Spectral tag method for enhancing FBG multiplexing capability

Fiber Bragg gratings (FBGs) have been frequently employed for the strain and temperature measurement in many distributed sensor systems. For multipoint measurements with a very large number of measurement points such as smart structure applications, the multiplexing of FBG sensors is one of the most detrimental techniques to reduce both installation and operation cost for multipoint measurements. We proposed a new method of increasing the multiplexing capability of a multipoint FBG sensor system without increasing the system complexity by providing a unique spectral response to each FBG at a different location as an identification tag. FBG elements were fabricated to furnish reflectance spectrums to have a multi peaked structure. The number of sensors in the present spectral tag method increases as a multiple power of N, the number of spectral code. The free spectral range available for spanning the parameter to be measured is as wide as a substantial fraction of the whole spectral bandwidth of the system.