Research On Principle And Sensing Technology Of Microstructured Optical Fiber In-line Interferometer

In-line interferometer based optical fiber sensors have important research value and great potential in the field of optical fiber sensing,and have attracted wide attention because of their unique advantages,such as simple and flexible structure,easy fabrication and low cost.However,In-line interferometers based on traditional optical fibers have the disadvantages of low sensitivity and high temperature crossover.In this thesis,a series of optical fiber in-line interferometers are designed and fabricated based on microstructured optical fiber(MOF)to solve the problems of existing fiber interferometers,for example,low sensitivity,low detection accuracy,and high temperature crossover.The main contents of this article are:(1)Based on the single material property of single-mode MOF,a solution to reduce the high temperature cross-sensitivity of optical fiber sensors was proposed and used to measure tilt angle and refractive index,with a refractive index sensitivity and angular sensitivity of 252 nm/RIU and 55.6 pm/°,respectively,while retaining a low temperature.(2)Based on the above single parameter sensors,we combined with optical microcavity and proposesd a combination interference method.In this method,Mach-Zehnder and Fabry-Perot interferences cam be achieved in a single fiber.And based this method,we achieved the simultaneous measurement of temperature and refractive index.Further,by replacing the multimode fiber with a hollow core fiber,which was filled with alcohol,the temperature sensitivity is increased by 20 times.(3)Based on the combined interferometer,by combining with double filling characteristics of MOF,optical fiber microcavity and sensitive materials,we achieved the simultaneous measurement of temperature and magnetic filed by simultaneously filling of alcohol and magnetic fluid.Further,We achieved the simultaneous measurement of strain and electric filed by filling liquid crystal.(4)Based on the exposed-core microstructured fiber,a novel biosensor with high sensitivitya and large dynamic range was designed and implemented for the first time.The theoretical and experimental analysis shows that the sensor could resolve the problem of trade-off between high sensitivities,high detection limit and large dynamic range present in most interferometric RI sensors.In the thesis,we theoretically and experimentally designed a series of in-line interferometers based on microstructured fibers,and used for physical,chemical,and biological sensing,such as tilt angle,pressure,temperature,electric field,magnetic field,refractive index,and biomolecules.Compared with the existing optical fiber sensors,those sensors achieved significant performance improvement,such as low temperature cross sensitivity,high sensitivity,high detection accuracy,and simultaneous multi-parameter measurement,etc.