Patent ID: 7418171
Filing Date: 2008-08-26
Classification: G01K,G01L

Abstract:
1. A method of sensing variations in a structure, including: providing a fibre optic cable comprising a plurality of zones wherein each zone contains a plurality of fibre Bragg gratings, each one of the fibre Bragg gratings having a respective grating period, the respective grating periods of the fibre Bragg gratings in any one zone being substantially identical to one another, fibre Bragg gratings in different zones having different respective grating periods, wherein each two adjacent fibre Bragg gratings of the same grating period in any one zone are spaced apart by a respective inter-grating spacing that is different from the grating period of the fibre Bragg gratings in that zone; locating the fibre optic cable with respect to the structure such that the fibre optic cable is subject to variations selected from the group consisting of spatial variations, temperature variations, and variations that are both spatial and temperature related; providing a radiation receiver configured to receive radiation reflected by the Fibre Bragg gratings contained within each zone; transmitting radiation in a direction along the fibre optic cable, the transmitted radiation being reflected back down the fibre optic cable by each one of the Fibre Bragg gratings to the radiation receiver; and receiving the radiation reflected by each one of the Fibre Bragg gratings.