WO1997005513A1 - Method and device for coupling an optical fibre to a laser or photodetector - Google Patents

Method and device for coupling an optical fibre to a laser or photodetector Download PDF

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Publication number
WO1997005513A1
WO1997005513A1 PCT/FR1996/001142 FR9601142W WO9705513A1 WO 1997005513 A1 WO1997005513 A1 WO 1997005513A1 FR 9601142 W FR9601142 W FR 9601142W WO 9705513 A1 WO9705513 A1 WO 9705513A1
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WIPO (PCT)
Prior art keywords
base
brackets
optical fiber
end piece
coupling device
Prior art date
Application number
PCT/FR1996/001142
Other languages
French (fr)
Inventor
Michel Biet
Isabelle Neubauer
Blandine Capitanio
Original Assignee
Thomson-Csf Semiconducteurs Specifiques
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Publication date
Application filed by Thomson-Csf Semiconducteurs Specifiques filed Critical Thomson-Csf Semiconducteurs Specifiques
Publication of WO1997005513A1 publication Critical patent/WO1997005513A1/en

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G02B6/4201—Packages, e.g. shape, construction, internal or external details
    • G02B6/4219—Mechanical fixtures for holding or positioning the elements relative to each other in the couplings; Alignment methods for the elements, e.g. measuring or observing methods especially used therefor
    • G02B6/4236—Fixing or mounting methods of the aligned elements
    • G02B6/4237—Welding

