Design of expendable fiber Bragg grating bathythermograph system

Sea water temperature gradient is an important parameter in oceanographic survey and research. Expendable bathy thermograph (XBT) is a measuring instrument of ocean temperature profile under the sailing state of ship with real-time, fast and low-cost features. XBT usually does not use the depth sensor, but uses an empirical formula to calculate the probe depth according to water intake time of the probe, so the depth error is large. In this paper, the principle, design and implementation of the expendable fiber Bragg grating bathythermograph system are introduced. A prototype of the system is developed and tested, and the gathered measurement data are analyzed. The results show that this system provides a way of fast real-time measurement of temperature and depth with a small depth error, and provides a reference for the further research on XBT system.