SYSTEMS AND METHODS FOR DISTRIBUTED PRESSURE SENSING

• US 20160018277A1
• Filed: 07/21/2014
• Published: 01/21/2016
• Est. Priority Date: 07/21/2014
• Status: Active Grant

• Current Assignee: Baker Hughes, a GE Company, LLC (Baker Hughes Company)
• Original Assignee: General Electric Company
• Inventors: Challener, William Albert, Palit, Sabami
• Granted Patent: US 9,240,262 B1
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01D 5/35316 using a Bragg gratings
• 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: G01L 1/242 the material being an optical fibre
• CPC Class Codes: G01L 1/246 using integrated gratings, e.g. Bragg gratings
• CPC Class Codes: G01L 11/025 using a pressure-sensitive optical fibre
• CPC Class Codes: G01M 11/31 with a light emitter and a light receiver being disposed at the same side of a fibre or waveguide end-face, e.g. reflectometers
• CPC Class Codes: G02B 2006/12138 Sensor
• CPC Class Codes: G02B 6/02042 Multicore optical fibres
• CPC Class Codes: G02B 6/022 using mechanical stress, e.g. tuning by compression or elongation, special geometrical shapes such as "dog-bone" or taper G02B6/02204 takes precedence; optical modulation using photo-elastic effect G02F1/0131
• CPC Class Codes: G02B 6/02328 Hollow or gas filled core
• CPC Class Codes: G02B 6/02347 Longitudinal structures arranged to form a regular periodic lattice, e.g. triangular, square, honeycomb unit cell repeated throughout cladding
• CPC Class Codes: G02B 6/024 with polarisation maintaining properties
• CPC Class Codes: H01B 9/005 including optical transmission elements

Abstract

A pressure sensing cable in one embodiment includes an optical fiber having a first core and a second core. The first core extends along a length of the cable, and is sized and configured to provide propagation of light along the first core along the length of the cable. The first core has a first mode index corresponding to the speed of light propagation along the first core. The second core extends along the length, is spaced a distance from the first core, and is sized and configured to provide propagation of light along the second core along the length of the cable. The second core has a second mode index corresponding to the speed of light propagation along the second core. The second mode index is different from the first mode index, wherein light propagates along the second core at a different speed than along the first core.

Claims

1. A pressure sensing cable comprising:

an optical fiber comprising;

a first core extending internally along a length of the cable, the first core sized and configured to provide propagation of light along the first core along the length of the cable and having a first mode index corresponding to the speed of light propagation along the first core; and

a second core extending internally along the length of the cable, the second core spaced a distance from the first core, the second core sized and configured to provide propagation of light along the second core along the length of the cable and having a second mode index corresponding to the speed of light propagation along the second core, the second mode index being different from the first mode index, wherein light propagates along the second core at a different speed than along the first core.

2. The pressure sensing cable of claim 1, further comprising a plurality of openings extending along the length of the cable and disposed around at least one of the first core or the second core, the openings having a size that substantially prevents the openings from operating as cores for the propagation of light along the length of the cable.

3. The pressure sensing cable of claim 1, wherein the first core comprises a first solid material and the second core comprises a second solid material that is different than the first solid material.

4. The pressure sensing cable of claim 1, wherein at least one of the first core or the second core has one or more embedded Fiber Bragg Gratings disposed along the length of the cable.

5. The pressure sensing cable of claim 1, wherein the first core comprises an open core and the second core comprises a solid material.

6. The pressure sensing cable of claim 5, comprising a mirror disposed at a return end of the second core.

7. The pressure sensing cable of claim 1, further comprising a protective sleeve extending along at least a portion of the length of the cable and surrounding the optical fiber, the protective sleeve comprising an outer shell and an inner material, the inner material interposed between the outer shell and the optical fiber.

8. The pressure sensing cable of claim 7 in which the outer shell is substantially noncircular in cross section.

9. The pressure sensing cable of claim 1, wherein the protective sleeve comprises sealingly separated chambers having a predetermined length along the length of the cable.

10. A measurement system comprising:

a pressure sensing cable comprising;

a transmission core extending internally along a length of the cable, the transmission core sized and configured to provide propagation of light along the transmission core along the length of the cable and having a first mode index corresponding to the speed of light propagation along the transmission core; and

a reception core extending internally along the length of the cable, the reception core spaced a distance from the transmission core, the reception core sized and configured to provide propagation of light along the reception core along the length of the cable and having a second mode index corresponding to the speed of light propagation along the reception core, the second mode index being different from the first mode index, wherein light propagates along the reception core at a different speed than along the transmission core;

a light source configured to provide light energy to the transmission core;

a detection unit configured to detect signals from the reception core formed responsive to the light energy in the transmission core; and

a processing unit configured to determine a pressure distribution based on the signals from the reception core detected with the detection unit.

11. The measurement system of claim 10, wherein the light energy comprises a pulse, wherein the processing unit is configured to group portions of the signals detected by the detector unit into bins based on time of detection, wherein the time of detection corresponds to a measurement position along the length of the cable.

12. The measurement system of claim 11, wherein each measurement position along the length of the cable corresponds to two time periods symmetrically disposed about an intermediate time, wherein each bin comprises portions of the signals detected by the detector unit corresponding to the two time periods.

13. The measurement system of claim 10, wherein the light energy comprises at least one of a broadband light or a laser swept across a range of wavelengths, wherein the processing unit is configured to group portions of the signals detected by the detector unit based on wavelength, wherein the wavelength corresponds to a measurement position along the length of the cable.

14. The measurement system of claim 10, wherein the transmission core comprises an open core and the reception core comprises a solid material.

15. The measurement system of claim 10, wherein the transmission core comprises a first solid material and the reception core comprises a second solid material that is different than the first solid material.

16. A method comprising:

transmitting, via a light source, light energy down a first core of a pressure sensing cable, the first core having a first mode index corresponding to the speed of light propagation along the first core;

receiving, via a detector unit, signals from a second core of the pressure sensing cable formed responsive to the transmitting the light energy down the first core, the second core having a second mode index corresponding to the speed of light propagation along the second core, the second mode index being different from the first mode index, wherein light propagates along the second core at a different speed than along the first core; and

determining, using one or more processors, a pressure distribution along a length of the pressure sensing cable based upon the signals received from the second core via the detector unit.

17. The method of claim 16, wherein transmitting light energy comprises transmitting a series of light energy pulses, and wherein determining the pressure distribution comprises grouping portions of the signals received from the second core into bins based on time of detection, wherein the time of detection corresponds to a measurement position along the length of the pressure sensing cable.

18. The method of claim 17, wherein each measurement position along the length of the cable corresponds to two time periods symmetrically disposed about an intermediate time, wherein each bin comprises portions of the signals detected by the detector unit corresponding to the two time periods.

19. The method of claim 16, wherein transmitting light energy comprises transmitting at least one of a broadband light or a laser swept across a range of wavelengths, and wherein determining the pressure distribution comprises grouping portions of the signals received from the second core into bins based on wavelength, wherein the wavelength corresponds to a measurement position along the length of the pressure sensing cable.

20. The method of claim 16, comprising determining a pressure for predetermined intervals over the length of the cable.