EP2171509A1

EP2171509A1 - Optical plug connection for optical waveguides

Info

Publication number: EP2171509A1
Application number: EP08759090A
Authority: EP
Inventors: Ludwig Bergann; Ralf Malz; Jens Konetzny
Original assignee: Lasos Lasertechnik GmbH
Current assignee: Lasos Lasertechnik GmbH
Priority date: 2007-07-20
Filing date: 2008-06-07
Publication date: 2010-04-07
Also published as: US8622624B2; DE102007051294B4; US20100254655A1; JP5602627B2; DE102007051294A1; JP2010533879A; WO2009012845A1

Abstract

The invention relates to an optical plug connection for optical waveguides comprising a plug (1) and a matching socket (2), and also comprises a method for adjusting the plug connection. In the case of such a plug connection, the plug (1) has at least one planar, smoothed contact area (19) oriented with respect to a propagation direction of a light beam passing from or into the plug (1), for bearing on a corresponding planar, smoothed mating contact area (19) of the socket (2) that is oriented with respect to the propagation direction of the light beam.

Description

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Optical connector for optical fibers

FIELD OF THE INVENTION The invention relates to an optical connector for optical fibers and their components, a plug and a mating receptacle, and a method of manufacturing an optical connector for optical fibers.

Numerous applications are based on the use of laser beams, for example medical surgical methods, material analysis and processing, or the examination and manipulation of biological samples, for example in the context of laser scanning microscopy. In many of these applications, laser radiation is supplied to the devices used for this purpose with the aid of optical waveguides. For this purpose, the laser beam after its exit from the radiation source or other optical assembly coupled with a coupling device in the optical waveguide and at the site of the application, i. be decoupled in the corresponding device using a further coupling device again. In the device, the laser beam runs as a free beam - i. not in an optical waveguide - and is used in corresponding applications. In order to keep radiation losses and aberrations as low as possible and overall the beam quality when coupled into the device as high as possible, the optical waveguide must be positioned very accurately with respect to the coupling optics. Accordingly, when the beam is coupled out, it must be introduced into the corresponding apparatus with high accuracy with respect to the direction and position of the beam propagation. Such coupling devices, usually connectors from male-female pairs, are internationally classified according to quality in four stages from A to D. The higher the quality, the higher is usually the effort in the production.

It is common to all the coupling devices known in the prior art that during the separation and subsequent restoration of such an optical waveguide Connection at least in cases where the optical fiber is plugged into another device or on the same device another optical fiber is also fixed of the same type, regularly consuming readjustments are necessary, if not significant performance and quality losses of the transmitted light or Strahldejustierungen in the device Purchase should be taken. Such a separation of the optical waveguide connector may be required, for example, to allow a simple change of the light sources - for example, the use of a laser with a different wavelength - and / or the feed points - ie, for example, the use of another device. In the prior art there are various products in which recording and adjustment mechanism are combined with focusing optics. With different principles of action and adjustment strategies, the necessary, maximum of up to six degrees of freedom are set. However, all known in the prior art solutions require a high Justieraufwand, which must be performed in the integration of a corresponding device usually by trained service personnel on site. Nevertheless, the coupling is then usually not so fixed that a long-lasting stability of the quality of the radiation coupling in or out is achieved.

For example, in DE 198 40 935 B4 a terminator for the optical fibers is described, which serves for coupling and decoupling of laser radiation in or from an optical fiber. As shown in Figure 11 of the cited document, the end piece is connected via a socket to the housing in which the pump source is housed. The end piece has one or more outer fits, which serve as reference surface (s) for the alignment of the beam. These fits are all circumferentially mounted around the terminator circumferentially. The end piece is then inserted into the housing, so that it rests with the fits on the socket. Furthermore, means are provided for adjusting the position of the optical fiber with respect to the fits at the end piece. With these adjustment means, such as screws, the optical fiber is aligned with respect to the cylindrical or conically shaped reference surfaces. At the front end of the end piece sits a converging lens for coupling or decoupling the radiation. If the terminator separated from the housing and used in another housing of the same type, so while the adjustment of the optical fiber with respect to the fits remains, a further difficulty is to correctly fit the fits in the socket of the housing, so that the Alignment of the terminator in the housing is optimal. Since the reference surfaces or fits and sockets are cylindrical or conically shaped, the necessary and unavoidable tolerances during manufacture result in the symmetry axes of the end piece and the housing, as a rule, being at a small angle to one another during the simple insertion of the end piece into the housing form. Even if the deviations are very small, this leads to quality losses. An exactly parallel alignment is usually possible, but requires a lot of time and tact. Another device for adjusting an optical fiber is described in DE 32 38 049 C1. Here, a housing is described, which contains a focusing element - such as a collimator lens - wherein the adjusting device consists essentially of a Justierkugel with a through-bore, which receives the optical fiber. The Justierkugel is not only rotatably mounted, but can also be moved parallel to the optical axis of the collimator lens. This ensures that the exit surface of the optical fiber can be positioned in the focal point of the collimator lens to achieve the highest possible input or output coupling. If the adjustment is achieved, the guide sleeve or the housing can be connected to a corresponding other element, so that the beam can be used. The outer surfaces of the guide sleeve serve in this case as fits, so that when inserting and separating such a compound also the problem of readjustment, as described in the case of the aforementioned document, occurs.

The same problem also occurs with the terminator described in US 6,796,720 B2: An optical fiber is inserted into a ferrule, this ferrule is inserted into the terminator and aligned there by means of adjusting screws axially and radially with respect to a collimator lens at the front end the end piece is attached. The on its outside cylindrically shaped end piece itself can then be plugged back into a corresponding socket.

Another arrangement with which the most efficient optical coupling or decoupling of radiation is to be achieved is described in US Pat. No. 6,925,234 B2. While in the arrangements described so far fiber and lens were arranged in one and the same end piece, in the cited document high flexibility with respect to the adjustment of the fiber and the lens is achieved to each other by the end piece is made in several parts. In a first part of the plug, the fiber is fixed in a ferrule, the lens is fixedly arranged in a second part of the plug. First and second part of the plug can now be connected, for example by means of screws. However, the first part of the plug which receives the fiber is designed such that, despite the fixed connection of the two plug parts, a flexible adjustment of the position of the fiber exit surface axially and radially, also by means of adjusting screws, is possible. This is made possible by the fact that the first plug part, although one piece, quasi consists of two parts, wherein between the two parts so much material is taken away that a flexible connection remains in the manner of a solid state joint. The end piece itself or the multi-part plug is in turn cylindrically shaped on its outer side, so that when disconnecting and reestablishing a connection with a device which is to use the radiation, the calibration problems already mentioned above occur. Since the Direction of Faserendfläche and lens is made via adjustments to the one-piece flexible connection, an adjustment is very expensive.

