Non-linear interactions with backscattered light
First Claim
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1. A system for measuring vibration in a structure, comprising:
- an optical fiber proximate to the structure having a first end and a second end, wherein a characteristic of the structure causes a backscatter through the optical fiber in response to light being emitted into the optical fiber;
a measurement component configured to measure the vibration in the structure as related to the backscatter in the optical fiber, wherein the measurement component is positioned proximate the first end of the optical fiber;
a first laser source configured to emit a first laser into the optical fiber proximate the first end of the optical fiber, the first laser having a first frequency; and
a second laser source configured to emit a second laser into the optical fiber proximate the first end of the optical fiber, the second laser having a second frequency, wherein a difference between the first frequency and the second frequency is delta-f, wherein delta-f causes an attenuation of a Rayleigh backscatter through a stimulated Brillouin scattering process that causes energy to be transferred from the backscatter to the first laser or the second laser.
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Abstract
Using hDVS techniques to detect a disturbance in a coherent Rayleigh backscatter caused by the presence of another optical signal in the fiber. The interaction can be caused by a pump pulse travelling shortly after a probe pulse and at a frequency close to that of the probe plus or minus a Brillouin frequency shift. This results in gain or attenuation of the backscatter signal. The Brillouin shift is a function of temperature and strain.
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Citations
13 Claims
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1. A system for measuring vibration in a structure, comprising:
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an optical fiber proximate to the structure having a first end and a second end, wherein a characteristic of the structure causes a backscatter through the optical fiber in response to light being emitted into the optical fiber; a measurement component configured to measure the vibration in the structure as related to the backscatter in the optical fiber, wherein the measurement component is positioned proximate the first end of the optical fiber; a first laser source configured to emit a first laser into the optical fiber proximate the first end of the optical fiber, the first laser having a first frequency; and a second laser source configured to emit a second laser into the optical fiber proximate the first end of the optical fiber, the second laser having a second frequency, wherein a difference between the first frequency and the second frequency is delta-f, wherein delta-f causes an attenuation of a Rayleigh backscatter through a stimulated Brillouin scattering process that causes energy to be transferred from the backscatter to the first laser or the second laser. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of detecting vibration in a structure, the method including:
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positioning an optical fiber proximate to the structure such that displacement of the structure affects reflective properties of the optical fiber; emitting a probe laser into the optical fiber at a first end of the optical fiber; emitting a pump laser into the optical fiber at the first end, wherein the pump laser and the probe laser have different frequencies separated by a delta-f frequency, and wherein the pump laser is configured to interact with the probe laser to improve a backscatter signal through the optical fiber, wherein the delta-f frequency causes an attenuation of a Rayleigh backscatter through a stimulated Brillouin scattering process that causes energy to be transferred from the backscatter signal to the probe laser or the pump laser. - View Dependent Claims (12, 13)
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Specification