Adaptive two-wave mixing wavelength demodulation of fiber bragg grating sensor for monitoring dynamic strains

Yi Qiao*, Yi Zhou, Sridhar Krishnaswamy

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review


A two-wave mixing (TWM) wavelength demodulator using InP:Fe photorefractive crystal (PRC) in the C-band (1530-1570nm) is demonstrated. The system can be used as a wavelength demodulator for use with Fiber Bragg Grating (FBG) sensors to monitor dynamic strains. In this configuration, the FBG is illuminated with a broadband source, and any strain in the FBG is encoded as a wavelength shift of the light reflected by the FBG. The reflected light from the FBG is spilt into two unbalanced paths and both beams (pump and signal) mix in the PRC. Any wavelength shift of the reflected light results in an equivalent phase shift between the pump and signal beams as they travel unbalanced path lengths. Since TWM is an adaptive process, the two interfering beams are naturally in quadrature and remain in quadrature even in the presence of large quasi-static strains. We demonstrate that FBG demodulation using TWM has the ability to selectively monitor dynamic strains without the need for active compensation of large quasi-static strains that otherwise would cause the FBG sensor to drift. As TWM interferometers can be readily multiplexed at relatively low cost; the proposed technique can be used to demodulate signals from a network of FBG sensors for use in structural health monitoring.

Original languageEnglish (US)
Article number03
Pages (from-to)20-27
Number of pages8
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - Oct 3 2005
EventSmart Structures and Materials 2005 - Smart Sensor Technology and Measurement Systems - San Diego, CA, United States
Duration: Mar 7 2005Mar 9 2005


  • Fiber bragg grating
  • Photorefractive
  • Two-wave mixing
  • Wavelength demodulation

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

Fingerprint Dive into the research topics of 'Adaptive two-wave mixing wavelength demodulation of fiber bragg grating sensor for monitoring dynamic strains'. Together they form a unique fingerprint.

Cite this