Description of the invention

The essential object of the invention is to provide an optical connector that allows the user to easily separate them and reassemble them in another, however, of the components of equivalent configuration, without a re-adjustment is necessary. In addition, simple and robust ways to factory-side adjustment of the components of such an optical connector in the production are created, in particular the adjustment of the fiber with respect to a lens through which the light beam enters and exits, as well as the adjustment of Unit of fiber and lens with respect to external mating surfaces.

This object is achieved in an optical connector of the type described above in that the plug at least a flat, smoothed and aligned with respect to a propagation direction of a light beam contact surface for resting on at least one corresponding flat, smoothed and aligned with respect to the propagation direction of the light beam Having mating contact surface of the socket.

Such a plug connection has considerable advantages over the plug connections known in the prior art: the contact surfaces or mating contact surfaces known in the prior art are designed as fits and sockets with cylindrical surfaces which surround the collimated beam. Although such cylindrical surfaces provide a higher area content and thus a higher contact surface, they can not be produced with the required high accuracy, or only with extreme effort, which would allow the plug to be disconnected from the socket and replaced without re-adjustment. wherein the plug can also be replaced by an equivalent plug.

Basically, this problem also occurs with flat surfaces, but these can be smoothed by simple methods, so that accuracies in the flatness of 100 nm height difference and less can be achieved. The contact surface is aligned with respect to a direction of propagation of a passing of the or in the plug light beam, the same is preferably true for the corresponding flat, smoothed mating contact surface of the socket. The contact surface of the plug is in the connected state on the mating contact surface of the socket. For the mating contact surface, however, the evenness is the more important criterion, since this determines the support. Thus, if the contact surface at a certain angle with respect to the direction of propagation of the light beam, for example, collimated from the plug, aligned, the Gegenkon- contact surface of the socket is necessarily aligned accordingly, unless equal at the entrance to the bushing deflection means for the beam are provided. The angle which includes the light beam with the contact surface or with the counter contact surface, it may also have a value of 0 °, ie that the light beam is parallel to the contact surface or mating contact surface. Corresponding plugs and sockets into which the plug is simply inserted, for example, are conceivable for such embodiments.

However, the alignment of the beam with respect to such a parallel plane is relatively expensive. In a preferred embodiment of the invention therefore intersects the light beam, a plane in which the at least one contact and the at least one mating contact surface is located; preferably at right angles of 90 °. Of course, all other angles between 0 ° and 90 ° are possible, but with vertical section, the construction can be easily performed, also a slight check of the orientation of the surface is possible with respect to the beam. For this purpose, for example, the deposition of the beam is determined by the solder on the contact surface by means of the rotation method described below at a distance of one meter. From this it is immediately possible to read at which points of the contact surface corrections are still necessary and to what extent they are necessary in order to achieve the required flatness and alignment. With oblique incidence of light or even parallel beam this is more difficult, since the direction of the light always has a component in the plane, so that the area in which it is necessary to correct is not immediately apparent. This is especially true at very small angles and a ray parallel to the plane.

In a particularly preferred embodiment of the invention, the at least one contact surface and the at least one mating contact surface are mechanically smoothed, preferably lapped or polished. These types of mechanical smoothing are particularly suitable for producing the desired flatness with high accuracy. However, the smoothing does not necessarily have to be mechanical, and other smoothing methods such as laser machining or electrochemical machining are conceivable and equivalently applicable as long as the required accuracy is achieved.

While the above-described characteristics are essential to the functioning of the optical connectors of the invention, regardless of a specific form of plug or socket, the invention also relates to a plug and socket particularly suitable for use in the optical connector of the invention are. Such a plug comprises a first plug part with a holder for receiving a socket in a socket of an optical waveguide, a second plug part with a lens, means for aligning and fixing the end of the optical waveguide in the holder along a beam direction, means for aligning the lens, and a third plug part, which has the at least one contact surface, and which is connected to the first and / or second plug part. The connection of the respective plug parts can be positive or positive, for example, with rivets, adhesive, by welding or soldering, but preferably done with screws. The non-mandatory division into three connector parts offers a number of advantages during production and adjustment. Thus, first the position of the socket - which can be configured, for example, as a ferrule - be pre-adjusted with the optical waveguide in the first plug part. Subsequently, the second connector part is connected to the first and the lens aligned with respect to the socket, wherein a further fine adjustment of the light exit surface of the optical waveguide in the socket is also possible. If the lens and the fiber end are adjusted, the third plug part can be attached. This third plug part contains the at least one contact surface, which according to the invention is planar, smoothed and aligned with respect to the propagation direction of a light beam or is aligned during adjustment.

Likewise and equally considered by a person skilled in the art, the second plug part does not necessarily have to be adjustable in the plane perpendicular to the direction of propagation of the light beam; it can even be dispensed with, since the effect can also be achieved in the manner described below. The lens would then be fixed in the first connector part. With regard to the light exit surface, the lens can then be centered by means of a fit, which can be produced for example by adjustment turning. Especially with longer focal lengths, this only leads to small angle errors. The pre-adjustment of the light beam with respect to the contact surface can also be done by tilting the first relative to the third plug part, e.g. by inserts between the two plug parts or by chamfering at least one of the two contact surfaces of the first and third plug part, for example by turning, milling or grinding.

The lens may be a single lens or equivalent and with equivalent effect an optical system of a plurality of individual lenses which may be cemented together or mounted at predetermined distances from one another in a holder, for example an achromatic lens. For the sake of simplicity, the term "lens" is taken to mean a summary here, and of course the reversed light path in which the light beam enters the optical waveguide and thus has a light entry surface is of course also detected. The multi-part design described makes it possible to perform the smoothing and alignment of the at least one contact surface only after the lens and the fiber end have been adjusted to each other and fixed. By this decoupling of the system lens-fiber on the one hand and the beam guidance of the beam on the other hand, one of the conditions for the reproducible separation and reassembly of plug and socket without re-adjustment is created.

