Optical interrogator for performing interferometry using fiber Bragg gratings

Patent metadata

Field	Value
Publication number	US-11609086-B2
Application number	US-202117521052-A
Country	US
Kind code	B2
Filing date	Nov 8, 2021
Priority date	Jun 8, 2017
Publication date	Mar 21, 2023
Grant date	Mar 21, 2023

Abstract

There is described a method for interrogating optical fiber comprising fiber Bragg gratings (“FBGs”), using an optical fiber interrogator. The method comprises (a) generating an initial light pulse from phase coherent light emitted from a light source, wherein the initial light pulse is generated by modulating the intensity of the light; (b) splitting the initial light pulse into a pair of light pulses; (c) causing one of the light pulses to be delayed relative to the other of the light pulses; (d) transmitting the light pulses along the optical fiber; (e) receiving reflections of the light pulses off the FBGs; and (f) determining whether an optical path length between the FBGs has changed from an interference pattern resulting from the reflections of the light pulses.

First claim

The invention claimed is:

1. A system for interrogating optical fiber comprising fiber Bragg gratings (“FBGs”), the system comprising:
an interrogator comprising:
a light source operable to emit phase coherent light;
amplitude modulation circuitry optically coupled to the light source and operable to generate one or more light pulses from the light;
an optical splitter optically coupled to the amplitude modulation circuitry and being configured to split a light pulse received from the amplitude modulation circuitry into a pair of light pulses;
an optical delayer optically coupled to the optical splitter and configured to introduce a delay to one light pulse of the pair of light pulses relative to the other light pulse of the pair of light pulses;
control circuitry comprising a controller, communicatively coupled to the amplitude modulation circuitry, and configured to perform a method for interrogating the optical fiber comprising generating a light pulse by using the amplitude modulation circuitry to modulate light emitted by the light source, wherein the generated light pulse is split into a pair of light pulses by the optical splitter, and wherein one of the light pulses is delayed relative to the other light pulse by the optical delayer; and
a phase modulator optically coupled to the amplitude modulation circuitry and operable to introduce a phase shift to at least one of the light pulses, and wherein the method further comprises phase shifting each of the light pulses by using the phase modulator; and

one or more optical fiber segments optically coupled to the interrogator.

2. The system of claim 1 , further comprising an outgoing optical splitter and an incoming optical combiner, the outgoing optical splitter being optically coupled to the light source and being configured to split light received at the outgoing optical splitter and transmit the split light out each of multiple outputs of the outgoing optical splitter, and wherein the incoming optical combiner is optically coupled to receiver circuitry and is configured to combine light received at each of multiple inputs of the incoming optical combiner and transmit the combined light to the receiver circuitry.

3. The system of claim 2 , further comprising one or more filter and balance units optically coupled to one or more of the multiple inputs of the incoming optical combiner.

4. The system of claim 1 , further comprising one or more optical circulators optically coupled to each of the one or more optical fiber segments, wherein, for each optical fiber segment, light sent from the interrogator to the optical fiber segment passes through the optical circulator, is reflected off FBGs comprised in the optical fiber segment, and is redirected by the circulator to receiver circuitry comprised in the interrogator.

5. The system of claim 4 , wherein the system further comprises one or more lead-in optical fiber segments optically coupling the interrogator to each of the one or more optical circulators, and one or more return optical fiber segments optically coupling each of the one or more optical circulators to the receiver circuitry.

6. The system of claim 5 , further comprising an outgoing optical splitter optically coupled to the light source and being configured to split light received at the outgoing optical splitter and transmit the split light out each of multiple outputs of the outgoing optical splitter, and wherein the one or more lead-in optical fiber segments are optically coupled to the multiple outputs of the outgoing optical splitter.

7. The system of claim 5 , further comprising an incoming optical combiner optically coupled to receiver circuitry and configured to combine light received at each of multiple inputs of the incoming optical combiner and transmit the combined light to the receiver circuitry, and wherein the one or more return optical fiber segments are optically coupled to the multiple inputs of the incoming optical combiner.

8. The system of claim 7 , further comprising one or more filter and balance units optically coupled to one or more of the multiple inputs of the incoming optical combiner, and wherein the one or more return optical fiber segments are further optically coupled to the one or more filter and balance units.

9. The system of claim 5 , wherein the one or more lead-in optical fiber segments and the one or more return optical fiber segments do not comprise FBGs.

10. The system of claim 1 , wherein the interrogator is communicatively coupled to a signal processing device configured to receive data packets from the interrogator.

11. The system of claim 10 , wherein the signal processing device is further configured to determine whether any of the data packets meet a data error condition and, if so, add an indication to the data packet that the data packet contains erroneous data.

12. The system of claim 11 , wherein the data error condition is determined to be met if:
the frame identifiers of consecutively assembled data packets do not meet a first predetermined requirement; or
the keys of consecutively assembled data packets do not meet a second predetermined requirement.

13. The system of claim 12 , wherein the first predetermined requirement comprises the frame number of an earlier assembled data packet being one less than the frame number of the next consecutively assembled data packet.

14. The system of claim 12 , wherein the second predetermined requirement comprises the key of one of the consecutively assembled data packets being separated from the key of the next consecutively assembled data packets by a preset number of bits.

15. The system of claim 10 , the signal processing device is configured to extract phase data from the data packet if no data error condition is met, wherein the phase data is obtained from interference of reflections of one light pulse of the pair of light pulses off the FBGs with reflections of the other light pulse of the pair of light pulses off the FBGs.

Assignees

• Hifi Eng Inc

Inventors

• Moore Brian H
• Shakespeare Walter Jeffrey
• Wallace Phillip William
• Hoang Viet
• Henrikson Chris
• Sandhu Ajay
• Dumitru Adrian
• Clement Thomas
• Huang Dongliang
• Jalilian Seyed Ehsan

Classifications

• G01B11/161 Primary

  by interferometric means · CPC title

• G01D5/35316

  using a Bragg gratings · CPC title

• G01K11/3206

  at discrete locations in the fibre, e.g. using Bragg scattering · CPC title

• G01L1/246

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

• G01D5/35383

  using multiple sensor devices using multiplexing techniques · CPC title