Optical Cable Fault Locator Based On Birefringence Effect

In the field of optical fiber cable maintenance and rush repairment,traditional optical time domain reflectometry(OTDR)cannot satisfy the urgent requirement of on-field engineers.A portable equipment that can help engineers fix the fault position of optical fiber cable is indispensable for the purpose of rush repairment.The thesis is focused on the fault locator based on the birefringent effect arising in the single-mode fiber,after we investigate the technical characteristics of traditional OTDR,together with the operation principle of polarization OTDR(P-OTDR).The research topic covers fiber optical sensing,data processing and analysis,and embedded system design,in order to develop an equipment with capabilities of quick and accurate fault position.The research outcomes can be summarized as follows:(1)We explore the fiber optical sensing technique based on the Rayleigh backscattering as an information source to deliver the fault position.The optical path design of equipment has all advantages of P-OTDR,for the ease of characterizing the disturbance point according to the birefringence effect.(2)We design the algorithm suitable for the fault location of optical cable,based on the wavelet algorithm.We comprehensively discuss the wavelet base selection,wavelet decomposition level,denoising method,and disturbance point recognition.Meanwhile,as for the embedder system design,by using field programmable gate array(FPGA)as the core and STM32F4 as the main controller unit,a portable equipment with functions of optical pulse generation,signal detection,data processing and analysis,and human-computer interaction is successfully developed.(3)We carry out on-field trial of optical cable fault locator,in order to identify its measurement accuracy.The measurement error of the long distance characterization(35km ?40km)is within ±80m,while the short distance(less than 3km)is within ±10m.