Abstract
A novel approach to interrogating in real time a linearly chirped fiber
Bragg grating (LCFBG) sensor based on spectral-shaping and wavelength-to-time
(SS-WTT) mapping with improved interrogation resolution and signal-to-noise
(SNR) ratio is proposed and experimentally demonstrated. The proposed system
consists of a mode-locked laser source, an optical interferometer incorporating
an LCFBG, and a dispersive element. The optical interferometer has a spectral
response with an increasing free spectral range (FSR). The incorporation of
the LCFBG in the interferometer would encode the sensing information in the
spectral response as a change in the FSR. After SS-WTT mapping, a linearly
chirped microwave waveform is obtained. The correlation of the linearly chirped
microwave waveform with a chirped reference waveform would provide a sharp
correlation peak with its position indicating the wavelength shift of the
LCFBG. A theoretical analysis is carried out, which is validated by a numerical
simulation and an experiment. The experimental results show that the proposed
system can provide an interrogation resolution as high as 0.25 $\mu \varepsilon$ at a speed of 48.6 MHz.
© 2011 IEEE
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