An elastomer-embedded distributed optical fiber sensor based on optical frequency domain reflectometry

Abstract

This study investigates a U-shaped low-bend-loss single-mode fiber embedded in an elastomer pad and interrogated by optical frequency domain reflectometry (OFDR) for distributed deformation sensing. The OFDR measurements used a 2.6 mm gage pitch over an approximately 1.27 m measurement path. Steady-state strain was calculated from the final portions of the recorded signals for flat and spherical-indentation loading. In the single flat upward-loading test, mean P1 strain increased from 16.73 to 759.34 µε over nominal contact pressures of 5.09–20.37 MPa. A linear fit yielded an apparent slope of 48.07 µε/MPa (R 2 = 0.9817; four load levels). During continued loading between 400 and 500 N, the OFDR return disappeared, and post-test inspection confirmed sensor fracture; the exact fracture force was not recorded. In three curved-deformation cycles from 0 to 444.82 N, the loading-branch linear-fit slopes at P1–P5 ranged from 7.71 to 9.38 µε/N (R 2 = 0.941–0.956). The corresponding unloading fits gave R 2 = 0.925–0.996, and the maximum absolute hysteresis ranged from 22.8% to 42.6% of the loading full-scale strain span. These results demonstrate distributed, position-dependent strain mapping and indicate that loading history and time-dependent deformation of the packaged pad affect the measured response.