Research On Sensitization Technology Of Microfiber Sensor

Optical fiber sensing has been widely used in environmental monitoring,biology,medicine,communication,aerospace,and other fields.In recent years,how to achieve the new optical fiber sensors with high sensitivity,high detection accuracy and large dynamic range has become one of research hotspot in the field of optical fiber sensing.The micro-nano fiber sensor is used to measure the external environment parameters with the help of its strong evanescent field and taking the micro-nano fiber as sensitive element.Compared with the ordinary optical fiber sensor,the micro-nano fiber sensor has many advantages,such as integration,fast response,and high sensitivity.For the past few years,with the research on the optical properties for graphene materials and a series of research results,researchers are going to combine the micro-nano fiber and graphene materials,to enhance the sensing properties of micro-nano fiber,and to achieve the sensors with higher precision,larger measuring range and the selectivity.This paper mainly focused on the study of the sensitivity enhancement of micro-nano fiber.First,it introduced the current situation of micro-nano fiber sensors,and illustrated the significance of the sensitization research of micro-nano fiber.Then it described the optical waveguide characteristics of micro-nano fiber,and the sensing mechanism of interferometric micro-nano fiber sensor and micro-nano fiber Bragg grating sensor.Finally,we designed and produced the interferometric micro-nano fiber sensor and the micro-nano fiber Bragg grating sensor,and improved the performance of the micro-nano fiber sensor by means of oxide graphene materials.(1)The fabrication of tapered micro-nano fiber sensors utilized the fused biconical taper method.By adjusting parameters of tapering continuously,we eventually made the excellent tapered micro-nano fiber devices based on polarization-maintaining fiber.By combining tapered micro-nano fiber devices with the graphene oxide,a micro-nano fiber sensor based on graphene oxide(GO)was built,and its gas response characteristics was studied.The experimental results show that the tapered micro-nano fiber sensor with the uniform region with diameter and length of 13 ?m and 6 mm,respectively,has more outstanding performance.Without GO coating,the sensor is not sensitive to ethanol gas.However,sensitivity for ethanol gas of the sensor coated with GO significantly is increased,and the sensitivity for ethanol gas is 0.138 nm/ppm in the range of 0-80 ppm,and the sensor has good repeatability.The interferometric micro-nano fiber sensor made with photosensitive fiber taper technique is also very sensitive,and its sensitivity for ethanol gas is 0.113 nm/ ppm in the range of 40-80 ppm.(2)The micro-nano fiber Bragg grating sensor was fabricated by etching fiber Bragg grating(FBG)through the phase mask method and treating it against corrosion,and its sensing characteristics was studied.In experiments,different types of fibers were used to fabricate micro-nano fiber Bragg grating(MFBG),and it was found that the micro-nano fiber Bragg grating sensor based on photosensitive fiber has better sensing performance.The micro-nano fiber Bragg grating sensor with diameter of 5 ?m has a sensitivity of 0.156 nm/ ppm in the range of ammonia concentration of 0-50 ppm;the micro-nano fiber Bragg grating sensor with diameter of 21 ?m,in the range of ammonia concentration of 0-32 ppm;the sensitivity is 0.003 nm/ ppm without GO coating,and is 0.028 nm/ ppm with GO coating.The micro-nano fiber Bragg grating sensor with diameter of 8 um has a sensitivity of 0.011 nm/% RH under the humidity of 20%-65% RH;for the sensor with diameter of 21 ?m,the sensitivity is 0.002 nm/% RH without GO coating,and is 0.008 nm/% RH with GO coating under the relative humidity of 20%-90% RH.Micro-nano fiber sensors play an increasingly important role in sensing field.It is an important research direction about further improving its sensitivity,expanding the measuring range and achieving its selectivity.The breakthrough of research in this direction makes the micro-nano fiber sensor broader application prospects and value.