Butt welding optical fiber preforms with a plasma torch

A method of assembling an optical fiber preform and a cylindrical endpiece of vitreous material end-to-end, the method comprising the following operations:

• said cylindrical preform and said endpiece are placed in alignment along a common longitudinal axis;
• said preform and said endpiece are rotated about said common longitudinal axis;
• the facing ends of said preform and of said endpiece are heated by a heater;
• and
• said preform and said endpiece are moved towards each other parallel to said common axis to press them against each other so as to form intimate contact between said ends after cooling,
• wherein said heating is performed by causing relative movement between said heater and said ends in a radial direction orthogonal to said common longitudinal axis so as to heat the periphery of said preform initially and then heat the core of said preform and said endpiece.