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.
Inside a service function chain (SFC), traffic flow follows a certain route, namely a service function path (SFP), to travel through each service function (SF) entity. A SFP consists of several end-to-end segments, whose source and destination are named anchor node (AN). SFs are located in multiple datacenters (DCs), and inter-DC light-paths need to be provisioned between separated SFs. In this paper, we introduce geography information of optical nodes and DCs, define special geographic distance between ANs in inter-DC elastic optical networks (EONs). Then following minimal geographic distance principle, we propose a geography-based SFP provisioning solution, which contains two heuristic algorithms, named geography-based shortest path and first-fit algorithm (GSP-FF) and geography-based k-shortest paths and first-fit algorithm (GK-FF). These algorithms can compress AN selection procedure extremely in fixed time, which cost little time for the AN selection of resource allocation. And benchmark algorithm use Dijkstra shortest path calculation and first-fit FS selection to allocate IT resources in DCs and FS resources in EONs. Then GSP-FF and GKFF are proposed to provision SFPs efficiently. In our simulation, we compare our proposed algorithms with benchmark algorithm deeply on blocking probability, running time, average hops, average geographic distance, et al. under different traffic load and other simulation environment. We also analyze the trend and reason for the performance difference among these algorithms. According detailed evaluation, simulation proves that the proposed algorithms in this paper could use geographic information efficiently, and achieve lower blocking probability with lower running time compared with the benchmark algorithm.
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