Patent ID: 8335405
Filing Date: 2012-12-18
Classification: G01D,G01M,G02B

Abstract:
1. An apparatus comprising: a polarization controller operable to adjust polarization of launched light; a multi-core optical fiber comprising a center core and a plurality of peripheral cores at a distance radially from said center core and running parallel to said center core, said center core comprising at least one fiber Bragg grating (FBG) with polarization-dependent reflectivity, said FBG at a specified distance from the launch end of the fiber, said multi-core optical fiber being operably located to receive the launched light, said fiber Bragg grating reflecting the launched light as reflected light; a multi-core optical fiber bend sensing system operable to communicate with said multi-core optical fiber, said multi-core optical fiber bend sensing system being operable to measure curvature in said multi-core optical fiber; a processor operable to communicate with said polarization controller; a single core optical fiber; an optical fiber coupler; a light source communicating with said single core optical fiber and operable to transmit said launched light through said single core optical fiber thence through said optical fiber coupler and into said multi-core optical fiber; a spectrometer communicating with said single core optical fiber and said processor; a beam splitter with fiber-coupling optics communicating with said single core optical fiber, said polarization vector analyzer, and said multi-core optical fiber; and one of a switch and a fan-out operably communicating with said beam splitter and said multi-core optical fiber, and a polarization vector analyzer operable to communicate with said single-core optical fiber and said processor, said polarization vector analyzer being operable to measure the polarization state of said launched light, wherein said FBG exhibits a minor axis and a major axis of birefringence, said polarization controller being operable to vary the polarization of the launched light so that light arriving at the FBG is linearly polarized and aligned with one of the minor axis and the major axis of birefringence, wherein said processor is operable, after said polarization controller adjusts the polarization of the launched light, to determine a twist in said multi-core optical fiber based on the polarization of the launched light and the bend in said multi-core optical fiber, and the specified distance from the launch end of the fiber to the FBG.