Method and system for non-contact optical-power measurement

• US 9,791,347 B2
• Filed: 08/08/2016
• Issued: 10/17/2017
• Est. Priority Date: 04/11/2014
• Status: Active Grant

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Guimond, Stephen J.
• Primary Examiner(s): Radkowski, Peter
• Application Number:
  US15/231,360
• Publication Number:
  US 20160349144A1
• Time in Patent Office: 435 Days
• CPC Class Codes: G01J 1/0295 Constructional arrangements for removing other types of optical noise or for performing calibration
• CPC Class Codes: G01J 1/0425 using optical fibers
• CPC Class Codes: G01J 1/0429 using polarisation elements
• CPC Class Codes: G01J 1/4228 arrangements with two or more detectors, e.g. for sensitivity compensation
• CPC Class Codes: G01J 1/4257 applied to monitoring the characteristics of a beam, e.g. laser beam, headlamp beam monitoring arrangements for lasers in general H01S3/0014
• CPC Class Codes: G01M 11/02 Testing optical properties
• CPC Class Codes: G02B 6/024 with polarisation maintaining properties
• CPC Class Codes: G02B 6/0283 Graded index region external to the central core segment, e.g. sloping layer or triangular or trapezoidal layer G02B6/0288, G02B6/0286 take precedence
• CPC Class Codes: G02B 6/03622 having 2 layers only
• CPC Class Codes: G02B 6/4216 incorporating polarisation-maintaining fibres polarisation-maintaining fibres per se G02B6/105
• CPC Class Codes: G02B 6/4287 Optical modules with tapping or launching means through the surface of the waveguide G02B6/2852, G02B6/4286 take precedence

Abstract

The present invention provides methods and systems for measuring optical power that require neither alterations to the optical fiber nor physical contact with the optical fiber, the system including an optical fiber configured to propagate an optical signal, wherein the optical fiber includes a core and at least a first cladding layer, wherein a portion of the optical signal scatters out of the optical fiber along a length of the optical fiber to form scattered fiber light; a detector system configured to receive the scattered fiber light along the length of the optical fiber and to output a detection signal based on the received scattered fiber light; and a processor configured to receive the detection signal and to determine a power value of the optical signal based on the received detection signal.

Claims

1. A method for measuring optical power comprising:

providing an optical fiber configured to propagate an optical signal, wherein the optical fiber includes a core and at least a first cladding layer, wherein a portion of the optical signal scatters out of the optical fiber along a length of the optical fiber to form scattered fiber light;

detecting, at a first time period, the scattered fiber light along the length of the optical fiber and outputting a first detection signal based on the detected scattered fiber light;

modulating a polarization of the scattered fiber light after the scattered fiber light has exited the optical fiber and before the detecting of the scattered fiber light;

polarization filtering the scattered fiber light after the modulating of the polarization of the scattered fiber light and before the detecting of the scattered fiber light; and

determining a first power value of the optical signal based on the first detection signal.

2. The method of claim 1, wherein the scattered fiber light includes scattered pump light, the method further comprising:

focusing the scattered fiber light prior to the detecting of the scattered fiber light; and

wavelength filtering the scattered fiber light to separate the portion of the optical signal from pump light.

3. The method of claim 1, wherein the optical signal propagates through the optical fiber in a core-signal-light propagation direction, wherein the optical fiber is a polarization-maintaining (PM) fiber that provides a polarization-electric-field direction, wherein the detecting includes receiving a portion of the scattered fiber light that scatters out of the optical fiber in a direction that is perpendicular to both the polarization-electric-field direction and the core-signal-light propagation direction.

4. The method of claim 1, wherein the determining of the first power value of the optical signal includes data filtering light-intensity defects along the length of the optical fiber associated with the scattered fiber light.

5. The method of claim 1, further comprising:

performing a functional fit of the determined first power value to the scattered fiber light;

detecting, at a second time period, subsequent to the first time period, the scattered fiber light along the length of the optical fiber and outputting a second detection signal; and

determining, using the functional fit, a second power value of the optical signal based on the second detection signal.

