Research On Measurement Of The Ocean Temperature-depth Profile Based On Fiber Bragg Grating

The temperature and depth are the most basic physical parameters of the ocean.It is an important method to obtain the data of ocean temperature-depth profile by observing the change of temperature with depth.FBG(Fiber Bragg Grating)rely on their own application characteristics and advantages such as small size,intrinsic insulation,anti electromagnetic interference and easy to scale array,which have attracted extensive experimental research and application of domestic and foreign experts and scholars in the field of ocean exploration.Aiming at the requirement of high density,high space-time resolution real time continuous measurement of ocean temperature profile,this paper carries out a series of in-depth study on the theory,technology and experimental methods of the temperature-depth profile measurement system based on the fiber Bragg grating sensing technology.The main research contents are as follows.Firstly,aiming at the requirement of high space-time resolution measurement of ocean temperature profile,a measurement scheme combining shipboard drag and all fiber temperature-depth chain is proposed,and a ship towed ocean temperature-depth profile measurement system is developed.The system is based on Fiber Bragg grating sensing technology,which give full play to the advantages of high-precision measurement of FBG temperature sensor and FBG pressure sensor.Secondly,for the problem of low sensitivity and slow response of traditional marine temperature sensor,a FBG temperature sensor based on stainless steel pipe structure and polymer sensitized package is developed,which has the advantages of high sensitivity,fast response and without pressure cross sensitive effect.Thirdly,in order to meet the requirements of high sensitivity and creep resistance of Marine Sounding sensor,an fiber Bragg grating pressure sensor based on elastic diaphragm encapsulation is developed by using the technology of structural sensitization,which not only avoids the long-term creep of the glue,but also makes the sensor meet the requirements of small volume,high sensitivity and high consistency by taking the scheme of replacing traditional glue packaging by laser welding.Fourthly,aiming at the measurement of FBG temperature sensor and FBG pressure sensor sensitivity and analysis of relationship between the measured physical quantity and wavelength,the temperature and pressure calibration test platform is built,which makes the selection of sensors easy and convenient.Fifthly,aiming at the engineering application of the ship towed fiber optic temperature-depth profile measurement system,two marine verification tests were carried out.The FBG temperature sensor and the FBG pressure sensor reached a high consistency with their standard sensor by analyzing comparison data,and the accuracy of the former is better than 0.1? and the latter measurement accuracy is better than 0.1m,which meet the measurement requirements of ocean temperature-depth profile.