| Fiber Bragg grating (FBG) sensors have generated great interests base on their unique advantages such as small structures, strong anti-jamming abilities, multiplexing capabilities. Currently, FBG sensors have been widely used for temperature, bending, strain, acceleration, and refractive index measurement as well as quasi-distributed measurement. According to the research of study and application of current refractive index and the optical fiber sensor, in this paper we design and develop a refractive index sensor structure. The sensor is fabricated and demonstrated for refractive index monitoring in experiment.This paper is based on the literature research of the development of fiber Bragg grating, classification, features and application; then the structure and principle of FBG is introduced in detail. Finally, the technology about fabrication of FBG is introduced in detail. The FBG is fabricated by using phase mask method, while193nm ArF excimer laser is used as a photo writing source. Through the theory analysis and simulation of fiber grating sensor, we know that there are different sensitive degree to external refractive index with different order modes, and receive the regular pattern of sensor output signal changes VS refractive index changes; Sensitivities of various optical wave modes are obtained by the Rsoft software. The proposed sensor approach by concatenating an FBG and a core-offset structure is a highly promising and simplified method for a wide range of refractive index sensing applications.; we demonstrated that this sensor is an effectively structure to measure refractive index though the result of this paper. Theory and experiment of this paper shows that using Leak modes is an effectively way to measure refractive index, and sensitive degree to external refractive index increase by mode order increased. In the future work, we will optimize and improve sensitivity of this sensor through gradually design the controllable order sensor structure. |
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