| 摘要 |
<p>Fiber is drawn from a glass preform having a diameter of about 60 mm or greater, formed from an MCVD process, such that the glass passes through the neck-down region at a rate of about 20 g/min or greater. The invention reflects the finding that glass of a large diameter preform should be passed through the neck-down region at a relatively fast rate that reduces the extent of oxygen diffusion. Reducing such oxygen diffusion, it is believed, substantially maintains transition metal impurity atoms in their most oxidized valence state, and thereby reduces the impurities' detrimental effect on losses. Using the process of the invention, it is possible to obtain commercially desirable losses, e.g., 0.23 dB/km or less at 1550 nm, from large diameter preforms capable of producing over 200 km of 125 mu m diameter fiber.</p> |
