Sensing systems using quartz sensors and fiber optics

• US 6,305,227 B1
• Filed: 09/02/1998
• Issued: 10/23/2001
• Est. Priority Date: 09/02/1998
• Status: Expired due to Term

• Current Assignee: Weatherford Technology Holdings, LLC (Weatherford International PLC)
• Original Assignee: Cidra Sarl (Nordic Cultural & Educational Foundation)
• Inventors: Pruett, Phillip E., Didden, Kevin F., Kersey, Alan D., Wu, Jian-Qun, Hay, Arthur D.
• Primary Examiner(s): Oen, William
• Application Number:
  US09/145,621
• Time in Patent Office: 1,147 Days
• Field of Search: 737/05, 731/525.1, 731/525.2, 731/525.3, 250/227.14, 250/227.24, 356/345, 350/96.1
• US Class Current: 73/705
• CPC Class Codes: E21B 47/135 using light waves, e.g. infrared or ultraviolet waves
• CPC Class Codes: G01H 9/004 using fibre optic sensors light guides per se G02B6/00, acousto-optical devices specially adapted for gating or modulating in optical wave guides G02F1/125

Abstract

A quartz sensing system includes a quartz sensor, an electromechanical converter, an optical source, an optical fiber and a signal processor. The quartz sensor responds to a pressure, and further responds to an electrical power signal, for providing a quartz sensor electrical signal containing information about the pressure. The electromechanical converter responds to the quartz sensor signal, for providing an electromechanical converter force containing information about the sensed voltage or current signal. The optical source for provides an optical source signal. The optical fiber responds to the electromechanical converter force, for changing an optical parameter or characteristic of the optical source signal depending on the change in length of the optical fiber and providing an electromechanical converter optical signal containing information about the electromechanical converter force. The signal processor responds to the electromechanical converter optical signal, for providing a signal processor signal containing information about the pressure. In one embodiment, the electromechanical converter includes a piezoelectric or magnetostrictive transducer that responds to the quartz sensor signal, for providing an piezoelectric or magnetostrictive transducer force containing information about the quartz sensor signal. In another embodiment, the electromechanical converter includes an acoustic transducer and a piezoelectric or magnetostrictive transducer. The acoustic transducer responds to the quartz sensor signal, for providing an acoustic transducer wave containing information about the quartz sensor signal. The piezoelectric or magnetostrictive transducer responds to the acoustic transducer wave, for providing a piezoelectric or magnetostrictive transducer force containing information about the acoustic transducer wave.

Claims

1. A pressure sensing system, comprising:

a quartz sensor having an input and two outputs, responsive to pressure, and further responsive to an electrical power signal received in the input, for sensing the pressure free of temperature effect over time, and providing from the two outputs quartz sensor electrical signals containing information about the pressure;

a transducer having two inputs, responsive to the quartz sensor electrical signals received in the two inputs, for providing an electromechanical transducer force containing information about the quartz sensor electrical signals;

an optical source for providing an optical source signal;

an optical fiber, responsive to the electromechanical transducer force, for changing an optical parameter or characteristic of the optical source signal depending on the change in length of the optical fiber and providing a transduced optical signal containing information about the electromechanical force from the transducer; and

a measurement unit, responsive to the transduced optical signal, for providing a measurement unit signal containing information about the pressure.

2. A pressure sensing system according to claim 1,

wherein the transducer is a piezoelectric or magnetostrictive transducer.

3. A pressure sensing system according to claim 2,

wherein the optical fiber is wrapped around the piezoelectric or magnetostrictive transducer and affixed thereon.

4. A pressure sensing system according to claim 2,

wherein the optical fiber is bonded to the piezoelectric or magnetostrictive transducer;

wherein the optical fiber has fiber Bragg Grating pairs arranged on a part thereof not bonded to the transducer; and

wherein the piezoelectric or magnetostrictive transducer is arranged between the fiber Bragg Grating pairs.

5. A pressure sensing system according to claim 2,

wherein the optical fiber has one fiber Bragg Grating arranged on a part thereof bonded to the piezoelectric transducer.

6. A pressure sensing system according to claim 1,

wherein the sensing system is a coupler-based interferometer sensing system.

