Device, system and process for detecting tensile loads on a rope having an optical fiber incorporated therein

• US 5,182,779 A
• Filed: 04/05/1990
• Issued: 01/26/1993
• Est. Priority Date: 04/05/1990
• Status: Expired due to Fees

• Current Assignee: Vought Aircraft Industries, Inc. (Triumph Group, Inc.)
• Original Assignee: LTV Aerospace and Defense Company
• Inventors: D'Agostino, William L., Williams, Glen R., Barrick, Michael D.
• Primary Examiner(s): Lee, John D.
• Assistant Examiner(s): Wise, Robert E.
• Application Number:
  US07/506,034
• Time in Patent Office: 1,027 Days
• Field of Search: 350/96.23, 350/96.15, 350/96.16
• US Class Current: 385/13
• CPC Class Codes: D07B 1/145 comprising elements for indicating or detecting the rope or cable status
• CPC Class Codes: D07B 2201/2096 Light guides
• CPC Class Codes: G01B 11/18 using photoelastic elements
• CPC Class Codes: G01D 5/35316 using a Bragg gratings
• CPC Class Codes: G01L 5/105 using electro-optical means

Abstract

A system for monitoring strains and stresses on rope structures and rigid structures containing the ropes is provided wherein a fiber optic is included in a rope structure and change in the fiber'"'"'s light transmissive/reflective properties, which are caused by strains and stresses on the fiber, are monitored.

Claims

1. A system for detecting tensile loads on a rope comprising:

a plurality of elongated load-bearing members, said elongated load-bearing members being arranged into an elongated shape of a rope, said elongated shape having a long axis, said elongated shape being capable of a change in length along the long axis and structured for bearing tension loads along the long axis;

at least one fiber optical incorporated with the elongated load-bearing members along the length thereof;

an input signal transmitter, said input signal transmitter transmitting electromagnetic radiation into said fiber optic; and

a signal monitor, said signal monitor monitoring electromagnetic radiation exiting from said fiber optical and comparing an observed set of characteristics of the electromagnetic radiation exiting from said fiber optic to an expected set of characteristics of electromagnetic radiation exiting from said fiber optic.

2. A system as in claim 1 wherein said input signal transmitter comprises a coherent light source.

3. A system as in claim 1 wherein said input signal transmitter comprises an incoherent light source.

4. A system as in claim 1 wherein said signal monitor monitors electromagnetic radiation that is transmitted through said fiber optic.

5. A system as in claim 1 wherein said signal monitor monitors electromagnetic radiation that is reflected from said fiber optic.

6. A system as in claim 1 wherein said fiber optic is a multimode fiber optic.

7. A system as in claim 1 wherein said fiber optic is a single mode fiber optic.

8. A system as in claim 1 wherein said fiber optic has a core and a cladding.

9. A system as in claim 8 wherein said core has substantially the same index of refraction for a given frequency of electromagnetic radiation for substantially the entire length of said core.

10. A system as in claim 8 wherein said core has differing indices of refraction for different frequencies at various locations along the length of said core.

11. A system as in claim 1 wherein said fiber optic contains Bragg gratings.

12. A system as in claim 1 wherein said fiber optic is constructed from a series of spliced pieces of fiber optic.

13. A system as in claim 1 wherein said fiber optic has a plurality of cores.

14. A system as in claim 1 wherein said signal monitor comprises a Fresnel reflection detector.

15. A system as in claim 1 wherein said signal monitor comprises a Rayleigh reflection detector.

16. A system as in claim 1 wherein said signal monitor comprises a Raman reflector detector.

17. A system as in claim 1 wherein said signal monitor comprises a Brillouin reflection detector.

18. A system as in claim 1 wherein said plurality of elongated members bears tension loads in a structural element.

19. A system as in claim 18 wherein said structural element is a truss.

20. A process for detecting tensile loads on a plurality of elongated load-bearing members, said elongated load-bearing members being arranged in an elongated shape of a rope, said elongated shape having a long axis, said elongated shape being capable of a change in length along the log axis and structured for bearing tension loads along the along axis, at least one of said elongated load-bearing members being a fiber optic, said process comprising the steps of:

1) positioning said rope so as to be subjected to a tension load along the long axis;

2) transmitting a reference input signal into the fiber optical of the thus positioned rope;

3) monitoring the resulting transmitted reference output signal exiting the fiber optical of the thus positioned rope;

analyzing the change between the characteristics of the reference input signal and the characteristics of the reference output signal exiting the fiber optic of the thus positioned rope to detect the tensile load on the thus positioned rope.

21. The process of claim 20 wherein said analyzing step further comprises the step of:

comparing the characteristics of the reference input signal to the characteristics of the reference output signal exiting the fiber optic of the thus positioned rope to determine the presence of a continuing tensile load on the thus positioned rope.

22. The process of claim 20 wherein said analyzing step further comprises the step of:

comparing the characteristics of the reference input signal to the characteristics of the reference output signal exiting the fiber optical of the thus positioned rope to determine the past occurrence of a non-continuing tensile load on the thus positioned rope.

23. The process of claim 22 wherein the reference output signal comprises a reflected reference signal.

24. The process of claim 22 wherein the reference output signal comprises a transmitted reference signal.

25. The process of claim 20 wherein said analyzing comprises OTDR.

26. The process of claim 20 wherein said analyzing comprises OTDR/spliced optical fiber.

27. The process of claim 20 wherein said analyzing comprises Photon-Counting OTDR/Macrobends.

28. The process of claim 20 wherein said analyzing comprises Photon-Counting OTDR/Microbends.

29. The process of claim 20 wherein said analyzing comprises OTDR Bragg Grating.

30. The process of claim 20 wherein said analyzing comprises Tuned Reflector/Bragg Grating.

31. The process of claim 20 wherein said analyzing comprises Dual Fiber Sensor.

32. The process of claim 20 wherein said analyzing comprises Modal Domain/Polarization.

33. The process of claim 20 wherein the reference output signal comprises a Fresnel reflection.

34. The process of claim 20 wherein the reference output signal comprises a Rayleigh reflection.

35. The process of claim 20 wherein the reference output signal comprises a Raman reflection.

36. The process of claim 20 wherein the reference output signal comprises a Brillouin reflection.

37. A device for sensing tensile loads on a rope comprising:

an optical fiber, said optical fiber being integral with the rope along the length of the rope;

an optical source, connected to said optical fiber to transmit a signal into said optical fiber;

an optical detector connected to said optical fiber to receive an exit signal from said optical fiber and provide an output signal; and

a processor to receive said output signal from said optical detector and compare said output signal to an expected output signal.

38. A device as in claim 37 in which said optical detector comprises a Fabry-Perot interferometer.