Group delay reference artifact based on molecular gas absorption

We propose a novel group delay reference for optical communication systems based on a molecular gas cell absorption characteristic. A 1.53 /spl mu/m C/sub 2/H/sub 2/ acetylene gas absorption cell commonly used as a wavelength reference is shown to have an important dispersive nature that forms the basis of a novel group delay reference. Group delay measurements are compared to theoretical predictions based on the amplitude response of the molecular gas cell. The formulated analytical approach is applicable to an arbitrary absorption spectra described by a Lorentzian function.