Research On Dual-parameter Measuring Interferometric Optical Fiber Sensor Based On Abrupt Taper Structure

With the advancement of times and the development of society,the field of sensing has developed rapidly.It is applied in the fields of biomedicine,urban architecture,environmental monitoring,communication technology,mechanical control and other fields.Among them,the interferometric optical fiber sensor has the advantages of simple structure,low transmission loss,low cost,small size,corrosion resistance and so on.It can be widely used to measure parameters such as temperature,strain,refractive index(RI),humidity and curvature.The basic theory used in this paper is the optical transmission characteristics and inter-mode interference.Interferometric optical fiber sensor for simultaneous measurement of temperature and RI,interferometric optical fiber sensor for simultaneous measurement of temperature and humidity have been proposed.These two kinds of optical fiber sensor have different application backgrounds and different application fields.The main research contents include:1.An interferometric optical fiber sensor based on spherical structure and abrupt taper structure is proposed and fabricated.The spherical structure and the abrupt taper structure are used as couplers.The middle sensing area is single-mode fiber(SMF).The experimental results show that the temperature sensitivities of the sensing structure are 0.052nm/? and 0.037nm/?,respectively.The RI sensitivities are-56.59nm/RIU and-43.53nm/RIU,respectively.2.An interferometric optical fiber sensor based on abrupt taper structure cascaded at both ends of thin-core fiber(TCF)is proposed and fabricated.Two abrupt taper structures are used as couplers.The middle sensing area is TCF.The experimental results show that the temperature sensitivities of the sensing structure are 0.086nm/? and 0.092nm/?,respectively.The RI sensitivities are-43nm/RIU and-31.83nm/RIU,respectively.3.An interferometric optical fiber sensor based on abrupt taper structure and lateral-offset structure is proposed and fabricated.The abrupt taper structure and the lateral-offset structure are used as couplers.The middle sensing area is SMF.In order to improve the humidity sensitivity of the sensor,the graphene dispersion is coated to the middle sensing area by using the optical driven deposition(ODD)method.The experimental results show that the temperature sensitivities of the sensing structure are 0.097nm/? and 0.127nm/?,respectively.The humidity sensitivities are-0.039nm/%RH and-0.042nm/%RH,respectively.4.An interferometric optical fiber sensor based on abrupt taper structure and peanut taper structure is proposed and fabricated.The abrupt taper structure and the peanut taper structure are used as couplers.The middle sensing area is SMF.The humidity parameter response experiments on whether or not to coat graphene dispersion are compared,and it is confirmed that coating the graphene dispersion can make the sensor more sensitive to humidity measurement.The experimental results show that the temperature sensitivities are 0.254nm/? and 0.269nm/?,respectively.The humidity sensitivities are 0.059nm/%RH and 0.133nm/%RH,respectively.The two resonance interference dips measured experimentally exhibit different parameter sensing measurement characteristics,so simultaneous measurement of dual parameters can be achieved by calculating the coefficient matrix.