Fiber Optic Bragg Grating Sensor Based On Hydrogels

Recently, a considerable research effort has been focused on fiber Bragg gratings (FBGs), particularly on systems using these devices for sensing applications. Because FBG is compact, simple in fabrication, and can be operated in a wavelength-coding manner, it has become an important component for optical sensing devices in measuring temperature and strains.Hydrogels are crosslinked polymers which swell to an appreciable extent in water, and are considered as biocompatible materials. The water content depends on the polymer structure, and can be made responsive to environmental factors such as inorganic salt concentration and pH value. Many research efforts have been done to study volume changes in response to different environmental factors, and develop sensors based on hydrogels for pH, soil water potentials and other chemical parameters.Here we report a fiber Bragg grating sensor for measuring salinity using a water swellable hydrogel as the active sensing component. By modifying the hydrogel chemistry, parameters other than salinity can be detected using the same basic approach. In this thesis, we focus on the several points below:1. The design and fabrication of the Fiber Optic Bragg Grating Sensor Based On Hydrogels.2. The introduction of our experiment for the sensor, which is conducted in the 0.1mol/L~0.7mol/L NaCl solution.3. Regarding to the results of our experiments, some improvements and the potential applications of the sensor are put forward.