U.S. Philips Corporation

Hans-Jurgen E Hagemann

Jacques P Warnier

Peter K Bachmann

Howard J Wilson

Peter E Geittner

Hans-Jurgen Lydtin

In the PCVD method glass is deposited in layers on the inner wall of a glass tube by heating the tube to a temperature between 1100.degree. and 1300.degree. C., by passing a reactive gas mixture through the glass tube from a gas inlet side at a pressure between 1 and 30 hPa, by forming a plasma in the interior of the glass tube, and by reciprocating the plasma between two reversal points. After a quantity of glass corresponding to the desired fiber optical construction has been deposited, the tube is collapsed to form a solid preform from which optical fiber are draw. The range of nonconstant deposition geometry at the preform entrance, (i.e. on the gas inlet side), is reduced by interrupting the reciprocating movement of the plasma at the reversal point on the gas inlet side.

Method of manufacturing optical fibres

In the manufacture of optical fibers according to the PCVD method, a method is provided wherein the yield of the method (.eta.), in particular at increased deposition rates (m), is raised by reducing the geometrical taper, without forming optical tapers. This is obtained in that glass is deposited in layers on the inside of a glass tube and, simultaneously, on a glass rod having a circular cross-section, which rod is arranged inside the glass tube, such that its longitudinal axis coincides with that of the glass tube, the radius of the glass rod being adjusted to at most 0.67 times and at least 0.2 times the inner radius of the glass tube, and the glass rod being removed from the glass tube upon completion of the deposition process.

Polarization-retaining optical fibres are manufactured according to the PCVD method, in which on the inside of a glass tube and, simultaneously on at least two glass rods which are arranged inside the glass tube such that their longitudinal axes run parallel to the longitudinal axis of the glass tube, glass is deposited in layers and the glass rods are removed from the glass tube upon completion of the glass deposition process. Alternatively, a single glass rod, the radial dimensions of which in two mutually perpendicular directions are in a ratio unequal to one, i.e. elliptical, is arranged in a glass tube such that its longitudinal axis coincides with the longitudinal axis of the glass tube.

In the manufacture of preforms for optical fibres, the materials of the core (.alpha.) and of the light-conducting cladding layer (.beta..sub.1) are previously deposited from the gaseous phase. Deposition time is here considerably reduced in that only the materials of the core (.alpha.) and a part of the light-conducting cladding layer (.beta..sub.1) are deposited from the gaseous phase and the remaining light-conducting cladding material (.beta..sub.2 +.beta..sub.3) is supplied as pre-formed tubes of cladding material.

Method of manufacturing a monomode optical fiber

Polarization-retaining optical fibres are manufactured according to the PCVD method, in which on the inside of a glass tube (1) and, simultaneously on at least two glass rods (2, 3) which are arranged inside the glass tube such that their longitudinal axes run parallel to the longitudinal axis of the glass tube, glass is deposited in layers and the glass rods are removed from the glass tube upon completion of the glass deposition process. Alternatively, a single glass rod, the radial dimensions of which in two mutually perpendicular directions are in a ratio unequal to one, is arranged in a glass tube such that its longitudinal axis coincides with the longitudinal axis of the glass tube.

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Aachen, Germany

Hans-Jurgen E Hagemann