Research On Frequency Scanning Interferometry Based On Double-sideband Modulation

Frequency scanning interferometry(FSI)is an effective method based on laser technology of distance measurement,which has the characteristics of high precision and simple structure as conventional interferometry measurement.In addition,FSI can be used in all-fiber structure,which makes this distance measurement system strong anti-interference capacity and wider measuring range.The advantages of FSI system brings great developmental prospects and research value for industrial applications and metrology.Theoretical and experimental studies of the FSI system based on double-sideband(DSB)modulation are the focus on this research.The main research details can be listed as following:1.Firstly,a novel dual-sweep FSI system is proposed in this paper.The relative distance between reference arm and measuring arm can be determined by a swept signal in conventional FSI methods.However,this method with one single swept laser source is very sensitive to vibrations in the optical path length(OPL).Variations during the measurement of the OPL may cause a lot of measuring errors.The proposed FSI system use DSB technology to generate two swept laser signals with opposite directions,which can reduce measuring errors effectively.2.Secondly,the dual-sweep FSI system based on DSB technology is emulated in Optisystem.The simulations of the dual-sweep system in Optisystem are presented in Chapter III.Traditional FSI method with single swept laser source are also emulated as comparisons.Simulation results show that the rejection ration of the disturbance in the OPL is more than 11 dB,which means that the measuring errors caused by variations in the OPL are effectively reduced by this dual-sweep FSI system.3.Thirdly,this dual-sweep FSI method is verified experimentally.The experiment is operated in the following three conditions:(1)fixed distances;(2)vibrations in the OPL;(3)uniform linear motion.The experimental results indicate that the dual-sweep FSI method has higher precision than conventional FSI technology with single swept laser source.Particularly,results show that the vibrations in the OPL are suppressed for more than 14 dB.4.Finally,a novel FSI system based on four wave mixing(FWM)is proposed in this paper.A swept laser signal with the speed twice of the original measuring signal is generated through FWM based on DSB technology.The measuring accuracy is improved by using swept signal with lager speed in this FSI system based on FWM.The system is emulated in Optisystem as well.Simulation results indicate that the accuracy could be improved for 7 dB..