High speed and high spatial density parameter measurement using fiber optic sensing technology

Patent metadata

Field	Value
Publication number	US-9664506-B2
Application number	US-201514827533-A
Country	US
Kind code	B2
Filing date	Aug 17, 2015
Priority date	Aug 17, 2015
Publication date	May 30, 2017
Grant date	May 30, 2017

Abstract

The present invention is an improved fiber optic sensing system (FOSS) having the ability to provide both high spatial resolution and high frequency strain measurements. The inventive hybrid FOSS fiber combines sensors from high acquisition speed and low spatial resolution Wavelength-Division Multiplexing (WDM) systems and from low acquisition speed and high spatial resolution Optical Frequency Domain Reflection (OFDR) systems. Two unique light sources utilizing different wavelengths are coupled with the hybrid FOSS fiber to generate reflected data from both the WDM sensors and OFDR sensors operating on a single fiber optic cable without incurring interference from one another. The two data sets are then de-multiplexed for analysis, optionally with conventionally-available WDM and OFDR system analyzers.

First claim

The invention claimed is:

1. A hybrid fiber optic strain sensor, comprising:
a first plurality of densely spaced fiber Bragg gratings, each of said first plurality of densely spaced fiber Bragg gratings having a first resonant wavelength; and
a second plurality of fiber Bragg gratings, spaced at intervals for WDM interrogation, each of said second plurality of fiber Bragg gratings having a second resonant wavelength domain;
wherein said first resonant wavelength comprises 1550 nm and second resonant wavelength domain comprises 1310 nm plus or minus 70 nm.

2. A fiber optic strain sensing system, comprising:
at least one hybrid fiber optic strain sensor as claimed in claim 1 ;
a first light source;
a second light source;
a multiplexing device operably coupled between said at least one hybrid fiber optic sensor on a first side and said first and second light sources on a second side, said multiplexer being configured to multiplex light from said first and second light sources and to de-multiplex reflections from said at least one hybrid fiber optic sensor;
a first signal analyzer operatively coupled to said multiplexing device; and
a second signal analyzer operatively coupled to said multiplexing device.

3. The fiber optic strain sensing system of claim 2 , wherein said first signal analyzer is a WDM analyzer.

4. The fiber optic strain sensing system of claim 2 , wherein said second signal analyzer is an 8 fiber OFDR analyzer.

5. The fiber optic strain sensing system of claim 4 , further comprising 7 additional FOSS fibers operatively coupled to said second signal analyzer.

6. The fiber optic strain sensing system of claim 2 , further comprising a narrowband reflector box operatively connected between said at least one hybrid fiber optic strain sensor and said multiplexing device.

7. The fiber optic strain sensing system of claim 2 , further comprising a 3-point circulator operatively coupled between said first light source, said first signal analyzer, and said multiplexing device.

8. The fiber optic strain sensing system of claim 7 , further comprising a 3-point circulator operatively coupled between said second light source, said second signal analyzer, and said multiplexing device.

9. The fiber optic strain sensing system of claim 2 , wherein said at least one hybrid fiber optic strain sensor is at least partially embedded into the structure of a vehicle.

10. The fiber optic strain sensing system of claim 9 , wherein said at least one hybrid fiber optic strain sensor is fully embedded into the structure of a vehicle.

11. The fiber optic strain sensing system of claim 10 , wherein said vehicle is an aircraft, and further comprising a CPU having a monitor mounted in the cabin of said aircraft, said CPU being operatively connected to said first and second signal analyzers.

12. The fiber optic strain sensing system of claim 2 , wherein said at least one hybrid fiber optic strain sensor is at least partially embedded into the structure of a structure selected from the group comprising a rotorcraft blade, bridge, building, or wind turbine.

13. A fiber optic strain system, comprising:
a hybrid fiber optic strain sensor, comprising:
a first plurality of fiber Bragg gratings, each of said first plurality of fiber Bragg gratings having a first resonant wavelength; and
a second plurality of fiber Bragg gratings, each of said second plurality of fiber Bragg gratings having a second resonant wavelength domain;
wherein said first resonant wavelength and second resonant wavelength domain are not equal;

a multiplexer configured to de-multiplex reflections from said at least one hybrid fiber optic sensor such that reflections from said first plurality of fiber Bragg gratings are separated from said second plurality of fiber Bragg gratings: and,
a narrowband reflector box operatively connected between said at least one hybrid fiber optic strain sensor and said multiplexing device.

14. The fiber optic strain sensing system of claim 13 , wherein said at least one hybrid fiber optic strain sensor is at least partially embedded into the structure of a vehicle.

15. The fiber optic strain sensing system of claim 14 , wherein said first resonant wavelength is longer than said second resonant wavelength domain, and wherein said second plurality of fiber Bragg gratings are physically concentrated along a portion of said structure of said vehicle expected to experience large or unique forces.

Assignees

• Nasa
• Nasa

Inventors

• Parker Jr Allen R
• Chan Hon Man
• Richards William Lance
• Piazza Anthony
• Hamory Philip J

Classifications

• G02B6/0208

  characterised by their structure, wavelength response (G02B6/02114, G02B6/02171, G02B6/02195 take precedence; multiple layer cores or claddings G02B6/036, protective coverings G02B6/4429) · CPC title

• G01B11/18

  using photoelastic elements · CPC title

• G01B11/165 Primary

  by means of a grating deformed by the object · CPC title

• G02B6/2938

  for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g. 1xN, NxM · CPC title