Limitations to the manufacture of specialty optical fiber

There is an emerging demand for specialty fibers whose diameter variability is an order of magnitude less than current requirements. This study considers three potential impediments to producing such fibers: on-line measurement, control techniques, and furnace design. Existing laser-gage technology appears to be quite adequate provided suitable digital filtering is used, but it is unlikely that any controller would be able to eliminate the high-frequency diameter variability. The most likely source of these high-frequency variations are flow instabilities within the draw furnace. Thus, it would seem that furnace redesign is the key to providing the level of diameter control needed in emerging specialty, optical fibers.