Definitions

  • the invention relates to the coupling between an optoelectronic element, for example a laser diode or a photodiode, and an optical fiber, in particular for application to optical information transmissions, but also for other applications such as interferometry for example.
  • an optoelectronic element for example a laser diode or a photodiode
  • an optical fiber in particular for application to optical information transmissions, but also for other applications such as interferometry for example.
  • transmission head In the case of a laser diode, this is known as an optical transmission head, intended to be placed upstream of a transmission network by optical fiber. In the case of a photodiode, an information reception head is produced at a downstream end of the network. Transmission heads and reception heads are concerned with the invention, but the case of transmission heads is more important because the positioning tolerances are smaller; the invention will therefore be more precisely described in this case.
  • the coupling of the optoelectronic component and the fiber must be done with very high mechanical precision. And the precise positioning must be maintained throughout the service life of the component, which can reach several years.
  • the accuracy is even more important. It is in fact the core of the optical fiber which must be placed exactly opposite the emitted laser beam.
  • the fiber has a diameter of about 125 micrometers, but the core has a diameter of 5 or 8 micrometers ; the laser beam has a diameter of about 2 micrometers.
  • the order of magnitude of the tolerance for transverse positioning is approximately 0.1 to 0.3 micrometer; otherwise, you lose 5 to 10% of the laser power; for an offset of
  • the power loss can reach 50%.
  • the fixing of the fiber can be carried out by three kinds of technologies: bonding of the fiber, brazing, welding with YAG laser.
  • the bonding and brazing technologies which appeared first, are still widely used with fairly good performance.
  • the YAG laser welding technique tends to replace them because it allows an almost instantaneous assembly which lends itself better to industrialization.
  • the assemblies produced by YAG welding accept wider operating temperature ranges.
  • the coupling is carried out using micromanipulators making it possible to place the fiber in exactly the right position relative to the optoelectronic component, finding this optimal position by means of light energy measurements; for example, in the case of coupling with a laser diode, the energy transmitted at the end of the fiber is measured when the laser diode is operating; when it is maximum, it means that the coupling is optimal.
  • the fiber and the component are then permanently secured in this position.
  • the optoelectronic component is fixed to a support plate; the end of the optical fiber is immobilized in a retaining tip, also called a ferrule, which is most often a cylinder enclosing the end of the fiber and sealed to it by glue, or solder, or glass welding; and other intermediate parts are used such as, as the case may be:
  • - a jumper which encloses the ferrule and rests on the support plate; YAG laser shots are used to fix the jumper on the support plate and the ferrule in the jumper; correct positioning remains difficult, however, because of the very precise manufacturing tolerances of the rider, and because of the need to point the laser extremely precisely at the junction points between the ferrule and the rider; - a guide, elongated in the direction of the fiber, in which the ferrule slides, to ensure positioning along the length of the fiber, this guide having a planar transverse face which slides against a planar transverse (vertical) face of the support plate (assumed to be horizontal) to ensure transverse positioning; final fixation is done by laser shots at the junction angles of the different rooms; the defect of this system is that the flat transverse plate is massive and of complex shape; the flatness must be perfect, a special tool is necessary to handle this transverse plate, and good firing precision must be ensured towards the junctions between the different parts.
  • a coupling device between an optoelectronic element and an optical fiber comprising a base on a part of which the optoelectronic element is fixed, and a tip for holding the end of the optical fiber, surrounding the fiber and keeping it parallel to the surface of the base opposite the optoelectronic element, characterized in that, on the one hand, the retaining tip comprises two flat surfaces perpendicular to the surface of the base and on the other hand the device comprises two lateral brackets each placed on one side of the end piece and each having two plane surfaces perpendicular to each other, one welded to the surface of the base and the other welded to a respective flat surface of the retaining tip.
  • the retaining tip may comprise either a simple cylindrical ferrule enclosing the end of the optical fiber and comprising two parallel flats, constituting the two flat surfaces perpendicular to the surface of the base. But the retaining tip may also comprise several parts fixed together, and in particular on the one hand a cylinder (or ferrule) enclosing the end of the optical fiber, and on the other hand a jumper welded to this cylinder, this jumper comprising the two square surfaces perpendicular to the surface of the base.
  • a cylinder or ferrule
  • the base is pierced with suction holes under the flat faces of the brackets, so as to maintain the latter in position for the time of the laser welding of the brackets on the flat surfaces of the retaining tip and brackets on the surface of the base.
  • the invention also proposes a corresponding manufacturing method, which is a coupling method between an optoelectronic element and an optical fiber, comprising the following steps:
  • brackets each comprising two perpendicular flat faces, the brackets each being placed on one side of the end piece, and the brackets each comprising a flat face applied against the surface of the base and another flat face applied against a flat face of the nozzle;
  • brackets are preferably held face against the base by a suction of air through holes drilled in the base under these brackets.
  • FIG. 1 shows a perspective view of an optical transmission head according to the invention
  • FIG. 2 shows a detailed front view of the end of the optical fiber fixing system
  • a retaining tip in the following exemplary embodiments is either a simple cylindrical ferrule with flats, or a part which may be composed of several different parts fixed together, for example a cylindrical ferrule and a jumper.
  • the retaining tip is composed of a cylindrical ferrule of revolution 12 and a jumper 14.
  • the holding end piece is intended to be fixed permanently and rigidly, by laser welding, to a base 20 which serves as a support for the laser diode.
  • the base is preferably metallic; an iron-nickel-chromium alloy such as kovar is very suitable because it is thermally compatible with alumina substrates; we can therefore fix such substrates on the base 20; on the other hand this alloy is easily weldable by laser.
  • the fixing of the retaining tip 10 on the base 20 is done by means of two lateral brackets 32 and 34.
  • the ferrule 12, the jumper 14, the brackets 32 and 34 are preferably made of the same metal as the base 20 to allow easier laser welding between these parts and to avoid differential expansion.
  • the fixing of the laser diode 40 on the base 20 can be done via an intermediate substrate 42, for example a hybrid alumina substrate carrying not only a laser diode chip but also various connections and possibly other electronic components.
  • the intermediate substrate 42 also serves to electrically connect the laser diode and the other components to terminals of connection not shown used to supply the laser diode with electrical signals as a function of the light to be emitted.
  • the connecting wires to the outside are not shown.
  • the base 20 can also carry other parts; in the example shown, a hybrid substrate 50, fixed vertically, can be placed at the rear of the substrate 42 (opposite to the main direction of emission of the laser diode which is turned towards the optical fiber).
  • This substrate 50 can carry a photodiode 52 placed so as to receive the fraction of light energy emitted towards the rear by the laser diode. The photodiode then serves as a feedback element to control the control current of the laser diode.
  • the jumper 14 which constitutes a part of the retaining endpiece 10, is in the shape of an inverted U, with a bottom 142 resting horizontally (taking as reference horizontal the main surface of the base 20) on the cylindrical ferrule 12.
  • the two lateral branches 144 and 146 of the U are vertical flat plates which enclose the cylindrical ferrule 12.
  • the lateral branches of the jumper 14 are therefore spaced apart by a distance equal to the diameter of the ferrule.
  • the cylindrical ferrule of revolution can have a diameter of approximately 1 millimeter and comprises over its entire length a central opening in which is inserted and bonded (or brazed or welded by welding to glass) the optical fiber 11; this has for example a diameter of about 100 to 150 micrometers, typically 125 or 140 micrometers.
  • the brackets 32 and 34 each have a flat vertical plate and a flat horizontal plate. The horizontal face rests on the base 20; the vertical face is applied against the flat outer face of a respective lateral branch 144 or 146 of the jumper 14.
  • the jumper is preferably welded by YAG laser to the cylindrical ferrule.
  • the step of precise positioning of the fiber is then carried out with a view to its final fixing on the base 20.
  • the fiber is now in place in the holding end piece comprising the ferrule and its jumper.
  • the brackets 32 and 34 are then placed on the base 20, and they are applied laterally against the vertical faces of the jumper 14. They are preferably held in place, by suction, against the upper surface of the base 20.
  • This ci has holes 62 and 64 in the region where the brackets must be. These holes open out under the base opposite corresponding holes 72 and 74 formed in the mounting bench 70 on which the base is placed during the mounting operation of the optical head.
  • These holes 72 and 74 are connected to an air suction system not shown; the vacuum created by this suction keeps the brackets in place during laser welding.
  • the retaining end piece always has two parallel and flat vertical faces, but instead of being composed of two parts, cylindrical ferrule and jumper, it is composed of a single part which is a cylindrical ferrule comprising two vertical parallel flats 13 and 15, against which the vertical flat surfaces of the brackets 32 and 34 come to bear.
  • the laser welding is carried out on the horizontal faces of the brackets for attachment to the base, and on the vertical faces of the brackets for attachment to the ferrule.

Abstract

A method for coupling an optoelectronic component (laser diode or photodiode) to an optical fibre in an optical signal transmitting or receiving head is disclosed. The fibre may more easily be fixed accurately and permanently in front of the component by using a fibre holder assembly (12, 14) having two planar parallel vertical surfaces, and two angle brackets (32, 34) arranged on respective sides of the assembly and engaging the horizontal surface of the base (20) of the head and the vertical surfaces of the assembly. Attachment is achieved by laser welding on the horizontal and vertical surfaces of each angle bracket. The method is simpler to implement than prior art methods.

