Abstract: A method of manufacturing a multi-core optical fiber, the method including assembling together a plurality of substantially identical single-core optical fiber preforms (2', 2"), referred to as "single-core preforms", each of which includes a core bar (3) surrounded by a layer of optical cladding (4), so as to form a "multi-core preform" (10) and drawing down the multi-core preform (10) so as to obtain the multi-core optical fiber. The assembly step includes securing the single-core preforms (2', 2") to one another by fusing them over their entire lengths or over portions thereof along their tangential lines of contact (T), without inserting the multi-core preform (10) into a holding tube. A vacuum is maintained in the preform during the drawing step, the vacuum being formed before or during the drawing step.

Abstract: A method of manufacturing a multi-core optical fiber, the method including assembling together a plurality of substantially identical polished single-core optical fiber preforms (2', 2"), referred to as "single-core preforms", each of which includes a core bar (3) surrounded by a layer of optical cladding (4), so as to form a "multi-core preform" (10), and drawing down the multi-core preform (10) so as to obtain the multi-core optical fiber. The assembly step includes securing the single-core preforms (2', 2") to one another by fusing them over their entire lengths or over portions thereof along their tangential lines of contact (T), without inserting the multi-core preform (10) into a holding tube. A vacuum is maintained in the preform during the drawing step, the vacuum being formed before or during the drawing step.

Abstract: A method of applying an amorphous boron-based protective coating to an optical fiber comprising an optical core enclosed in optical cladding, both made of a silica-based material, wherein the boron is applied to the surface of said optical fiber chemically from the vapor phase at a temperature lying in the range 1050.degree. C. to 1250.degree. C., by reducing boron chloride BCl.sub.3 by means of hydrogen H.sub.2. The amorphous boron protective coating imparts mechanical protection to the fiber, and enhanced abrasion resistance, enabling the fiber to be used in optical cables of high capacity and that are highly compact. The thickness of the resin coating can be about half that required when a carbon protective coating is used, and can even be eliminated. The coating further provides sealing properties comparable to those provided by a carbon coating.

Abstract: An optical fiber comprising an optical core enclosed in optical cladding, both made of a silica-based material, and a protective layer constituted by amorphous boron. The amorphous boron layer is deposited on a non-crystalline carbon which is itself deposited directly on the optical cladding. Also, a method is provided for depositing an amorphous boron layer on an optical fiber and includes a deposition step of depositing a layer of carbon on the fiber, followed by a subsequent step of depositing the amorphous boron protective layer chemically from the vapor phase on the layer of carbon.

Abstract: The present invention concerns a monomode optical fiber comprising an optical core for guiding the majority of light waves, surrounded by an optical sheath, the difference between the maximum refraction coefficient of the core and that of the optical sheath being indicated as .DELTA.n and the radius of the core being indicated as a, characterized in that:a .epsilon.?0.6a.sub.c :1.1a.sub.c !, a.sub.c being provided, in .mu.m, by the formula: ##EQU1## where k=2.pi./.lambda., .lambda. being (in .mu.m) the wavelength of the transmission, and where n.sub.g is the coefficient of said optical sheath, equal within 10.sup.-3 to that of pure silica,.DELTA.n is greater than or equal to 0.01,and in that, .phi. being the diameter of said optical sheath, in .mu.m: .phi..epsilon.?.phi..sub.min :100!, .phi..sub.min being provided, in .mu.

Abstract: A method of detecting variation in the diameter of an optical fiber includes the following steps:transversely illuminating a portion of the fiber by means of an incident light beam,measuring a radiation pattern produced by the fiber portion in a predetermined acute angular sector around the fiber, anddetecting variation in the diameter of the optical fiber causing modification of the angular radiation pattern produced in this way.The angular sector is defined by angles of 90.degree. and 105.degree. or by angles of 255.degree. and 270.degree..

Abstract: The multiferrule for connecting optical fibers together has a series of internal capillary channels of transverse dimensions that are defined to leave substantial clearance for the fibers, at least in the two end portions of the channels where they open out into two end faces of the multiferrule. The multiferrule further includes middle necking in which the corresponding middle portions of the channels have their transverse dimensions reduced so as to leave only minimal clearance for the fibers, to enable them to be put into contact and connected together directly in this location. The multiferrule is applicable to making an optical fiber connector.

