The Applied Research Of OTDR Curve Analytic Technique In Optical Fiber Fault Diagnosis

Firstly, the thesis introduces the background of fibre diagnosis system and OTDR technology. Secondly, it details description of the theory of wavelet transform method and the applicability of OTDR curve analysis. Thirdly, By using the MATLAB tool realizes the simulation of signal denoising, OTDR curve analysis based on wavelet transform, and on the basis of the accuracy support confirms base wavelet and the scale of wavelet in fibre diagnosis system by various experiments. And then this paper elaborates on the overall design framework, the curve analysis process of fibre diagnosis system, and according to feedback from project implementation workers to modify the OTDR curve analysis algorithm. Finally, through practical engineering tests, the error of fiber fault location is less, and fault type judgement is accurate.But inaccurate positioning is generally found in the fibre diagnosis system, the reason is that the analysis and location algorithm for curve signal gained by OTDR is inappropriate in the diagnosis system. The theory of wavelet transform has a distinct advantage on the signal denoising, singularity analysis and fault diagnosis. To introduce wavelet transform method into fibre diagnosis system and toapply it to the analysis of curve signal gained by OTDR can improve the accuracy of fiber fault location and the maintenance efficiency of fibre network.This paper analysis the main technical of the current optical fiber fault diagnosis system and the curve analysis, principles of fault location and key technologies of OTDR. Secondly, we explanation that the using of wavelet transform to solve OTDR curve analysis in the fiber optic fault diagnosis system is feasible based on the characteristics of the fault diagnosis system. The third, This paper take denoise and singularity location test with the typical OTDR curve from the actual cable lines in the tool of Matlab. We select the universal threshold and using the soft-threshold to noise reduction for the original OTDR single. This paper has completed the effect comparison for the different wavelet basis and scales. According to the actual needs of engineering, we make the choice of haar wavelet, scale 2 as the base wavelet and wavelet scale for the system. The results show that the wavelet transform in optical fiber fault diagnosis is effective and accurate. Finally, the paper applied the wavelet analysis to the cable fault diagnosis, and completes the critical OTDR curve analysis module. The module could real-time, accurate positioning the points in cable fault. Actual operation results show: location accuracy of fiber fault has increased larger than the original performance curve analysis. The effect is significant, the results has broad application prospects.