Dynamic studies of fibre Bragg gratings

The dynamic performance of standard fibre Bragg gratings (FBGs) is assessed by 1) Straining the grating between two fixed points and subjecting it to a displacement corresponding to 1g over a frequency range of 100Hz to 1kHz. The induced strain on the grating is calculated and used in conjunction with the strained grating spectra to determine the minimum detectable length change of the grating as a function of frequency. 2) Studies were made where the FBG is wrapped under tension and modulated at frequencies up to 100 kHz. 3) Measuring large strains at low frequencies and high resolution is demonstrated by comparing the relative phase of a FBG subject to increasing strain to a reference FBG held under constant environmental conditions. The interrogating system used for all the reported measurements was a fibre optic Mach Zehnder interferometer used to generate an optical carrier at frequencies up to 2 MHz.