The Detection Algorithm And System Design Of OTDR Event

In recent years, with the rapid development of optical fiber communication, thescale of optical fiber network is also becoming larger and larger, as a result, the fibermaintenance and fault detection will become more and more severe. As the traditionalmethod of manual inspection by the technical staff have many shortcomings, such as,low efficiency, time-consuming and low accuracy, making online monitoring systemof optical fiber has gradually become the mainstream. The work I have done in thispaper is to design and implement a core module of online monitoring system ofoptical fiber-the algorithm design and system implementation of the OTDR eventdetection.Firstly, the online monitoring system of optical fiber has been introduced,especially the module of OTDR event detection for its working principle, hardwarestructure and performance parameters, which is very important of the system. Theresearch status of the detection algorithm and the types of the optical fiber events arealso described in detail.Secondly, with the analysis of the OTDR test curve, determining to use thewavelet method for signal de-noising, and using the combination method of wavelettransform and the slope method for the event detection. Clearly illustrates theprinciple of wavelet analysis and its advantages lie in signal analysis, as same as themulti-resolution analysis and Mallat algorithm which are used in the detectionprogress. In the signal de-nosing progress, several methods of de-nosing used wavelettransform are compared, and the Minimaxi method and the hard threshold method arechosen. In the event detection progress, according to the characteristics of thedifferent types of events, the reflective events are detected by wavelet analysis, andothers are detected by slope method. The select of the wavelet function and the scaleare very important in wavelet analysis, which are explained in detail in this paper.Finally, the design and implementation of the entire OTDR event detectionsystem is completed, and the whole process of the system, from reading data, tooutputting the result, has been introduced. There are several parts of the process Iintroduce in detail, such as ghosting events and the pseudo-events caused by noise,the method to solve these problems are also explained. After the tests of several optical fibers, the detection results prove that the detection accuracy and reliability ofthe system are high enough to the application requirements.