Localized dual-wavelength fiber-optic polarimeter for the measurement of structural strain and orientation.

A single-ended, all-fiber polarimetric strain sensor with wide dynamic range and linearized response is described. Linear response is achieved by using a dual-wavelength technique, with modified pseudoheterodyne signal recovery. Single-valued, multiple-fringe phase tracking is obtained by using a binary signal division technique. An average strain sensitivity of 0.050 +/- 0.02 deg microepsilon(-1) cm(-1) is found for sensors that are surface adhered to cantilever beams. The sensor system is applied successfully to the measurement of the local orientation of a 1-m structural beam, with an accuracy of +/-0.02 deg of beam slope. Limitations on the applicability of this sensing technique are discussed.