Abstract: Process for making preforms for multicore optical fibers. According to this process, several elementary preforms are made, a first machining is performed on them such that a chosen geometric model will be obtained after they are assembled, a second machining is performed such that the assembly (11) has at least one hole (12), the preforms are assembled and an induction furnace (18) is used to fuse the preforms, while creating a vacuum in each hole.

Abstract: Small, high precision, multicore optical guides and process for the production of said guides. Such a guide includes elementary guides (G1 to G4) and a matrix (M) in which they are located. These elementary guides are very accurately positioned with respect to one another in the matrix and with respect to the external contours (5) thereof and have high precision geometrical characteristics. According to the process, manufacturing and machining of the blanks so as to obtain, after assembly, the chosen geometrical model for the multicore guide. They are assembled in accordance with this model, welded together by means of a bait and the assembly is drawn.

Abstract: According to the invention, a hollow silica bar (2) is produced with a thick wall and high geometrical precision, the bar is then cleaned and an oven (24) is used able to heat the silica to its melting temperature and with respect to which the bar is moved so as to embody an external thermic glazing of the bar, an internal vapor phase depositing a vitreous coating in this bar by making circulate inside it a mixture of suitable gaseous constituents, this coating being intended for the subsequent formation of the core of the optical fibers, and an area contraction of the bar, the various temperatures of the bar required to embody these operations being obtained by varying the temperature of the oven or speed of the bar with respect to the oven.