Method and apparatus for reducing noise in a fiber-optic sensor

• US 20090080898A1
• Filed: 09/24/2007
• Published: 03/26/2009
• Est. Priority Date: 09/24/2007
• Status: Abandoned Application

• Current Assignee: Fiber Sensys, Inc. (OPTEX GROUP Co., Ltd.)
• Original Assignee: Fiber SenSys, LLC (Integris (United States))
• Inventors: Anderson, Duwayne, Singh, Shailesh Kumar
• Application Number:
  US11/902,608
• Publication Number:
  US 20090080898A1
• Time in Patent Office: Days
• US Class Current: 398/140
• CPC Class Codes: G08C 23/06 through light guides, e.g. optical fibres

Abstract

An optical detection system includes an optical transmit-receive system, an optical conduit in optical communication with the optical transmit-receive system, and an optical sensor in optical communication with the optical conduit. The optical transmit-receive system provides pulsed optical signals to the optical sensor by way of the optical conduit that have a maximum pulse width of about 100 nanoseconds and further have a maximum pulse width that is less than a maximum distance of reflection of the pulsed optical signals in the optical detection system to decrease false alarms.

Claims

1. An optical detection system, comprising:

an optical transmit-receive system;

an optical conduit in optical communication with the optical transmit-receive system; and

an optical sensor in optical communication with said optical conduit,

wherein said optical transmit-receive system provides pulsed optical signals to said optical sensor by way of said optical conduit that have a maximum pulse width of about 100 nanoseconds and further have a maximum pulse width that is less than a maximum distance of reflection of said pulsed optical signals in said optical detection system to thereby decrease false alarms.

2. The optical detection system according to claim 1, wherein said optical transmit-receive system comprises an optical transmitter.

3. The optical detection system according to claim 2, wherein said pulsed optical signals have a pulse repetition rate selected such that said optical transmitter is off when all reflections from each pulse return to said optical transmit-receive system.

4. The system according to claim 1, wherein the shape of the pulsed light signals comprises at least one of a square, a triangle, or a sinusoid.

5. The system according to claim 1, wherein the transmit-receive system comprises a component to generate the pulsed optical signals when forward biased and detect the reflected portions of said pulsed optical signals when reverse biased.

6. The system according to claim 1, wherein the transmit-receive system comprises at least one of:

a distributed feedback (DFB) laser, or

a Fabry Perot (FB) laser.

7. The system according to claim 1, wherein the transmit-receive system comprises a vertical cavity surface emitting laser (VCSEL).

8. The system according to claim 1, wherein the optical sensor comprises optical fiber adapted to establish a detection zone.

9. The system according to claim 1, further comprising:

a first optical sensor in optical connection to the optical conduit at a first location; and

a second optical sensor in optical connection to the optical conduit at a second location,

wherein a time between transmission and reception of the pulse of light from the pulsed signals provides information to determine a position of coupling of at least one of the first or second optical sensor to the optical conduit.

10. An optical detection system, comprising:

an optical transmit-receive system;

an optical conduit in optical communication with the optical transmit-receive system; and

an optical sensor in optical communication with said optical conduit,

wherein said optical transmit-receive system provides a continuous wave optical signal to said optical sensor by way of said optical conduit to be returned to said optical transmit-receive system for detection, and

wherein said continuous wave optical signal is selected to have a frequency such that there is no optical standing wave from any optical reflections within said optical detection system.

11. The system according to claim 10, wherein the transmit-receive system comprises at least one of:

a distributed feedback (DFB) laser, or

a Fabry Perot (FB) laser.

12. The system according to claim 10, wherein the transmit-receive system comprises a vertical cavity surface emitting laser (VCSEL).

13. The system according to claim 10, wherein the optical sensor comprises an optical fiber adapted to establish a detection zone.

14. The system according to claim 10, further comprising:

a first optical sensor in optical connection to the optical conduit at a first location; and

a second optical sensor in optical connection to the optical conduit at a second location,

wherein a time between transmission and reception of light provides information to determine a position of coupling of at least one of the first or second optical sensor to the optical conduit.

15. An optical detection system, comprising:

an optical transmit-receive system;

an optical conduit in optical communication with the optical transmit-receive system; and

an optical sensor in optical communication with said optical conduit,

wherein said optical conduit comprises a single mode optical fiber and said optical sensor comprises a multimode optical fiber, and

wherein, in operation, said single mode optical fiber of said optical conduit provides spatial filtering of a time-varying speckle pattern from the optical sensor.

16. The system according to claim 15, further comprising:

a first optical sensor in optical connection to the optical conduit at a first location; and

a second optical sensor in optical connection to the optical conduit at a second location,

wherein a time between transmission and reception of light provides information to determine a position of coupling of at least one of the first or second optical sensor to the optical conduit.

17. A method of detecting an intruder, comprising:

directing a pulse of light into an optical conduit;

splitting off a portion of said pulse of light into an optical sensor, wherein said optical sensor is structured to reflect light back into said optical conduit; and

detecting a return portion of said pulse of light after having been reflected back by said optical sensor,

wherein said pulse of light has a width that is less than a minimum distance of reflection, and

wherein said width of said pulse of light is also less than about 100 nanoseconds.

18. The method according to claim 17, wherein the pulse of light is generated by at least one of:

a distributed feedback (DFB) laser, or

a Fabry Perot (FB) laser.

19. The method according to claim 17, wherein the pulse of light is generated by a vertical cavity surface emitting laser (VCSEL).

20. A method of detecting an intruder, comprising:

directing a beam of continuous wave light into an optical conduit;

splitting off a portion of said beam of continuous wave light into an optical sensor, wherein said optical sensor is structured to reflect light back into optical conduit; and

detecting a return portion of said beam of continuous wave light after having been reflected back by said optical sensor,

wherein said beam of continuous wave light has a frequency selected such that there is no optical standing wave from any optical reflections received during said detecting.

21. The method according to claim 20, wherein the beam of light is generated by at least one of:

a distributed feedback (DFB) laser, or

a Fabry Perot (FB) laser.

22. The method according to claim 20, wherein the beam of light is generated by a vertical cavity surface emitting laser (VCSEL).

23. A method of detecting an intruder, comprising:

directing light into a single mode optical fiber;

splitting off a portion of said light into an optical sensor, wherein said optical sensor comprises multimode optical fiber and is structured to reflect light back into said single mode optical fiber; and

detecting a return portion of said light after having been reflected back by said optical sensor,

wherein said single mode optical fiber provides spatial filtering of a speckle pattern of light from said optical sensor, and

wherein said detecting is based on a time-varying signal obtained from said spatial filtering of said speckle pattern.