Optical system and method for gas detection and monitoring

• US 7,929,144 B1
• Filed: 12/16/2008
• Issued: 04/19/2011
• Est. Priority Date: 12/16/2008
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Korman, Valentin, Hendrickson, Adam Gail, Witherow, William K., Sinko, John Elihu, Polzin, Kurt A.
• Primary Examiner(s): Lyons; Michael A
• Application Number:
  US12/336,260
• Time in Patent Office: 854 Days
• Field of Search: 356/451, 356/454, 356/477, 356/480, 356/519
• US Class Current: 356/477
• CPC Class Codes: G01N 2021/458 using interferential sensor, e.g. sensor fibre, possibly on optical waveguide
• CPC Class Codes: G01N 21/45 using interferometric methods; using Schlieren methods

Abstract

A free-space optical path of an optical interferometer is disposed in an environment of interest. A light beam is guided to the optical interferometer using a single-mode optical fiber. The light beam traverses the interferometer'"'"'s optical path. The light beam guided to the optical path is combined with the light beam at the end of the optical path to define an output light. A temporal history of the output light is recorded.

Claims

1. A system for detecting and monitoring the presence of a gas, comprising:

a source generating a light beam;

an optical interferometer defining a free-space optical path disposed in an environment of interest;

an optical detector;

a single-mode optical fiber coupled between said source and said optical interferometer, wherein said light beam incident on said optical interferometer is guided to said optical path and traverses therealong to an end of said optical path, wherein said light beam guided to said optical path is combined with said light beam at said end of said optical path to define an output light;

said optical detector optically coupled to said optical interferometer wherein said output light is guided to said optical detector; and

means coupled to said optical detector for recording a temporal history of said output light.

2. A system as in claim 1, further comprising a second single-mode optical fiber coupled between said optical interferometer and said optical detector, wherein said output light is guided to said optical detector.

3. A system as in claim 2, further comprising means for fixing orientations of said single-mode optical fiber and said second single-mode optical fiber.

4. A system as in claim 1, wherein said optical interferometer is selected from the group consisting of a Fabry-Perot interferometer, a Mach-Zehnder interferometer, and a Michelson interferometer.

5. A system as in claim 1, wherein said optical interferometer comprises a solid-body optical interferometer.

6. A system as in claim 1, wherein said source is a continuous wave laser.

7. A system as in claim 1, further comprising means for fixing an orientation of said single-mode optical fiber.

8. A system as in claim 1, wherein a portion of said light beam incident on said optical interferometer is back-reflected therefrom into said single-mode optical fiber, said system further comprising detection means coupled to said single-mode optical fiber for detecting said portion of said light beam.

9. A method of detecting and monitoring the presence of a gas, comprising the steps of:

generating a light beam;

disposing a free-space optical path of an optical interferometer in an environment of interest;

guiding said light beam to the optical interferometer using a single-mode optical fiber wherein said light beam traverses along said optical path to an end thereof;

combining said light beam guided to said optical path with said light beam at said end of said optical path to define an output light;

guiding said output light to an optical detector; and

recording a temporal history of said output light.

10. A method according to claim 9, wherein the environment of interest is space.

11. A method according to claim 9, wherein the environment of interest is a vacuum.

12. A method according to claim 9, wherein the optical interferometer is selected from the group consisting of a Fabry-Perot interferometer, a Mach-Zehnder interferometer, and a Michelson interferometer.

13. A method according to claim 9, wherein the optical interferometer is a solid-body optical interferometer.

14. A method according to claim 9, wherein said light beam comprises a continuous wave laser beam.

15. A method according to claim 9, further comprising the step of fixing an orientation of the single-mode optical fiber.

16. A method according to claim 9, wherein a portion of said light beam incident on the optical interferometer is back-reflected therefrom into the single-mode optical fiber, said method further comprising the step of detecting said portion of said light beam.

17. A system for detecting and monitoring the presence of a gas, comprising:

a laser source generating laser light;

a plurality of optical interferometers distributed in an environment of interest, each of said optical interferometers defining a free-space optical path disposed in a region of the environment of interest;

a corresponding plurality of optical detectors;

first means coupled between said laser source and each of said optical interferometers wherein, for each of said optical interferometers, said laser light is guided to said optical path associated therewith by said first means and traverses therealong to an end of said optical path associated therewith, and wherein each of said optical interferometers combines said laser light guided to said optical path associated therewith said laser light at said end of said optical path associated therewith to define an output light associated therewith;

second means coupled between each of said optical interferometers and a corresponding one of said optical detectors, wherein each said output light is guided by said second means to said corresponding one of said optical detectors; and

means coupled to each of said optical detectors for recording a temporal history of each said output light.

18. A system as in claim 17, wherein each of said optical interferometers is selected from the group consisting of a Fabry-Perot interferometer, a Mach-Zehnder interferometer, and a Michelson interferometer.

19. A system as in claim 17, wherein each of said optical interferometers comprises a solid-body optical interferometer.

20. A system as in claim 17, wherein said laser source is a continuous wave laser.

21. A system as in claim 17, further comprising means for fixing orientations of said first means and said second means.

22. A method of detecting and monitoring the presence of a gas, comprising the steps of:

generating laser light;

distributing a plurality of optical interferometers in an environment of interest, each of said optical interferometers defining a free-space optical path in a region of the environment of interest;

guiding said laser light to each of the optical interferometers using a first single-mode optical fiber wherein, for each of the optical interferometers, said laser light traverses along said optical path associated therewith to an end thereof, and wherein each of the optical interferometers combines said laser light guided to said optical path associated therewith said laser light at said end of said optical path associated therewith to define an output light associated therewith;

guiding each said output light to an optical detector using a second single-mode optical fiber; and

recording a temporal history of each said output light.

23. A method according to claim 22, wherein the environment of interest is space.

24. A method according to claim 22, wherein the environment of interest is a vacuum.

25. A method according to claim 22, wherein each of the optical interferometers is selected from the group consisting of a Fabry-Perot interferometer, a Mach-Zehnder interferometer, and a Michelson interferometer.

26. A method according to claim 22, wherein each of the optical interferometers is a solid-body optical interferometer.

27. A method according to claim 22, wherein said laser light comprises a continuous wave of optical energy.

28. A method according to claim 22, further comprising the step of fixing orientations of the first single-mode optical fiber and the second single-mode optical fiber.