Research On Pressure/Temperature Measurement Using Fiber Optic Grating For Under-Water Towed Cable

With a project background of water-depth measurement for underwater towed cable and supported by National Natural Science Foundation of China, theoretical and experimental investigations have been carried out on the temperature and pressure sensing properties of the fiber grating applied to underwater towed cable. Major researches are as following:1. Optical transmission theory of the fiber grating has been studied, and analyzed by simulation.2. Guided by the fiber grating temperature and pressure sensing theory, experimental investigations have been performed.3. Associative with the design of two kinds of package structures, the improved-sensitivity fiber gratings have been investigated experimentally using the finite element analysis. In an experimental demonstration, a press sensitivity enhancement of 2771 times has been achieved together with a depth resolution better than 5cm.4. The fiber grating's cross-sensitivity caused by temperature and pressure is studied and verified by the experimental phenomenon.5. Temperature and press sensing of single-point has experimented with dual-grating method in a lake , and a calculative precision of 2cm has been gained using the press sensitivity-enhancement sensor.The study of this issue can not only promote the development of the attitude control method used in underwater towed cables, but also provide a feasible measurement of typical environment parameters for underwater towed cables using in deep-water situation. It also has positive significance on the assistant measurement of multi-line towed cable shape estimation for oil exploration.