Fiber optic pressure sensor using pressure sensitive fiber different from input and output fibers
First Claim
1. A fiber optic pressure sensor comprising, in combination:
- a sensing fiber comprising a short length of single region transparent fiber of a dielectric material surrounded circumferentially by a layer of a metal for which the real part of the complex permittivity in a predetermined range of wavelengths is negative, the layer of metal hermetically sealing the fiber and defining a dielectric/metal boundary;
mechanical means for producing microbends in the sensing fiber at the dielectric/aluminum boundary in response to a pressure to be sensed;
a source of light at the predetermined range of wavelengths;
a first optic fiber coupling light from the source of light to one end of the transparent sensing fiber;
a light detector; and
a second optic fiber coupling light from the other end of the transparent sensing fiber to the light detector, whereby microbends at the dielectric/aluminum boundary in response to the pressure to be sensed cause increased light loss from the transparent medium to the aluminum within the sensing fiber and thus decrease the light detected by the light detector.
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Accused Products
Abstract
A microbend fiber optic pressure sensor includes a short length of sensing fiber comprising a fiber of a transparent dielectric material surrounded by a layer of aluminum or similar metal for which the real part of the complex permittivity is negative over a range of electromagnetic radiation wavelengths. The layer of aluminum is hermetically sealed to the transparent material. The sensing fiber receives light in the range of wavelengths and is subjected to microbends on the dielectric/aluminum boundary by pressure responsive mechanical apparatus for a much greater microbend light loss and therefore greater sensitivity than is obtained with similar sensors using an all glass core/cladding boundary. The sensing fiber may be an aluminum coated single mode fiber with a very small core and a large cladding layer in which the cladding modes are used and the core modes ignored or it may comprise a single glass fiber coated with aluminum. The sensing fiber is used only in the sensing region, with light coupled to one end from a light source and from the other end to a light detector through lower loss multimode optic fibers.
48 Citations
5 Claims
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1. A fiber optic pressure sensor comprising, in combination:
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a sensing fiber comprising a short length of single region transparent fiber of a dielectric material surrounded circumferentially by a layer of a metal for which the real part of the complex permittivity in a predetermined range of wavelengths is negative, the layer of metal hermetically sealing the fiber and defining a dielectric/metal boundary; mechanical means for producing microbends in the sensing fiber at the dielectric/aluminum boundary in response to a pressure to be sensed; a source of light at the predetermined range of wavelengths; a first optic fiber coupling light from the source of light to one end of the transparent sensing fiber; a light detector; and a second optic fiber coupling light from the other end of the transparent sensing fiber to the light detector, whereby microbends at the dielectric/aluminum boundary in response to the pressure to be sensed cause increased light loss from the transparent medium to the aluminum within the sensing fiber and thus decrease the light detected by the light detector. - View Dependent Claims (2, 3, 4, 5)
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Specification