Process and apparatus for detecting a critical stage during collapse of a glass optical fibre preform

摘要

The detection of a critical state of closure of a preformer (1) succeeding a phase of deposition of layers of material that radially reduce an opening formed in the preformer, is claimed. The method consists of a) injection of a gas (3) through the opening; b) measurement of a pressure (5) in an element of the duct (13) through which the injected gas circulates; and c) detection of the critical point of closure of the optical preformer as a function of a measured current pressure. In response to the detection of the critical state of closure of the optical preformer, a valve is opened to evacuate the injected gas and lower the pressure applied in the opening. The system used to put this method into service is also claimed and comprises:- a) a duct (10) leading to one end of the preformer (1); b) a mechanism for the injection of gas through the opening via this duct; and c) some sensors (5) for measuring a pressure in the duct.