It is advantageous if at least one outer layer of the at least one contact surface consists of hardened material, preferably of a metallic alloy. The metallic alloy can be hardened by surface hardening. In particular, metallic alloys can be smoothed mechanically with relatively simple means, for example by lapping or polishing. Other contact surfaces, for example made of hard plastic, which was smoothed with appropriate methods, are conceivable. The third plug part can for example be made in one piece, so that the at least one contact surface forms a surface of this third plug part. In this case, the entire third plug part may be made of the hardened material, but it is also conceivable to subsequently harden by appropriate curing methods, for example by heating the surface layers by means of lasers. Likewise, hard coatings can be produced on light metal alloys by anodizing or anodizing. When using aluminum or titanium, hard oxide layers are formed. The hard coat can also be created by applying an additional layer of another material of appropriate hardness. In the latter case, for example, SiO ₂ or Al ₂ O ₃ are suitable as materials to be applied. In this case, then only the surfaces must be edited, which contain the at least one contact surface. Another possibility is to provide the plug at the locations provided for the contact surfaces with corresponding inserts of a hardened or hard material. Suitable materials include, for example, in addition to the already described inserts made of hardened metal and ceramic, sapphire or quartz glass. Other, similarly hard materials can be used. If only inserts made of hardened or hard material are used, the requirements for the remaining material of the plug or the third plug part are not so high, so it can be made cheaper.

The easiest way is to design contact surface - and also the corresponding mating contact surface on the socket - as a coherent surface. If these areas are not too large, the required flatness of less than 100 nm height difference can be achieved with relatively little effort. However, if contaminants are deposited on one of the surfaces, dirt particles are trapped between the two surfaces when the joints are assembled. This can lead to a noticeable misalignment. In a particularly preferred embodiment of the invention, the plug therefore has a plurality of contact surfaces in the form of Kontaktfü- eat up. These contact feet only have to extend over a small area of the surface, which can serve as a contact surface or contact plane as a whole. The inserts mentioned above can then be integrated in the feet, for example. Since, when assembling the plug and socket and the locking of the plug in the socket, the contact surface and the Gegenkon- contact surface are shifted by a sliding or rotating movement usually against each other, it can be prevented that the dirt particles settle between the surfaces. Since the two surfaces are in register, dirt particles are pushed away by the movements, they can not get between the two surfaces. Between the surfaces lying dirt particles are removed by the rotation. In addition, the use of multiple, smaller contact surfaces offers the advantage of easier machining and alignment. In this case, as few as possible, for example three or four, and as small contact feet as possible should be used.

The properties just described of the contact surface with respect to the composition and the configuration in its shape can also be transferred to the mating contact surface of a socket according to the invention. Again, counter-contact surfaces may be provided in the form of mating contact feet, but it is important that there is a contact between the contact and mating contact surface when assembling the plug and socket until final locking. This is especially important when assembling involves a turning and / or pushing movement.

The socket that receives the optical waveguide, for example, can be configured as a ferrule. The optical fiber with the ferrule is usually adjusted by moving in the longitudinal direction. The ferrule is moved in the holder and locked in the desired position. This can be done for example by means of a locking screw. However, such a screw presses on the ferrule on the fiber, so that the light-guiding properties of the fiber can change. Instead of a screw or equivalent means, it is also possible to produce a cohesive connection, for example by gluing the ferrule to the holder. However, a subsequent readjustment is then no longer possible. Advantageously, the means for aligning the end of the optical waveguide therefore comprise a sleeve in which the ferrule is fixed. This sleeve can be made of metal or ceramic, for example. The sleeve completely surrounds the ferrule, and the sleeve is displaced with the ferrule to adjust the optical fiber. In this way, there is no abrasion on the ferrule, and the ferrule is also protected against displacements transversely to the axis of symmetry by the sleeve. Instead of a collar, a collet can alternatively be used. This also protects the ferrule from abrasion and prevents displacements. The adjustment is carried out by moving the ferrule or the collet, which comprises the ferrule firmly, along the beam direction or the symmetry axis of the light wave. lenleiters. After alignment, the sleeve or collet can be fixed by a locking screw. The walls of the collar or collet are so thick that the locking by means of one or more screws prevents the ferrule and thus the fiber from being displaced. In principle, however, it is also possible to design the sleeve or collet so that the ferrule can be moved within the sleeve or collet before the locking takes place. Preferably ferrule and sleeve or collet should be made of ceramic, since then also no abrasion. Adhesive compounds are also possible.

Finally, the plug also includes means for aligning the lens across the optical axis of the lens. When the optical axis of the lens is denoted by z, the alignment means allow alignment in the x-y plane. The orientation in this plane thus takes place independently of the orientation in the z direction, for which only the optical waveguide is displaced. Preferably, the means for aligning the lens comprise at least one spring element for non-positive connection of the second connector part with the first connector part. By the spring element, which may be configured for example as a rubber element or as a spiral spring, but preferably designed as a membrane, the second plug part is pressed with the lens against the first plug part with the fiber and the fiber end. The spring force or the contact pressure act in the z-direction, their amount is chosen so that a shift in the x-y plane by force, as it is mediated for example by adjusting screws, remains possible. However, an unwanted shift in the x-y plane under the effect of shock should be excluded. By decoupling z-adjustment and x-y adjustment, the adjustment is simplified as a whole.

In a particularly preferred embodiment of this embodiment of the invention, the at least one spring element is connected by one or more screws which connect the second with the first plug part, with the second plug part and presses this against the first plug part. The second connector part has a clearance for alignment. Instead of screws, other equivalent fasteners can be used. The screws are precisely connected via a thread with the first connector part, the corresponding holes in the second Stekkerteil are larger, so that alignment in the x-y plane is possible. In a diaphragm designed as a spring, this means that the support point for the spring on the second plug part is not directly on the circumference of the screw. This increases the stability.

In an alternative embodiment of the plug, the at least one spring element is connected by one or more screws not with the first, but with the third plug part. The third plug part is likewise connected to the first plug part, preferably by means of screws. tied - alternatively, however, the connection can also be designed so that the at least one spring element is connected to the third and the first plug part with the screws, so that a firm screw connection is formed between all three parts. Also in this case, the second connector part has sufficient clearance for alignment.

