This paper proposes a Brillouin and Rayleigh fusion system for multi-parameter monitoring of power OPGW cables. Temperature, strain, and vibration measurements are important indicators for safe cable operation of OPGW cables. Temperature monitoring helps detect ice-coating, mountain fire, and lightning. Strain measures cable stress, fiber core safety, ice-coating, and fatigue damage caused by wind-induced vibrations. Vibration monitoring is useful for ice covering and wind vibration. The proposed system overcomes limitations such as nonlinear effects and limited sensing distance. By using a fixed delay of 500ns, mutual position calibration of temperature/strain and vibration measurements is achieved. The system uses a two-wavelength distributed optical fiber fusion scheme with dual light sources, ensuring no interference or degradation due to index conflicts.
KEYWORDS: Vibration, Ice, Optical fiber cables, Fiber optics sensors, Optical sensing, Scattered light, Signal to noise ratio, Signal attenuation, Temperature metrology, Sensing systems
OPGW power overhead fiber optic cable suffers from fiber core aging, ice-covering dance and stress damage in long-term operation due to laying method and geographical environment. The monitoring of multi-fiber parameters such as vibration, strain, temperature and attenuation based on distributed fiber optic sensing can realize early warning of malfunction. In order to solve the problems of multiple deployment devices, occupying multiple core resources and high operation and maintenance costs of existing multiparameter measurement technologies, the fusion sensing technology based on ΦOTDR, BOTDR and OTDR is studied. The system employs multiplexing of light sources, two-way coherent reception of Brillouin scattered light and Rayleigh scattered light, and joint demodulation of phase and intensity to achieve distributed measurements of vibration, temperature, strain and long-range attenuation measurement on a single fiber. The system achieves linear reduction of 100Hz perturbation signal with 10m spatial resolution and 80kmsensingdistance, and the signal-to-noise ratio of demodulated vibration signal is about 35dB, and the accuracy of temperature measurement is about ±1°C. For the practical application of OPGW overhead optical fiber cable, the mathematical model of the inherent vibration frequency of the cable and the over-ice tension as well as the stress calibration method of the pole and tower joints are studied to realize the monitoring and early warning of the over-ice thickness of optical fiber cable and the decoupling measurement of BOTDR temperature/strain. The error between the demodulated ice thickness and the actual ice observation result is less than 10%, and the decoupling accuracy of temperature and strain is ±2°C and ±40με respectively.
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