The Development Of Signal Processing Module In Optical Time-domain Relfectometry Based On FPGA

Optical time domain reflectometry (OTDR) is an instrument to measure the transmissioncharacteristics of the fiber. It not only can measure the attenuation and detail with the length ofthe fiber but also can monitor and locate any kind of events along the fiber such as slice loss, endpoint reflection and so on. In FTTH engineering practice, optical time domain reflectometry canbe used for network installation and maintenance of optical wiring system. It could locate thebroken point along the fiber from one end without breaking the fiber accurately and rapidly.Firstly, this paper introduces the history of development of OTDR and its status of research,then analyzes the working principle and important technical specifications of OTDR. There areso many problems in the fiber diagnosis system such as inaccurate positioning. This paperintroduces the wavelet transform algorithm in the fiber fault diagnosis system.The theory of the wavelet transform has a great advantage on the signal denoising and eventdiagnosis. To introduce wavelet transform algorithm into fiber diagnosis system can improve theaccuracy of fiber fault location and the maintenance efficiency of fiber network.This paper implements a new type of OTDR signal processing module based on FPGA.Firstly, the wavelet reconstruction algorithm is used to remove the noise, secondly the OTDRsignal is decomposed by Harr wavelet based on the Mallat algorithm.This system using DSP Builder design process is convenient, intuitive and can greatlyshorten the cycle of the design characteristics of DSP. The experimental results show that thewavelet decomposition and reconstruction algorithm is proved to be effective for real-timeOTDR signal fault location.The value of this OTDR design not only provides the methodology for improving in laterdevelopment version, but also offers the valuable technical reference for the manufacture of suchkind of OTDR product embedded in FTTx.