Fiber optic 2-D sensor for measuring the strain inside the concrete specimen

Based on white-light Michelson interferometric fiber optic sensing techniqu e, a fiber optic two-dimensional (2-D) strain sensing system is presented. The system employs a light emitting diode (LED) as a broadband optical sour ce and a single mode fiber that was fabricated in definite length as the st rain sensor heads, The light signals are guided by the same lead in and lea d out fiber, so the changing caused by the environmental temperature fluctu ation of the fiber path can automatically be compensated. The two independe nt fiber optic strain sensors were embedded in the cubic concrete specimens along the main axial (horizontal) direction and the vertical direction. Th e sensor gauge length is 103 and 115 mm, respectively. And its resolution i s about +/-5 micro strain ( ts). It is in agreement with the conventional e xtensometer in the range of 0-6000 mu epsilon. (C) 2001 Elsevier Science B. V. All rights reserved.