Description

PROCEDE ET DISPOSITIF DE COUPLAGE ENTRE UNE FIBRE OPTIQUE ET UN LASER OU UN PHOTODETECTEUR METHOD AND DEVICE FOR COUPLING BETWEEN AN OPTICAL FIBER AND A LASER OR A PHOTODETECTOR
L'invention concerne le couplage entre un élément optoélectronique, par exemple une diode laser ou une photodiode, et une fibre optique, notamment pour l'application à des transmissions optiques d'information, mais aussi pour d'autres applications telles que l'interférométrie par exemple.The invention relates to the coupling between an optoelectronic element, for example a laser diode or a photodiode, and an optical fiber, in particular for application to optical information transmissions, but also for other applications such as interferometry for example.
Dans le cas d'une diode laser, on réalise ainsi ce qu'on appelle une tête d'émission optique, destinée à être placée en amont d'un réseau de transmission par fibre optique. Dans le cas d'une photodiode, on réalise une tête de réception des informations à une extrémité aval de réseau. Têtes d'émission et têtes de réception sont concernées par l'invention, mais le cas des têtes d'émission est plus important parce que les tolérances de positionnement sont plus faibles; c'est donc à propos de ce cas que l'invention sera plus précisément décrite.In the case of a laser diode, this is known as an optical transmission head, intended to be placed upstream of a transmission network by optical fiber. In the case of a photodiode, an information reception head is produced at a downstream end of the network. Transmission heads and reception heads are concerned with the invention, but the case of transmission heads is more important because the positioning tolerances are smaller; the invention will therefore be more precisely described in this case.
Le couplage du composant optoélectronique et de la fibre doit être fait avec une très grande précision mécanique. Et le positionnement précis doit être maintenu pendant toute la durée de vie du composant, qui peut atteindre plusieurs années. Dans le cas des fibres de transmission monomode, utilisées lorsqu'on veut une plus grande bande passante dans la transmission des informations, la précision est encore plus importante. C'est en effet le coeur de la fibre optique qui doit être placé exactement en face du faisceau laser émis. Pour donner un exemple, dans le cas d'une transmission monomode à 0,8 ou 1 ,3 micromètres de longueur d'onde, la fibre a un diamètre d'environ 125 micromètres, mais le coeur a un diamètre de 5 ou 8 micromètres; le faisceau laser a un diamètre d'environ 2 micromètres. L'ordre de grandeur de la tolérance pour le positionnement transversal est de 0,1 à 0,3 micromètre environ; sinon, on perd de 5 à 10% de la puissance du laser; pour un décalage deThe coupling of the optoelectronic component and the fiber must be done with very high mechanical precision. And the precise positioning must be maintained throughout the service life of the component, which can reach several years. In the case of single-mode transmission fibers, used when a greater bandwidth is required in the transmission of information, the accuracy is even more important. It is in fact the core of the optical fiber which must be placed exactly opposite the emitted laser beam. To give an example, in the case of a single mode transmission at 0.8 or 1.3 micrometers in wavelength, the fiber has a diameter of about 125 micrometers, but the core has a diameter of 5 or 8 micrometers ; the laser beam has a diameter of about 2 micrometers. The order of magnitude of the tolerance for transverse positioning is approximately 0.1 to 0.3 micrometer; otherwise, you lose 5 to 10% of the laser power; for an offset of
0,8 micromètre entre le centre du coeur et le centre du faisceau, la perte de puissance peut atteindre 50%.0.8 micrometer between the center of the heart and the center of the beam, the power loss can reach 50%.
La fixation de la fibre peut être réalisée par trois sortes de technologies : collage de la fibre, brasure, soudure au laser YAG. Les technologies de collage et de brasure, apparues les premières, sont encore largement utilisées avec d'assez bonnes performances. Mais la technique de soudure au laser YAG tend à les remplacer parce qu'elle permet un assemblage quasi-instantané qui se prête mieux à une industrialisation. D'autre part les assemblages réalisés par soudure YAG acceptent des gammes de températures de fonctionnement plus larges.The fixing of the fiber can be carried out by three kinds of technologies: bonding of the fiber, brazing, welding with YAG laser. The bonding and brazing technologies, which appeared first, are still widely used with fairly good performance. But the YAG laser welding technique tends to replace them because it allows an almost instantaneous assembly which lends itself better to industrialization. On the other hand, the assemblies produced by YAG welding accept wider operating temperature ranges.
Dans les assemblages par soudure laser, le couplage est réalisé à l'aide de micromanipulateurs permettant de placer la fibre exactement à la bonne position par rapport au composant optoélectronique, en trouvant cette position optimale grâce à des mesures d'énergie lumineuse; par exemple, dans le cas du couplage avec une diode laser, on mesure l'énergie transmise en bout de fibre lorsque la diode laser fonctionne; lorsqu'elle est maximale, c'est que le couplage est optimal. On solidarise alors définitivement la fibre et le composant dans cette position.In assemblies by laser welding, the coupling is carried out using micromanipulators making it possible to place the fiber in exactly the right position relative to the optoelectronic component, finding this optimal position by means of light energy measurements; for example, in the case of coupling with a laser diode, the energy transmitted at the end of the fiber is measured when the laser diode is operating; when it is maximum, it means that the coupling is optimal. The fiber and the component are then permanently secured in this position.
