Abstract: The invention concerns an optical fiber pumped through the cladding, including: a core having an optical index n1, around the core, a first cladding having an index n2 lower than n1, and around the first cladding, a second cladding having an index n3 lower than n2, characterized in that the interface between the first cladding and the second cladding has a substantially polygonal cross section. The invention also concerns a method of fabricating an optical fiber pumped through the cladding, characterized in that it consists in executing the following steps: placing around a central optical preform including a core having an index n1 surrounded by a first cladding having an index n2 lower than n1, a plurality of rods having an index n3 lower than n2, and drawing the optical preform and the rods in a vacuum to obtain an optical fiber including a core and two claddings.

Abstract: The invention concerns an optical fiber pumped through the cladding, including:

Abstract: The multi-core optical fiber comprises cores embedded in common cladding, with each core containing a dopant. A "peculiar" one of the cores has a central zone that is not doped by the dopant, the other cores all being completely doped by the dopant, thereby enabling the peculiar core to be used as a local reference point in order to locate the cores of the optical fiber individually.

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: The present invention relates to a method of detecting and/or measuring changes in a physical magnitude by means of a distributed sensor, changes being detected and/or measured at a plurality of "measurement" points along said sensor, said sensor comprising an optical fiber having an optical core for guiding the majority of light waves, said optical core including a plurality of diffraction gratings distributed along said optical fiber, each situated at one of said measurement points, said diffraction gratings all having substantially the same central reflection wavelength in the absence of strain, the method comprising the following steps: injecting a "detection" light signal into an "inlet" end of said optical fiber, the wavelength of the light signal being close to said central reflection wavelength; determining the power of one of the reflected signals, referred to as the "detected reflected power", as a function of time; comparing said detected reflected power as a function of time with the power reflect

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: The present invention relates to a method of coupling a multi-core optical fiber to a plurality of single-core optical fibers, the multi-core optical fiber comprising N mutually parallel optical cores (N.gtoreq.4) embedded in common optical cladding, and each of the single-core optical fibers comprising one optical core surrounded by optical cladding. In this method, the coupling is distributed over P coupling levels (2.ltoreq.P<N), each coupling level including at least two single-core optical fibers. The coupling levels are offset longitudinally relative to one another along said multi-core optical fiber, and are such that each of said fibers belonging to the coupling levels is disposed parallel to and facing a core of the multi-core fiber, and is secured to the optical cladding of the multi-core fiber so as to obtain lateral evanescent-wave coupling.

Abstract: The multi-fiber optical cross-coupler includes N peripheral fibers and a central fiber that are coupled together optically. The method of the invention for manufacturing such a cross-coupler consists in forming a multi-waveguide conductor by drawing a composite primary preform, the waveguides of the conductor being cylindrical elementary fibers embedded so that they are mutually parallel in mechanical and optical coupling cladding, said waveguides defining the fibers of the cross-coupler, and having opto-geometrical characteristics so that they are optically coupled over a defined length of said conductor, which length is cut off accordingly. Application to an optical coupler.

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 optical sensor includes a support (2), an optical fiber (15) and two elements (9, 10) mounted on the support (2) in such a manner as to move as a function of the variations of a quantity to be measured, such as pressure. The attenuation of an optical radiation in the optical fiber (15) deformed by reverse bending is measured. The support (2) is constructed in the form of a bending beam including two end parts (2b, 2c) bearing on two fixed abutments and a central part (2a) connected to a metal membrane (16) actuated as a function of the variations of the quantity to be measured. The optical fiber (15) is disposed between the two movable elements (9, 10) in the form of a comb, each fixed on an end part (2b, 2c) of the support. The elements (9, 10) include active surfaces coming into contact with the fiber (15) to produce a variable reverse bending of the fiber (15) in the course of their relative movement.

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: An optical tapping coupler for a cable including at least one optical conductor (1) constituted by a step-index glass fiber which is covered by a plastic covering. First means (3 & 4, 5 & 6, 7, 8, 12) enable a determined position and a determined curvature to be given to a portion of each optical conductor of the cable, with each optical conductor being dissociated from the rest of the cable at the tapping location. Second means (21, 22) enable one end of each auxiliary optical conductor (30) to be mechanically brought against a respective cable optical conductor, with a small angle of incidence, in the region in which the cable conductor presents the determined curvature. Optical-index-matching third means are provided between the end of each auxiliary optical conductor and the cable optical conductor against which the end is positioned. The invention is used in particular for multi-station local network buses.

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: Twenty temperature sensors follow one another along a measurement fiber. Each successively reflects a small fraction of the energy of an interrogation light pulse running along said fiber, with the value of the fraction being indicative of temperature. To do this, each sensor is constitutred by a gap between two successive lengths (F2, F3) of an optical fiber, said gap being filled with a transparent glue (36) whose refractive index varies as a fuction of temperature. The interrogation pulse is returned solely by the optical surface constituted by the end face (38) of the upstream length (F2) of the fiber.

Abstract: The invention relates to a method and to apparatus for remotely measuring the distribution of a physico-chemical parameter in a medium. The method consists in exciting measurement points (20) situated in a medium (17) in succession via an optical fiber (18), with each point (20) being excited by two light pulses of different wavelengths offset from each other in time occurring simultaneously at said point, each measurement point returning radiation at a third wavelength representative of the temperature of the measurement point. The apparatus includes two lasers (3, 4) emitting different wavelengths, a delay circuit (5) for delaying the light pulse from one (4) of the two lasers, and the measurement points include a material sensitive to biphotonic excitation.

Abstract: Fibre-retaining grooves are formed in-between a set of fibre locating pins (M) laid side by side. The pins and a base plane (4) on which they are laid are made of hard, rigid material. Guidance for connection and disconnection is provided by guide pins (G1 to G4) of larger diameter which are therefore robust enough to stand up to handling. The guide pins are in direct contact with the locating pins in order to ensure positional accuracy.

Abstract: The invention relates to an optical fibre connector.A short segment of fibre with a diameter which is accurately known and which is held in the connector is connected by welding to the end of a very long transmission fibre.Application to telecommunications.

Abstract: In an optical fibre connector, the optical fibre is accurately positioned by clamping it in the channel formed between three parallel rollers each of which bears tangentially on the other two. If the fibre is of exactly the expected diameter such clamping is firm and precise, but given the variation in fibre diameters that must be accommodated there is a danger of there being excessive fibre play. This connector overcomes the problem of fibre tolerances by inserting resilient means in the said channel. Such resilient means may for example be constituted by a set of three resiliently deformable elastomer rings, one mounted on each rod.