7. A pressure sensing system according to claim 6,

wherein the optical source and detection unit (12) provides an optical signal on the fiber (F_i);

wherein the sensing system further comprises a coupler (C₁) that responds to the optical signal, for providing two optical signals, one optical signal (Sφ

_R) of which has a reference phase (φ

_R);

wherein the sensor is a quartz sensor (Q_i) that responds to the pressure, for providing the sensor signal in the form of a quartz sensor signal containing information about the pressure;

wherein the transducer T_i responds to the quartz sensor signal, for providing the transducer force containing information about the quartz sensor signal;

wherein the optical fiber (F) is wrapped around the transducer (T_i), responds to the transducer force, changes the phase of the optical signal depending on the change in length of the fiber (F_i), for providing a transduced optical signal Sφ

_i having a transduced phase (φ

_i) containing information about the transducer force;

wherein the sensing system further comprises a coupler C₂ that combines the optical signal (Sφ

_R) and the transduced optical signal (Sφ

_i), for providing a coupled optical signal (Sφ

_Ri); and

wherein the measurement unit (140) processes the coupled optical signal (Sφ

_Ri), for providing the measurement unit signal containing information about the physical property such as the pressure.

8. A pressure sensing system according to claim 1, wherein the measurement unit performs signal processing on the transduced signal using direct spectroscopy utilizing conventional dispersive elements such as line gratings or prisms, and a linear array of photo detector elements or a CCD array.

9. A pressure sensing system according to claim 1, wherein the measurement unit performs signal processing on the transduced optical signal using passive optical filtering using both optics or a fiber device with wavelength-dependent transfer function, such as a WDM coupler.

10. A pressure sensing system according to claim 1, wherein the measurement unit performs signal processing on the transduced optical signal using tracking with a tuneable filter such as, for example, a scanning Fabry-Perot filter, an acousto-optic filter or fiber Bragg Grating based filters.

24. A pressure seismic sensing system according to claim 3,

wherein the optical fiber is wrapped under tension on the piezoelectric or magnetostrictive transducer.

25. A pressure seismic sensing system according to claim 3,

wherein the optical fiber is bonded to the piezoelectric or magnetostrictive transducer.

11. A pressure sensing system (10) using optical fiber, comprising:

a plurality of quartz sensors (Q₁, Q₂, . . . , Q_n), each having a respective input and two respective outputs, responsive to pressure, and further responsive to an electrical power signal received in the respective input, each quartz sensor (Q₁, Q₂, . . . , Q_n) sensing the pressure free of temperature effect over time, for providing from the two outputs respective quartz electric sensor signals (S₁₁, S₁₂;

S₂₁, S₂₂;

. . . ;

S_n1, S_n2) containing information about the change in pressure;

a plurality of transducers (T₁, T₂, . . . , T_n), having two inputs, responsive to the respective quartz electric sensor signals (S₁₁, S₁₂;

S₂₁, S₂₂;

. . . ;

S_n1, S_n2) received in the two inputs, for providing a plurality of electromechanical transducer forces containing information about the plurality of quartz electric sensor signals;

a broadband optical source (12) for providing a broadband optical source signal;

an optical fiber (F) having fiber Bragg Grating pairs therein (20, 22;

24, 26;

28, 30) each with a respective wavelength (λ

₁, λ

₂, . . . , X_n), responsive to the plurality of electromechanical transducer forces, for changing an optical parameter or characteristic of the broadband optical source signal depending on the change in length of the optical fiber and providing a plurality of fiber Bragg Grating optical signals containing multiplexed information about the plurality of electromechanical transducer forces; and

a measurement unit (40), responsive to the plurality of fiber Bragg Grating optical signals, for providing a measurement unit signal containing information about the change in pressure.

12. A sensing system according to claim 11,

wherein the plurality of transducers include one or more piezoelectric or magnetostrictive transducers.

13. A sensing system according to claim 12,

wherein the optical fiber is separately wrapped around each of the plurality of piezoelectric or magnetostrictive transducers and bonded thereon.