In a particularly preferred embodiment of this variant, the plug on a Anpreßstück which presses the spring element itself and by means of the spring element, the second plug part against the first plug part. The Anpreßstück can be screwed for example via a thread inserted into the third plug part against the spring element. Alternatively, screws are conceivable with which the Anpreßstück is bolted to the first connector part, the holes for the screws in the spring element and in the second connector part for the reasons mentioned above are greater than true to size. When not tightened contact pressure is thus still an adjustment of the second connector part in the x-y plane possible. In this way it can be achieved that upon tightening of the screws and thus during the tensioning of the membrane a change in position of the already adjusted second connector part is excluded.

The embodiment just described with a Anpreßstück can be used by simple design changes, of course, with the first alternative. She is u.a. especially well suited for use with connectors for coupling laser light into a fiber. A high-precision parallel alignment of the first and third connector part is then not required. Therefore, it is also possible in this case, first and third connector part as an integral unit to design.

The contact surfaces can in principle be attached to the first or second plug part, however, for a simple adjustment, it is advantageous to provide a third plug part on which the

Contact surfaces are attached. If the contact point at which the plug is plugged into the socket essentially has rotational symmetry with a rotation axis parallel to the beam, then the unit of the first and second plug part can be opposite the third plug part in a direction to the

Light beam vertical plane to be moved. In this way, the parallel position of the beam is centered, i. adjust with high accuracy so that the axis of rotation and the optical axis coincide.

A bushing according to the invention initially has the at least one mating contact surface already described in detail above. These countercontact surfaces are preferably mechanically smoothed, can likewise be hardened or consist of a hard material, for example in the form of inserts, several mating contact surfaces in the form of mating contact feet can be provided. The socket according to the invention has - especially when plug and socket are configured with respect to the optical axis substantially rotationally symmetrical with respect to their contact points parallel to the light beam - preferably a centering ring for aligning the plug and thus the light beam in a plane perpendicular to the beam direction. First, the plug is placed in the socket. The centering ring may, for example, have a circular fit which acts on the circumference of the plug or a housing. He will then be put on the jack later. Instead of a circular fit and a three-point system can be used. In this way, a lateral alignment of the beam is possible. This alignment can be done easily and easily by hand, with 3-4μm the tolerance is a lot higher here than with the alignment of the contact surfaces with respect to the beam direction. The centering ring can be moved and fixed on the sleeve so that the parallel position of the beam can be fixed at any desired point, for example relative to external contact points by detecting the centering ring. If the plug does not have to be aligned with a subsequent optical system, but this system is aligned once on the plug, the centering ring can also be immovable, ie centering ring and socket are not movable relative to each other. This can be achieved in advance by a fixed connection, but also by manufacturing the ensemble of socket and centering ring in one piece. Also in this case, no readjustment must be performed when changing the connector.

Instead of a centering ring can be used to align the connector or light beam in a plane perpendicular to the beam direction, a V-bearing. In this case, the plug is pressed by means of a screw or a spring element against the contact positions of the V-bearing.

Preferably, the socket also has a spring ring with which the plug is fixed in the socket. For this purpose, he may for example have projections on its circumference, which engage under the spring ring. Instead of a circular fit is used here preferably a perforated fit, which allows insertion of the plug with subsequent rotational movement under the centering ring. The spring ring may for example also be provided with projections. When screwing the plug into the socket creates a frictional connection between the projections of the plug and the spring ring. The plug is pushed into the socket. The projections on the spring ring are - at least partially - designed as springs, so that when screwing the plug under the spring ring, the spring force increases and thus amplifies the contact pressure. Finally, by means of screws, the contact pressure can be further enhanced. When using polarization-maintaining fibers, the first or the third plug part may also include a lateral index pin, with respect to which the polarization axis of the fiber is aligned by rotation of the same about the z-axis. The plug associated with the socket must then have a corresponding stop for the index pin.

It is understood that the features mentioned above and to be explained below can be used not only in the specified combinations, but also in other combinations or in isolation, without departing from the scope of the present invention.

The invention also relates to a method for producing an optical connector for optical fibers, comprising a plug and a socket, as have been described in particular above. For such a method, the object is achieved by (i) inserting a socketed in a socket end of an optical waveguide in a holder of a first plug part for receiving the socket, (ii) the first plug part of the plug with a second part of the plug, which comprises a lens, (iii) the distance of a light exit surface of the optical waveguide is adjusted to the lens and the optical waveguide is fixed in the first Stekkerteil, (iv) the position of the second connector part in a plane substantially perpendicular to the optical axis of the lens by displacement adjusted in this plane and locked in the adjusted position so that a predetermined angular position is set, and (v) at least one flat contact surface of the plug and at least one corresponding flat mating contact surface of the socket into which the plug is placed, by smoothing with respect to a propagation direction of a light beam be addressed.

Are used in the prior art cylindrical sockets or derived therefrom four-point or V-bearing for receiving cylinders for plug and socket so that the corresponding contact and mating surfaces have cylindrical shape or support points are arranged on an imaginary cylinder in space, so planar surfaces are used in the present invention. This may at first glance appear to be a disadvantage, since a socket with a cylindrical receptacle seems to offer a better grip for a correspondingly shaped plug. Due to manufacturing tolerances, however, cylindrical surfaces can not be made so that a simple change of the plug or removing and reinserting would be possible without readjustment. Each fit has a certain play, which causes the plug with a small tilt, a Achswinkelfehler to Zylindersymmetrieachse the socket of the socket inserted and fixed in this. A certain balance can be achieved by a corresponding repositioning of the lens, a complex and time-consuming procedure. Even high-precision connectors only reach accuracies of 0.35 μm in with respect to the deviation from the symmetry axis of the fit, which corresponds to an angular error of 70 μrad for a guide length of 5 mm.

Flat surfaces made by conventional methods such as grinding, such as the cylindrical bearings or V-type bearings used in the prior art as contact and mating contact surfaces, have certain tolerances in plane accuracy, i. surface roughness, typically several microns, resulting in positioning accuracy of the same order of magnitude. The angle errors are in this case at several 100 μrad up to a few mrad.

The smoothing performed on the contact and mating contact surfaces can reduce the flatness error to less than 100 nm, so that the remaining deviations from an actual flat surface are so small that it is easy to disconnect and connect the plug and socket becomes possible, whereby the high initial accuracy can be reproducibly set, without the need for a new adjustment. The ensemble of frame and lens remains fixed in the once adjusted positions, even if the plug is disconnected from the socket.

