Research On Related Technology Of Optical Fiber Composite Sensing Network Based On Tunable Laser

Due to the advantages of low loss,high sensitivity,and fast response speed,optical fiber sensing is being focused in the sensing detection field.Physical quantities can be detected by modulating light characteristics(such as light intensity,polarization state,etc.).In response to the important requirements of mechanical and thermal parameters real-time sensing and security monitoring in practical engineering applications,this paper constructs a hybrid optical fiber sensing network,which utilizes laser devices as the system core.In this network,optical fiber is the transmission part.Based on the tunable laser,an optical fiber high and low temperature multi-parameter sensing system was proposed.Besides,a visual video linkage monitoring platform of the optical fiber perimeter security sensing system was developed based on the Unmanned Aerial Vehicle(UAV)control technology.The research work of this thesis mainly includes the following aspects:(1)Discrete fiber grating sensing technology has been applied in the mechanical and thermal multi-parameter sensing field,which mainly includes construction projects such as spacecraft test and structure detection.In order to realize the composite sensing of mechanical and thermal parameters in special environments,this paper proposes an optical fiber high and low temperature multi-parameter sensing system.First of all,the theory of fiber Bragg gratings(FBG)is illustrated.With the consideration of improving demodulation accuracy of the mechanical and thermal parameters in high and low temperature environments,an optical fiber high and low temperature multi-parameter sensing system was constructed.The system uses fiber Bragg gratings as the sensing unit,utilizes a tunable laser as the incident light source.Besides,the etalon is used to provide the wavelength reference signal.The system can realize dual-parameter sensing of temperature and strain.Besides,the manufacturing process of the temperature and strain sensor has been improved.Taking into account the characteristics of sensitivity reducing of the sensor in low temperature environment,a second-order fitting method was used in the process of wavelength calculation of the FBG sensors.This demodulation method improves the accuracy of mechanical and thermal parameters sensing.The results show that the composite sensing system proposed in this paper can realize accurate and stable dual-parameter sensing in the temperature range of-252.75℃～200.94℃.(2)Distributed optical fiber vibration sensing can realize continuous distributed measurement by constructing optical fiber interferometer.DMZI optical fiber intrusion sensing system has unique advantages,which include high sensitivity and long-distance positioning detection.Due to the fact that the traditional all-fiber perimeter security system can only provide early warning of intrusion events and cannot perform visual video monitoring,it has deficiencies in the application of large-scale and complex terrain.Considering of these problems,quad-rotor UAV technology and optical fiber sensing system are combined.The UAV has good flexibility and can carry cameras for aerial photography.An optical fiber vibration sensing network based on single frequency laser was proposed.In this network,A quad-rotor drone hardware platform was built,the ground station was compiled to achieve the video linkage monitoring function.The sensing network experiment proves that the UAV can quickly respond to the intrusion events and perform flight missions.