Interferometric determination of dispersion variations in single-mode fibers

Interferometry is used to study the variation of the zero dispersion wavelength (λ0) and the absolute group index (Ng) along the lengths of depressed cladding single-mode fibers. All of the results are for 34-cm samples of AT&T fibers drawn on production facilities. For two 7.5-km fibers sampled approximately every 1 km,{λ₀} = 1299.6 ± 2.7and 1300.5 ± 2.9 nm. For five additional 0.8-km fibers, the average of the end-to-end differences of λ0is 2.0 nm. These results indicate the feasibility of inferring λ0for long lengths of these fibers from measurements made on a 34-cm length. At 1.30 μm,{Ng}and σ are 1.4659 and 0.0003, respectively (60 fibers from 28 preforms). The corresponding values at 1.55 μm are 1.4666 and 0.0003 (46 fibers from 19 preforms). These results place a lower limit of 0.02 percent on the accuracy of pulse delay measurements of unstressed lengths of AT&T production fibers.