A Multi-channelhigh Speed Demodulator Of Optical Fiber Fabry-perotvibration Sensor

Optical fiber Fabry-Perot sensor is a kind of all-optical sensor based on fibermedia and takes optical wavelength as calculating scale.It can achieve very highaccuracy in non-contact measurement, which makes it has goodprospects in the microdisplacement and micro vibration detection. At present, the methods of intensitydemodulation and phase demodulationare widely applied.The method ofnone-scanning correlation demodulation belongs to phase demodulation,it has beenwidely applied because it realizes non-scanning demodulation, which not onlysimplifies the system but improves the precision. But it always is limited to low speeddynamic measurements, which cannot meet multipoint measurements and high speeddynamic measurement.Now, it realizesmultipointmeasurements by using multiplexing,but it’s application scope still has been limited because of its low speed, single-pointmeasurement and high-cost.Therefore, in this paper, we propose a high speedmulti-channel optical fiber Fabry-Perot demodulation system, which not onlyachievesmultipoint measurement and low-cost, but also improves demodulation speed.So it can be applied to high speed micro displacement and micro vibrationoccasions.Meanwhile,it broadensthe application.Firstly, this paper expounds systematically the basic principles of optical fiberFabry-Perot sensor, derivatives the non-scanning correlation demodulationtheory,buildsthe theoretical model for it and optimizessystem parameters based onsimulation results.And based on that, the multi-channel demodulation design planandimplementation method of high speed demodulation are proposed, optical wedge andhigh performance linear array CCD have been adopted to realize non-scanningcorrelation demodulation. High speed demodulation is realized by means ofeliminating stray light of light paths and improving hardware system’s signal-to-noiseratio.Secondly, the multi-channel high speed demodulation system is designed,whichcontains of the optical part and the hardware part. Optical design mainly includesdemodulation light path and module design.Hardware design divides intosingle-channel demodulation modular and master control modular.Finally, the example prototype was calibrated, the stability of itwas tested andmicro displacement and micro vibration measurement experiments were conduct. Experimental results indicate that the stability is±4.7nm, the system resolution is4.7nm and the demodulation speed is up to5KHZ. This system has improved thedemodulation speed of optical fiber Fabry-Perot sensor, broadened its presence in thehigh speed micro displacement and micro vibration applications.