A method to measure reference strain in FBG strain sensor interrogation system involving actuators

A method for reference strain measurement for FBG strain sensor in the testing stage while applying strain using actuators like piezo translators or micro screw is introduced. Unlike conventional methods of surface mounting, in our method the strain gauge is affixed directly to the optical fibre, which allows it to use with systems where the strain is applied directly using actuators while testing the FBG sensing system. Different bonding techniques were tested and a comparison with the results from calculated values are presented. Since the contact area between the fibre and strain gauge is very small, a corrected gauge factor is calculated and is used to measure the strain transfer. As a demonstration of the developed method, the strain gauge is used as a reference in an edge filter based FBG sensors interrogation system, where the strain was applied using a micro screw. The measured strain using foil strain gauge affixed to the optical fibre and FBG sensor interrogation system are in close agreement.