US 11,054,288 B2
Optical interrogator for performing interferometry using Bragg gratings
Brian H. Moore, Edmonton (CA); Walter Jeffrey Shakespeare, Macungie, PA (US); Phillip William Wallace, Bernardsville, NJ (US); Viet Hoang, Edmonton (CA); and Tom Clement, Calgary (CA)
Assigned to Hifi Engineering Inc., Alberta (CA)
Filed by Hifi Engineering Inc., Calgary (CA)
Filed on Jul. 26, 2019, as Appl. No. 16/523,864.
Application 16/523,864 is a continuation of application No. 15/532,963, granted, now 10,416,005, previously published as PCT/CA2015/051269, filed on Dec. 4, 2015.
Claims priority of provisional application 62/207,251, filed on Aug. 19, 2015.
Claims priority of provisional application 62/087,669, filed on Dec. 4, 2014.
Prior Publication US 2019/0346295 A1, Nov. 14, 2019
Int. Cl. G01D 5/353 (2006.01); G01B 11/16 (2006.01); G01B 9/02 (2006.01); G01D 18/00 (2006.01)
CPC G01D 5/35316 (2013.01) [G01B 9/02067 (2013.01); G01B 11/161 (2013.01); G01B 11/18 (2013.01); G01D 18/00 (2013.01); G01B 2290/70 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A method for interrogating optical fiber comprising fiber Bragg gratings (“FBGs”), the method comprising:
(a) generating a first pair of light pulses and a second pair of light pulses from phase coherent light emitted from a light source, wherein the light pulses are generated by modulating the intensity of the light without splitting the light, and wherein the second pair of light pulses immediately follows the first pair of light pulses;
(b) for each of the first and second pairs of light pulses, applying a phase shift to at least one of the light pulses in the pair relative to the other of the light pulses in the pair, wherein the phase shift applied to the at least one of the light pulses in the first pair of light pulses and the phase shift applied to the at least one of the light pulses in the second pair of light pulses are the same;
(c) transmitting the light pulses along the optical fiber;
(d) receiving reflections of the pulses off the FBGs; and
(e) determining whether an optical path length between the FBGs has changed from an interference pattern resulting from the reflections of the pulses.