In a previous study, we compared experiments on drawing of axisymmetric tubular optical fibres to a mathematical model of this process. The model and experiments generally agreed closely. However, for some preforms and operational conditions, the internal channel of the drawn fibre was larger than predicted by the model. We have further investigated this phenomenon of an oversized channel with to determine the mechanism behind the size discrepancy. In particular we have explored the possibility of channel expansion similar to ‘self-pressurisation’ in fibres drawn from preforms that have been first sealed to the atmosphere, as previously described by Voyce et al. [J. Lightwave Technol. 27, 871 (2009) [CrossRef] ]. For this, two pieces from each of two preforms with different inner to outer diameter ratios were drawn to fibre, one open to the atmosphere and the other with a sealed end. In addition, we have sectioned a cooled neck-down region from a previous experiment, for which the fibre had an oversized channel compared to the model prediction, and measured the cross-sectional slices. We here compare this new experimental data with the predictions of the previously derived model for drawing of an unsealed preform and a new model, developed herein, for drawing of a sealed tube. We establish that the observed oversized channels are not consistent with the self-pressurisation model for the sealed tube.

中文翻译：

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管状纤维拉伸中超大通道的研究

在先前的研究中，我们将拉制轴对称管状光纤的实验与该过程的数学模型进行了比较。该模型和实验大致吻合。但是，对于某些瓶坯和操作条件，拉制纤维的内部通道比模型预测的要大。我们进一步研究了通道过大的现象，以确定尺寸差异背后的机制。特别是，如Voyce等人先前所描述的，我们已经探索了从先密封到大气中的预成型坯拉制而成的纤维中类似于“自加压”的通道扩展的可能性。[J. 光波技术。27，871（2009）[交叉引用] ]。为此，将两种具有不同内径比的预成型坯中的每一个拉伸成两块，将它们拉制成纤维，一个向大气敞开，另一个则密封端。此外，我们已经从先前的实验中切下一个冷却的颈缩区域，该区域的纤维与模型预测相比具有较大的通道，并测量了横截面切片。我们在这里将这一新的实验数据与先前推导的未密封预成型件的模型的预测以及本文开发的用于密封管的绘制的新模型的预测进行比较。我们确定观察到的过大通道与密封管的自加压模型不一致。