21.2 km graded-index v.a.d. fibre with low loss and wide bandwidth

Abstract
A 21.2 km graded-index optical fibre has been fabricated by the v.a.d. method. Special attention was paid to the temperature distribution on the growing surface of the porous preform to obtain the desired refractive-index profile. In the 21.2 km fibre, the transmission loss and 6 dB down bandwidth achieved were 0.64 dB/km and 57 MHz at 1.3 μm, respectively.