Fiber Bragg Grating Strain Sensors

Fiber Bragg Grating is a fiber optic device that is expected to be great applicative prospect in fiber communication and fiber sensor. As a sensor element, fiber optic and grating transformed the information into reflecting wavelength shift. It also named wavelength demodulation which is immune for light power waving and system loss. Besides, FBG has those advantages, reliance, resisting for electromagnetic signals and antisepsis. It is constructed as FBGs network by being put together on a single fiber so as to realize distributed sensing, which is an unexampled merit for FBG.In FBG sensors technology, it is very important to choose the light source. In experimental method for this paper, a new face, twin-stage and double-passing structure ASE super-fluorescence fiber source is chose as the sensor-based system. The source has these characteristics, low cost, high bandwidth, high power and fine flatness. So it not only can apply to sensor-based systems, but also can apply to other experiments. For example, optic fiber gyro and erbium-doped fiber amplifier, so it has largeness value both in academy and experiment.The key point in FBG sensors lies in precise measurement of minute shift of Bragg reflecting wavelength. It is used for demodulating the coded signals of wavelength. Though it is can be achieved by OSA with high resolution, OSA can not be applied into practical situation because of its huge-size and high-cost. So developing high-resolution and low-cost FBG demodulator is the key issue when FBG sensors industrializations are coming. Although a large number of research and investigations on the demodulation methods of FBG, but most of the researches are still in the phase of lab experiments and have not yet met the requirements of the practical industrial mass productions.In this paper, a new method is put forward which using the transformation of the power of reflected light for signal demodulator, its rationale is deduced in the paper, and in the experiment, a approach named "couple-grating demodulation" has been used, so it realized accurate measurement for stress with gometer. Therefore it greatly reduce the system costs.In this paper, experiments with OSA and gometer are all proceeded, and they both achieved accuracy measure to stress, the fitted curve also preferably anastomosed with theoretical value.