Interferometric determination of dispersion and group index variations in single mode fibers.

Interferometry is used to study the variation of the zero dispersion wavelength (lambda0) and the group index (Ng) along the lengths of type 5D production single mode fibers. For two 7.5 km fibers sampled approximately every 1 km, mean of lambda0 = 1299.6 and 1300.5 nm with sigma = 2.7 and 2.9 nm, respectively. For five additional 0.8 km fibers, the average of the end-to-end differences of lambda0 is 2.0 nm. For the same samples along the two 7.5 km lengths, (Ng)1.30 = 1.4659 and 1.4658, and sigma = 0.0002. Also, (Ng)1.55 = 1.4667 and 1.4665 and sigma = 0. 0002 and 0.0003, respectively. Averaging all of the group indices in this study, (Ng)1.30 = 1.4659 from 60 fibers (28 preforms) and (Ng)1.55 = 1.4666 from 46 fibers (19 preforms). For both group indices, sigma = 0.0003.