The Research On Characteristics Of Novel Mode Interferometric Optical Fiber Sensor And Polarization Maintaining Fiber

Optical fiber sensing technology plays an important role in environmental detection,fine control,biosensor and military security in modern society.As an indispensable part of optical fiber network,optical fiber sensors have been paid more and more attention gradually.Optical fiber sensors have the advantages of high sensitivity,anti-electromagnetic interference,and can be measured in complex environment.Optical fiber sensors based on mode interference have compact structure and can measure multi-parameters simultaneously which has become an important direction of modern sensing technology.We studied and fabricated a variety of optical fiber sensors based on mode interference used special optical fibers like no-core fiber,polarization maintaining fiber and multimode fiber.Their spectral characteristics are analyzed and their responses to the changes of different physical parameters are verified by experiments.On this basis,through the study of polarization maintaining fiber,a new type of polarization-maintaining few mode fiber is proposed and its mode characteristics are simulated and analyzed.The main research results are listed as follows1.A new type optical fiber sensor based on mode interference in no-core fiber has been proposed.Based on the basic single-mode-no-core-single-mode fiber,a composite optical fiber sensor is obtained by adding fiber grating and fused taper technology,Through expernments,the data of simultaneous measurement of axial stress and temperature are obtained.The experimental results show that the sensitivities of the selected interference peak and FBG to the axial stress are-2.93pm/?? and 0.823pm/??,to the temperature are 115.48 pm/? and 8.24 pm/?.Supported by the above data,the matrix expression of simultaneous measurement is obtained2.A composite sensor based on panda polarization-maintaining fiber is proposed.The birefringence characteristics of polarization-maintaining fibers are analyzed and explained.The sensing characteristics of axial stress and temperature of polarization-maintaining fibers are measured by experiments.Good linear fitting results are obtained,and the matrix expression of simultaneous measurement of bi-parameters is obtained.On this basis,polarization-maintaining fiber-multimode fiber-polarization-maintaining fiber sensor is fabricated using polarization-maintaining fiber.Under the same experimental conditions,comparative experiments on different structures of polarization-maintainning fiber are completed3.A composite optical fiber sensor based on panda polarization maintaining fiber and fiber etching is proposed.The optical fibers are etched to make them more sensitive to the changes of environmental parameters.Simultaneous measurement results of refractive index and temperature of the etched optical fibers sensor are obtained The sensitivity of the selected two interference peaks to the refractive index is 237.837 nm/RIU,318.279 nm/RIU,and the temperature sensitivity is 0.188 nm/?and 0.160 nm/?.The refractive index sensitivity of the sensor is competitive4.A model of a few-mode fiber based on polarization-maintaining fiber and multilayer-core fiber is proposed.Its mode field diagram and transmission performance are obtained by simulation.The fiber can accommodate 12 characteristic modes simultaneously.At the same time,the core structures which can transmit 16 and 22 characteristic modes are obtained by ellipticizing the core.