Brillouin-based distributed bend fiber sensor and method for using same

Patent metadata

Field	Value
Publication number	US-10145681-B2
Application number	US-201715646820-A
Country	US
Kind code	B2
Filing date	Jul 11, 2017
Priority date	Jul 19, 2016
Publication date	Dec 4, 2018
Grant date	Dec 4, 2018

Abstract

A Brillouin-based distributed bend fiber sensor and method for using the Brillouin-based distributed bend fiber sensor are described herein. In one example, the Brillouin-based distributed bend fiber sensor is specially configured to measure a temperature distribution (ΔT), a bend angle β, and a bend radius R along a deployed fiber (e.g., four-core fiber).

First claim

The invention claimed is:

1. A Brillouin-based distributed fiber sensor comprising:
a fiber comprising a first core, a second core, a third core, and a fourth core, wherein the first core, the second core, and the third core are located at three different positions along a circular path within the fiber, wherein the circular path has a radius (r) to a center of the fiber, and wherein the fourth core is located at the center of the fiber; and,
a Brillouin backscattering sensing mechanism coupled to the first core, the second core, the third core, and the fourth core.

2. The Brillouin-based distributed fiber sensor of claim 1 , further comprising:
a processing system, coupled to the Brillouin backscattering sensing mechanism, configured to:
obtain, prior to deployment of the fiber when the fiber has no bend applied thereto, from the Brillouin backscattering mechanism a first Brillouin frequency shift (BFS) baseline measurement (v B1 ) along the first core, a second BFS baseline measurement (v B2 ) along the second core, a third BFS baseline measurement (v B3 ) along the third core, and a fourth BFS baseline measurement (v B4 ) along the fourth core;
obtain, after deployment of the fiber and when there is a bend applied to the fiber, from the Brillouin backscattering mechanism a first BFS bend measurement (v′ B1 ) along the first core, a second BFS bend measurement (v′ B2 ) along the second core, a third BFS bend measurement (v′ B3 ) along the third core, and a fourth BFS bend measurement (v′ B4 ) along the fourth core;

calculate a change of a first, second, third, and fourth BFS distribution (Δv B1 , Δv B2 , Δv B3 , Δv B4 ) respectively along the first, second, third, and fourth cores;
calculate a temperature distribution (ΔT) along the deployed fiber;
calculate a first, second, and third bend induced strain distributions (Δε 1 , Δε 2 , Δε 3 ,) respectively along the first, second, and third cores;
calculate a bend angle β along the deployed fiber; and
calculate a bend radius R along the deployed fiber.

3. The Brillouin-based distributed fiber sensor of claim 2 , wherein the processing system is further configured to calculate the change of the first, second, third, and fourth BFS distribution (Δv B1 , Δv B2 , Δv B3 , Δv B4 ) using the following equations:
Δ v B1 = v′ B1 − v B1 ;

Δ v B2 = v′ B2 − v B2 ;

Δ v B3 = v′ B3 − v B3 ; and,

Δ v B4 = v′ B4 − v B4 .

4. The Brillouin-based distributed fiber sensor of claim 2 , wherein the processing system is further configured to calculate the temperature distribution (ΔT) along the deployed fiber using the following equation:
Δ v B4 = K ε4 Δε 4 + K T4 66 = K T4 ΔT

wherein: K T4 is a temperature coefficient of the fourth core; and,
wherein there is no fourth bend induced strain distribution (Δε 4 ) associated with the fourth core because the bend applied to the fiber does not cause a change in a length of the fourth core.

5. The Brillouin-based distributed fiber sensor of claim 2 , wherein the processing system is further configured to calculate the first, second, and third bend induced strain distribution (Δε 1 , Δε 2 , Δε 3 ) using the following equations:

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Assignees

• Corning Inc

Inventors

• Bennett Kevin Wallace
• Li Ming-Jun
• Li Shenping

Classifications

• G01B11/255 Primary

  for measuring radius of curvature {(measuring diameter G01B11/08)} · CPC title

• G01K11/32

  using changes in transmittance, scattering or luminescence in optical fibres · CPC title

• G01B11/26

  for measuring angles or tapers; for testing the alignment of axes · CPC title

• G01L1/242

  the material being an optical fibre · CPC title

• G01K2011/322

  Physics · mapped topic