In Fiber Mach-Zehnder Interferometer Sensing

Several kinds of Mach-Zehnder interferometer (MZI) sensors based on intermodalinterference have been designed and fabricated in this paper. Responses to liquid refractiveindex(RI)、temperature and pH of sensors are experimentally studied. The main aspects arelisted as follows:1、The overviewandprogress oftheopticalfibersensorapplicationintemperature、RIandpH,weredescribed,themainresearchcontentandinnovationwerealsointroducedinthepaper.2、The structure and the type of optic fiber, the optic fiber fabrication processes theprinciple of fiber optical transmission, and analyses of wave equation were introduced. Theprinciples of intermodal interference were described in detail, and the measuring principle ofoptical fiber in temperature、refractive index and pH sensing was systematically expound.3、The fabrication and performance of the sensors were introduced in details. Thepreprocessing included fiber splicing and welding parameter adjustment, Optic fibercorrosion controlling and Sol-gel preparing and coating. The fabrication methods mainlycomprising of core mismatch, fused taper and air-bubble were introduced.4、The sensors with different structures were studied on their RI, temperature and pHresponses. When liquid RI changes in the range of1.378-1.402, the sensitivity of themultimode double taper sensor was783nm/RIU. When the external solutiontemperature changes in the range of26-90℃, the sensitivity of the multimode fiber-thin corefiber-multimode fiber sensor was42.6pm/℃. When pH changes every0.82in the pH rangeof5.11-10.01, the dispersion compensation fiber-multimode fiber-dispersion compensationfiber sensor response wavelength drifted-230pm;5、In order to distinguish the temperature and RI responses of the sensor and eliminatethe cross sensitivity, a new kind of sensor was proposed and experimentally studied. Whenthe external solution temperature changes in the range of19.8-70℃, the sensitivity of themultimode fiber-multimode fiber-multimode fiber sensor was98.14pm/℃, while the sensorwas insensitive to RI change. When RI changes in the range of1.345-1.385, the sensitivity ofthe thin core-multimode-thin core sensor was394.0nm/RIU, while the sensor was insensitiveto temperature change.