The Generation Of Optical Fiber Orbital Angular Momentum Beam And Its Sensing Applications

With the development of orbital angular momentum technology,optical fiber sensors based on orbital angular momentum are being widely attention by researchers.Combining orbital angular momentum with optical fiber sensing is one of the most important directions in the future development of optical fiber sensing technology.Optical fiber sensors based on orbital angular momentum are becoming the research hotspot in the field of optical fiber sensing because of their advantages of high sensitivity,small size,high temperature resistance and anti-electromagnetic interference.Based on the study of orbital angular momentum and fiber sensing technology,this thesis focuses on how to generate orbital angular momentum in optical fiber and combines the orbital angular momentum with optical fiber sensing technology.By using the characteristics of orbital angular momentum beam,the fiber grating temperature sensing and optical fiber strain sensing system are proposed respectively for high sensitivity measurement.After referring a mass of correlative literatures,the main contents in this thesis are listed as follows:(1)The optical fiber orbital angular momentum beam is introduced into the optical fiber sensing field to solve the problems existing in the measurement process of the traditional optical fiber temperature sensor and optical fiber strain sensor.By using the characteristics of orbital angular momentum beam,the fiber optic sensor based on orbital angular momentum beam is proposed to measure temperature and strain.(2)The generation principle of orbital angular momentum beam is studied.By analyzing the optical fiber mode theory,it is deduced that the power exchange occurs between the modes when the diameter of the fiber varies along the longitudinal direction.According to the orbital angular momentum generation theory in optical fiber,the structural parameters of single mode and few-mode fiber are simulated and analyzed by Rsoft.Finally,the structure parameters are determined and a scheme for generating orbital angular momentum beam in optical fiber is proposed.(3)The experimental device for generating orbital angular momentum in optical fibers is designed and constructed.The fabrication process of single mode fiber and few-mode fiber malposition structure is studied and optical fiber rotating device is designed.The generation of orbital angular momentum beam in fiber is experimentally studied and the experimental phenomena and results are analyzed.The orbital angular momentum beam verification experiment is designed to determine whether the circular beam produced in the experiment is orbital angular momentum beam.(4)The fiber grating temperature sensor based on orbital angular momentum beam is proposed and designed to realize temperature measurement.The results show that the temperature measurement range of the sensor can be adjusted by adjusting the structural parameters of the fiber grating,and the relationship between temperature measurement range,sensitivity and resolution is given.The sensor sensitivity is 23.8°/? and the minimum temperature change to be resolved is 9.6×10-3? in the low temperature measurement range of 0?15?,the resolution is higher than the traditional fiber Bragg grating temperature sensor.(5)The optical fiber strain sensor based on orbital angular momentum beam is designed and fabricated,and its strain characteristics are experimentally studied.The measurement principle of optical fiber strain sensor is studied by theoretical analysis,and the feasibility of the sensory structure is verified.Principal component analysis is used to extract the strain information contained in the image.The strain sensitivity of the sensor is 6.3×10-3a.u/?? in the range of 0?100??,it can distinguish minimum strain change is 5.61×110-4?? in theory.Sensitivity of such optical fiber strain sensor can be increased by using sensitive materials and improving structural parameters.