Abstract: The optical amplifier (1) comprises two amplifying stages, an upstream amplifying stage (S.sub.M) and a downstream amplifying stage (S.sub.V). The former stage comprises an upstream active fiber (9) doped with a fluorescent dopant and connected serially to the optical fiber line (2), an upstream optical coupler (10) connected serially downstream from the upstream section of active fiber (9), a laser diode (11) for supplying pumping energy towards the upstream active fiber (9) through the coupler (10), said coupler being oriented to cause pump energy travel towards said upstream active fiber (9) in the opposite direction from the predetermined signal direction (S); the latter stage (S.sub.

Abstract: A process and an apparatus to make composite insulators, consisting of a central core (3) provided with an insulating coating (4) of elastomeric material, for electric overhead lines. The apparatus comprises a base structure (6) to which a first and a second end pieces (5a, 5b) of the core (3) are respectively fastened by a bracket (7a), and two injection mould halves (8a) designed to be moved close to each other. Mounted to the base structure (6) are at least two forming mould halves (9a, 9b) arranged to define a filling housing (9c) around the core (3). An injection nozzle (11) communicates with a conveying hollow space (12) coaxial with the central core (3), which is formed between the injection mould halves (8a) and a containing sleeve (13) mounted on the second end piece (5b).

Abstract: An optical amplifier for telecommunication lines over which communication signals at a predetermined wavelength are transmitted. The amplifier has portions of two optically coupled fibers, at least one of the fibers being an active fiber, interconnected by a length of active fiber connected to the one fiber of successive portions. Preferably, the active fibers are doped with erbium, and the coupling wavelength of the two fibers is different from the communication signal wavelength so that energy of the spontaneous emission of erbium is transferred from the one fiber to the other fiber and absorbed in the latter permitting amplification of communication signals in a range of wavelengths corresponding to the tolerance range of commercial laser signal emitters.

Abstract: Active-fiber optical amplifier connected to optical fiber lines or a telecommunication signal source through energy reflection limiting means, such as optical isolators, for limiting the reflected energy, due to Rayleigh scattering, which reaches the active fiber, to permit increased amplifier gain. The input of the active fiber is connected to a dichroic coupler which is also connected to a pumping energy source by an optical fiber having a bevelled end surface or an antireflection coating at the energy source end to limit reflection of energy to the active fiber. Also, a telecommunication system including one or more of such protected amplifiers.

Abstract: A unit for amplifying light signals in optical fiber transmission lines includes a fiber optical amplifier to which light signals are transmitted through an input optical fiber line, and from which the signals, after having been amplified, are introduced into an output optical fiber line. First and second optical insulators are interposed between the fiber optical amplifier and the input and output lines to prevent the transmission of optical noise signals from the input and output lines, respectively, to the amplifier.

Abstract: The described ribbon optical fibre cable comprises a cylindrical core (9) provided, on the outer surface thereof, with parallel grooves (10) extending in a helical manner along the cable axis, at least a pair of ribbons (1) being radially superposed within at least one of said grooves (10). Each ribbon (1a, 1b, 1c, 1d, 1e) comprises a plurality of optical fibres (2) each of which is covered with a primary layered coating (3), and a common coating (4) covers all the optical fibres of the ribbon. The primary coating (3) is formed with a first layer (5) directly in contact with the fibres (2) and a second layer (6) external to the first layer (5), the modulus of elasticity of said first layer (5) being lower than the modulus of elasticity of said second layer (6). Applied to each ribbon (1a, 1b, 1c, 1d, 1e) is a longitudinal tension greater than the longitudinal tension applied to the ribbon radially overlying the former.

Abstract: The optical fibre element comprises at least one optical fibre housing constituted by a polyolefin material having at least one additive which protects it against degradation due to oxidation, heat or the proximity of metals, and (b) at least one H.sub.2 -absorbing buffer. The additive is selected from the group comprising anti-oxidants, stabilizers and metal deactivators which cause a reduction in the hydrogen absorption capacity of less than 30% in the, or each, H.sub.2 -absorbing buffer when the, or each, buffer has been in contact with said polyolefin containing the, or each, additive for 30 days at 100.degree. C. in an air atmosphere saturated with water vapor at 150 mbar.

