Distributed fiber-optic bi-directional strain-displacement sensor modulated by fiber bending loss

The distributed fiber-optic bi-directional strain-displacement sensor is composed of fiber-optic bi-directional strain-displacement chips and optical time domain reflectometer (OTDR). The operational principle is the modulation of fiber loss in OTDR, i.e. the strain and the displacement in monitoring positions are measured by the bending loss of optical fibers bonded on the tension-sensitized and compression-sensitized regions of the fiber-optic strain-displacement chips. Additionally, by inserting the time delay optic fiber, the moving direction of the substrate free ends in the fiber-optic bi-directional strain-displacement sensor can be identified by the trace taken with high spatial resolution in OTDR. The experiments indicate that the fiber-optic bi-directional strain-displacement sensor could measure strain and displacement by adopting the lengths of sensitive region and freely suspended fiber, the chip length, and attachment methods. (C) 2003 Elsevier B.V. All rights reserved.