Distributed Optical Fiber Fast Temperature Sensing System Based On Graphene-coated Fiber

Distributed optical fiber sensing technology was proposed in the late 1970s,since then it developed with the emergence of optical time-domain reflectometer（OTDR）technology,and then produced different distributed optical fiber sensing mechanism and measurement system,and now it has become one of the most widely used technologies in optical fiber sensing technology.Distributed Temperature Sensing（DTS）is a sensing system for fast,real-time,multi-point temperature measurement,which has important application value in downhole real-time monitoring,fire alarm,rapid dynamic temperature feedback and so on.However,the current distributed optical fiber temperature measurement system is limited by the thermal conductivity of optical fiber materials,and the temperature response speed is slow,and the performance of the temperature measurement system needs to be improved urgently.To solve the above problems,this thesis has done the following research work.（1）The research status of graphene materials and their applications is systematically investigated,and the development status of the technology of distributed optical fiber temperature sensing and graphene-based optical fiber sensing are reviewed.For the scientific problems in the rapid temperature measurement requirements of distributed optical fiber,the research significance of this topic is proposed.（2）The theoretical basis of thermal conductivity and the thermal effect of graphene materials is introduced,and the sensing theory involved in the distributed optical fiber temperature measurement system is analyzed and introduced.The"Intercalation-exfoliation"technique of large-scale preparation of graphene nanosheets and the characterization test of graphene coatings are described.（3）A kind of industrial production level of kilometers long graphene-coated fiber preparation process is proposed and realized,characterized the physical properties of the graphene-coated fiber to ensure that graphene inherent properties of graphene in the optical fiber coating materials.The direct thermal conductivity test of graphene-coated fiber shows that the axial thermal diffusivity of the graphene-coated fiber is about 24.99mm~2/s,which is 30-fold larger than the axial thermal diffusion of conventional fiber,and the thermal conductivity of graphene-coated fiber is 19-fold higher than conventional fiber.（4）Using the preparation process of graphene-coated fiber,a graphene-coated optical fiber Bragg grating temperature sensor is prepared,and the thermal diffusivity of the graphene-coated fiber is 18-fold higher than that of conventional optical fiber through optical testing,based on these,a graphene-coated of quasi-distributed optical fiber Bragg grating temperature sensing system is designed.The graphene-coated fiber is used in distributed fiber temperature sensing system based on Raman scattering and distributed fiber temperature sensing system based onφ-OTDR respectively.A distributed fast temperature sensing system based on graphene fiber is proposed and implemented.The system is built,and then tested and the temperature response speed of the system is increased by more than 15-fold faster.