Optical fiber grating sensor network for monitoring refractive index and temperature distributions in fluids

In a fiber-optic multi-point sensor network basing on optical fiber Bragg gratings, simultaneous measurements of refractive indices and of temperature are performed. The Bragg wavelength of a side-polished fiber grating is determined by the refractive index of the surrounding fluid, and is measured using a high-resolving low-cost compact spectrometer. The influence of temperature is separated considering the temperature-induced Bragg wavelength shift in an adjacent non-polished part of the fiber grating. The sensor network can be applied for on-line process control in chemical, biochemical and petrol technologies, and for environmental and geotechnical monitoring, especially in flammable or corrosive surroundings, and in electromagnetic fields. A buffer layer between fiber core and analyte allows to adjust the sensor characteristic to appear with high sensitivity in the refractive index range of the interesting fluids.