Smoothing is particularly easy to perform on flat surfaces and the flatness can be easily checked by means of optical interference methods. Advantageously, the at least one contact surface of the plug and the at least one mating contact surface of the socket is mechanically smoothed, preferably polished, lapped, or diamond-turned. Even simple turning polishing without diamond is possible. With all methods, the required surface qualities can be achieved in a simple manner. The methods can be performed both manually and by machine. Other mechanical smoothing methods which lead to the same result are alternatively usable.

Finally, other smoothing methods than mechanical ones can be used as long as they lead to the desired result. In principle, the method can also be used with cylindrical fits, in which case the error is not the flatness, but the deviations of the radius of the cylinder at each position on the cylindrical surfaces of the contact and mating contact surfaces is the decisive criterion. Cylindrical surfaces with such accuracy are, however, more difficult to manufacture, and checking for accuracy is much more difficult than with flat surfaces.

As an angular position, ie the angular orientation of the outgoing or entering light beam is often specified that the optical axis of the lens substantially with the center of the Lichtaus-. The incident surface of the optical waveguide coincides, which corresponds to an angle of zero degrees. However, depending on the required application, other angular positions can also be set. In a preferred variant of the method, the at least one contact surface and / or the at least one mating contact surface is hardened before smoothing or covered with hardened material. This embodiment is advantageous, for example, if one surface is designed as a continuous flat surface of the two surfaces, but in the other component several smaller surfaces are provided for contact. For example, the plug may be provided with feet, wherein the foot surfaces form the contact surfaces. In this case, only the foot surfaces need to be hardened or coated with hardened material such as ceramic, sapphire or glass, or they are made entirely from these materials. The - usually metallic - mating contact surface can also be cured. The hardening of the surfaces can be done for example by anodizing or anodizing. As materials for this hardcoating, for example, titanium or aluminum are suitable. Alternatively, it is possible to make the entire contact or mating contact surface as an insert of a hard material such as ceramic, sapphire or glass. Also inserts made of pre-hardened material are conceivable.

It is expedient to align the contact and mating contact surface perpendicular with respect to the propagation direction of the light beam. The directional vector of the light beam then has no component in the plane of the contact or mating contact surface, which facilitates alignment.

Preferably, the quality of the smoothing of the surface is checked by means of interference measurements, as known in the art. Due to the result of the interference measurements, a planar surface within the required tolerances, ie with an error in the flatness of less than 100 nm, can be produced iteratively in a few steps. The orientation with respect to the propagation direction of the light beam can be checked by plugging the plug with its at least one contact surface being processed into a reference socket with a flat mating contact surface. Then, the position of the exiting light beam can be determined and a corresponding correction can be made, so that the alignment can be adjusted iteratively in a few steps correctly. The light beam can be detected, for example, with a high-resolution CCD camera at the focal point of an auxiliary lens with a long focal length of, for example, f = 50 cm in order to determine as accurately as possible the filing. In this case, the plug can be rotated on the mating contact surface about an axis perpendicular thereto; the light spot which the beam forms on the CCD array then describes a circular path around the optical axis. The center of the circle corresponds exactly to the vertical position to be corrected. This rotation measuring method offers a significantly higher and above all absolute accuracy compared to individual measurements. Depending on the lens and CCD camera used, resolutions of fractions of an arc second can be achieved. So that the connector can be reassembled separately and without re-adjustment, so that the same beam position is adjusted, one adjusts the distance from the light exit surface of the optical waveguide or the fiber in the first connector part and the lens in the second connector part, the advance in the assembly of the connector usually from a single lens, a cemented or single lenses, which are mounted or fixed at predetermined intervals from each other, once at the beginning and then fixes the optical waveguide at the corresponding position. Preferably, the adjustment of the distance from the light exit surface and lens by means of Divergenzminimierung. Of course, other methods for adjusting the distance known in the prior art can equally be used; the method of minimizing divergence has been selected by way of example. The light exit surface, ie the end of the optical waveguide, which can be made flat or angled flat, for example, is first positioned near the focal point of the lens and then moved along the z direction until minimal divergence is achieved. In this way, a collimated beam is generated, convergent or divergent beams can be adjusted by introducing or switching accordingly ausgestalteter Meßoptiken between plug and Divergenzmeßsystem if necessary also. A subsequent adjustment of the angular position of the light beam emerging from the plug is achieved by the second plug part with the lens being displaced laterally, ie in the planes perpendicular to the optical axis of the lens. This position can be adjusted with a high precision of about 100 nm. The adjustment of the angular position can also be performed in the frame or before or after the rotation measurement described above. The adjustment is best when the angle of the beam to the z-axis is smallest. For fixing the optical waveguide and / or the socket and / or the first plug part can be glued together, soldered or welded. A fixation of the parts to each other each with screws is one possibility.

The contact surfaces can in principle be attached to the first or second plug part, but for a simple adjustment it is advantageous to provide a third plug part to which the contact surfaces are attached. If the contact point at which the plug is plugged into the socket essentially has rotational symmetry with an axis of rotation parallel to the beam, the unit of first and second plug part can be displaced in relation to the third plug part in a plane perpendicular to the light beam. In this way lets see the parallel position of the beam in the middle, ie adjust with high accuracy so that the axis of rotation and optical axis coincide. Other, off-center positions are, if necessary, adjustable by adjustment. In the position set during the adjustment, the unit of first and second plug part is finally fixed. The achievable by this and the adjustment measures described above total precision is about 3 microns. With reference to a typical With a beam diameter of 700 μm, this is less than 0.5% of the beam diameter. In contrast, the accuracy of the most accurate, previously known in the art flat-connector Sleckem at 0.35 microns at a beam diameter of 5 microns, ie 7% of the beam diameter.

In view of the fact that the product of angular deviation and parallel deviation remains constant when passing through an ideal optical system, so an inventive plug offers the advantage that the - inevitable - manufacturing tolerances are placed so that they have as little impact on the overall behavior during use to have. This is achieved by only extremely small angular errors remain by smoothing flat surfaces, while the parallel positioning is performed on the expanded beam, so that here too the relative error is very low.

The position measurement is advantageously carried out again by means of the rotation method, e.g. Now the CCD camera is placed as close as possible behind the plug without any optics. Finally, by repolishing the contact surface (s) on the third plug part, the angle deviation can be further reduced to fractions of an arc second.

