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An optical fiber water vapor sensor based on a distributed feedback (DFB) diode laser was reported. The DFB diode laser was internally driven by a low-frequency current to realize wavelength scanning; simultaneously, laser output was externally modulated through an electro-optic modulator to realize high-frequency intensity modulation. Measurement precision of water vapor concentration could be improved by two main aspects, absolute absorption profile and high signal-to-noise ratio. The experiment was carried out at 1 atm/296 K and the recovered absolute absorption profile of water vapor at 1368.597 nm was described by Voigt profile with a difference of 1%. A well linearity was achieved with an R-square of 0.9999 and the sensitivity for a 10-cm absorption length was achieved to be 6.7 × 10−8 Hz−1/2.
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Wang et al. (2014) studied this question.
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