DE9010419U1 - Connector for a fiber optic optical fiber - Google Patents

Description

In recent years, fiber optic light waveguides have been increasingly used for terrestrial communication, but also for microsurgical operations, for example. The light waveguides often serve as conductors for laser light, which is then focused accordingly and transferred into the light waveguide.

This already shows that the front surface of the optical waveguide must be positioned at the focal point of the corresponding lens system in order to achieve the most complete energy transfer possible. For this purpose, it is also necessary to have an absolutely flat front surface on the optical waveguide in order to prevent scattered rays and reflections as far as possible.

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There are known connectors which have a central axial through-channel in which the optical waveguide is arranged. After the fiber has been conformed, its front face is ground flat together with the front face of the connector tip.

Particularly when using fiber optic light waveguides for high-energy applications, for example in material processing or medical technology, where energies in the milliwatt to watt range must be transmitted, there is a risk when using the plug described above that obliquely incident light components or reflections will lead to burn-off losses at the transition point from focused laser light to the optical waveguide due to the high transmission energies. These burn-off losses arise primarily in the area of the polymer sheath that envelops the optically active core of the fiber, which is usually covered by an outer coating in order to give the fiber a certain flexibility as a whole, as is necessary for endoscopy, for example. The consequence of such burn-off losses is that reliable energy transmission can no longer be guaranteed and the plug with the connected optical waveguide must be replaced. The aim of the present invention is therefore to provide a plug for the application area mentioned at the beginning, with which the disadvantages described can be avoided. The connector should preferably be designed in such a way that it can also be used for single-use applications, as is often the case in medical technology, where the associated endoscope is discarded after an operation for hygienic reasons.

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The main reason for this is that the "closed installation" of the light guide in a certain location means that there is insufficient heat transfer and cooling of the fiber must therefore be ensured. The invention also recognized that external cooling, for example via a cooling unit, is practically impossible for technical reasons because the section of the light guide to be cooled, with a diameter of, for example, 0.5 mm and a length of a few millimeters, is too small to achieve targeted cooling using a cooling unit.

It is all the more surprising that it has now been found that the desired cooling can be achieved amazingly quickly by removing the coating from the free end section of the fiber and leaving it to consist only of the optically effective core and a thin jacket surrounding it, and arranging this free end section in such a way that it has no direct contact with the through-opening in the connector or its front face. In other words: the free end section of the fiber should now protrude freely forwards beyond the through-channel or the associated parts for positioning the optical waveguide.

Surprisingly, it has been found that in some cases a free section of the optical waveguide of about 1 mm is sufficient to completely prevent the burn-off losses described above, because the exposed end of the optical waveguide enables unhindered radiation of light waves and thus of energy from the polymer sheath into the environment.

The invention then relates to a connector for a fiber optic connector with an optically active core, a polymer sheath enveloping the core and an outer coating adapted to the core for removable coupling to electro-optical components emitting energetic laser light, with the following features:

The plug has a plug housing,

an axial through-channel and, if necessary, positioning means for receiving and installing the optical fiber are arranged in the connector housing,

the optical fiber runs up to the area of the plug tip,

the optical waveguide is designed without an external coating at its free end,

the free end of the optical waveguide is arranged at a distance from the wall of the through-channel and/or it projects beyond the through-channel or the corresponding positioning means.

In the simplest case, the connector would differ from a known connector in that the optically active core with its associated jacket protrudes with its free end beyond the front surface of the connector tip. Although such an embodiment realizes the core idea of the present invention, there is a risk that the protruding tip of the optical waveguide will break off when using such a connector.

For this reason, it is proposed in an advantageous embodiment to arrange the waveguide in such a way that its front surface at the free end is flush with the front surface of the plug tip or ends at a certain distance to the rear.

Based on the above explanations, it follows implicitly that in this embodiment a cavity similar to an annular channel must remain between the peripheral surface of the free end of the fiber and the corresponding wall of the through-channel. This cavity is easily created by the fact that the corresponding section of the optical waveguide has no external coating. It can also be advantageous to design the corresponding front section of the through-channel with a larger opening width, especially if a centering element for the optical waveguide is arranged in this area.