Advantageously, a locking of the second connector part relative to the first connector part by means of spring force. Appropriately, the spring force is adjusted so that the arrest shocks and acceleration changes, as they may occur, for example, when changing and transporting such plug, withstood. On the other hand, but at the same time an adjustment of the lens by moving the second connector part in the plane perpendicular to the optical axis of the lens, for example by means of adjusting screws, are made possible. In this way, the adjusting screws used, for example, can be removed later. Another possibility is to use several adjustment screws or similar means and then leave them in the plug, but this is the material consuming method. Alternatively, the spring force can be further increased even after adjustment.

When both the light beam is aligned as described above, and the contact surface of the plug and the mating contact surface of the socket are polished and aligned, must be aligned in the connection of plug and socket, the plug in the socket, so centered at a substantially rotationally symmetrical connection so that the light beam can enter through a corresponding opening in the device in which the socket is located. The light beam must be positioned so that the well-defined exit point is reached in the opening without affecting its angular position. The accuracy depends on the requirements of the following optical device, typical values are about 5 μm at one Beam diameter of 700 μm. Appropriately, the radial adjustment of the plug in the socket therefore takes place by means of a centering ring and its locking. The plug is thus placed in the socket, so that an alignment in a plane which is parallel to the plane in which contact and mating contact surface are possible. The adjustment is made by moving the centering ring in this plane, which has a corresponding displacement of the plug with respect to the socket result. Once the optimum function has been achieved, the centering ring is locked on the bushing. The gap between the plug and centering ring must be smaller than the permissible tolerance of the positioning, for example, less than 5 microns. Preferably, the centering ring has two radial contact points at an angle of, for example, 90 ° to each other, against which the plug is pressed, whereby errors are excluded by a gap. The plug is then finally locked by another device, such as a spring ring in the socket or the centering ring.

The process steps do not necessarily have to be carried out in the specified order. It is also possible to carry out the alignment of the contact and mating contact surfaces in two steps, for example, to perform a first Planpolitur, then put the plug in the socket and make an adjustment of the lens using the rotation method described above and then a second fine polishing final alignment of the beam perpendicular to these surfaces with an accuracy of about 2 μrad.

Brief description of the drawings

The invention will be explained in more detail with reference to the accompanying drawings, which also show features essential to the invention. Show it:

1 shows a longitudinal section through an optical connector, consisting of plug and socket, Figure 2 shows a longitudinal section through the plug, which is rotated relative to the longitudinal section of Figure 1 by 45 °, and

3 shows an alternative embodiment of a plug in longitudinal section. Detailed description of the drawings

1 shows an inventive plug 1 is shown on a socket 2 according to the invention. The plug 1 consists of a first plug part 3, a second plug part 4, and a third plug part 5. The first plug part 3 and the third plug part 5 are enclosed by a housing 6. The first connector part 3 has a tilted with respect to the axis of symmetry bore, which serves as a holder for the rimmed in a ferrule 7 optical fiber. The optical fiber 7 is enclosed by a sleeve 8 and held. To adjust the optical fiber 7 along its axis of symmetry, the sleeve 8 is moved in the holder. The adjustment should be made so that the focal point of a lens 9, which is designed here as a collimator, on the exit surface 10 of the optical fiber 7 as possible in the center and a collimated beam is generated. In the optical fiber 7 shown in Fig. 1 is an optical waveguide of the type AFC (angled flat connector), wherein the light exit surface 10 is at an angle to the axis of symmetry of the optical fiber 7 or beam direction to reflect back into the laser or the optical system to prevent. Due to the refraction of light at the light exit surface 10, therefore, the position of the optical fiber 7 is slightly tilted relative to the optical axis of the lens 9 and the connection between the plug 1 and socket 2. Also fibers of the FC type (flat connector) can be used, in which case no Tilting of the fiber layer is done. The first plug part 3 also has an opening 11. In the opening 11, a screw, not shown here can be sunk, with the position of the sleeve 8 with respect to the first Stek- kerk part 3 can be fixed and locked. The housing 6 may be designed so that it covers the opening 11 in the assembled state.

The lens 9 is held in the second connector part 4. The second plug part 4 rests with its one side on the first plug part 3. On the side opposite this side, the second plug part 4 has a circular contact surface 12, on which a likewise round membrane 13 rests. The membrane 13 has in its center an opening from which the light beam collimated through the lens 9 emerges.

By means of screws 14, the second plug part 4 is connected to the first plug part 3. The second plug part 4 has holes 15 through which the screws 14 are inserted.

The diameter of the holes 15 is greater than the thread diameter of the screws, so that the second plug part 4 relative to the screws 14 game has. However, the screws 14 also connect the membrane 13 with the second connector part 4. Since the membrane 13 rests only on the contact surfaces 12 on the second connector part 4, by the screws 14 ultimately a frictional connection between the first connector part 3 and second connector part

4 produced. The screws 14 can be tightened so tightly that an arbitrary displacement of the second connector part 4 relative to the first connector part 3 along the contact surface, the xy plane is possible by means of adjusting screws, an involuntary displacement by slight shocks, however, is prevented. In this case, the third plug part 5 can already be placed and connected to the first plug part. The adjustment screws can then be performed for example through openings 16. Later, these openings 16 can be used to connect the housing 6 to the third plug part 5.

The adjustment of the lens 9 with respect to the light exit surface 10, i. along the z-axis, is preferably carried out by means of divergence minimization, for example in a plug simulator. It is of course also possible, the position of the light exit surface 10 by moving the

Cuff 8 with the optical fiber 7 to vary. The adjustment of the collimator lens in the x-y-

Plane is preferably carried out in the course of a rotation measurement, in which the position of the z

Axis is determined and then the shelf to the z-axis is minimized. It does not have to coincide with the desired optical axis at this stage.

The third plug part 5 is then connected to the first plug part 3 and surrounds the second plug part 4. The connection of the first plug part 3 and third plug part 5 can be produced, for example, by means of screws 17, as shown in FIG. The section through the plug shown in Figure 2 is rotated relative to the section shown in Figure 1 by 45 °, the second plug part 4 is designed cloverleaf-shaped, the third plug part 5 has the shape of a hollow cloverleaf. In this way, it is possible to connect the second and third plug part 4 and 5, each independently with the first plug part 3. This is particularly advantageous for the adjustment and the alignment with respect to the direction and position of the collimated light beam.

