Real-time non-linear optical strain gauge system
First Claim
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1. A system for measuring strain between two fixed points, comprising:
- an optical fiber having a first end, a second end, and a central portion secured between the two fixed points;
a first light source outputting a light signal having predetermined characteristics and a first frequency and coupled to the first end of the optical fiber;
a second light source outputting a light signal having the same predetermined characteristics and a second frequency different from the first frequency and coupled to the first end of the optical fiber;
a back scatter detector coupled to the first end of the optical fiber for receiving a return light signal from the optical fiber and for outputting a signal based thereon, the back scatter detector including an associated frequency control element having a frequency corresponding to a predetermined calculated response frequency based on the first frequency and the second frequency, the predetermined calculated response frequency different from the first frequency and the second frequency;
a forward scatter detector coupled to the second end of the optical fiber for receiving a forward light signal from the optical fiber and for outputting a signal based thereon, the forward scatter detector including an associated frequency control element having a frequency corresponding to the predetermined calculated response frequency;
a processor coupled to receive the signals from the back scatter detector and the forward scatter detector, the processor generating an output signal proportional to the strain between the two fixed points based on a magnitude of the signals from the back scatter detector and the forward scatter detector at the predetermined calculated response frequency; and
wherein the output signal at the predetermined calculated response frequency is produced based on second order effects applied to the light signal at the first frequency and to the light signal at the second frequency.
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Abstract
A system for measuring strain includes an optical fiber having a central portion secured between two fixed points. A first light source outputs light at a first frequency and a second light source outputs light at a second different frequency. The two light sources are both coupled to a first end of the optical fiber. A back scatter detector is also coupled to the first end to receive a return light signal from the optical fiber and outputs a signal based thereon. A forward scatter detector is coupled to a second end of the optical fiber to receive a forward light signal from the optical fiber and outputs a signal based thereon. A processor receives the signals from the back scatter detector and the forward scatter detector and generates an output signal proportional to the strain between the two fixed points based on the received signals.
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Citations
16 Claims
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1. A system for measuring strain between two fixed points, comprising:
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an optical fiber having a first end, a second end, and a central portion secured between the two fixed points; a first light source outputting a light signal having predetermined characteristics and a first frequency and coupled to the first end of the optical fiber; a second light source outputting a light signal having the same predetermined characteristics and a second frequency different from the first frequency and coupled to the first end of the optical fiber; a back scatter detector coupled to the first end of the optical fiber for receiving a return light signal from the optical fiber and for outputting a signal based thereon, the back scatter detector including an associated frequency control element having a frequency corresponding to a predetermined calculated response frequency based on the first frequency and the second frequency, the predetermined calculated response frequency different from the first frequency and the second frequency; a forward scatter detector coupled to the second end of the optical fiber for receiving a forward light signal from the optical fiber and for outputting a signal based thereon, the forward scatter detector including an associated frequency control element having a frequency corresponding to the predetermined calculated response frequency; a processor coupled to receive the signals from the back scatter detector and the forward scatter detector, the processor generating an output signal proportional to the strain between the two fixed points based on a magnitude of the signals from the back scatter detector and the forward scatter detector at the predetermined calculated response frequency; and wherein the output signal at the predetermined calculated response frequency is produced based on second order effects applied to the light signal at the first frequency and to the light signal at the second frequency. - View Dependent Claims (2, 3, 4, 5)
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6. A system for measuring strain between two fixed points, comprising:
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an optical fiber having a first end, a second end, and a central portion secured between the two fixed points; a first light source outputting a light signal having predetermined characteristics and a first frequency and coupled to the first end of the optical fiber; a second light source outputting a light signal having the same predetermined characteristics and a second frequency different from the first frequency and coupled to the first end of the optical fiber; a back scatter detector coupled to the first end of the optical fiber for receiving a return light signal from the optical fiber and for outputting a signal based thereon, the back scatter detector including an associated frequency control element having a frequency corresponding to a predetermined calculated response frequency based on the first frequency and the second frequency, the predetermined calculated response frequency different from the first frequency and the second frequency; a processor coupled to receive the signal from the back scatter detector, the processor generating an output signal proportional to the strain between the two fixed points based on a magnitude of the signal from the back scatter detector at the predetermined calculated response frequency; and wherein the output signal at the predetermined calculated response frequency is produced based on second order effects applied to the light signal at the first frequency and to the light signal at the second frequency. - View Dependent Claims (7, 8, 9, 10, 11)
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12. A system for measuring strain between two fixed points, comprising:
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an optical fiber having a first end, a second end, and a central portion secured between the two fixed points; a first light source outputting a light signal having predetermined characteristics and a first frequency and coupled to the first end of the optical fiber; a second light source outputting a light signal having the same predetermined characteristics and a second frequency different from the first frequency and coupled to the first end of the optical fiber; a forward scatter detector coupled to the second end of the optical fiber for receiving a forward light signal from the optical fiber and for outputting a signal based thereon, the forward scatter detector including an associated frequency control element having a frequency corresponding to a predetermined calculated response frequency based on the first frequency and the second frequency, the predetermined calculated response frequency different from the first frequency and the second frequency; a processor coupled to receive the signal from the forward scatter detector, the processor generating an output signal proportional to the strain between the two fixed points based on a magnitude of the signal from the forward scatter detector at the predetermined calculated response frequency; and wherein the output signal at the predetermined calculated response frequency is produced based on second order effects applied to the light signal at the first frequency and to the light signal at the second frequency. - View Dependent Claims (13, 14, 15, 16)
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Specification
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Current AssigneeThe Boeing Co.
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Original AssigneeThe Boeing Co.
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InventorsHunt, Jeffrey H., Belk, John H.
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Primary Examiner(s)Chowdhury, Tarifur
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Assistant Examiner(s)Ahmed, Jamil
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Application NumberUS14/493,187Publication NumberTime in Patent Office946 DaysField of SearchUS Class CurrentCPC Class CodesG01B 11/168 by means of polarisationG01L 1/246 using integrated gratings, ...
