Modeling Of Distributed Fiber Optical Vibration Sensor Based On OFDR

Distributed Optical Fiber Sensing(DOFS)has become the hot spot in recent years,Among which Optical frequency domain reflectometry(OFDR)is a very important technology in DOFS systems.OFDR has been applied in many fields due to the high dynamic range,sensitivity and spatial resolution.However,when the OFDR system is applied in vibration sensing,the theoretical analysis is simplified to a single scattering point and the mathematical model considered multiple scattering points is not given.In this thesis,we focus on the distributed optical fiber vibration sensing and the main contents are as follows:(1)According to the Rayleigh scattering principle and the theory of elastic mechanics,the mathematical model of OFDR fiber optic vibration sensor system with single scattering point is extended to the case of multiple scattering points.A mathematical model is established for the received signal of distributed optical fiber vibration sensing(DVOFS).The mathematical model is established for the received signal of distributed optical fiber vibration sensing(DVOFS)with the situations of Vibration and without vibration respectively.By comparing the real signal with the received signal that under the condition of vibration and non-vibration calculated by simulation,the pretty approximation result is found.(2)An optimized demodulation algorithm is proposed,which assigns a small weight to the data with high noise and gives a large weight to the data with lower noise.the purpose of suppressing noise is achieved.The spatial resolution of 16.5m with the sensing distance of90 km is achieved by this algorithm,which result is nearly doubled compared with previous research.