Method and apparatus for optical noise cancellation

• US 20050058457A1
• Filed: 09/15/2003
• Published: 03/17/2005
• Est. Priority Date: 09/15/2003
• Status: Abandoned Application

• Current Assignee: Weatherford/Lamb Incorporated (Weatherford International PLC)
• Original Assignee: Weatherford/Lamb Incorporated (Weatherford International PLC)
• Inventors: MacDougall, Trevor, Taverner, Domino
• Application Number:
  US10/662,969
• Publication Number:
  US 20050058457A1
• Time in Patent Office: Days
• US Class Current: 398/149
• CPC Class Codes: H04B 10/2513 due to chromatic dispersion

Abstract

A method and apparatus for removing optical noise from an optical system. A light source produces optical signals applied to a remote optical element that produces reflected optical signals and is subject to optical background noise such as reflections from splices and optical connections. Part of the reflected optical signals and at least some of the background noise is applied to a receiver. The receiver output is analyzed to determine either the amount of noise (if broadband) or the frequency components of the noise. If broadband, the noise is subtracted from the composite signal, thus increasing the signal to noise ratio. If periodic, the frequency components of the noise are gated out of the receiver output.

Claims

1. An optical system comprising:

a source for producing optical signals;

an optical waveguide having a noise producing element and an optical filter element;

a receiver for converting applied optical signals into electrical signals;

a coupler for coupling said produced optical signals into said optical waveguide and for coupling reflections from said noise producing element and from said optical filter element to said receiver as applied optical signals; and

a noise reduction system for removing noise produced by said noise producing element from said electrical signals.

2. The system of claim 1 wherein the noise reduction system averages broadband noise and then subtracts the averaged level from the electrical signals.

3. The system of claim 1 wherein the noise reduction system performs a frequency analysis of the electrical signals to identify periodic noise.

4. The system of claim 3 wherein the noise reduction system further removes the periodic noise from the electrical signals.

5. The system of claim 4 wherein the noise reduction system removes the periodic noise by gating the periodic noise out of the electrical signals.

6. The system of claim 3 wherein the frequency analysis is a Fourier analysis.

7. The system of claim 5 wherein the noise reduction system averages broadband noise and then subtracts the averaged level from the electrical signals.

8. The system of claim 1 wherein the optical filter element includes a fiber Bragg grating.

9. The system of claim 1 wherein the optical waveguide includes a discontinuity.

10. The system of claim 1 wherein the discontinuity is a splice.

11. A sensor comprising:

a source for producing optical signals;

an optical waveguide having a noise producing element and an optical filter element;

a receiver for converting applied optical signals into amplified electrical signals;

a coupler for coupling said produced optical signals into said optical waveguide and for coupling reflections from said optical waveguide as applied optical signals to said receiver; and

a signal processor for removing noise produced by said noise producing element from said electrical signals.

12. The sensor of claim 11 wherein said signal processor subtracts an averaged noise level from the electrical signals.

13. The sensor of claim 11 wherein said signal processor performs a frequency analysis of the electrical signals to identify and remove periodic noise from the electrical signals.

14. The sensor of claim 13 wherein the frequency analysis is a Fourier analysis.

15. The sensor of claim 13 wherein said signal processor subtracts an averaged noise level from the electrical signals.

16. The sensor of claim 11 wherein the source includes a tunable laser.

17. The sensor of claim 11 wherein the source includes a broadband light source and a tunable filter.

18. The system of claim 11 wherein the optical filter element includes a fiber Bragg grating.

19. The system of claim 11 wherein the optical waveguide includes a discontinuity.

20. The system of claim 11 wherein the discontinuity is a splice.

21. A method of compensating for optical reflection comprising:

producing an optical signal;

coupling the optical signal into an optical waveguide having a noise producing element and an optical filter element;

converting reflections along the optical waveguide into electrical signals; and

removing noise produced by the noise producing element from the electrical signals such that the electrical signals from the optical filter element are retained.

22. The method of claim 21 wherein removing noise includes finding an average noise level and subtracting that average noise level from the electrical signals.

23. The method of claim 21 wherein removing noise includes performing a frequency analysis and then gating out noise produced by the noise producing element from the electrical signals.

24. The method of claim 22 wherein removing noise includes performing a frequency analysis and then gating out noise produced by the noise producing element from the electrical signals.