Optical Fiber Sensor Based On Tip Structure

To response to the rapid development of optical fiber sensor network,sensor heads that exhibit ultra-compact size and good capability of performing multiple sensing functions with high sensitivity are critically important.Optical fiber sensors,particularly those operated at the fiber tip,become increasingly attractive due to their features of simple and compact structure,good reliability,fast response,high sensitivity,and convenient reflection mode of operation.The work of this thesis is to research the theory,fabrication of fiber sensor based on fiber tip structure,and research on their performance in physical quantities experiments to prove their prospects in different applications.The main contents of this thesis are as follows:1.A new type of fiber tip Fabry-Perot(F-P)cavity sensor head based on a glass microsphere glued at the etched end of multimode fiber(MMF).The temperature,refractive index,and pressure experiments are performed,outcomes are analyzed respectively.And the experimental results of fitting line are drawn for the sensitivity of the sensor to measure different environmental factors.2.We propose and experimentally demonstrate a new type of optical fiber tip Fabry-Perot interferometer(FPI)pressure sensor based on an etched end of MMF filled with ultraviolet adhesive(UV).Pressure experiment is operated,the reflection spectrum was monitored.And the effect of changing the temperature and the refractive index are discussed,the temperature-pressure cross sensitivity is also studied.3.We also proposed a new type of microsphere whispering gallery mode(WGM)resonator with microsphere-microsphere coupling.The coupler consists of a microsphere glued to a single mode fiber(SMF)tip by use of UV adhesive.The incident light from fiber core at the fiber end diverges and arrives at the surface of microsphere with different angles.Part of diverged light beam is picked up by the second microsphere,which is glued to the first microsphere at the fiber tip.When the second microsphere is positioned properly or in other words,the angle between the connection line of the two microsphere centers and the fiber axis is appropriate,WGM resonance is excited.And the temperature experiment,obtained the reflection spectra at different temperatures.