WO1997001120A1

WO1997001120A1 - Process and mounting device for producing a multiple plug for light waveguides

Info

Publication number: WO1997001120A1
Application number: PCT/EP1996/002685
Authority: WO
Inventors: Wolfgang Ehrfeld; Lutz Weber
Original assignee: INSTITUT FüR MIKROTECHNIK MAINZ GMBH
Priority date: 1995-06-23
Filing date: 1996-06-20
Publication date: 1997-01-09
Also published as: AU1192997A; DE19522859A1

Abstract

A device is disclosed for producing connectors for light waveguides (8) with several fibres (9). The connectors have a base body with a contact area (81) that contains the free ends of the fibres (9) and a connecting area that holds the light waveguide (8). Coupling elements, for example fitting holes and pins (14), are associated with the contact area. At least one positioning member (12, 13) is provided for the fibres (9) and coupling elements (14, 82).

Description

METHOD AND ASSEMBLY DEVICE FOR PRODUCING A MULTIPLE CONNECTOR FOR LIGHT WAVE GUIDES

The invention relates to a device and a method for producing a multiple plug connector for optical waveguides and to a multiple plug connector for optical waveguides produced by means of the device or by the method.

For example, a fiber holder is known from the magazine "Laser Focus World", January 1993, page 165 ff., In which up to 18 fibers are guided between two silicon plates, each of which has a field of parallel, V-shaped grooves in the desired position The forces for holding the two parts together are exerted by an external clamp. Two guide bolts, also guided in such V-grooves, ensure the positioning of two such fiber holders relative to one another. The V-grooves are produced in silicon by anisotropic etching.

A multiple fiber holder is known from the magazine "Polymer Engineering and Science", 1989, Volume 29, No. 17, page 1193 ff., In which the individual fibers of a band are inserted into a strain relief part, which in a second Part is attached, the fiber ends are inserted into holes in the end face of the second part. These have a diameter which allows the largest possible fiber diameter to be taken up and have a spacing which corresponds to the grid dimension of the fiber sliver. The fibers are then glued in the fiber holder. The end face, including the fiber ends, is then polished in order to achieve the required values for insertion and return loss. The positioning of two fiber holders relative to one another is carried out by means of a pair of additional guide bolts to be attached, which are inserted into two holes in each of the two plug ends. The contact between two plugs is made by pressing them together, for which purpose a clamp is required which presses the two fiber holders axially together. An immersion gel supports the coupling. EP 0 514 722 A1 shows a fiber holder which corresponds to the type described above, but which can, however, be installed in a connector housing. In addition, the end faces are polished obliquely in order to optimize the return loss. In addition, direct fiber-to-fiber contact takes place, the force required for this being applied by springs in the connector housing. Here, too, two fiber holders are positioned relative to each other by means of two guide bolts. The two plugs must be connected to one another by a third part, a type of adapter.

DE 43 13 185 A1 discloses a mold for simultaneously casting a plurality of sleeves on a corresponding number of optical fibers. By means of this device, each individual fiber is provided with a sleeve, a so-called ferrule, which can be used for handling and positioning the fiber, for example in a plug. The fiber is positioned in the rotationally symmetrical cavity of the mold provided for the production of the sleeve by means of bores which are coaxial with the cavity. Consequently, only individual fibers can be provided with sleeves with this device, but not fiber bundles. Elastic positioning elements are also not provided. Due to the fixation of the optical fiber in bores, the known shape cannot achieve sufficient accuracy for single-mode optical fibers.

Finally, it is known from DE 43 22 660 to integrate microstructured devices in the fiber holder, which allow the centering of the optical fibers on the fiber cladding and thus the compensation of the tolerances of the outer diameter. The principle of operation of the multiple connectors according to this document corresponds to the multiple connectors discussed above.

The fundamental technical problem with connectors for optical fibers is that the fibers to be connected must face each other as precisely as possible at the end, that is to say they have the least possible deviation from one another in the transverse direction of the fiber. In addition, the fibers must be arranged axially parallel to each other as much as possible. For single-mode fibers with an outer diameter of 125 μm, whose light-guiding region has a diameter of approximately 10 μm, the required accuracy is in the region of approximately 1 μm. The connectors discussed above ensure such precise positioning of the fiber ends relative to one another essentially in that the connector itself has guiding or positioning structures that are manufactured with corresponding accuracy. If each connector contains these positioning devices, which are usually manufactured using microtechnology, the unit price of such a connector is very high. The capacity of a possible series production is also limited by the fact that each individual connector is manufactured using microtechnology and used in confectionery. tioning a complex assembly process must be carried out.

