Accession Number:

AD1173786

Title:

Temperature-Strain Discrimination Using the Brillouin Frequency and Linewidth

Descriptive Note:

[Technical Report, Memorandum Report]

Corporate Author:

NAVAL RESEARCH LAB WASHINGTON DC

Personal Author(s):

• Murray, Matthew J.
• Murray, Joseph B.
• Redding, Brandon

Report Date:

2022-07-07

Pagination or Media Count:

18

Abstract:

Distributed fiber optic sensors that can measure and discriminate between temperature and strain have many important applications including 3-dimensional shape sensing and structural health monitoring. A Brillouin-based sensor is a promising choice for these applications since the Brillouin frequency and the Brillouin linewidth have different dependencies on the temperature and strain in the fiber. Here, we designed and constructed a Brillouin optical time-domain analysis BOTDA system for this purpose using an optical frequency comb. The system extracts the Brillouin frequency and linewidth at each position in the fiber from the measured Brillouin gain spectrum. The temperature and strain can then be recovered at each position along the fiber under test. We show that this approach enables a temperature resolution of 2 oC and a strain resolution of 50 with a 10 m sensing aperture. Finally, we discuss the limitations of this technique due to non-uniformities within the sensing aperture and provide a comparison with alternative schemes for temperaturestrain discrimination.

Descriptors:

• frequency combs
• frequency shift
• acousto-optic modulators
• detectors
• brillouin scattering
• frequency
• lasers
• modulation
• modulators
• optical fibers
• scattering
• figure of merit
• measurement
• repetition rate
• spectra
• three dimensional
• time domain

Subject Categories:

• Optics
• Fiber Optics and Integrated Optics

Distribution Statement:

[A, Approved For Public Release]