OFDR system for localized vibration detection

Patent metadata

Field	Value
Publication number	US-9791312-B2
Application number	US-201514713044-A
Country	US
Kind code	B2
Filing date	May 15, 2015
Priority date	Jun 26, 2014
Publication date	Oct 17, 2017
Grant date	Oct 17, 2017

Abstract

A vibration detector and method of measuring vibration are described. The vibration detector includes an optical fiber comprising a reference reflector and a delay coil, and one or more sensors comprised at respective one or more locations in the optical fiber, each of the one or more sensors including a center reflector and two side reflectors on either side of the center reflector, the delay coil eliminating detection of interference among reflections from the one or more sensors. The vibration detector also includes a light source to introduce light into the optical fiber to interrogate the optical fiber, a detector to obtain interference signals, each of the interference signals being based on interference between reflections from the reference reflector and one of the one or more sensors; and a processor to process each of the interference signals to obtain vibration measurements.

First claim

The invention claimed is:

1. A vibration detector, comprising:
an optical fiber comprising a reference reflector;
one or more sensors comprised at respective one or more locations in the optical fiber, each of the one or more sensors including a center reflector and two side reflectors on either side of the center reflector, each of the center reflector and the two side reflectors being broadband reflectors that reflect a plurality of wavelengths;
a light source configured to introduce light into the optical fiber to interrogate the optical fiber;
a detector configured to obtain interference signals, each of the interference signals being based on interference between reflections from the reference reflector and one of the one or more sensors; and
a processor configured to process each of the interference signals to obtain vibration measurements.

2. The detector according to claim 1 , wherein the vibration detector includes two or more sensors and the optical fiber further comprises a delay coil, the delay coil is disposed between the reference reflector and the two or more sensors, and the delay coil is configured to eliminate detection of interference among reflections from the two or more sensors.

3. The detector according to claim 2 , wherein a length of the delay coil is greater than a length between one of the two or more sensors closest to the delay coil and another of the two or more sensors farthest from the delay coil on the optical fiber.

4. The detector according to claim 1 , wherein a reflectance of the center reflector of each of the one or more sensors is at least two times greater than a reflectance of each of the two side reflectors.

5. The detector according to claim 1 , wherein the light source is a swept laser configured to sweep a linear range of wavenumbers.

6. The detector according to claim 1 , further comprising a circulator configured to channel light from the light source into the optical fiber and channel the interference signals to the detector.

7. The detector according to claim 1 , wherein the processor isolates each of the interference signals resulting from the one or more sensors based on a length between the reference reflector and the center reflector of the respective one or more sensors.

8. The detector according to claim 1 , wherein the processor performs amplitude demodulation of each of the interference signals to obtain amplitude signals associated with each of the one or more sensors.

9. The detector according to claim 8 , wherein the processor performs phase demodulation on the amplitude signals associated with each of the two or more sensors.

10. The detector according to claim 9 , wherein the vibration measurements are based on the phase demodulation for each of the two or more sensors.

11. A method of measuring vibration, comprising:
obtaining interference signals based on a reference reflector and one or more sensors located along respective one or more locations on an optical fiber, each of the one or more sensors comprising a center reflector and two side reflectors on either side of the center reflector, wherein the center reflector and the two side reflectors are broadband reflectors that reflect a plurality of wavelengths;
isolating each of the interference signals from each of the one or more sensors;
performing amplitude demodulation on each of the interference signals to obtain amplitude signals associated with each of the one or more sensors;
performing phase demodulation of each of the amplitude signals; and
obtaining vibration measurements based on the performing the phase demodulation of each of the amplitude signals.

12. The method according to claim 11 , wherein the obtaining the interference signals includes obtaining each of the interference signals based on interference between reflections from the reference reflector and reflections from a respective one of the one or more sensors.

13. The method according to claim 12 , wherein, based on the obtaining the interference signals from two or more sensors, the obtaining the interference signals further includes disposing a delay coil between the reference reflector and the two or more sensors.

14. The method according to claim 13 , wherein the disposing the delay coil includes fabricating the delay coil with a length greater than a length between one of the two or more sensors closest to the delay coil and another of the two or more sensors farthest from the delay coil on the optical fiber.

15. The method according to claim 11 , wherein the isolating each of the interference signals includes performing a Fourier transform.

16. The method according to claim 15 , wherein the isolating each of the interference signals is based on a length, corresponding with the Fourier transform, between the reference reflector and the center reflector of the respective one or more sensors.

17. The method according to claim 11 , wherein the performing the phase demodulation includes performing a Hilbert transform.

18. The method according to claim 11 , further comprising interrogating the optical fiber with light from a swept laser sweeping a linear range of wavenumbers to obtain the interference signals.

19. The method according to claim 11 , further comprising disposing at least one of the one or more sensors on a portion of an electronic submersible pump to monitor vibration and predict failure of the electronic submersible pump.

20. The method according to claim 11 , wherein the performing the amplitude demodulation includes performing envelope detection.

Assignees

• Cooper Daniel Boyd
• Baker Hughes Inc

Inventors

• Cooper Daniel Boyd

Classifications

• G01M11/3172

  Reflectometers detecting the back-scattered light in the frequency-domain, e.g. OFDR, FMCW, heterodyne detection · CPC title

• G01H9/004 Primary

  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) · CPC title