Standard Article

Intensity-, Interferometric-, and Scattering-Based Optical-Fiber Sensors

Sensors

  1. Kara Peters

Published Online: 15 SEP 2009

DOI: 10.1002/9780470061626.shm026

Encyclopedia of Structural Health Monitoring

Encyclopedia of Structural Health Monitoring

How to Cite

Peters, K. 2009. Intensity-, Interferometric-, and Scattering-Based Optical-Fiber Sensors. Encyclopedia of Structural Health Monitoring. .

Author Information

  1. North Carolina State University, Department of Mechanical and Aerospace Engineering, Raleigh, NC, USA

Publication History

  1. Published Online: 15 SEP 2009

Abstract

This article presents the sensing mechanics, strain and temperature sensitivity, and data-acquisition techniques for optical-fiber sensors based on intensity, phase shifts, and intrinsic scattering. Such sensors are well suited for health-monitoring applications. The utilization of standard optical fibers for the measurement of strain through fiber fractures or microbending is described. Afterward, the equation for the phase shift in a lightwave propagating through an optical fiber is derived. The sensitivity of this phase shift to external parameters such as strain and temperature is also derived and typical values for fused silica optical fibers cited. The measurement of this phase shift through Mach–Zehnder and Michelson in-fiber interferometer configurations is presented. Active and passive homodyne techniques for the interrogation of these periodic phase shift signals to alleviate directional ambiguity and signal fading near quadrature points are described. The alternative interferometer configurations of low-coherence and Fabry–Perot interferometers are described, which provide absolute measurements of strain and/or temperature for large structural applications. Finally, the measurement of distributed strain and temperatures through intrinsic scattering phenomena with the optical fiber and, in particular, stimulated Brillouin scattering is summarized.

Keywords:

  • intensiometric sensor;
  • microbend sensor;
  • in-fiber interferometer;
  • Mach–Zehnder interferometer;
  • Michelson interferometer;
  • low-coherence inteferometry;
  • Fabry–Perot interferometer;
  • Brillouin scattering