14. A sensing system according to claim 12,

wherein the fiber Bragg Grating pairs are arranged on a part of the optical fiber not bonded to each of the plurality of transducers;

and

wherein each of the plurality of piezoelectric transducer is arranged between the fiber Bragg Grating pairs.

15. A sensing system according to claim 12,

wherein the at least one fiber Bragg Grating includes a respective fiber Bragg Grating separately arranged on a part of the optical fiber bonded to each of the plurality of transducers.

16. A sensing system according to claim 11, wherein the measurement unit performs signal processing on the transduced signal using one of the following methods:

direct spectroscopy utilizing conventional dispersive elements such as line gratings or prisms, and a linear array of photo detector elements or a CCD array, or

passive optical filtering using both optics or a fiber device with wavelength-dependent transfer function, such as a WDM coupler, or

tracking with a tuneable filter such as, for example, a scanning Fabry-Perot filter, an acousto-optic filter or fiber Bragg Grating based filters.

17. A pressure sensing system, comprising:

a quartz sensor, responsive to pressure, and further responsive to an electrical power signal, each quartz sensor sensing the pressure free of temperature effect over time, for providing an electrical quartz sensor signal containing information about the pressure;

an acoustic transducer, responsive to the quartz sensor signal, for providing an acoustic wave containing information about the quartz sensor signal;

an optical source for providing an optical source signal;

an optical fiber, responsive to the acoustic wave, for changing an optical parameter or characteristic of the optical source signal depending on the change in length of the optical fiber and providing a transduced optical signal containing information about the acoustic wave from the acoustic transducer; and

a measurement unit, responsive to the transduced optical signal, for providing a measurement unit signal containing information about the pressure.

18. A pressure sensing system, comprising:

a quartz sensor having an input and two outputs, responsive to a pressure, and further responsive to an electrical power signal received in the input, each quartz sensor sensing the pressure free of temperature effect over time, for providing from the two outputs quartz sensor electrical signals containing information about the pressure;

electromechanical converter means having two inputs, responsive to the electrical quartz sensor signals received in the two inputs, for providing a mechanical converter force containing information about the sensed voltage or current signal;

an optical source for providing an optical source signal;

an optical fiber, responsive to the mechanical converter force, for changing an optical parameter or characteristic of the optical source signal depending on the change in length of the optical fiber and providing an electromechanical converter optical signal containing information about the mechanical converter force; and

signal processor means, responsive to the electromechanical converter optical signal, for providing a signal processor signal containing information about the pressure.

19. A pressure sensing system according to claim 18, wherein the electromechanical converter means includes a piezoelectric or magnetostrictive transducer that responds to the quartz sensor signal, for providing an piezoelectric or magnetostrictive transducer force containing information about the quartz sensor signal.

20. A pressure sensing system according to claim 18, wherein the electromechanical converter means includes an acoustic transducer that responds to the quartz sensor signal, for providing an acoustic transducer wave containing information about the quartz sensor signal;

wherein the electromechanical converter means includes a piezoelectric or magnetostrictive transducer that responds to the acoustic transducer wave, for providing an piezoelectric or magnetostrictive transducer force containing information about the acoustic transducer wave.

21. A pressure sensing system according to claim 19, wherein the measurement unit performs signal processing on the transduced signal using one of the following methods:

direct spectroscopy utilizing conventional dispersive elements such as line gratings or prisms, and a linear array of photo detector elements or a CCD array;

or

passive optical filtering using both optics or a fiber device with wavelength-dependent transfer function, such as a WDM coupler;

or

tracking with a tuneable filter such as, for example, a scanning Fabry-Perot filter, an acousto-optic filter or fiber Bragg Grating based filters;

or interferometry utilizing a grating-based or coupler-based scheme processing signals from fiber Bragg Grating or coupler pairs for detecting a change in phase as a function of a change in length of the optical fiber.

22. A pressure sensing system according to claim 18,

wherein the change in length of the optical fiber causes a change in the phase or wavelength of the optical source signal being transmitted or reflected through the optical fiber.

23. A pressure sensing system according to claim 18, wherein sensing system further comprises a cable for housing the plurality of quartz connections, the plurality of transducers and the optical fiber.