En général on utilise diverses pièces intermédiaires : le composant optoélectronique est fixé sur une plaque de support; l'extrémité de la fibre optique est immobilisée dans un embout de maintien, appelé aussi ferrule, qui est le plus souvent un cylindre enserrant l'extrémité de la fibre et scellé à celle-ci par colle, ou brasure, ou soudure au verre; et on utilise d'autres pièces intermédiaires telles que, selon les cas :In general, various intermediate parts are used: the optoelectronic component is fixed to a support plate; the end of the optical fiber is immobilized in a retaining tip, also called a ferrule, which is most often a cylinder enclosing the end of the fiber and sealed to it by glue, or solder, or glass welding; and other intermediate parts are used such as, as the case may be:
- un cavalier qui enserre la ferrule et repose sur la plaque de support; des tirs laser YAG permettent de fixer le cavalier sur la plaque support et la ferrule dans le cavalier; le positionnement correct reste malgré tout difficile, à cause des tolérances de fabrication très précises du cavalier, et à cause de la nécessité de pointer le laser extrêmement précisément sur les points de jonction entre la ferrule et le cavalier; - un guide, allongé dans la direction de la fibre, dans lequel coulisse la ferrule, pour assurer le positionnement selon la longueur de la fibre, ce guide possédant une face transversale plane qui glisse contre une face transversale plane (verticale) de la plaque support (supposée horizontale) pour assurer le positionnement transversal; la fixation définitive se fait par des tirs lasers aux angles de jonction des différentes pièces; ie défaut de ce système est que la plaque transversale plane est massive et de forme complexe; la planéité doit être parfaite, un outillage spécial est nécessaire pour manipuler cette plaque transversale, et une bonne précision de tir doit être assurée vers les jonctions entre les différentes pièces.- a jumper which encloses the ferrule and rests on the support plate; YAG laser shots are used to fix the jumper on the support plate and the ferrule in the jumper; correct positioning remains difficult, however, because of the very precise manufacturing tolerances of the rider, and because of the need to point the laser extremely precisely at the junction points between the ferrule and the rider; - a guide, elongated in the direction of the fiber, in which the ferrule slides, to ensure positioning along the length of the fiber, this guide having a planar transverse face which slides against a planar transverse (vertical) face of the support plate (assumed to be horizontal) to ensure transverse positioning; final fixation is done by laser shots at the junction angles of the different rooms; the defect of this system is that the flat transverse plate is massive and of complex shape; the flatness must be perfect, a special tool is necessary to handle this transverse plate, and good firing precision must be ensured towards the junctions between the different parts.
Le besoin se fait sentir d'un procédé de fixation plus simple à mettre en oeuvre. La présente invention a donc pour objet l'amélioration des techniques d'assemblage par soudure au laser YAG de fibres optiques et de composants optoélectroniques. On propose selon l'invention un dispositif de couplage entre un élément optoélectronique et une fibre optique, comportant une embase sur une partie de laquelle est fixé l'élément optoélectronique, et un embout de maintien de l'extrémité de la fibre optique, entourant la fibre et maintenant celle-ci parallèle à la surface de l'embase en face de l'élément optoélectronique, caractérisé en ce que d'une part l'embout de maintien comporte deux surfaces planes perpendiculaires à la surface de l'embase et d'autre part le dispositif comporte deux équerres latérales placées chacune d'un côté de l'embout et ayant chacune deux surfaces planes perpendiculaires entre elles, l'une soudée sur la surface de l'embase et l'autre soudée sur une surface plane respective de l'embout de maintien.There is a need for a fixing method which is simpler to implement. The present invention therefore relates to the improvement of assembly techniques by YAG laser welding of optical fibers and optoelectronic components. According to the invention, there is provided a coupling device between an optoelectronic element and an optical fiber, comprising a base on a part of which the optoelectronic element is fixed, and a tip for holding the end of the optical fiber, surrounding the fiber and keeping it parallel to the surface of the base opposite the optoelectronic element, characterized in that, on the one hand, the retaining tip comprises two flat surfaces perpendicular to the surface of the base and on the other hand the device comprises two lateral brackets each placed on one side of the end piece and each having two plane surfaces perpendicular to each other, one welded to the surface of the base and the other welded to a respective flat surface of the retaining tip.
L'embout de maintien peut comporter soit une simple ferrule cylindrique enserrant l'extrémité de la fibre optique et comportant deux méplats parallèles, constituant les deux surfaces planes perpendiculaires à la surface de l'embase. Mais l'embout de maintien peut aussi comporter plusieurs pièces fixées ensemble, et notamment d'une part un cylindre (ou ferrule) enserrant l'extrémité de la fibre optique, et d'autre part un cavalier soudé sur ce cylindre, ce cavalier comportant les deux surfaces places perpendiculaires à la surface de l'embase. Ce dernier cas est préférable dans le cas de fibres à maintien de polarisation, dans lesquels il faut assurer un positionnement angulaire correct de la fibre autour de son propre axe longitudinal.The retaining tip may comprise either a simple cylindrical ferrule enclosing the end of the optical fiber and comprising two parallel flats, constituting the two flat surfaces perpendicular to the surface of the base. But the retaining tip may also comprise several parts fixed together, and in particular on the one hand a cylinder (or ferrule) enclosing the end of the optical fiber, and on the other hand a jumper welded to this cylinder, this jumper comprising the two square surfaces perpendicular to the surface of the base. The latter case is preferable in the case of fibers with polarization maintenance, in which it is necessary to ensure correct angular positioning of the fiber around its own longitudinal axis.
