Sensing device having a large diameter D-shaped optical waveguide

• US 20040179765A1
• Filed: 01/13/2004
• Published: 09/16/2004
• Est. Priority Date: 03/18/2002
• Status: Active Grant

• Current Assignee: Weatherford Technology Holdings, LLC (Weatherford International PLC)
• Original Assignee: Weatherford/Lamb Incorporated (Weatherford International PLC)
• Inventors: Kersey, Alan D., Putnam, Martin A., Sanders, Paul E., Dowd, Edward Michael
• Granted Patent: US 8,073,293 B2
• Time in Patent Office: Days
• US Class Current: 385/12
• CPC Class Codes: G01B 11/18 using photoelastic elements
• CPC Class Codes: G01D 5/353 influencing the transmission properties of an optical fibre
• CPC Class Codes: G01D 5/35377 Means for amplifying or modifying the measured quantity
• CPC Class Codes: G01D 5/3538 using a particular type of fiber, e.g. fibre with several cores, PANDA fiber, fiber with an elliptic core or the like
• CPC Class Codes: G01K 11/32 using changes in transmittance, scattering or luminescence in optical fibres
• CPC Class Codes: G01L 1/242 the material being an optical fibre
• CPC Class Codes: G02B 6/02 Optical fibres with cladding with or without a coating
• CPC Class Codes: G02B 6/02052 comprising optical elements other than gratings, e.g. filters comprising gratings G02B6/02057
• CPC Class Codes: G02B 6/02057 comprising gratings
• CPC Class Codes: G02B 6/03611 Highest index adjacent to central axis region, e.g. annular core, coaxial ring, centreline depression affecting waveguiding
• CPC Class Codes: G02B 6/03627 arranged - +
• CPC Class Codes: G02B 6/03644 arranged - + -
• CPC Class Codes: G02B 6/274 based on light guide birefringence, e.g. due to coupling between light guides G02B6/105, G02B6/024 take precedence; mechanically induced birefringence G02F1/0134
• CPC Class Codes: G02B 6/2817 using reflective elements to split or combine optical signals
• CPC Class Codes: G02B 6/2821 using lateral coupling between contiguous fibres to split or combine optical signals
• CPC Class Codes: G02B 6/2826 using mechanical machining means for shaping of the couplers, e.g. grinding or polishing grinding, polishing in general B24
• CPC Class Codes: G02B 6/29334 Grating-assisted evanescent light guide couplers, i.e. comprising grating at or functionally associated with the coupling region between the light guides, e.g. with a grating positioned where light fields overlap in the coupler
• CPC Class Codes: G02B 6/29377 controlling dispersion around 1550 nm, i.e. S, C, L and U bands from 1460-1675 nm
• CPC Class Codes: G02B 6/4214 the intermediate optical element having redirecting reflective means, e.g. mirrors, prisms for deflecting the radiation from horizontal to down- or upward direction toward a device G02B6/4246 takes precedence
• CPC Class Codes: H01S 3/06708 Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering optical fibres as passive waveguides G02B6/02
• CPC Class Codes: H01S 3/0675 : Resonators including a grating structure, e.g. distributed Bragg reflectors [DBR] or distributed feedback [DFB] fibre lasers
• CPC Class Codes: H01S 3/094003 : the pumped medium being a fibre
• CPC Class Codes: H01S 3/094007 : Cladding pumping, i.e. pump light propagating in a clad surrounding the active core
• CPC Class Codes: H01S 3/094019 : Side pumped fibre, whereby pump light is coupled laterally into the fibre via an optical component like a prism, or a grating, or via V-groove coupling
• CPC Class Codes: Y10T 29/49815 : Disassembling
• CPC Class Codes: Y10T 29/49817 : with other than ancillary treating or assembling

Abstract

An optical sensor formed from an optical waveguide having at least one core surrounded by a cladding and a large diameter generally D-shaped portion is disclosed. Axial or compressive strain across the D-shaped cross section may be determined by measuring the change in polarization or birefringence of the light output from the sensor. A layer responsive to a parameter may be disposed on a flat portion of the D-shaped portion of the sensor. The refractive index of the layer changes and/or the layer applies a strain on the sensor in response to the parameter. Changes in the refractive index of the layer alters the light output from the sensor, which is measured over time and correlated to the parameter.

Claims

1. An optical sensor for sensing a measurand, comprising:

an optical waveguide having an outer cladding and at least one inner core disposed therein which propagates light; and

a D-shaped portion of the optical waveguide having a generally D-shaped cross-section, wherein a property of the D-shaped portion changes in response to the measurand.

2. The optical sensor of claim 1, further comprising a layer disposed on a flat surface of the D-shaped portion, wherein the layer is sensitive to the measurand.

3. The optical sensor of claim 2, wherein the measurand includes at least one of the members of the group consisting of heat, humidity, light, electric field, magnetic field and chemicals.

4. The optical sensor of claim 2, wherein the refractive index of the layer changes in response to a change in the measurand.

5. The optical sensor of claim 2, wherein the layer strains the D-shaped portion in response to a change in the measurand.

6. The optical sensor of claim 1, wherein a transverse outer dimension of the waveguide is greater than 0.3 millimeters.

7. The optical sensor of claim 1, wherein a strain applied to the sensor changes a polarization of the light.

8. An optical sensor for sensing a measurand, comprising:

a first D-shaped waveguide having a generally D-shaped cross-section;

a second D-shaped waveguide having a generally D-shaped cross-section, wherein the first and second D-shaped waveguides are optically coupled together; and

a layer disposed between the first and second D-shaped waveguides, the layer capable of changing thickness in response to the measurand.

9. The optical sensor of claim 8, wherein the first D-shaped waveguide has at least one first inner core disposed therein which propagates light in substantially a few spatial modes and the second D-shaped waveguide has at least one second inner core disposed therein which propagates light in substantially a few spatial modes.

10. The optical sensor of claim 8, wherein the measurand includes at least one member of the group consisting of heat, humidity, light, electric field, magnetic field and chemicals.

11. The optical sensor of claim 8, wherein the first and second D-shaped waveguides include a plurality of cores.

12. A method of detecting a parameter using an optical sensor, comprising:

transmitting light through the optical sensor;

exposing a D-shaped portion of the optical sensor to the parameter, wherein the D-shaped portion provides a change in one or more properties of the light transmitted through the optical sensor in response to the parameter; and

detecting the one or more properties of the light transmitted through the optical sensor as a measure of the parameter.

13. The method of claim 12, wherein a layer sensitive to the parameter is disposed on a flat surface of the D-shaped portion.

14. The method of claim 13, wherein the parameter includes at least one of the members of the group consisting of heat, humidity, light, electric field, magnetic field and chemicals.

15. The method of claim 13, wherein the refractive index of the layer changes in response to a change in the parameter.

16. The method of claim 13, wherein the layer strains the D-shaped portion in response to a change in the parameter.

17. The method of claim 12, wherein a transverse outer dimension of the sensor is greater than 0.3 millimeters.

18. The method of claim 12, wherein a strain applied to the sensor changes a polarization of the light.

19. The method of claim 12, wherein the D-shaped portion comprises a first D-shaped waveguide and a second D-shaped waveguide optically coupled together with the layer disposed between the first and second D-shaped waveguides.

20. The method of claim 19, wherein the first and second D-shaped waveguides include a plurality of cores.