Such a centering element is therefore preferred in order to ensure a safe and exact positioning of the fiber in the connector and an exact assignment of the front face of the fiber at the ' focal point of the laser light to be received.

The centering element is then offset from the free end face : of the connector tip, while the fiber tip s protrudes beyond it and is aligned in front of or with the end face of the v connector tip. In this way, the end face > of the connector tip can be used at the same time to position the j·· connector on a corresponding electro-optical component.

The section of the optical waveguide covered by the centering element can also be designed without an external coating, while the section behind it, in the through-channel of the connector

the inserted section of the optical waveguide is designed in the usual way. In this embodiment, the centering element simultaneously serves for additional cooling of the inserted section of the optical waveguide and is preferably made of a material that conducts heat well for this purpose.

For example, for medical applications such as endoscopy, the optically active core of the optical waveguide has a diameter of less than _0.1 mm. The jacket surrounding the core, which is made of a polymer in particular but can also be made of other materials such as glass, is only a few μm thick. Together with the outer coating, this results in a total diameter of about 1 mm. In this case, it is sufficient to allow the free end section of the optical waveguide to protrude freely by about one millimeter in the manner described. This allows light waves that are incident at a relatively steep angle to radiate unhindered through the jacket into the free surrounding space, while light that is incident at relatively flat angles is reflected. in the rear area of the optical waveguide are totally reflected at the interface between the optically active core and the surrounding polymer cladding. This is ultimately the principle of the fiber optic light waveguide.

The plug itself is preferably made of metal and the optical waveguide is secured to the plug housing, for example by crimping, whereby the crimping point is provided in an area of the conductor in which it has an outer coating in order to prevent deformation of the polymer sheath or the optically active core.

Of course, the front surface of the free end of the optical fiber must also be as

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be absolutely flat in order to prevent scattered radiation. Grinding the end face of the connector tip together is not possible here, as the brittle conductor would protrude freely over the associated connector components and break off. Surprisingly, however, it has been shown that an absolutely flat end face can also be achieved by simply breaking it.

Further features of the invention emerge from the features of the subclaims and the other application documents.

The invention is explained in more detail below using an embodiment, wherein the single figure shows a connector with an embedded fiber optic light waveguide in section in a highly schematic representation.

For reasons of clarity, the rear part of the plug 10, which is not of interest here, is not shown. The front part of the plug 10, on the right in the figure, is made of metal and has a front-side, inward-facing hole 12 in which a plug tip 14 is fixedly positioned.

Coaxially to the central longitudinal axis M, a through-channel IG with a circular cross-section is arranged in the plug 10 and the tip of the plug. The through-channel has a diameter d. Towards the front end, on the right in the figure, the through-channel IG is designed with an enlarged inner diameter D. The plug 10 thus has a cup-shaped recess 18 in the area of the free end 14g of the plug tip 14.

In the through-channel IG there is a fiber-optic light wave gate 9 &Pgr; annonrrli^nt &Pgr;&iacgr; ocor h &rgr; c f &rgr; h t nuc &eegr;&iacgr;&eegr;&agr; m &eegr;&eegr; l·. i Q &Ggr;. hi

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active glass fiber core 22 with a diameter of approximately 0.5 mm and a thin polymer sheath 24 surrounding the core 22 as well as a coating 26 arranged around it, for example made of a plastic.

The optical fiber 20 is on the left, not shown in the figure

shown end of the plug 10 to the plug housing *

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16 to the area of the front face 14b of the plug- §

tip 14. n.

As can be seen from the figure, the free end section 20a of the optical waveguide running within the cup-shaped recess 18 is freed from the outer coating 26.

