Patent ID: 7702190

Claim:
A method of strain sensing comprising the steps of: providing an optical fiber having at least a first fiber Bragg grating (FBG) and a second FBG formed therein; providing a packaging structure having, in a quiescent state, substantially an arc-shape such that the first FBG is disposed on an outer side of an apex of the arc-shaped packaging structure, and the second FBG is disposed on an inner side of the apex; subjecting the optical fiber to a strain inducing force that is applied substantially at the apex of the arc-shaped packaging structure such that a grating period in the first FBG compresses and a grating period in the second FBG extends; and optically interrogating the first and second FBGs to determine peak reflection wavelengths of the first and second FBGs respectively; wherein the first and second FBGs, in the quiescent state, have different grating periods for providing an initial separation of the peak reflection wavelengths of the first and second FBGs and such that a grating period of the first FBG is shorter than a grating period of the second FBG, whereby a separation between the peak reflection wavelengths of the first and second FBGs is representative of the strain induced.