Fiber optic strain sensor
AssigneeUnited Technologies Corporation
InventorsGerald Meltz, Elias Snitzer
Life of this patent
Estimating the term…
Abstract
An optical fiber having at least two cores positioned in a common cladding can be fabricated to be responsive to strain or hydrostatic pressure but not to temperature through the selection of materials, spacing and shape of the cores and cladding in the fiber. Accordingly, the cross-talk between adjacent cores in the optical waveguide can be optimized to respond to a change in hydrostatic pressure or in unidirectional strain along the length of the fiber. The strain or pressure change, can be determined by measuring the relative intensity of light emerging from the different cores of the fiber. A larger unambiguous range for strain or hydrostatic pressure changes can be provided by a multi-core optical fiber embodiment.
Claims11
A strain monitor, comprising:
- strain responsive means including an optical fiber positionable where strain is to be measured, said optical fiber having a plurality of cores which are spaced apart from each other in a cladding, said cladding and each of said plurality of cores being sized and fabricated from such materials as to support only the lowest order propagation mode, thereby allowing cross-talk to occur between said cores;
- source means for generating light to be coupled into one of said cores, said light being cross-talked to adjacent cores in a manner related to strain acting on said optical fiber;
- detector means for receiving light energy emerging from each of said plurality of cores, and for providing an electrical signal related to the intensity of said emerging light;
- and
- whereby a strain acting on said optical fiber causes a change in the dimensions and refractive indices of said plurality of cores and said cladding such that mode interference between the modes of propagating light energy within said plurality of cores produces a change in the intensity of light emerging from said cores which is uniquely related to such strain acting on said optical fiber.
Dependencies are inferred from the claim text.