In the area of the cup-shaped recess 18, a centering element 28 is arranged, which sits flush there and encloses the free end area 20a of the optical waveguide 20, but only in a partial area, so that the tip 20b of the optical waveguide 20 protrudes beyond the end face 28a of the centering element 28. As can be seen from the figure, the centering element 28 rests with its rear surface against the step 30 in the area of the cup-shaped recess 18. In the present case, the centering element 28 is glued into the recess 18.

The essential feature of the plug is that the tip 20b of the optical waveguide 20 has no surface contact with the wall of the passage channel 16 or the recess 18 and freely projects beyond the passage opening 16 or the centering element 28, so that a cavity 32 is formed between the tip 20b and the wall of the recess 18.

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The front surface 20c of the optical waveguide 2G is absolutely flat perpendicular to the central longitudinal axis M, namely by breaking the optically active core 22 at this point and is otherwise flush with the front surface 14μ of the connector tip 14.

This prevents the tip 20b from breaking off even if the plug 10 is used improperly, which protected by the Stacker:. ^tze 14. At the same time

-ent the front surface 14b of the plug tip 14 for positioning the plug in ^a rotary component. The plug is positioned so that the focal point of the laser light emitted and irradiated by the component is directly in the middle of the front surface 20c of the light

P waveguide 20.

If, during use of the device, light waves should penetrate the tip 20b of the optical waveguide 20 at a relatively steep angle, they will be emitted unhindered into the cavity 32. Overheating due to reflections is prevented. This prevents burn-off losses due to uncontrollable reflections and a corresponding build-up of heat in the area of the jacket.

Claims (1)

■.ThomasU.Becker &Bgr;&thgr;&Pgr;(<&THgr;&Ggr; &* &Mgr;&udigr;&Igr;&Igr;&thgr;&Ggr; Dr. Karl-Ernst Müder ropean Patent Attorney · ■ · · ·" · &igr; ' fcatentilhivältß* * · European Patent Aftofnoy fc · * &igr; it · ti· » · > » 1* 11 I · Applicant: 10 July 1990 SOUHIAU Electric GmbH
Heinrich-Hertz-Strasse 1 frkrath S 11360-G Connector for a fiber optic cable Protection claims Plug for a fiber optic light waveguide (20) with an optically active core (22), a jacket (24) enclosing the core and an outer coating (26) arranged around it for detachable coupling to electro-optical components emitting high-energy laser light, with a plug housing (10, 14) which has an axial through-channel (16) and optionally positioning means (28) for receiving and fixing the light waveguide (20), wherein the light waveguide (20) runs into the area of the plug tip (14) and is designed on such a free ground (20b) without an outer coating (26) and is arranged at a distance from the wall of the through-channel (16) and/or projects beyond the through-channel (16) or the corresponding positioning means (28). ■'. I-."' k ■' I- ■' . Plug according to claim 1, in which the light waveguide (20) is arranged such that its end face (?0r) at the free end is flush with the end face (Mb) of the plug tip (14). 'J. Plug according to claim 1, in which the optical ^conductor is arranged such that its front surface at the free end slightly projects beyond the front surface of the plug section. . Plug according to one of claims 1 to 3, in which the optical waveguide (20) is positioned in the region of the plug tip (14) by a zone element (28). . Plug according to claim I, in which the centering element ( ? ü) consists of a high-strength but good heat-conducting material. 6. Plug according to claim 4 or 5, in which the centering element (28) is arranged in an expanded section (18) of the through-channel (15) open towards the end face (14b) of the plug tip (14) immediately in front of the freely projecting end section (20b) of the optical waveguide (20). 7. Plug according to one of claims 1 to 6, in which the freely projecting end section (20b) of the optical waveguide (20) is one to five times as long as the diameter of the optical core (22) of the optical waveguide (20). O. Plug according to one of claims 1 to 7, in which the centering element (28) consists of Hubin. 9. Plug mn · <j &igr;μgr;&eeacgr;π of claims 1 to 7, in which the /entrain element (28) consists of a nickel silver alloy. lü. Plug according to one of claims 1 to '), in which the plug tip (14) is made of ceramic.