An extrinsic Fabry-Perot interferometer-based large strain sensor with high resolution

A three-layer packaged structure is proposed for an extrinsic Fabry-Perot interferometer-based optical fiber sensor in order to produce high resolution for large strains. The resolutions of three data processing algorithms including interference frequency tracking, period tracking and phase tracking are investigated and compared. Laboratory tests indicate that the proposed sensor structure can measure a strain of up to +/- 120 000 mu epsilon (+/- 12%) with resolution as high as 10 mu epsilon. The sensor prototype is insensitive to fiber misalignment, enabling the study of progressive structural failures with an integrated use of the three algorithms.