Distributed fiber sensor with interference detection and polarization state management
DCFirst Claim
1. An apparatus for detecting and locating disturbances, comprising:
- at least one light source;
an optical system with at least one optical waveguide, the optical waveguide having at least one detection zone at which a disturbance can occur and affect optical signals from the light source when traveling through the waveguide, in the detection zone, along counter-propagating optical channels;
at least one beam separator between the light source and the optical system, wherein the beam separator couples at least two beams into the optical waveguide for each of the at least two counter-propagating optical channels;
at least one polarization controller operable to manage optical properties of said counter-propagating optical channels, the polarization controller adjusting optical properties for at least one of the optical signals when propagating toward the detection zone;
at least one detector coupled to the optical waveguide and responsive to the optical signals after traversing the detection zone;
a data processing unit coupled to the detector, the data processing unit being operable to localize a place of the disturbance in the detection zone from a difference between times at which effects of the disturbance appear at the detector; and
,a feedback control coupled to the optical system and to at least one said polarization controller, wherein the feedback control and the polarization controller are configured to maximize a signal-to-noise ratio and to minimize a polarization contribution to said difference between times, by at least one of;
seeking a predetermined relationship between polarization phase transformations along the counter-propagating optical channels, maximizing a peak swing in intensity at a point of interference of the beams, and varying an input state of polarization for one of testing and adjusting a balance between said polarization transformations for the counter-propagating channels.
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Abstract
Polarization effects are managed to provide differential timing information for localizing disturbances affecting two or more counter-propagating light signals on one or more optical waveguides passing through a detection zone. Activity can be localized to a point for a security perimeter. Events causing optical disturbance can be mapped to points along a straight line, a perimeter or arbitrary pattern or an array. Events cause local changes in optical properties in the optical waveguide, in particular an optical fiber. Short term local changes are distinguishable from phase changes of light travel in the waveguide by managing the polarization state of input and output beams.
24 Citations
56 Claims
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1. An apparatus for detecting and locating disturbances, comprising:
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at least one light source; an optical system with at least one optical waveguide, the optical waveguide having at least one detection zone at which a disturbance can occur and affect optical signals from the light source when traveling through the waveguide, in the detection zone, along counter-propagating optical channels; at least one beam separator between the light source and the optical system, wherein the beam separator couples at least two beams into the optical waveguide for each of the at least two counter-propagating optical channels; at least one polarization controller operable to manage optical properties of said counter-propagating optical channels, the polarization controller adjusting optical properties for at least one of the optical signals when propagating toward the detection zone; at least one detector coupled to the optical waveguide and responsive to the optical signals after traversing the detection zone; a data processing unit coupled to the detector, the data processing unit being operable to localize a place of the disturbance in the detection zone from a difference between times at which effects of the disturbance appear at the detector; and
,a feedback control coupled to the optical system and to at least one said polarization controller, wherein the feedback control and the polarization controller are configured to maximize a signal-to-noise ratio and to minimize a polarization contribution to said difference between times, by at least one of;
seeking a predetermined relationship between polarization phase transformations along the counter-propagating optical channels, maximizing a peak swing in intensity at a point of interference of the beams, and varying an input state of polarization for one of testing and adjusting a balance between said polarization transformations for the counter-propagating channels. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40)
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41. A method for detecting and locating disturbances, comprising:
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establishing an optical system including at least one optical waveguide extending along at least one detection zone at which a disturbance can occur, so as to affect optical signals propagating along counter-propagating optical channels from at least one light source to a detector; separating from the at least one light source, and coupling into each of the counter-propagating optical channels, at least two beams; managing optical properties in the counter-propagating optical channels using a polarization controller to vary optical properties for at least one of the optical signals while propagating toward the detection zone; detecting the optical signals after traversing the detection zone and determining a difference between times at which effects of the disturbance appear in the respective counter-propagating channels after traversing said detection zone; calculating from said difference between times and localizing in the detection zone a place where the disturbance occurred; wherein said managing of the optical properties comprises providing a control signal to the polarization controller that maintains a signal-to-noise ratio and minimizes a contribution to said difference between times caused by polarization effects, including at least one of; seeking a predetermined relationship between polarization phase transformations along the counter-propagating optical channels, maximizing a peak swing in intensity at a point of interference of the beams, and varying an input state of polarization for one of testing and adjusting a balance between said polarization transformations for the counter-propagating channels. - View Dependent Claims (42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55)
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56. An improved method for detecting and locating disturbances affecting an optical system including at least one optical waveguide extending along at least one detection zone at which a disturbance can occur, thereby affecting optical signals propagating along counter-propagating optical channels from at least one light source to a detector, wherein at least two beams are separated from the at least one light source and coupled into each of the counter-propagating optical channels, and an effect of the disturbance is detected after the beams have traversed the detection zone and a time difference is determined for calculating a location of the disturbance in the detection zone, wherein the improvement comprises:
managing optical properties in the counter-propagating optical channels using a polarization controller to vary optical properties for at least one of the optical signals while propagating toward the detection zone, wherein said managing includes providing a control signal to the polarization controller that maintains a signal-to-noise ratio and minimizes a contribution to said difference between times caused by polarization effects, and comprises at least one of; seeking a predetermined relationship between polarization phase transformations along the counter-propagating optical channels, maximizing a peak swing in intensity at a point of interference of the beams, and varying an input state of polarization for one of testing and adjusting a balance between said polarization transformations for the counter-propagating channels.
Specification