DRAW RESONANCE OF OPTICAL MICROCAPILLARIES IN NONISOTHERMAL DRAWING

The paper studies the process of drawing of glass microcapillaries fro m hollow cylindrical preforms, accounting for surface and gravity forc es as well as for heat exchange with the surrounding medium. The quasi -one-dimensional model for hollow fiber drawing is generalized to incl ude heat-transfer effects. The draw resonance (instability) phenomenon under non-isothermal conditions is studied and compared with the corr esponding effect in the isothermal case. The method permits analysis o f various flow regimes including stable steady-state drawing, sensitiv ity of fibers to external perturbations, drawing instability (self-sus tained oscillations), and the effect of thermal conditions on the as-s pun fibers. The frequency spectrum and correlation function of the tim e series corresponding to non-isothermal drawing are analyzed. The res ults show that under non-isothermal conditions (an additional degree o f freedom) draw resonance continues to be a quasi-periodic phenomenon with no tendency to chaos. (C) 1997 Elsevier Science Ltd.