Abstract: A method of preparing a subassembly for connecting an integrated optical device (21) to an optical cable:a multiferrule is used having internal passages (2) opening onto its opposite first and second faces (6, 7),an intermediate optical cable is used,the intermediate fibers (27) are inserted into the passages (2) through the first face (6),the fibers (27) are fixed in the passages (2) over part of their length,the multiferrule and the fixed fibers (27) are cut to obtain a multiferrule section (34) in which the fibers are partly fixed,the fixed fibers (27) in the section (34) are connected to the device (21),the fibers (27) are cut near the second face (7) and removed to leave the passages (2) partially empty to produce the connection subassembly (36).

Abstract: The method of manufacturing a multiferrule for optical fibers, the method consisting in fiber drawing a preform of silica that includes a plurality of mutually parallel channels, the method being characterized by the fact that said preform is made from a rod (1) of silica having a plurality of longitudinal grooves (3) uniformly distributed about an axis (2) and closed by at least one piece of silica (4) for defining said plurality of channels.

Abstract: A method of splicing two optical fiber cables uses a glass multi-ferrule having a series of parallel axis internal capillary channels opening onto respective end surfaces of the multi-ferrule and two exterior reference surfaces. An adhesive that is polymerized by ultraviolet light is introduced into these channels. The multi-ferrule is cut into three sections. The splicing is achieved by jointing the outermost two sections.

Abstract: Apparatus for heating a silica optical fiber in a fiber-drawing installation. The apparatus is disposed at the outlet of a fiber-drawing oven to raise the optical fiber to a temperature greater than 1000.degree. C. The apparatus is constituted by a microwave generator coupled to a resonant cavity formed by a helically-wound metal wire helix fixed at opposite ends to two short circuit metal plates respectively, with the optical fiber running substantially along the axis of the helix and the helix concentric about the running fiber.

Abstract: Apparatus for treating the surface of a body by corona discharge, the apparatus comprising:a reaction enclosure through which said body to be treated can run along a "through" axis;an electrode raised to a "treatment" potential;a counter-electrode raised to a potential that is lower in absolute value than the potential of said electrode, said counter-electrode surrounding said through axis and said electrode and said counter-electrode together being disposed so as to define a "plasma-generating" zone in the vicinity of said through axis and in which said corona discharge takes place; andat least one passage formed in said enclosure to feed a plasma-generating reagent gas for treatment purposes;wherein said electrode is provided with a plurality of portions having small radius of curvature, i.e.

Abstract: The invention relates to a method of making multi-ferrules. It provides a method of making multi-ferrules from a vitreous material, the multi-ferrules having a series of cylindrical channels with parallel axes.

Abstract: Optical fiber suitable for use in optical time domain reflectometry and method of manufacturing the fiber. The method of manufacturing the optical fiber suitable for use in optical time domain reflectometry includes, during drawing of the fiber (2), a thin continuous coating is deposited on the fiber. A part of the coating is thereafter removably ablated in the form of a helix (15) coaxial with the fiber by rotating a laser beam (17) in a plane orthogonal to the axis simultaneously with axial movement of the fiber.

Abstract: A method of providing a preform for a polarization-maintaining optical fiber, starting from a basic preform (1) having two orthogonal planes of symmetry intersecting along its axis, and mechanically applying two discrete preformed oblong elements (15) of silica doped with boron oxide on the outside face of said basic preform symmetrically about the first plane (20), and two oblong elements of silica doped with titanium oxide on the outside face of said basic preform and symmetrically about the second plane (30). The shapes of the basic preform and the four oblong elements are selected to define a substantially solid cylinder.

Abstract: The invention relates to a high-frequency furnace whose wall is formed by superposed wall-forming members. This furnace includes in particular an inner tubular wall comprising a zirconia tube (38), an alumina washer (39) laid on the zirconia tube and a silica tube (40) laid on the washer. There is a large groove (41) in a top plate (37) to accommodate the silica tube (40). The furnace also includes an outer tube (36) of silica. This structure makes it possible to accommodate differential expansion of the zirconia and the silica in two separate steps. The axial difference is accommodated at the groove (41) while the radial difference is accomodated at the washer (39). Leakage of inert gas pumped into the chamber during operation can then be maintained within acceptable limits throughout the temperature range. Application to the production of optical fibers.