Key Techniques For Temperature Measurement System Based On Fiber Bragg Grating For Ocean Application

Temperature is an important parameter of the ocean. Description and analysis of the distribution and changes of temperature play a decisive role in ocean monitoring as well as scientific studies. FBG(Fiber Bragg Grating) have a natural resistance to electromagnetic interference, long distance transmission, a large number of multiplexing and high sensitivity, which have gradually aroused people’s concern in ocean exploration application. This paper is in order to realize the goal of high sensitivity, high precision and rapid ocean temperature measurement and carries out a series of in-depth study with related theory and implementation method. The following are the main research work of the study.Firstly, for the slow response, poor linearity of the traditional ocean temperature sensors, a FBG based on the metal tube and the spring structure was designed, which was fit for ocean temperature detecting. It was highly sensitive and also had high accuracy and quick response.Secondly, for the slow demodulation speed, high price and low precision of Bragg grating measuring systems at present, an optical fiber grating temperature demodulation method based on FBGA(Fiber Bragg Grating Analyzer) was proposed for the requirement of ocean temperature monitoring which had a small volume, low cost, quick response and good accuracy. A wavelength calibration algorithm was proposed in which an F-P etalon with a good thermal stability was considered as reference gratings. In this way, the problem of wavelength stability and accuracy of FBGA was addressed and the precision and stability of the system could be improved.Thirdly, in view of the application demand and the target of design of FBG temperature sensor, further design optimization was carried out based on the ocean work environment. The research results showed that the effect of temperature and strain was completely avoided. The temperature sensitivity was 27pm/℃ and the response time could be up to 58.5ms.Forthly, a FBG temperature measurement system for marine applications was developed. Tests of temperature demodulation system were implemented, which showed that this system had a good linearity, repetition and excellent stability. It could meet the demand for precision of ±0.1℃ and fast response.