6. The method of claim 1, further comprising:

dumping pump light along the length of the optical fiber; and

calibrating the determining of the first power value of the optical signal.

7. The method of claim 1, further comprising:

providing a detector system configured to perform the detecting; and

fixing a position of the detector system with respect to the optical fiber.

8. The method of claim 1, wherein the determining of the first power value of the optical signal includes detecting a power-versus-time profile of the optical signal.

9. The method of claim 1, wherein the determining of the first power value of the optical signal includes detecting a power-versus-time profile of the optical signal, the method further comprising controlling the optical signal based at least in part on the power-versus-time profile.

10. The method of claim 1, wherein the detecting includes collecting the scattered fiber light at a plurality of different light-sensing positions.

11. A method for measuring optical power comprising:

providing an optical fiber configured to propagate an optical signal, wherein the optical fiber includes a core and at least a first cladding layer, wherein a portion of the optical signal scatters out of the optical fiber along a length of the optical fiber to form scattered fiber light;

detecting, at a first time period, the scattered fiber light along the length of the optical fiber and outputting a first detection signal based on the detected scattered fiber light;

modulating a polarization of the scattered fiber light after the scattered fiber light has exited the optical fiber and before the detecting of the scattered fiber light; and

polarization filtering the scattered fiber light after the modulating of the polarization of the scattered fiber light and before the detecting of the scattered fiber light.

12. The method of claim 11, further comprising:

containing pump light inserted into the first cladding layer within the first cladding layer along the length of the optical fiber.

13. The method of claim 11, wherein the optical signal propagates through the optical fiber in a core-signal-light propagation direction, wherein the optical fiber is a polarization-maintaining (PM) fiber that provides a polarization-electric-field direction, wherein the detecting includes receiving a portion of the scattered fiber light that scatters out of the optical fiber in a direction that is perpendicular to both the polarization-electric-field direction and the core-signal-light propagation direction.

14. The method of claim 11, wherein the optical signal propagates through the optical fiber in a core-signal-light propagation direction, wherein the optical fiber is a polarization-maintaining (PM) fiber that provides a polarization-electric-field direction, wherein the modulating of the polarization of the scattered fiber light includes receiving a portion of the scattered fiber light that scatters out of the optical fiber in a direction that is perpendicular to both the polarization-electric-field direction and the core-signal-light propagation direction.

15. The method of claim 11, further comprising determining a first power value of the optical signal based on the first detection signal, wherein the determining of the first power value includes:

data filtering light-intensity defects along the length of the optical fiber associated with the scattered fiber light, and

controlling a lock-in detection module based on the modulating of the polarization.

16. The method of claim 11, wherein the scattered fiber light includes scattered pump light, the method further comprising:

focusing the scattered fiber light prior to the detecting of the scattered fiber light; and

wavelength filtering the scattered fiber light to separate the portion of the optical signal from pump light.

17. The method of claim 11, further comprising:

determining a first power value of the optical signal based on the first detection signal, wherein the determining of the first power value includes detecting a power-versus-time profile of the optical signal; and

controlling the optical signal based at least in part on the power-versus-time profile.

18. The method of claim 11, wherein the detecting includes collecting the scattered fiber light at a plurality of different light-sensing positions.

20. The method of claim 11, further comprising:

determining a first power value of the optical signal based on the first detection signal, wherein the determining of the first power value includes controlling a lock-in detection module based on the modulating of the polarization.

19. An apparatus comprising:

an optical fiber configured to propagate an optical signal, wherein the optical fiber includes a core and at least a first cladding layer, wherein a portion of the optical signal scatters out of the optical fiber along a length of the optical fiber to form scattered fiber light;

means for detecting the scattered fiber light along the length of the optical fiber and outputting an image signal based on the imaged scattered fiber light;

means for modulating a polarization of the scattered fiber light after the scattered fiber light has exited the optical fiber and before the scattered fiber light has reached the means for detecting;

means for polarization filtering the scattered fiber light after the scattered fiber light reaches the means for modulating and before the scattered fiber light has reached the means for detecting; and

means for determining a first power value of the optical signal based on the image signal.