On prévoit ensuite de préférence que l'embase est percée de trous d'aspiration sous les faces planes des équerres, de manière à maintenir celle-ci en position le temps de la soudure au laser des équerres sur les surfaces planes de l'embout de maintien et des équerres sur la surface de l'embase.It is then preferably provided that the base is pierced with suction holes under the flat faces of the brackets, so as to maintain the latter in position for the time of the laser welding of the brackets on the flat surfaces of the retaining tip and brackets on the surface of the base.
L'invention propose également un procédé de fabrication correspondant, qui est un procédé de couplage entre un élément optoélectronique et une fibre optique, comportant les étapes suivantes :The invention also proposes a corresponding manufacturing method, which is a coupling method between an optoelectronic element and an optical fiber, comprising the following steps:
- fixation définitive de l'élément optoélectronique sur une partie d'une embase de support,- final fixing of the optoelectronic element on a part of a support base,
- fixation provisoire de l'embase sur une première partie d'un banc de montage; - fixation définitive d'une extrémité de la fibre optique dans un embout de maintien comportant deux faces planes parallèles, l'embout de maintien étant porté par une deuxième partie du banc de montage;- provisional fixing of the base on a first part of an assembly bench; - Definitive fixing of one end of the optical fiber in a holding end piece comprising two parallel flat faces, the holding end piece being carried by a second part of the mounting bench;
- mise en place de deux équerres comportant chacune deux faces planes perpendiculaires, les équerres étant placées chacune d'un côté de l'embout, et les équerres comportant chacune une face plane appliquée contre la surface de l'embase et une autre face plane appliquée contre une face plane de l'embout;- Installation of two brackets each comprising two perpendicular flat faces, the brackets each being placed on one side of the end piece, and the brackets each comprising a flat face applied against the surface of the base and another flat face applied against a flat face of the nozzle;
- recherche d'une position de couplage optimal entre la fibre et l'élément optoélectronique, par déplacement relatif des deux parties du banc de montage, en maintenant les équerres appliquées contre l'embout et contre l'embase, et, lorsque la position optimale est trouvée, soudure au laser de chaque équerre d'une part sur l'embase et d'autre part sur l'embout. Pendant la recherche de la position optimale de couplage, les équerres sont de préférence maintenues face contre l'embase par une aspiration d'air à travers des trous percés dans l'embase sous ces équerres.- search for an optimal coupling position between the fiber and the optoelectronic element, by relative displacement of the two parts of the assembly bench, keeping the brackets applied against the end piece and against the base, and, when the optimal position is found, laser welding of each bracket on the one hand on the base and on the other hand on the end piece. During the search for the optimal coupling position, the brackets are preferably held face against the base by a suction of air through holes drilled in the base under these brackets.
D'autres caractéristiques et avantages de l'invention apparaîtront à la lecture de la description détaillée qui suit et qui est faite en référence aux dessins annexés dans lesquels :Other characteristics and advantages of the invention will appear on reading the detailed description which follows and which is given with reference to the appended drawings in which:
- la figure 1 représente une vue en perspective d'une tête d'émission optique selon l'invention; - la figure 2 représente une vue de face de détail de l'extrémité du système de fixation de la fibre optique;- Figure 1 shows a perspective view of an optical transmission head according to the invention; - Figure 2 shows a detailed front view of the end of the optical fiber fixing system;
- la figure 3 représente une variante de réalisation.- Figure 3 shows an alternative embodiment.
Sur la figure 1, on voit le dispositif de couplage selon l'invention, dans le cas d'une tête d'émission optique dont l'élément actif est une diode laser. La fibre optique qui doit recueillir la lumière émise par la diode laser possède une extrémité enserrée dans un embout de maintien 10 qui permet sa fixation à la bonne position par rapport à la diode laser. La fibre optique n'est pas visible sur la figure 1, seul l'embout de maintien 10 est visible.In Figure 1, we see the coupling device according to the invention, in the case of an optical transmission head whose active element is a laser diode. The optical fiber which must collect the light emitted by the laser diode has one end enclosed in a retaining tip 10 which allows it to be fixed in the correct position relative to the laser diode. The optical fiber is not visible in Figure 1, only the retaining tip 10 is visible.
Ce qu'on appellera embout de maintien dans les exemples de réalisation qui suivent est soit une simple ferrule cylindrique à méplats, soit une pièce pouvant être composée de plusieurs parties différentes fixées ensemble, par exemple une ferrule cylindrique et un cavalier. Dans l'exemple représenté à la figure 1 , l'embout de maintien est composé d'une ferrule cylindrique de révolution 12 et d'un cavalier 14.What will be called a retaining tip in the following exemplary embodiments is either a simple cylindrical ferrule with flats, or a part which may be composed of several different parts fixed together, for example a cylindrical ferrule and a jumper. In the example shown in FIG. 1, the retaining tip is composed of a cylindrical ferrule of revolution 12 and a jumper 14.
