| 摘要 |
<p>An optical fibre such as might be used for the transmission of data or as a sensor, is formed of substantially torsion-free material which is twisted during drawing to have a rate of twist per unit length greater than the intrinsic birefringence. The material is torsion-free hence avoiding the torsional stresses which produce circular birefringence but the spinning averages out the stress induced linear birefringence and the form birefringence. The spinning thus ensures that residual polarisation mode dispersion is reduced to a negligible value. Figure 1 illustrates one technique for making such fibres, a preform (10) fed into a drawing furnace (13) is spun by a motor (11) to impart the required twist to the fibre (15).</p> |
