Application Of Microwave Photonic Filter Based On Incoherent Light Source In Optical Fiber Sensing

With the increasingly serious environmental problems,people gradually realize that there are more and more ecological environmental problems that need to be solved urgently.This puts forward higher requirements for the rapid development of environmental monitoring technology.The development of sensing technology is an indispensable support for the rapid development of environmental monitoring technology.With the continuous enrichment and promotion of large-scale IOT network,the development trend of FBG sensing technology is deepening to the research direction of larger capacity,lower cost and higher spatial resolution.The development of microwave photonic sensing technology is of great significance to the further promotion of optical fiber sensing research.The theoretical significance and engineering use value of the project.In this context,in order to improve the sensitivity of optical fiber sensing technology,reduce the cost of the system and achieve high-precision sensing as the goal,the microwave photonic filtering method is applied to optical fiber sensing,and a series of theoretical and experimental research work is carried out.The main research results are as follows:(1)In the study of FBG spectrum measurement,it is found that the wavelength dependent loss of incoherent broadband light source(BOS)will change the FBG spectrum.For different BOS optical power,the same length of fiber will produce different measured value of FBG center wavelength shifts,and with the increase of transmission fiber length,the measured value of FBG center wavelength will shift.This study has important significance for improving the sensing sensitivity.The significance of reference should be discussed.(2)In the research on the performance of microwave photonic sensor system with MZI structure,it is found that the end reflection of fiber grating will affect the performance of microwave photonic filter,and the microwave photonic sensor system can be used to detect the end reflection of fiber grating.It is proved by experiments that the reflection of the end face of the fiber will have an important impact on the performance of the microwave photonic filter,which will affect the performance of the microwave photonic sensing system.This research plays an important role in improving the performance of the microwave photonic filter.(3)Three kinds of microwave photon sensing systems are studied.Firstly,a FBG cascaded microwave photon sensing system for temperature sensing is proposed.Aiming at the problem of large data noise,a multi-point average algorithm is proposed to process the data and then fit it,which improves the sensitivity of the sensor.Then,a microwave photonic sensor system based on Fiber Bragg grating second-order dispersion fluctuation measurement is studied.The second-order dispersion fluctuation of FBG is detected by the method of phase intensity conversion,so that the wavelength change of FBG is converted into the phase difference between the fluctuation signals,and the change of RF signal intensity is reflected on the spectrometer to detect the second-order dispersion fluctuation of FBG.Finally,a microwave photonic liquid sensing system based on the reflection of two end faces of optical fiber is proposed.The sensing system can recognize the change of the type and concentration of the liquid to be measured,and can realize long-distance sensing,it also has good sensing linearity.