测量设备对其进行监测十分必要。为此,利用Brillouin光时域反射计(BOTDR)对110 kV光纤复合海底电缆中的复合光纤进行了应变和温度标定实验,比较了不同光纤Brillouin频移的应变/温度系数和初始频移的区别,给出了利用光纤中Brillouin频移分布曲线进行接续点精确定位的方法,对运行中的海缆进行了全面、实时、长期的状态监测和数据分析。结果表明:海缆光单元中不同光纤的Brillouin频移应变/温度系数基本相同,约为0.05 MHz/10-6和1.05 MHz/℃,但初始频移差别较大,变化范围约20 MHz;光路中接续点处的Brillouin频移变化明显,可作为定位依据;利用Brillouin频移监测海缆的应变和温度需结合海底地形、地质、洋流、环境温度、负荷电流等因素。

High voltage optical fiber composite submarine power cables have complex structure and are laid in particular environments, so it is difficult to conduct their routine inspection and status monitor. Thus using distributed optical strain and temperature measurement instrument to monitor these cables becomes quite necessary. Using the Brillouin optical time domain reflectometer （BOTDR）, we carried out strain and temperature calibration experiments of composited optical fiber in 110 kV optical fiber composite submarine power cable. The frequency shift coefficients to strain and temperature, as well as the initial frequency, of different optical fibers were compared. Then a method for accurately locating connec- tion points was proposed based on distributed Brillouin scattering frequency shift profiles. Using the proposed method, we realized the comprehensive, real-time and longtime status monitoring rtmning submarine cable, from which mass data were obtained and analyzed. Results indicate that the frequency shift coefficients to strain and temperature of single mode fibers in the same batch are almost identical, which are 0.05 MHz/10-6 and 1.05 MHz/℃, but the initial frequency shifts are different within a range of 20 MHz. The Brillouin frequency shifts at connection points along fiber change obviously, which can serve as basis for locating connection points. When Brillouin frequency shift is applied to monitor the strain and temperature of submarine cable, the submarine topography, geology, ocean current, environment temperature, and load current should be taken into consideration.