Chemical Bragg grating sensor network basing on side-polished optical fiber

An optochemical sensor network has been developed which performs on-line measurements of multi-point distributions of various chemicals. The side-polished optical fiber elements with wavelength multiplexed fiber optic Bragg gratings are sensitive to refractive index changes in thin film overlays as well as in the more extended superstrate material. A multi-layered slab waveguide model has been used for theoretical investigation of the efficiency of evanescent field interaction with fiber gratings. From these results, the structural parameters of the sensor can be optimized. The sensitivity to small refractive index changes is high for materials with a refractive index near to that of the fiber core. However, the deposition of a thin buffer layer with adapted high refractive index can enhance the sensor efficiency also for detecting materials with lower refractive index. The sensor network can be applied for process control in chemical and biochemical technology, and for environmental and geotechnical monitoring in hazardous or corrosive surrounding.