L'embout de maintien est destiné à être fixé définitivement et rigidement, par soudure au laser, à une embase 20 qui sert de support à la diode laser. L'embase est de préférence métallique; un alliage fer- nickel-chrome tel que le kovar convient bien car il est compatible thermiquement avec des substrats d'alumine; on pourra donc fixer des tels substrats sur l'embase 20; d'autre part cet alliage est facilement soudable par laser. La fixation de l'embout de maintien 10 sur l'embase 20 se fait par l'intermédiaire de deux équerres latérales 32 et 34. La ferrule 12, le cavalier 14, les équerres 32 et 34 sont de préférence réalisés dans le même métal que l'embase 20 pour permettre plus facilement les soudures au laser entre ces pièces et pour éviter les dilatations différentielles. La fixation de la diode laser 40 sur l'embase 20 peut se faire par l'intermédiaire d'un substrat intermédiaire 42, par exemple un substrat hybride d'alumine portant non seulement une puce de diode laser mais aussi diverses connexions et éventuellement d'autres composants électroniques. Le substrat intermédiaire 42 sert aussi à relier électriquement la diode laser et les autres composants à des bornes de connexion non représentées servant à alimenter la diode laser en signaux électriques en fonction de la lumière à émettre. Les fils de liaison vers l'extérieur ne sont pas représentés.The holding end piece is intended to be fixed permanently and rigidly, by laser welding, to a base 20 which serves as a support for the laser diode. The base is preferably metallic; an iron-nickel-chromium alloy such as kovar is very suitable because it is thermally compatible with alumina substrates; we can therefore fix such substrates on the base 20; on the other hand this alloy is easily weldable by laser. The fixing of the retaining tip 10 on the base 20 is done by means of two lateral brackets 32 and 34. The ferrule 12, the jumper 14, the brackets 32 and 34 are preferably made of the same metal as the base 20 to allow easier laser welding between these parts and to avoid differential expansion. The fixing of the laser diode 40 on the base 20 can be done via an intermediate substrate 42, for example a hybrid alumina substrate carrying not only a laser diode chip but also various connections and possibly other electronic components. The intermediate substrate 42 also serves to electrically connect the laser diode and the other components to terminals of connection not shown used to supply the laser diode with electrical signals as a function of the light to be emitted. The connecting wires to the outside are not shown.
L'embase 20 peut porter également d'autres pièces; dans l'exemple représenté, un substrat hybride 50, fixé verticalement, peut être placé à l'arrière du substrat 42 (à l'opposé de la direction principale d'émission de la diode laser qui est tournée vers la fibre optique). Ce substrat 50 peut porter une photodiode 52 placée de manière à recevoir la fraction d'énergie lumineuse émise vers l'arrière par la diode laser. La photodiode sert alors d'élément de contre-réaction pour contrôler le courant de commande de la diode laser.The base 20 can also carry other parts; in the example shown, a hybrid substrate 50, fixed vertically, can be placed at the rear of the substrate 42 (opposite to the main direction of emission of the laser diode which is turned towards the optical fiber). This substrate 50 can carry a photodiode 52 placed so as to receive the fraction of light energy emitted towards the rear by the laser diode. The photodiode then serves as a feedback element to control the control current of the laser diode.
Dans l'exemple représenté, visible également en vue latérale sur la figure 2, le cavalier 14, qui constitue une partie de l'embout de maintien 10, est en forme de U renversé, avec un fond 142 reposant horizontalement (en prenant comme référence horizontale la surface principale de l'embase 20) sur la ferrule cylindrique 12. Les deux branches latérales 144 et 146 du U sont des plaques planes verticales qui enserrent la ferrule cylindrique 12. Les branches latérales du cavalier 14 sont donc espacées d'une distance égale au diamètre de la ferrule. La ferrule cylindrique de révolution peut avoir un diamètre d'environ 1 millimètre et comporte sur toute sa longueur une ouverture centrale dans laquelle est insérée et collée (ou brasée ou soudée par soudure au verre) la fibre optique 11 ; celle-ci a par exemple un diamètre d'environ 100 à 150 micromètres, typiquement 125 ou 140 micromètres. Les équerres 32 et 34 comportent chacune une plaque verticale plane et une plaque horizontale plane. La face horizontale repose sur l'embase 20; la face verticale est appliquée contre la face extérieure plane d'une branche latérale respective 144 ou 146 du cavalier 14. Le cavalier est de préférence soudé par laser YAG à la ferrule cylindrique. Pour une fibre monomode à maintien de polarisation, qui n'est pas à symétrie de révolution, il est nécessaire que le couplage entre la fibre et la diode laser respecte une certaine position angulaire de la fibre autour de son axe. Les étapes de positionnement de la fibre commencent donc par une recherche de cette position et une soudure au laser du cavalier 14 sur la ferrule cylindrique (la fibre optique ayant été préalablement collée dans la ferrule). Pendant cette opération, la ferrule 12 peut être maintenue par une pince qu'on fait tourner progressivement jusqu'à trouver la bonne orientation; lorsqu'elle est obtenue, on effectue la soudure laser entre la ferrule 12 et le cavalier 14.In the example shown, also visible in side view in FIG. 2, the jumper 14, which constitutes a part of the retaining endpiece 10, is in the shape of an inverted U, with a bottom 142 resting horizontally (taking as reference horizontal the main surface of the base 20) on the cylindrical ferrule 12. The two lateral branches 144 and 146 of the U are vertical flat plates which enclose the cylindrical ferrule 12. The lateral branches of the jumper 14 are therefore spaced apart by a distance equal to the diameter of the ferrule. The cylindrical ferrule of revolution can have a diameter of approximately 1 millimeter and comprises over its entire length a central opening in which is inserted and bonded (or brazed or welded by welding to glass) the optical fiber 11; this has for example a diameter of about 100 