Abstract: A method and apparatus for adjusting the coating diameter and/or thickness during production of an elongated member being coated. In the preferred embodiment, the elongated member is an optical fiber. The apparatus includes a coating unit having a sizing die with an orifice through which the elongated member is conveyed, the diameter the orifice being adjustable. This is achieved by providing a helical spring in the sizing die with the inside of the spring defining the orifice. A tensioning mechanism adjusts the tension of the spring by causing relative rotation between opposite ends of the spring to change the diameter of the orifice. The apparatus further includes a measuring device, disposed downstream of the coating unit, for measuring the diameter of the coating; and a controller for adjusting the diameter of the orifice in response to the measured diameter of the coating.

Abstract: A method and apparatus for controlling an outside diameter of a preform bait tube during a glass layer deposition process. The apparatus includes a gas source in communication with an interior of the preform bait tube. A temperature monitor measures a temperature of a hot zone of the preform bait tube and generates a temperature output signal indicative of the measured temperature. A diameter monitor measures the diameter of the hot zone of the preform bait tube and generates a diameter output signal indicative of the measured diameter. A pressure measuring unit measures the pressure in the interior of the preform bait tube and generates a pressure output signal indicative of the measured pressure.