Spectrally coded multiplexing in a strain sensor system based on carrier-modulated fibre Bragg gratings

Abstract

In order to increase the number of channels available to a grating based strain sensor system specialised gratings were designed that would allow the sensor system to be able to distinguish between a number of gratings located in the one WDM channel independently of the amount by which they overlap each other in the wavelength domain. Distinguishing between gratings is achieved by inscribing a carrier frequency in the grating spectrum, so that each grating can be addressed in the Fourier domain via the spectral information centred around the inscribed carrier frequency. Tests performed on the gratings successfully show the ability to distinguish between three spectrally overlapping gratings. The calculated value for Young's modulus, 72+/-3GPa, was found to be in keeping with the standard value of 70.3GPa for fused silica.