Study Of An Optical Fiber Water Vapor Sensor Based On A Dfb Diode Laser: Combined Wavelength Scanning And Intensity Modulation

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 x 10(-8) Hz(-1/2).