New, simple technique to measure group effective indices of optical fibres

Measurements of effective group index are presented, performed by a technique based on a Fourier analysis of a frequency scan of the resonant cavity formed by a short section of a single-mode fibre. The technique is very simple, and provides accuracy to the fourth decimal place. The measured effective group index, for a standard reduced single-mode fibre at 1555 nm, is 1.4682.