Tuning Nonlinearity Compensation And Instrumentation In Optical Frequency Domain Reflectometry

Optical Frequency Domain Reflectometry(OFDR)is an interferometric technique which is used to sense the physical quality.It does so by detecting the back Rayleigh backscattered light and the Fresnel reflected light.Compared with the Optical Time Domain Reflectometry(OTDR),The OFDR has many advantages including high signal to noise radio,high spatial resolution and high sensitivity.Therefore,it has been already applied widely.But there are some shortages in the spatial resolution of the long distance optical fiber network and the location accuracy of the physical quality,which has some negative impact on the development in the future.Aimed at the questions we have addressed,this dissertation presents some solving scheme such as the optical frequency nonlinearity running compensation,the sensing method based on the back Rayleigh backscattered.Both of the method can promote the OFDR technique indexes which can be theoretically and experimentally demonstrated.Moreover,this dissertation also presents the instrument manufacture method of the distributed multiple parameter sensing in OFDR,which applied the feasible technological means for practical application.The major innovations of this dissertation are as follows:1.We build the theoretical mode of the external clock sampling and derivate the expression of the external clock sampling error by analyzing the principle of the optical frequency nonlinearity tuning.We also propose an algorithm to obtain the external sampling error in time and analyze each of the impact factor of it.So we can improve the performance by optimizing the experiment parameter in OFDR.At last,we raise a new compensation method call “software clock”,which can get a better experiment result.2.Based on the principle of the back Rayleigh backscattered generation and the theory analysis before,we present a method of continuous distributed strain sensing in the view of application and derivate associative mathematic expressions.The experiment result shows that this method can measure the strain at a length of 100 m with the location accuracy of 20 cm,which sensing sensitivity can be up to 3??.3.According to the related theory research,this paper present the instrument manufacture method of the distributed multiple parameter sensing in OFDR.This instrument combines many technologies such as optics,mechanical structure design,computer program development and integral design.This instrument can achieve a distributed measurement of temperature,strain,magnetic field and current,which is the first production whose core technology is OFDR in China.