FlexPatch: a rugged miniature FBG strain sensor

The design and development of a novel opto-mechanical strain sensor-called FlexPatch-based on the use of an optical fiber Bragg grating (FBG) mounted into a custom-made miniature metallic flexure is reported. The FBG sensing element is attached to a carrier flexure using proprietary bonding process which ensures a linear, drift-free and repeatable strain response even under severe moisture and temperature conditions. The sensor is uncompensated for temperature effects, but has undergone extensive mechanical and environmental testing and is qualified for use in a strain range of +/- 2,500me with a gage factor of 1.2pm/me over a temperature range from -40° to 120°C, and a fatigue life >100x10 6 cycles. The FlexPatch is intended for use in diverse sensing and monitoring applications and can be installed onto surfaces by epoxy bonding or spot welding.