Multiplexed adaptive two-wave mixing wavelength demodulation of fiber Bragg grating sensor for monitoring both dynamic and quasi-static drifts

Yi Qiao; Sridhar Krishnaswamy

doi:10.1117/12.658679

30 March 2006 Multiplexed adaptive two-wave mixing wavelength demodulation of fiber Bragg grating sensor for monitoring both dynamic and quasi-static drifts

Yi Qiao, Sridhar Krishnaswamy

Author Affiliations +

Proceedings Volume 6167, Smart Structures and Materials 2006: Smart Sensor Monitoring Systems and Applications; 616708 (2006) https://doi.org/10.1117/12.658679
Event: SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring, 2006, San Diego, California, United States

Abstract

A multiplexed 4-channel version of 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 both dynamic strains and quasi-static 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. In this paper, the demonstrated 4-channel TWM wavelength demodulator is able to demodulate dynamic strains from four FBG sensors simultaneously in the presence of quasi-static drifts. And with the aid of a spectrum analyzer, the quasi-static shifts caused by static strains or temperature changes are obtained by monitoring the spectral shift of the transmitted light through the FBG sensors.

Citation Download Citation

Yi Qiao and Sridhar Krishnaswamy "Multiplexed adaptive two-wave mixing wavelength demodulation of fiber Bragg grating sensor for monitoring both dynamic and quasi-static drifts", Proc. SPIE 6167, Smart Structures and Materials 2006: Smart Sensor Monitoring Systems and Applications, 616708 (30 March 2006); https://doi.org/10.1117/12.658679

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KEYWORDS

Sensors

Fiber Bragg gratings

Demodulation

Two wave mixing

Crystals

Multiplexing

Fiber optics sensors

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