Polymeric fiber sensor for sensitive detection of carbon dioxide based on apodized wavelength modulation spectroscopy

Abstract

The performance of an optical sensor that employs an unbuffered polydimethylsiloxane (PDMS)-cladding fber optic is demonstrated for the sensitive detection of CO2 gas in the near-infrared region for around 1.57 µm using the apodized 2f/1f wavelength modulation spectroscopy method. The permeability and diffusion characteristics of the PDMS fber have been theoretically examined and numerically simulated. The results of the simulation are verifed by an experimental setup containing a DFB laser source and 5-m-coiled unbuffered PDMS fber placed in a pre-vacuumed cell flled with about 980 ± 10 Torr of pure CO2 gas. A minimum detectable absorption of ~0.9 × 10-4 is measured, corresponding to a detection sensitivity of ~4.5 × 10-11 cm_1/Hz1/2. The effect of the scaling k-factor on the apodized signal is subsequently studied, showing close agreement between the simulation and experimental results. © Springer-Verlag Berlin Heidelberg 2014