Abstract: The optical fiber element comprises at least one layer of coating constituted by a polyacrylate reticulated by UV radiation and at least one H.sub.2 -absorbing buffer, said polyacrylate comprising at least one photo-initiator of UV reticulation possibly together with an activator for it wherein said photo-initiator and its activator, if any, are selected from the group which comprises those photo-initiators and those activators which cause a reduction in the hydrogen absorption capacity of less than 30% in a H.sub.2 -absorbing buffer which has been in contact with said polyacrylate containing them for 30 days at 100.degree. C. in an air atmosphere saturated with water vapor at 150 mbar.

Abstract: An optical amplifier, particularly useful for optical fiber telecommunication lines, which includes an active fiber doped with a fluorescent dopant which provides light energy emission at the wavelength of the transmission signals when the latter signals are applied thereto. One section of telecommunication line is connected to one input of a dichroic coupler, the output of which is connected to one end of the active fiber and the other input of which is connected to a source of pumping energy at a wavelength lower than that of the transmission signals. The other end of the active fiber is connected to another section of the telecommunication line. In rectilinear form, the active fiber provides single-mode propagation of the energy at the signal wavelength and multi-mode propagation of energy at the pumping energy wavelength.

Abstract: An optical fibers cable and the relative components comprise a barrier mixture, to protect the optical fibers, comprising (a) at least a silicon unsaturated organic compound having more than 0.2 mmoles of unsaturated groups per 100 g of said compound, (b) at least a catalyst selected from the group comprising inorganic and organic complexes of transition metals and organic salts of transition metals; said barrier mixture is a further object of the invention and consists of an homogeneous phase.

Abstract: An optical fibers cable and the relative components comprise a barrier mixture to protect the optical fibers; the barrier mixture is a further object of the invention and consists of an homogeneous phase comprising (a) at least a silicon unsaturated organic compound having more than 0.2 mmoles of unsaturated groups per 100 g of the compound, (b) at least a catalyst selected from the group comprising inorganic and organic complexes of transition metals and organic salts of transition metals, and (c) at least an organic solvent substantially non-volatile.

Abstract: A drawing head for ribbon type optical cables having optical fibres in ribbons with respective end connectors, a central strength member and a grooved core includes a drawing member connected at one end thereof to the axial strength member of the cable and at the other end thereof to a pulling and grasping member, which drawing member is surrounded by a flexible body. The drawing member has a length corresponding to a predetermined fibre ribbon length required for establishing cable connections, and the flexible body is provided with grooves adapted to accommodate the fibre ribbons disposed in alignment with the grooves of the cable core. The flexible body is followed by a deformable supporting body surrounding the drawing member and which can be deformed by the connector to provide longitudinally separated and aligned recesses for receiving the end connectors of the ribbons of each ribbon group accommodated in a given groove.

Abstract: A joint, and a method for forming such joint, between two optical fiber cables or cores having closed-helix grooves each loosely receiving at least one optical fiber. A cylindrical body having open-helix grooves is interposed between the two cores so that the latter grooves interconnect corresponding grooves of the cores. The ends of the optical fibers are joined, and the fibers are then placed in the grooves of the cylindrical body.

Abstract: An optical fiber transmission line which includes units for injecting into, and units for extracting, optical service signals from the line's optical fiber. The units include optical service signal emitters and receivers for receiving from the optical line and/or injecting into the optical line service signals in the form of optical signals having a wavelength which is substantially different from the wavelength of the telecommunication signals also transmitted over the optical line, each of the units is associated with an optical coupler which is inserted in the line and which is suitable for coupling it with the line fiber and/or for extracting the optical service signals from the line fiber.

Abstract: Optical connectors adapted to join optical fibers to an optical component, each connector having an outer support to be fixedly secured to the component and provided with a housing receiving a movable element having a spherical-surface portion to which an optical fiber-holding body is connected. The spherical surface of the movable element is in contact with a mating surface of the outer support and permits pivoting or rotation of the movable element and the body housing the fiber about any axis passing through the center of the spherical surface itself. Tightening means for locking the movable element against the housing surface is provided, and such tightening means is adapted to prevent pivoting or rotation of the movable element itself by friction. The connector can be made entirely of dielectric materials.