Wavelength modulation technique for intra-cavity absorption gas sensor

Wavelength modulation spectroscopy by the use of a tunable optical filter was applied to an intra-cavity fiber laser gas sensor. The optimum pump power and the modulation amplitude that maximized the signal-to-noise ratio were found. A minimum detectable gas (C/sub 2/H/sub 2/) concentration of 1000 ppm was experimentally achieved.