Study On Material-filled Micro-structured Fiber Sensor

Micro-structured fiber(MSF)has attracted much attention due to its rich preparation materials and flexible structure.Especially in the field of optical fiber sensing,MSF provides a new idea for sensor research.Due to its advantages of anti-electromagnetic interference,explosion-proof,flame-proof,light weight,small volume and long-term monitoring,MSF sensor has rapidly applied into the fields of national security,major projects and so on.Because of its special structure,it is possible to fill other materials into MSF.In recent years,the filled MSFs sensors have shown unique and excellent properties,achieved higher sensitivity,higher accuracy and longer distance sensing.In this paper,the theoretical and experimental researches on the material-filled MSF sensor are carried out,which are shown following.1.A microstructured optical fiber temperature sensor with high sensitivity based on Sagnac interference is designed.It has a high sensitivity by introducing MSF filled temperature sensitive material MSF into a Sagnac interference system.The birefringence of the proposed fiber will change with the variation of the temperatures,which makes the Sagnac transmission spectrum move accordingly.The results show that the average sensitivity is 16.55 nm/℃ in the temperature range 45 ℃ to 75 ℃.2.A high-sensitivity and high-integration sensor for magnetic field detection with dual-core MSF is designed.By filling the central air hole with magnetic fluid to realize the magnetic field sensitive characteristics.According to the coupling theory of two-core fiber,when the external magnetic field changes,the transmission period of light in the two cores changes,which eventually leads to the drift of the coupling transmission spectrum.The results show that the maximum sensitivity is-442.7pm/Oe,when the magnetic field intensity is in the range of 30 to 520 Oe.Furthermore,the length of the applied dual-core fiber is only 2000 μm.3.A MSF refractive index sensor with ultra-wide detection range based on surface plasma resonance(SPR)is designed.Surface plasmon resonance is excited by introducing gold into the optical fiber and the loss peak is formed in the transmission spectrum.The liquid to be tested is filled in the central hole of the fiber as the fiber core to improve the detection range of the sensor.The results illustrate that the proposed sensor has an ultra-wide refractive index range from 1.29 to 1.49 with a sensitivity of-4156.82 nm/RIU(refractive index unit).4.A multi-channel gas sensing network based on active cavity absorption and hollow core MSF is proposed and verified by experiments.Using optical switch and dense wavelength division multiplexer to combine the technology of time division multiplexing and wavelength division multiplexing,16 channel sensing is realized.The detection efficiency is increased about 6 times by voltage gradient method.The experimental results show that the lowest detection limits at the absorption wavelength of 1530.371 nm and 1531.588 nm are 25.91 ppm and 26.85 ppm,respectively.