On the sleeve 2 side facing the third connector part 5 are contact feet 18 with contact surfaces 19. Overall, at least three such contact feet 18 must be provided to allow a secure support and precise smoothing. The contact surfaces 19 can - as shown here by way of example - consist of the same material as the contact feet 18 and the third plug part 5, wherein the contact surfaces 19 are then preferably cured. Alternatively, inserts of hard material such as ceramic or quartz glass can be provided. The plane in which the contact surfaces 19 are formed forms a right angle with the optical axis of the lens 9, which corresponds to the light propagation direction. This allows a particularly simple alignment of the surfaces with respect to the optical axis, since in the aligned state the light propagation direction has no in-plane component. After assembly of the plug 1 - with or without housing 6 - the contact surfaces 19 are aligned by means of mechanical smoothing, for example by polishing or lapping.

After alignment of the contact surfaces 19 of the plug 1 is set in the socket 2, as indicated in Figure 1. The socket 2 has a mating contact surface 20 in the present example. The mating contact surface 20 as well as the contact surfaces 19 are polished or lapped. Also, the mating contact surface 20 is aligned with respect to the propagation direction of the collimated light beam perpendicular to this, so that a light beam highest position accuracy is coupled into the adjoining the socket 2 application optics.

However, the contact surfaces 19 of the plug 1 should be within the required accuracy in a plane perpendicular to the light propagation direction. This allows replacement with other connectors manufactured with the same precision. A new adjustment on the part of the application optics with respect to the beam direction when changing the plug is not necessary.

The plug 1 has projections 22 on its circumference. The socket 2 has a centering ring 24 which can be moved and fixed on the socket 2 or mating contact surface 20 within a predetermined game. During assembly, the plug 1 is placed in the centering ring 24. The projections 22 of the plug 1 are then substantially in registration on the inside of the socket 2. Advantageously, the inside is configured in a precise fit only in a small, annular area 23, this reduces frictional resistance and tilting of the plug 1 in the socket 2. An alignment of the beam in the plane of the mating contact surface 20 is now possible by means of the centering ring 24 with not shown screws on the socket 2 is attached. It can be fixed so shifted on the sleeve 2 that the parallel position of the beam at each desired point, for example, relative to external contact points, can be fixed by fixing the centering ring 24. In particular, the beam can be centered with an accuracy of about 5 μm.

In order to fix the plug 1 in the socket 2 in the desired position, a spring ring 28 is also provided. This is fastened with screws 25 on the centering ring 24. The spring ring has projections 26. A simple loosening and restoring the connection between the plug 1 and socket 2 is made possible by the projections 26 are also correspondingly fit on the projections 22 in recesses 27 on the plug 1, wherein the projections 26 are preferably designed as springs on the Plug 1 at its projections 22 in the recesses 27 exert a force and press into the socket 2. If the projections 26 and 22 attached only at selected locations of the circumference of the plug 1 and the socket 2, so can a non-positive connection between the plug 1 and socket 2 are made after insertion of the plug 1 with subsequent rotation.

An alternative embodiment of a plug 1 is shown in Fig. 3 in a longitudinal section. The membrane 13 is connected here by one or more screws 29 not with the first plug part 3, but with the third plug part 30. The third plug part 30 is - not shown in the drawing - similarly as shown in Fig. 2 also connected to the first Stekkerteil 3, preferably by screws - alternatively, the compound can also be designed so that with the screws 29 the Membrane 13 is connected to the third plug part 30 and the first plug part 3, so that between all three parts 3, 13, 30, a fixed screw connection is formed. Also in this case, the second connector part 31 has sufficient clearance for alignment.

The plug 1 also includes a Anpreßstück 32, which presses the membrane 13 and mediates through the membrane 13, the second plug part 31 against the first plug part 3. The Anpreßstück 32 can be screwed for example via a thread inserted into the third plug part 30 against the membrane 13. Alternatively, as shown in Fig. 3, also screws 33 are conceivable with which the Anpreßstück 32 is screwed to the first plug part 3, wherein the holes for the screws 33 in the membrane 13 and the second plug part 31 are greater than true to fit to allow an adjustment of the second connector part with the optical element even with slightly strained diaphragm 13. With this configuration can be achieved that when tightening the screws 33 and thus when tightening the diaphragm 13, a change in position of the already adjusted second connector part 31 is excluded.

The embodiment just described with a Anpreßstück 32 is particularly well suited for use in the case of connectors for the coupling of laser light in a fiber. These are usually not changed so often, which is why it is also sufficient for the adjustment when the contact surfaces 19 - for example, on contact feet (18) which are screwed to the third plug part 30 - simply. smoothed by grinding. The required accuracy in this case is not as high as in the coupling of light from the fiber into the beam path of an application device. A highly accurate parallel alignment of the first plug part 3 and third plug part 30 is then also not required. Therefore, it is also possible in this case, first connector part 3 and third connector part 30 to design as a one-piece unit. These are more or less simple couplers in this case.

The invention described above enables a user to assemble plug 1 of the type according to the invention with sockets 2 of the type according to the invention as often as desired. zen, again to separate and put together again, without a re-adjustment would be necessary if connector 1 and / or socket 2 are replaced. Thus, for example, in illumination optics, in which different laser light sources are to be alternately coupled via an optical connector of the type according to the invention, the light source by simply changing the plug - in which the light coming from the light source ends - be replaced without a re-adjustment would be necessary , The required effort in the production of such connectors is relatively low, since essentially only flat surfaces, but these must be made with high accuracy.

LIST OF REFERENCE NUMBERS

1 plug

2 socket

3 first connector part

4 second plug part

5 third plug part

6 housing

7 optical fiber

10 8 cuff

9 lens

10 light exit surface

11 opening

12 contact surface

15 13 membrane

14 screw

15 hole

16 opening

17 screw

20 18 contact foot

19 contact surface

20 mating contact surface

21 opening

22 lead

25 23 annular area

24 centering ring

25 screw

26 advantage

27 recess

30 28 spring washer

29 screws

30 third plug part

31 second plug part

32 pressing piece

35 33 screws

Claims

claims

Optical connector for optical fibers, comprising a plug (1) and a socket (2), characterized in that the plug (1) at least one flat, smoothed and with respect to a propagation direction of a from or into the plug (1) having passing light beam aligned contact surface (19) for resting on at least one corresponding, even, smooth and aligned with respect to the propagation direction of the light beam mating contact surface (20) of the socket (2).

2. An optical connector according to claim 1, characterized in that the light beam is a plane in which the at least one contact and the at least one mating contact surface (19, 20) lie, preferably perpendicular to this plane.

