Several key technologies for fiber gratings vibration sensing were studied systematically in this thesis, they are the enhanced sensitivity technology for fiber Bragg grating sensors, study and design of the vibration sensing head of fiber gratings, the dynamic demodulation technology for fiber gratings vibration sensing.Firstly, the problem that there is a low temperature response sensitivity for bare fiber grating had been solved by affixing bare fiber grating on metal substrate, and the effect that there are 3 times temperature response sensitivity for this sensors than that for bare fiber grating had been obtained. To solve the problem that there is a low pressure response sensitivity for bare fiber grating, a kind of fiber grating pressure sensors which is made by coupling cantilever with spring had been designed. The experimental result shows that the coefficient of the pressure sensitivity for this kind of sensors is 0.2218nm/Mpa, it is 74 times than that for bare fiber grating, meanwhile, the result agrees well with the theoretical value.Secondly, in the foundation above, a vibration sensing head of fiber gratings sensor, which has the structure of constant strength cantilever, was designed and made based on the theory of accelerometer and its dynamic characteristic. The sensitivity and free frequency of the sensing head had been calculated. The vibration experiment result for the sensing head qualitatively shows that it has a high sensitivity in detecting accelerated velocity.At last, the demodulation technology for fiber gratings vibration sensing was studied. Because the fiber grating sensor demodulation technology using in vibration measurement belongs to dynamic demodulation, several representative ways for dynamic demodulation were discussed in this thesis, and the virtue and shortcoming of them were compared with each other. Based on the characteristic of the sensing head we designed, the matching fiber grating demodulation was adopted, which can transform the accelerated velocity of vibration to optical intensity to measure. Using this demodulation technology, the experimental result for the sensing head shows that measuring frequency characteristic agrees well with vibration frequency characteristic. |