Device and system for detecting dynamic strain

Patent metadata

Field	Value
Publication number	US-2020249107-A1
Application number	US-201916679050-A
Country	US
Kind code	A1
Filing date	Nov 8, 2019
Priority date	Jul 4, 2014
Publication date	Aug 6, 2020
Grant date	—

Abstract

A device and system for detecting dynamic strain. The device comprises a longitudinally extending carrier and an optical fiber embedded along an outer surface of a length of the carrier. The optical fiber comprises at least one pair of fiber Bragg gratings (FBGs) tuned to reflect substantially identical wavelengths. The system comprises the device and an interrogator comprising a laser source and a photodetector. The interrogator is configured to perform interferometry by shining laser light along the optical fiber and detecting light reflected by the FBGs. The interrogator outputs dynamic strain measurements based on interferometry performed on the reflected light.

First claim

1 . (canceled)

2 . A method for detecting dynamic strain of a buried pipeline, comprising:
(a) burying in the ground a device for detecting dynamic strain such that the device when buried does not touch the pipeline, the device comprising:
(i) a longitudinally extending carrier; and
(ii) an optical fiber embedded along an outer surface of a length of the carrier, wherein the optical fiber comprises at least one pair of fiber Bragg gratings (FBGs) tuned to reflect substantially identical wavelengths;
(b) shining laser light along the optical fiber; and (c) detecting light reflected by the FBGs and performing interferometry on the reflected light to produce dynamic strain measurements based on the interferometry.

3 . The method of claim 2 , wherein the shining of the laser step comprises shining a reference light pulse and a sensing light pulse along the optical fiber, the reference light pulse being delayed compared to the sensing light pulse by a predetermined period of time selected such that the reference light pulse reflected by a first FBG of the pair of FBGs interferes with the sensing light pulse reflected by a second FBG of the pair of FBGs to form a combined interference pulse, and wherein the detecting of the light reflected by the FBGs and performing interferometry comprises detecting the combined interference pulse and detecting a phase difference between the reflected reference light pulse and the reflected sensing light pulse of the combined interference pulse to produce the dynamic strain measurements.

4 . The method of claim 2 , wherein the burying of the device in the ground comprises burying the device between the pipeline and another buried pipeline such that the device touches neither of the pipelines, and wherein the device is used to detect dynamic strain of both of the pipelines.

5 . The method of claim 2 , wherein the optical fiber is embedded to be flush with or below the outer surface of the carrier.

6 . The method of claim 2 , wherein the carrier comprises a carrier lining with a groove in the outer surface of the carrier lining and wherein the optical fiber is positioned in the groove.

7 . The method of claim 6 , wherein the carrier further comprises a coating which coats the optical fiber and fills any space in the groove between the carrier lining and the optical fiber.

8 . The method of claim 2 , wherein the optical fiber is embedded along the outer surface of the length of the carrier by extruding the carrier with the optical fiber.

9 . The method of claim 2 , wherein the carrier comprises a carrier lining and a coating with the optical fiber positioned on an outer surface of the carrier lining and wherein the coating covers the optical fiber and the carrier lining.

10 . The method of claim 2 , wherein the device further comprises a longitudinally extending strength member, and wherein the carrier surrounds at least a portion of the strength member.

11 . The method of claim 2 , wherein the optical fiber is embedded linearly along the outer surface of the length of the carrier.

12 . The method of claim 2 , wherein the optical fiber is embedded helically around the outer surface of the length of the carrier.

13 . The method of claim 12 wherein the pitch of the helix is constant along the length of the housing.

14 . The method of claim 2 , wherein the optical fiber is embedded along a path that changes direction at least once by approximately 180°.

15 . The method of claim 2 , wherein the optical fiber comprises at least one first pair of the FBGs and at least one second pair of FBGs, wherein the FBGs of the first pair are tuned to a first wavelength and the FBGs of the second pair are tuned to a second wavelength different from the first wavelength, wherein the optical fiber between the first pair of FBGs and the second pair of FBGs is embedded along different lengths of the carrier, and wherein the performing of the interferometry comprises using wavelength division multiplexing to measure dynamic strain at the different lengths of the carrier.

Assignees

• Hifi Eng Inc

Inventors

• Hull John
• Jalilian Seyed Ehsan

Classifications

• G01D5/35316

  using a Bragg gratings · CPC title

• G01L1/246 Primary

  using integrated gratings, e.g. Bragg gratings · CPC title