Research On Underground Infrastructure Fire Monitoring System With High Resolution And Long Distance Based On Sensing Fiber

As we all know,the traditional electrical temperature sensor is characterized by a short life,and being susceptible to the external interference and the distributed network can not be formed with it.Common quasi-distributed or distributed temperature sensors also have many drawbacks:low sensitivity,low temperature measurement accuracy,short measurement distances,and the possibility of cross-sensitivity between temperature and stress.Regarding these issues above,in this paper,the temperature sensing fiber is used as the sensing medium to carry out the research on the long-distance,high-resolution and high temperature monitoring system based on Raman scattering.We mainly deeply studied and experimented the theoretical basis,system research,demodulation algorithm and software design.(1)We studied the mechanism of temperature measurement based on Raman scattering and We have completed the development of a prototype based on a temperature-sensing optical fiber temperature measurement system with the OTDR technology and the dual demodulation scheme.(2)We made an in-depth study on the method of extending the sensing distance of the system via Raman amplification technology,and proposed the optimal Raman pump structure suitable for this system through simulation and analysis of the distribution of detected signal light power along the sensing fiber under the forward and backward pumping structures.In addition,for this structure,We also obtained the optimal pump parameters suitable for this system by studying and simulating the gains of the Raman amplifier modules with different pump parameters.Moreover,studies and analysis were conducted on the spatial resolution of the system and its improvement methods.(3)We studied and analyzed the temperature demodulation algorithm based on sensing fiber temperature measuring system,and put forward a temperature demodulation algorithm to eliminate the loss and attenuation and compensate the temperature sensitivity so as to avoid the large temperature measurement errors caused by the fiber loss,and realize the accurate temperature demodulation.(4)We implemented the software design of this subject system,and competed the design of the data collection program and the temperature demodulation program by using the development tool of LABVIEW.In addition,We completed the design of user interface and realized the online automatic fire monitoring and early warning of the temperature measuring system based on the temperature sensing optical fiber.