to 150 micrometers, typically 125 or 140 micrometers. The brackets 32 and 34 each have a flat vertical plate and a flat horizontal plate. The horizontal face rests on the base 20; the vertical face is applied against the flat outer face of a respective lateral branch 144 or 146 of the jumper 14. The jumper is preferably welded by YAG laser to the cylindrical ferrule. For a monomode fiber with polarization maintenance, which is not with symmetry of revolution, it is necessary that the coupling between the fiber and the laser diode respects a certain angular position of the fiber around its axis. The fiber positioning steps therefore begin with a search for this position and a weld to the jumper 14 laser on the cylindrical ferrule (the optical fiber having been previously glued into the ferrule). During this operation, the ferrule 12 can be held by a clamp which is gradually rotated until the correct orientation is found; when it is obtained, laser welding is carried out between the ferrule 12 and the jumper 14.
On effectue ensuite l'étape de positionnement précis de la fibre en vue de sa fixation définitive sur l'embase 20. La fibre est maintenant en place dans l'embout de maintien comprenant la ferrule et son cavalier. Les équerres 32 et 34 sont ensuite posées sur l'embase 20, et elles sont appliquées latéralement contre les faces verticales du cavalier 14. Elles sont de préférence maintenues en place, par aspiration, contre la surface supérieure de l'embase 20. Celle-ci est percée de trous 62 et 64 dans la région où doivent se trouver les équerres. Ces trous débouchent sous l'embase en regard de trous correspondants 72 et 74 formés dans le banc de montage 70 sur lequel est posée l'embase pendant l'opération de montage de la tête optique. Ces trous 72 et 74 sont reliés à un système d'aspiration d'air non représenté; le vide créé par cette aspiration maintient les équerres en place pendant la soudure au laser.The step of precise positioning of the fiber is then carried out with a view to its final fixing on the base 20. The fiber is now in place in the holding end piece comprising the ferrule and its jumper. The brackets 32 and 34 are then placed on the base 20, and they are applied laterally against the vertical faces of the jumper 14. They are preferably held in place, by suction, against the upper surface of the base 20. This ci has holes 62 and 64 in the region where the brackets must be. These holes open out under the base opposite corresponding holes 72 and 74 formed in the mounting bench 70 on which the base is placed during the mounting operation of the optical head. These holes 72 and 74 are connected to an air suction system not shown; the vacuum created by this suction keeps the brackets in place during laser welding.
La soudure des équerres sur l'embase 20 puis sur le cavalier 14 est très facile; en effet, il suffit d'effectuer un ou plusieurs tirs lasers sur les surfaces planes verticales et horizontales des équerres. La soudure se fait à travers l'épaisseur de ces plaques (épaisseur de quelques dixièmes de millimètres au plus). II n'est pas nécessaire de viser une position très précise de soudure, contrairement à ce qui était nécessaire dans les systèmes de couplage de la technique antérieure; ici, un point quelconque de la surface peut être utilisé puisqu'on a deux surfaces planes en regard l'une de l'autre, aussi bien sur la partie verticale que sur la partie horizontale de l'équerre. Quatre points de soudure 76 sont représentés à titre d'exemple sur la figure 1 pour l'équerre 32. La soudure par transparence (à travers la plaque horizontale de l'équerre) est possible, mais on peut envisager aussi une soudure par effondrement des bords des équerres, le laser de soudure étant dirigé sur le bord des équerres.The welding of the brackets on the base 20 then on the jumper 14 is very easy; indeed, it suffices to make one or more laser shots on the vertical and horizontal plane surfaces of the brackets. The welding is done through the thickness of these plates (thickness of a few tenths of a millimeter at most). It is not necessary to aim for a very precise position of welding, contrary to what was necessary in the coupling systems of the prior art; here, any point on the surface can be used since there are two flat surfaces facing each other, both on the vertical part and on the horizontal part of the square. Four weld points 76 are shown by way of example in FIG. 1 for the square 32. Transparent welding (through the horizontal plate of the square) is possible, but it is also possible to consider a weld by collapsing the edges of the brackets, the welding laser being directed at the edge of the brackets.
Sur la figure 3 on a représenté une variante de réalisation du couplage, utilisable lorsque la fibre optique n'est pas une fibre à maintien oIn Figure 3 there is shown an alternative embodiment of the coupling, usable when the optical fiber is not a holding fiber o
de polarisation et ne nécessite pas d'être calée à une position angulaire déterminée autour de son axe. L'embout de maintien comporte toujours deux faces verticales parallèles et planes, mais au lieu d'être composé de deux pièces, ferrule cylindrique et cavalier, il est composé d'une seule pièce qui est une ferrule cylindrique comportant deux méplats parallèles verticaux 13 et 15, contre lesquels viennent s'appuyer les surfaces planes verticales des équerres 32 et 34. La soudure au laser s'effectue sur les faces horizontales des équerres pour la fixation à l'embase, et sur les faces verticales des équerres pour la fixation à la ferrule. polarization and does not need to be locked at a determined angular position around its axis. The retaining end piece always has two parallel and flat vertical faces, but instead of being composed of two parts, cylindrical ferrule and jumper, it is composed of a single part which is a cylindrical ferrule comprising two vertical parallel flats 13 and 15, against which the vertical flat surfaces of the brackets 32 and 34 come to bear. The laser welding is carried out on the horizontal faces of the brackets for attachment to the base, and on the vertical faces of the brackets for attachment to the ferrule.

