Study On Temperature Characteristics For Germanium-doped Fiber Bragg Gratings

Fiber gratings fabricated in silica-base monomode optical fiber by laser expose is a kind of novel critical optical fiber component which have been developed rapidly since the end of twenty century, and they have been used in a wide range of applications for both optical communications and optical fiber sensors. Because of their intrinsic characteristics, the fiber gratings are particularly well suitable for monitoring temperature and strain changes in civil engineering, or other structures and composite materials of airplane, airspace, vessel, bridge and dam. In addition, the fiber gratings are applied to other harsh environments, for example, high-temperature environment etc.Theory and technology of fiber grating sensors for temperature sensing are discussed and developed experimentally in this paper. The major work is to study experimentally the temperature sensing characteristics in a larger range temperature; the development progress of fiber gratings is summarized in detail; the fiber gratings' application future for both optical communications and optical fiber sensors, the demodulation technology of fiber grating sensor, the fiber grating sensing network technology, and the sensing principle of fiber Bragg grating are analyzed and studied.In this article, transmission and reflection spectra of fiber Bragg gratings are experimental studied deeply and carefully, and good linearity relation between Bragg wavelength and temperature is proved, and the experimental results is identical to theoretical value. Besides, the thermal degradation of fiber Bragg gratings is carefully experimental studied. Experiment results indicate the thermal behavior of fiber Bragg gratings in the temperature range from room temperature to high temperature at 840℃, and the thermal behavior is similar to a spring's: the elasticity of "atom spring" will be destroyed when the grating temperature is heated to critical temperature, viz. the fiber Bragg gratings will be washed out. Therefore, a novel viewpoint, atomic elastic model is applied to explain the thermal degradation mechanism of fiber Bragg gratings at high temperature, is present in this article. This work is very useful to the application for fiber Bragg gratings in the large range of temperature, it therefore has important scientific and practical significance.