Abstract: The present invention relates to a method and an apparatus for fabricating a preform (1,10,100) that can be used for drawing an active optical fiber (8). The present invention further relates to an active optical fiber (8), designed for amplification or attenuation purposes, drawn from said preform (1,10,100) and to an optical amplifier (600, 601) using a laser active optical fiber.

Abstract: The method for fabricating an optical fiber comprises the steps of inserting a primary optical fiber preform (11) having a first primary axis (x1) and an outer surface (111) into an overcladding tube (12) having a second primary axis (x2) and an inner surface (120), so that said outer surface and inner surface define an interior space (15); holding the primary preform (11) in a centrally inserted position within the overcladding tube (12) with said first and second primary axes (x1, x2) in substantial alignment with each other; supplying overcladding grain (13) into the interior space (15) that is limited at the lower end of the overcladding tube (12) by means of a closure (125); generating a condition of reduced pressure within the interior space (15) that is limited at the upper end of the overcladding tube (12) by means of an adjoiner (3), which holds the primary optical fiber preform (11) and the overcladding tube (12) in position; and heating the unprocessed secondary preform (1), that consists of the pr