US4846547A — Microbend fiber-optic sensor

Claim 1

Independent Claim 135 words

A fiber-optic sensor for producing microbends in an optical fiber in response to variation of an environmental parameter, said optical fiber being embedded in a sheath made of a first material, said sheath being coated with a layer of a second material wherein said layer exhibits two lines of surface discontinuities according to a longitudinal direction of the fiber, said discontinuities being periodically distributed on each line at a distance d from each other and said lines being symmetrical according to the rotation axis of the fiber, but shifted on both sides of the rotation axis of the fiber whereby said first and second materials react in response to said environmental parameter in such a manner that a variation of said environmental parameter produces microbends of the same periodicity d as that of said discontinuities.

Claim 2

Dependent Claim 135 words

A fiber-optic sensor for producing microbends in an optical fiber in response to variation of an environmental parameter, said optical fiber being embedded in a sheath made of a first material, said sheath being coated with a layer of a second material wherein said layer exhibits two lines of surface discontinuities according to a longitudinal direction of the fiber, said discontinuities being periodically distributed on each line at a distance d from each other and said lines being symmetrical according to the rotation axis of the fiber, but shifted on both sides of the rotation axis of the fiber whereby said first and second materials react in response to said environmental parameter in such a manner that a variation of said environmental parameter produces microbends of the same periodicity d as that of said discontinuities.

Claim 3

Dependent Claim 28 words

Sensor according to claim 1, wherein said sensor is sensitive to a variation of temperature, and wherein said first and second materials exhibit differing coefficients of thermal expansion.

Claim 4

Dependent Claim 23 words

Sensor according to claim 2, wherein said first material is made of a plastic material, and said second material made of a metal.

Claim 5

Dependent Claim 25 words

Sensor according to claim 1, wherein said second material is made of a metal, and said discontinuities are obtained by mechanical attack of said metal.

Claim 6

Dependent Claim 25 words

Sensor according to claim 1, wherein said second material is made of a metal, and said discontinuities are obtained by chemical attack of said metal.

Claim 7

Dependent Claim 26 words

Sensor according to claim 1, wherein said sensor is sensitive to humidity, and wherein said first and second materials exhibit differing coefficients of adsorption of moisture.

Claim 8

Dependent Claim 22 words

Sensor according to claim 1, wherein said sensor is sensitive to pressure, and wherein said first and second materials exhibit differing rigidities.

Claim 9

Dependent Claim 13 words

Sensor according to claim 1, wherein said optical fiber is a monomode fiber.

Claim 10

Dependent Claim 13 words

Sensor according to claim 1, wherein said optical fiber is a multimode fiber.

Claim 11

Dependent Claim 13 words

Sensor according to claim 1, wherein said optical fiber is a bimode fiber.

Claim 12

Dependent Claim 49 words

Sensor according to claim 1, wherein said periodicity of said discontinuities is such that the microbends produced in response to said variation of said environmental parameter involve a transfer of energy from at least one mode guided by said fiber to at least one mode radiated outside said fiber.

Claim 13

Dependent Claim 50 words

Sensor according to claim 1, wherein said periodicity of said discontinuation is such that the microbends produced in response to said variation of said environmental parameter involve a transfer of energy from at least one mode guided by said fiber to at least one other mode guided by said fiber.

Claim 14

Dependent Claim 27 words

A fiber-optic sensor as claimed in claim 1, wherein said periodic discontinuities are shifted a half-period d/2 on each side of the rotation axis of the fiber.

Claim 15

Dependent Claim 97 words

A fiber-optical sensor for producing microbends in an optical fiber in response to a variation of an environmental parameter, wherein said optical fiber is embedded in a sheath made of a first material, said sheath being coated with a layer of a second material having periodic discontinuities in a longitudinal direction of the fiber optical sensor, said discontinuities being disposed asymmetrically with respect to a plane containing the fiber axis, said first and second materials reacting in response to a variation in said environmental parameter to produce microbends of the same periodicity as that of said discontinuities.

Claim 16

Dependent Claim 97 words

A fiber-optical sensor for producing microbends in an optical fiber in response to a variation of an environmental parameter, wherein said optical fiber is embedded in a sheath made of a first material, said sheath being coated with a layer of a second material having periodic discontinuities in a longitudinal direction of the fiber optical sensor, said discontinuities being disposed asymmetrically with respect to a plane containing the fiber axis, said first and second materials reacting in response to a variation in said environmental parameter to produce microbends of the same periodicity as that of said discontinuities.

Claim 17

Dependent Claim 29 words

A sensor according to claim 14, wherein said sensor is sensitive to a variation of temperature, and wherein said first and second materials exhibit differing coefficients of thermal expansion.

Claim 18

Dependent Claim 24 words

A sensor according to claim 15, wherein said first material is made of a plastic material, and said second material made of a metal.

Claim 19

Dependent Claim 27 words

A sensor according to claim 14, wherein said sensor is sensitive to humidity, and wherein said first and second materials exhibit differing coefficients of absorption of moisture.

Claim 20

Dependent Claim 23 words

A sensor according to claim 14, wherein said sensor is sensitive to pressure, and wherein said first and second materials exhibit differing rigidities.

Claim 21

Dependent Claim 14 words

A sensor according to claim 14, wherein said optical fiber is a monomode fiber.

Claim 22

Dependent Claim 14 words

A sensor according to claim 14, wherein said optical fiber is a multimode fiber.

Claim 23

Dependent Claim 14 words

A sensor according to claim 14, wherein said optical fiber is a bimode fiber.

Claim 24

Dependent Claim 50 words

A sensor according to claim 14, wherein said periodicity of said discontinuities is such that the microbends produced in response to said variation of said environmental parameter involve a transfer of energy from at least one mode guided by said fiber to at least one mode radiated outside said fiber.

Claim 25

Dependent Claim 51 words

A sensor according to claim 14, wherein said periodicity of said discontinuities is such that the microbends produced in response to said variation of said environmental parameter involve a transfer of energy from at least one mode guided by said fiber to at least one other mode guided by said fiber.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1992-07-10	1993-01-09	1993-07-11	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1996-07-10	1997-01-09	1997-07-11	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2000-07-10	2001-01-09	2001-07-11	$7700.00	Window Closed / Lapsed

Microbend fiber-optic sensor

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