Research On Optical Fiber Sensor Based On Peanut Shape Structure

This thesis mainly investigates optical fiber sensor based on peanut shape fusion structure and designs two kinds of relative fiber sensor.One sensor is constructed by a peanut shape structure spliced with a section of multimode fiber,another sensor is fabricated by a peanut-shape structure spliced with a long-period fiber grating.Experiments are carried out for the measurement of some conventional physical parameters such as angle,liquid level,refractive index and curvature.Optical fiber sensor based on peanut shape structure has a lot of distinctive advantages,for example,light structure,high sensitivity,good plasticity,quick response,but also it is simply produced and has good repeatability.Some introductions to the relevant interference theories involved in these fiber sensors based on peanut shape structure are covered,and the sensitivity and linearity of the two fiber sensors for the measurement of the above physical parameters are discussed.The main work of this thesis is as follows:1.Make some basic introductions to the Michelson fiber sensor,Mach-Zehnder fiber sensor,Sagnac fiber sensor,Fabry-Perot fiber sensor,respectively.The modal interference theories of M-Z interferometer are stated,and introduce the manufacture process,sensing theory and mode field distributions of the peanut shape structure.2.An optic fiber sensor based on peanut shape structure spliced with a section of multimode fiber is proposed,the multimode fiber is 4mm long,and there is a30 mm single mode fiber between the peanut shape structure and the multimode fiber,so the whole length of the fiber sensor is 34 mm.The research background and measuring principle of the liquid level,refractive index and temperature are introduced,respectively.Experiments are carried out for the measurement of these parameters by this sensor.Experimental results obtain good sensitivity and linearity,which shows this sensor structure has a favorable linear response to the threeparameters change.3.A fiber sensor constructed by a peanut shape structure spliced with long-period fiber grating(LPG)is proposed,the LPG is 24 mm long,and there is a10 mm single mode fiber between the peanut shape structure and the LPG,so the entire length of this sensor is 34 mm.LPG is fabricated by a high frequency CO2 laser pulses writing on the single mode fiber,the manufacturing method and mode coupling theories of LPG are stated detailly.Some basic introductions are maked to the measuring principle of the curvature and angle.Experiments are carried out for the measurement of the curvature,angle and temperature by this sensor.Experimental results obtain good sensitivity and linearity,which shows this sensor structure has a favorable linear response to the three parameters change.