| 摘要 |
1. A method for manufacturing an optical monomode fibre allowing to conserve the linear polarisation of a light wave guided through this optical fibre, the method comprising - a first step in which oxides are deposited inside a rotating quartz tube (1) of elliptical inner cross-section, along which a heat source (2) is displaced and to which halides and oxygen are fed, in order ot obtain an oxide layer which is thicker on the tube (1) surface in zone close to the major ellipse axis of said elliptical cross-section than in other zones, the tube being heated up to a first temperature by said heat source, this step including two phases, a first phase in which the sheath material is deposited and a second phase in which the core material is deposited, - a second step in which the tube (1) is contracted by increasing the temperature of the tube (1) due to the heat source (2) until a bar or preform is obtained, - a third step in which this preform is drawn to obtain a fibre of indentical dimensional ratios as that of the preform, including a central core zone (6) and at least one peripheral sheath zone (5) of different doping rates, characterized in that during the contraction operation of the second step, an overpressure is created inside the tube (1) with respect to the ambient pressure existing outside the tube (1), in order to obtain at the end of the third step an optical fibre having a core (4) of substantially circular cross-section and, simultaneously, a sheath of elliptical cross-section. |