3. Optical plug connection according to one of claims 1 or 2, characterized in that the at least one contact surface (19) of the plug (1) and the at least one mating contact surface (20) of the bushing (20) are mechanically smoothed, preferably lapped or polished.

4. plug (1) for an optical connector according to one of claims 1 to 3, comprising a first plug part (3) with a holder for receiving a socket in a socket end of an optical waveguide (7), a second plug part (4, 31) with a lens (9), - means for aligning and fixing the end of the optical waveguide (7) in the holder along a beam direction,

Means for aligning the lens (9) transversely to an optical axis of the lens (9), and a third plug part (5, 30) which has the at least one contact surface (19) and with the first and / or second plug part (3, 4, 31) is connected.

5. Plug (1) according to claim 4, characterized in that at least one outer layer of the at least one contact surface (19) made of hardened material, preferably a hardened metallic alloy.

6. Plug (1) according to claim 5, characterized in that the at least one contact surface (19) made of ceramic, sapphire, quartz glass or a similar material exists.

7. plug (1) according to one of claims 4 to 6, characterized in that it comprises a plurality of contact surfaces (19) in the form of contact feet (18).

8. Plug (1) according to one of claims 4 to 7, characterized in that the means for aligning and fixing the end of the optical waveguide (7) has a sleeve (8) or

Include collet in which the socket is fixed.

9. Plug (1) according to claim 8, characterized in that the means for aligning the end of the optical waveguide comprise a screw by means of which the sleeve (8) or collet is fixed.

10. Plug (1) according to one of claims 4 to 9, characterized in that the means for aligning the lens (9) at least one spring element, preferably a membrane (13), for non-positive connection of the second plug part (4, 31) comprise the first plug part (3).

11. Plug (1) according to claim 10, characterized in that the at least one spring element by one or more screws (14) which connect the second plug part (4) with the first plug part (3), with the second plug part (4) is connected and this presses against the first connector part (3), wherein the second connector part (4) has clearance for alignment.

12. Plug (1) according to claim 10, characterized in that the at least one spring element by one or more screws (29) with the third plug part (30) and this with the first plug part (3) is connected, whereby the second plug part ( 31) is pressed against the first plug part (3), and wherein the second plug part (31) has clearance for alignment.

13. Plug (1) according to claim 10 or 12, characterized in that the plug (1) has a Anpreßstück (32) which presses the spring element and by means of this the second Stekkerteil (31) against the first plug part (3).

14. Plug (1) according to any one of claims 10, 12 or 13, characterized in that the first plug part (3) and third plug part (30) form an integral unit.

15. Plug (1) according to one of claims 4 to 10, characterized in that first Stekkerteil (3) and second plug part (4, 31) form an integral unit.

16 socket (2) for an optical connector according to one of claims 1 to 3, characterized in that it comprises a centering ring (24) for aligning the plug in a plane perpendicular to the beam direction.

17. bush (2) according to claim 16, characterized in that the centering ring (24) and bushing (2) are not movable relative to each other.

18. socket (2) for an optical connector according to one of claims 1 to 3, characterized in that it comprises a V-bearing for aligning the plug in a plane perpendicular to the beam direction.

19. Socket (2) according to any one of claims 16 to 18, characterized in that it comprises a spring ring (28) for fixing the plug in the socket (2).

20. Socket (2) according to any one of claims 16 to 19, characterized in that at least one outer layer of the at least one mating contact surface (20) made of hardened material, preferably a metallic alloy.

21. Socket (2) according to any one of claims 16 to 19, characterized in that the at least one mating contact surface (20) made of a hard material, preferably with an absolute hardness of more than 100, preferably ceramic, sapphire or quartz glass.

22. socket (2) according to any one of claims 16 to 21, characterized in that it comprises a plurality of mating contact surfaces (20) in the form of mating contact feet.

23. A method for producing an optical connector for optical fibers, comprising a plug (1) and a socket (2), wherein a rimmed in a socket end of an optical waveguide (7) in a holder of a first connector part (3) for receiving the Holder is used, the first plug part (3) of the plug (1) with a second plug part (4, 31) of the plug (1), which contains a lens (9) is connected, the distance of a light exit surface (10) of the optical waveguide (7) adjusted to the lens (9) and the optical waveguide in the first plug part (3) is fixed, - the position of the second plug part (4, 31) in a plane substantially perpendicular to the optical axis of the lens (9) by displacement in this Level adjusted and locked in the adjusted position, so that a predetermined angular position is set, and at least one flat contact surface (19) of the plug (1) and at least one flat mating contact surface (20) of the socket (2) into which the plug (1) is placed are aligned by smoothing with respect to a propagation direction of a light beam.

24. The method according to claim 23, characterized in that the at least one contact surface (19) of the plug (1) and the at least one mating contact surface (20) of the socket (2) mechanically smoothed, preferably polished, lapped or diamond turned.

25. The method according to claim 23 or 24, that the at least one contact surface (19) and / or the at least one mating contact surface (20) hardened prior to smoothing or with hardened

Material is occupied.

26. The method according to any one of claims 23 to 25, characterized in that the contact and mating contact surface (19, 20) are aligned perpendicular to the propagation direction of the light beam, preferably by means of a Rotationsmeßverfahrens.

27. The method according to any one of claims 23 to 26, characterized in that the quality of the smoothing of the contact and / or mating contact surface (19, 20) are checked by means of interference measurements.

28. The method according to any one of claims 23 to 27, characterized in that an adjustment of the distance from the light exit surface (10) and collimator (9) by means of divergence minimization takes place.

29. The method according to any one of claims 23 to 28, characterized in that a refinement of the angular position of the light beam is made by repolishing the contact surface (19) and / or the mating contact surface (20).

30. The method according to any one of claims 23 to 29, characterized in that the Lichtwel- lenleiter (7) and / or the socket and / or the first plug part (3) are glued together, soldered or welded.

31. The method according to any one of claims 23 to 30, characterized in that a locking of the second plug part (4, 31) relative to the first plug part (3) takes place by means of spring force.

32. The method according to any one of claims 23 to 31, characterized in that the first and second plug part (3, 4, 31) arrested in a third plug part (5, 30) are used and the light beam with respect to its parallel position by moving the first and second plug part (3, 4, 31) relative to the third plug part (5, 30) is aligned in a plane perpendicular to the light beam.

33. The method according to any one of claims 23 to 32, characterized in that a radial adjustment of the plug (1) in the socket (2) by means of a centering ring (24) and the locking takes place