Optical distributed sensor with bragg grating sensing structure
First Claim
1. An optical device for distributed sensing of a measurand and/or changes thereof where the spectral transmission and reflection characteristics of the device depend upon the measurand comprising a sensing section having at least one Bragg grating sensing structure in a waveguide, said Bragg grating sensing structure comprising at least two superimposed or partly overlapping Bragg subgratings, said Bragg grating sensing structure having at least two different Bragg wavelengths, at least two of said Bragg subgratings comprise a phase-shift, said Bragg subgratings having their phase shifts spatially separated from each other along the waveguide sensing section.
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Abstract
Optical device for distributed sensing of a measurand and/or changes thereof where the spectral transmission and reflection characteristics of the device depend upon the measurand. A passive sensing section have at least one Bragg grating sensing structure in a waveguide. The Bragg grating sensing structure comprises at least two superimposed or partly overlapping Bragg subgratings with at least two different Bragg wavelengths. At least two of the said Bragg subgratings comprise a phase-shift. The Bragg subgratings have their phase shifts spatially separated from each other along the waveguide sensing section. The sensing section can be made active by at least partly doping it with rare earth ions and forming a laser medium, or an active component. Examples of using the passive as well as the active sensing sections in optical distributed sensors are described.
24 Citations
30 Claims
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1. An optical device for distributed sensing of a measurand and/or changes thereof where the spectral transmission and reflection characteristics of the device depend upon the measurand comprising
a sensing section having at least one Bragg grating sensing structure in a waveguide, said Bragg grating sensing structure comprising at least two superimposed or partly overlapping Bragg subgratings, said Bragg grating sensing structure having at least two different Bragg wavelengths, at least two of said Bragg subgratings comprise a phase-shift, said Bragg subgratings having their phase shifts spatially separated from each other along the waveguide sensing section.
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2. An optical device for distributed sensing of a measurand and/or changes thereof where the spectral emission characteristics of the device depend upon the measurand comprising
a sensing section having at least one Bragg grating sensing structure in a waveguide, said sensing section is at least partly doped with rare earth ions and forming a laser medium, said Bragg grating sensing structure comprising at least two superimposed or partly overlapping Bragg subgratings, said Bragg grating sensing structure having at least two different Bragg wavelengths, at least two of said Bragg subgratings comprise a phase-shift, said subgratings having their phase shifts spatially separated from each other along the sensing section.
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10. An optical distributed sensor for sensing an external physical parameter comprising
a tunable optical narrowband optical source for providing light to a first input port of an optical waveguide coupling section, said coupling section having an output port coupled directly to or via a first waveguide lead section to one end of an optical waveguide sensing section, detection means selected from at least one member of the group consisting of: -
a first optical detection means coupled to the other end of the sensing section directly or via a second waveguide lead section for obtaining a measure of light transmitted through the sensing section, and a second optical detection means coupled to a second input port of the said coupling section for obtaining a measure of light reflected by the sensing section, wherein said sensing section comprises, at least one Bragg grating sensing structure in a waveguide said Bragg grating sensing structure comprising at least two superimposed or partly overlapping Bragg subgratings, said Bragg grating sensing structure having at least two different Bragg wavelengths, at least two of said Bragg subgratings comprise a phase shift, said Bragg subgratings having their phase shifts spatially separated from each other along the waveguide sensing section. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18)
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11. An optical distributed sensor for sensing an external physical parameter comprising:
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an optical pump source for providing light to a first input port of a wavelength division coupler/multiplexer, an output port of said coupler/multiplexer being connected directly to or via a waveguide lead section to an end of the optical waveguide sensing section, optical detection means coupled to either one or both ends of the sensing section for monitoring light emitted in either one or both ends of the sensing section, wherein said sensing section comprises at least one Bragg grating sensing structure in a waveguide at least partly doped with rare earth ions, said Bragg grating sensing structure comprising at least two superimposed or partly overlapping Bragg subgratings, said Bragg grating sensing structure having at least two different peak wavelengths, at least two of said Bragg subgratings comprise a phase shift, said Bragg subgratings having their phase shifts spatially separated from each other along the waveguide sensing sections, and said structures are at least partly doped with rare earth ions. - View Dependent Claims (25, 26, 27, 28, 29, 30)
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Specification