Research For Positioning Technology Based On Mach-zehnde Distributed Optical Fiber

Optical fiber sensor which uses optical fiber as transmission medium and usesoptical signal as carrier uses this character which optical parameters such as phasechange over external parameters to be measured and detects the change of opticalparameters to achieve the purpose of detection of external physical quantity beingmeasured. It has been taked very seriously because of its characteristics ofanti-electromagnetic interference, reliability, corrosion resistant, high sensitivity, widemeasuring object, low cost, light in weight. Interferometric distributed optical fibersensor which has the highest sensitivity can apply to perimeter security system in ahousing estate, positioning the vibration and solve the traditional security monitoringsystem of disadvantages of low safely, easy damage, susceptible to electromagneticinterference, small range of measuring object.This paper mainly studies the positioning technology based on the Mach-zed ofdistributed optical fiber sensing system to provide an alarm and the precise location ofillegal intrusion for residential area. Based on the Mach-zed based distributed opticalfiber sensor, the paper self-developed a set of photoelectric conversion circuit andpreprocessing circuit and uses DSP2812embedded processors for the study of invadinginterference location. This paper first introduces principle and structure of the Mach-zehnder distributed optical fiber sensor, the sensing mechanism and the positioningprinciple， and deduces the conclusion which the time difference between twointerference signals is the key, analyses positioning algorithm and the optimization ofpositioning algorithm， put forward the innovative new event detection mechanism tomeet the requirements of real-time monitoring. In the aspect of hardware, setting thephotoelectric conversion circuit and preprocessing circuit which uses PIN photoelectricdiode as the photoelectric conversion device, using DSP2812as an embedded processorto gather the interference signal and compute positioning algorithm. In the aspect ofsoftware, CCS3.3is used as a development environment, in which the AD collectionprocedures, incident detection algorithm procedures and positioning algorithmprocedures are compiled. Last, Building experiment platform, operating the Positioningexperiment based Mach-zed distributed optical fiber sensor and analyzing experimental results.In this paper, Incident detection algorithm is added in front of the localizationalgorithm, to filter the useless signal, to reduce the burden on DSP, to improve accuracyand intrusion alarm system accuracy. At the same time, optimizing the localizationalgorithm and using DSP2812make the computing speed greatly increased. So thesystem can meet the requirements of for real-time monitoring.