Claims

REVENDICATIONS
1. Dispositif de couplage entre un élément optoélectronique (40) et une fibre optique, comportant une embase (20) sur une partie de laquelle est fixé l'élément optoélectronique, et un embout de maintien (10) de l'extrémité de la fibre optique, entourant la fibre et maintenant celle-ci parallèle à la surface de l'embase en face de l'élément optoélectronique, caractérisé en ce que d'une part l'embout de maintien comporte deux surfaces planes perpendiculaires à la surface de l'embase et d'autre part le dispositif comporte deux équerres latérales (32, 34) placées chacune d'un côté de l'embout et ayant chacune deux surfaces planes perpendiculaires entre elles, l'une soudée sur la surface de l'embase et l'autre soudée sur une surface plane respective de l'embout de maintien.1. Coupling device between an optoelectronic element (40) and an optical fiber, comprising a base (20) on a part of which is fixed the optoelectronic element, and a holding end piece (10) at the end of the fiber optic, surrounding the fiber and keeping it parallel to the surface of the base opposite the optoelectronic element, characterized in that on the one hand the retaining tip comprises two flat surfaces perpendicular to the surface of the base and on the other hand the device comprises two lateral brackets (32, 34) each placed on one side of the end piece and each having two plane surfaces perpendicular to each other, one welded to the surface of the base and the 'other welded to a respective flat surface of the retaining tip.
2. Dispositif de couplage selon la revendication 1 , caractérisé en ce que l'embout de maintien est une ferrule cylindrique (12) enserrant l'extrémité de la fibre optique et comportant deux méplats parallèles (13, 15), constituant les deux surfaces planes perpendiculaires à la surface de l'embase.2. Coupling device according to claim 1, characterized in that the retaining tip is a cylindrical ferrule (12) enclosing the end of the optical fiber and comprising two parallel flats (13, 15), constituting the two flat surfaces perpendicular to the surface of the base.
3. Dispositif de couplage selon la revendication 1 , caractérisé en ce que l'embout de maintien comporte d'une part une ferrule cylindrique de révolution (12) enserrant l'extrémité de la fibre optique, et d'autre part un cavalier (14) soudé sur cette ferrule, ce cavalier comportant les deux surfaces places perpendiculaires à la surface de l'embase.3. Coupling device according to claim 1, characterized in that the holding end piece comprises on the one hand a cylindrical ferrule of revolution (12) enclosing the end of the optical fiber, and on the other hand a jumper (14 ) welded to this ferrule, this jumper comprising the two square surfaces perpendicular to the surface of the base.
4. Dispositif de couplage selon l'une des revendications 1 à 3, caractérisé en ce que l'embase est percée de trous d'aspiration (62, 64) sous les faces planes des équerres.4. Coupling device according to one of claims 1 to 3, characterized in that the base is pierced with suction holes (62, 64) under the planar faces of the brackets.
5. Dispositif de couplage selon l'une des revendications précédentes, caractérisé en ce que l'élément optoélectronique est une diode laser. 5. Coupling device according to one of the preceding claims, characterized in that the optoelectronic element is a laser diode.
6. Tête d'émission optique comportant une diode laser, une fibre optique, et un dispositif de couplage selon l'une des revendications 1 à 4.6. Optical emission head comprising a laser diode, an optical fiber, and a coupling device according to one of claims 1 to 4.
7. Dispositif de couplage selon l'une des revendications 1 à7. Coupling device according to one of claims 1 to
4, caractérisé en ce que l'élément optoélectronique est une photodiode.4, characterized in that the optoelectronic element is a photodiode.
8. Tête de réception optique comportant une photodiode, une fibre optique, et un dispositif de couplage selon l'une des revendications 1 à 4.8. Optical reception head comprising a photodiode, an optical fiber, and a coupling device according to one of claims 1 to 4.
9. Procédé de couplage entre un élément optoélectronique (40) et une fibre optique, comportant les opérations suivantes :9. Method of coupling between an optoelectronic element (40) and an optical fiber, comprising the following operations:
- fixation définitive de l'élément optoélectronique sur une partie d'une embase de support (20),- final fixing of the optoelectronic element on a part of a support base (20),
- fixation provisoire de l'embase sur une première partie d'un banc de montage;- provisional fixing of the base on a first part of an assembly bench;
- fixation définitive d'une extrémité de la fibre optique dans un embout de maintien (10) comportant deux faces planes parallèles, l'embout de maintien étant porté par une deuxième partie du banc de montage ;- Definitive fixing of one end of the optical fiber in a holding end piece (10) comprising two parallel flat faces, the holding end piece being carried by a second part of the mounting bench;
- mise en place de deux équerres comportant chacune deux faces planes perpendiculaires, les équerres étant placées chacune d'un côté de l'embout, et les équerres comportant chacune une face plane appliquée contre la surface de l'embase et une autre face plane appliquée contre une face plane de l'embout;- Installation of two brackets each comprising two perpendicular flat faces, the brackets each being placed on one side of the end piece, and the brackets each comprising a flat face applied against the surface of the base and another flat face applied against a flat face of the nozzle;
- recherche d'une position de couplage optimal entre la fibre et l'élément optoélectronique, par déplacement relatif des deux parties du banc de montage, en maintenant les équerres appliquées contre l'embout et contre l'embase, et, lorsque la position optimale est trouvée, soudure au laser de chaque équerre d'une part sur l'embase et d'autre part sur l'embout.- search for an optimal coupling position between the fiber and the optoelectronic element, by relative displacement of the two parts of the assembly bench, keeping the brackets applied against the end piece and against the base, and, when the optimal position is found, laser welding of each bracket on the one hand on the base and on the other hand on the end piece.
10. Procédé selon la revendication 9, caractérisé en ce que pendant la recherche de la position optimale de couplage, les équerres sont maintenues face contre l'embase par une aspiration d'air à travers des trous (62, 64) percés dans l'embase sous ces équerres. 10. Method according to claim 9, characterized in that during the search for the optimal coupling position, the brackets are held face against the base by a suction of air through holes (62, 64) drilled in the base under these brackets.
PCT/FR1996/001142 1995-07-25 1996-07-19 Method and device for coupling an optical fibre to a laser or photodetector WO1997005513A1 (en)

Applications Claiming Priority (2)

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FR95/08996 1995-07-25
FR9508996A FR2737310B1 (en) 1995-07-25 1995-07-25 METHOD AND DEVICE FOR COUPLING BETWEEN AN OPTICAL FIBER AND A LASER OR A PHOTODETECTOR

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EP1271209A1 (en) * 2001-06-28 2003-01-02 Corning O.T.I. S.p.A. Optical bench for an opto-electronic device
US6712528B2 (en) 2001-06-28 2004-03-30 Corning O.T.I. S.R.L. Optical bench for an opto-electronic device
US7272273B2 (en) 2005-01-21 2007-09-18 Neophotonics Corporation Photodetector coupled to a planar waveguide

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Publication number Priority date Publication date Assignee Title
EP1271209A1 (en) * 2001-06-28 2003-01-02 Corning O.T.I. S.p.A. Optical bench for an opto-electronic device
US6712528B2 (en) 2001-06-28 2004-03-30 Corning O.T.I. S.R.L. Optical bench for an opto-electronic device
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US7574084B2 (en) 2005-01-21 2009-08-11 Neophotonics Corporation Photodetector coupled to a planar waveguide

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FR2737310B1 (en) 1997-08-29

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