Research On Carbon Nanotube Doped Polymer Enhanced Temperature Sensor Based On Optical Fiber Offset Structures

Compared with the traditional temperature measurement,optical fiber temperature sensing system has the advantages of corrosion resistance,anti-electromagnetic interference,small volume,high sensitivity,long service life,and can be distributed measurement and remote monitoring etc.The structure of dislocation was made by welding two single-mode optical fibers using welding machine.This structure was based on the theory of Mach-Zehnder interferometer and realized temperature sensing according to field theory of evanescent.The proposed sensor with small size,simple fabrication,but the temperature sensitivity is not high.In order to improve the sensitivity,using the thermal conductivity and heat transfer properties of carbon nanotubes to enhance its sensitivity in this paper.In addition,simulation analysis using Rsoft and temperature sensing experiment were conducted.The main contents are as follows:(1)This chapter introduced the research background and significance of the task and then elaborated classification and application of optical fiber temperature sensor at present and its research status in Chapter 1.Optical fiber temperature sensors based on MZ interferometer were introduced in this paper,especially the optical fiber temperature sensors based on polymer sensitive material,which provide the reference for the optimization design in the following chapters.(2)At first,Theoretical analysis of the proposed sensor was given in Chapter 2.Then,the principle of double beam interference was introduced,and the characteristics of the interference spectrum and the mechanism of temperature sensing were analyzed and deduced,and the influence of the length and the offset of the interferometer on the interference spectrum were simulation analyzed by the method of beam propagation.After that,the optical fiber structure with small dislocation fusion was fabricated by using a fusion splicer,and the refractive index and temperature sensing experiments were carried out.The experimental results show that it is not sensitive to the refractive index,the temperature detection sensitivity is 48.38pm/? in the temperature range of 20??80?.In order to improve the sensitivity of temperature detection,it is proposed to coat the temperature sensitive material on the core-offset sensor.(3)This chapter mainly introduced the definition,structure and preparation method,and the application fields of carbon nanotubes,especially its application in optical fiber sensor and then described the temperature sensitive mechanism of carbon nanotubes and the commonly methods of carbon nanotube coated on fiber in Chapter 3.According to the carbon nanotube material with high thermal conductivity and thermal expansion coefficient.It is proposed that it can improve the sensitivity of temperature measurement by combining it with the core-offset optical sensor.which lay the foundation for the polymer coating on the dislocation fusion structure in the following chapters.(4)The carbon nanotubes enhanced temperature sensors based on optical fiber offset splice structures were designed,which included small core-offset and big core-offset fusion structure of polymer optical fiber Chapter 4.The small displacement welding type temperature sensor structure was designed,the sensing principle and fabrication process were introduced.The effects of different small core-offset welding structures on the interference spectrum were investigated and the optimal structure parameters were obtained.Small core-offset dislocation welding structure were coated with pure UV glue and UV glue mixed carbon nanotubes and its sensitivity is 48.81pm/? and 52.36pm/?,respectively,in the temperature range of 35 ??80?.In order to improve the sensitivity of temperature detection,the temperature sensing principle and structure optimization of the large core-offset welding structures were investigated.It was found that when the temperature range of 30 ?-70?,the sensitivity is 120pm/? when the UV glue are coated with the large dislocation welding structure.Finally,the influence of different doping ratios on the sensitivity of temperature detection was studied.The experimental results show that the sensitivity reaches 324.62 pm/? when the ratio of UV glue and carbon nanotubes is 10:1.