Fiber optic grating sensor systems for sensing environmental effects

摘要

One or more optical fiber gratings are used to sense environmental effects that can vary the spacing between the lines of the grating to vary the center frequency of the spectral envelope, either reflected or passed thereby. Light of the sensor grating's spectral envelope is transmitted to a local grating unaffected by the environmental effect and compared with the spectral envelope of the local grating to produce an intensity modulated signal, which is detected to sense the environmental effect. The sensor systems so constructed may have one or more local gratings and those local gratings may be modulated to reduce the effects of noise, broaden the dynamic range, vary the sensitivity or discriminate in a multiplexed embodiment. The system can be operated either open or closed loop.