It is therefore an object of the invention to provide a device and a method by means of which multiple plug connectors for optical waveguides can be produced which enable sufficient precision in the positioning of the fiber ends relative to one another, but which are simpler than the known devices and methods.

This object is achieved by a device with the features of claim 1 and by a method with the features of claim 11 and by a multiple connector with the features of claim 13.

Because a microtechnically manufactured positioning device is provided for the fibers and the coupling elements, the relative position of the fibers and the coupling elements to one another can be determined with an accuracy that is required for the coupling elements to work properly when producing connecting pieces for optical fibers with multiple fibers. The manufacturing accuracy is thus determined by the positioning device for the fibers and the coupling elements, whereas in the previously known connecting pieces for optical waveguides the manufacturing accuracy had to be applied by the base body of the connecting pieces themselves.

If the device comprises a mold with a cavity for casting the base body, the fibers and the coupling elements can be poured into the base body of a connecting piece in a simple manner. Particularly good values for the accuracy result if the positioning device is assigned to the side of the mold that delimits the contact area is. In this case, demolding without contamination or damage to the positioning device is possible if it is arranged outside the cavity. It is also advantageous if the shape is at least in two parts because good results can be achieved during casting.

The accuracy of the relative position of fibers and coupling elements is promoted if the positioning device is at least in two parts, a separation point being provided in the plane of the optical fibers and essentially at right angles to the contact area. With such a positioning device, at least the fibers, but also the coupling elements, can be held resiliently and non-positively and thus centered in the positioning device, so that they cannot move out of their intended position when the base body of the connecting element is being shaped. It is possible to adjust the position of the fiber ends relative to the shape with which the base body is formed if the positioning device can be moved relative to the shape at least in the plane of the contact area.

Particularly good accuracy is also achieved if the positioning device by means of UV lithography and subsequent galvanic molding, according to the LIGA method by means of X-ray lithography and subsequent molding or by anisotropic or isotropic etching of a material, preferably silicon. Good coupling values, ie low damping, result if the fibers and the coupling elements are fixed in the plane of the contact area with a reproducible accuracy of better than 5 μm. These values are suitable for multimode fibers. Even better optical properties result if the repeatable accuracy of multimode fibers is better than 2.5 μm. For single-mode fibers, it is advantageous if the positioning of the fibers and the coupling elements can be carried out with a repeatable accuracy of better than 1 μm.

The device can preferably be used if the fibers are optical fibers of the singlemode type, optical fibers of the multimode type, electrical conductors or also hollow capillaries with an essentially round cross section.

Because the method for producing multiple plug-in connectors for optical waveguides provides for the position of the fibers and the coupling elements to be secured relative to one another by means of a positioning device which does not remain in the base body with the fibers and the coupling elements, there need not be one high-precision positioning device can be produced for each individual connector, but a positioning device that has been manufactured once can be used several times in the context of a series production process. Since the production of such precise positioning devices is associated with considerable effort and costs, the method according to the invention is advantageous for series production.

In an advantageous embodiment of the invention, a ceramic or metallic insert is used. The material of the insert can be selected with regard to particularly good properties with regard to temperature and climate stability. The amount of potting compound required to fix the fibers is thereby kept particularly low and the advantages of ceramic or metal materials are particularly evident. This insert can also be used to grasp the fibers before casting. It then also causes the fibers to be pre-positioned. In the drawing, an embodiment of the invention is shown.

Show it:

Figure 1: A device according to the invention, partially in cross section from the side;

FIG. 2: the hollow shape according to FIG. 1 in a view of the end face which forms the contact area of the plug connector;

FIG. 3: a preferred exemplary embodiment for the method according to the invention for producing a multiple connector using five method steps;

FIG. 4: five different possible structures for positioning devices that can be used in the device according to the invention; such as

FIG. 5: a connector, which is produced with the method according to the invention and with the device according to the invention, in a plan view of the level of the contact area.

1 shows a device according to the invention in a side view, a hollow mold 1 being shown in cross section. The hollow mold 1 comprises a lower mold part 2, an upper mold part 3 and a filling opening 4 machined into the upper mold part. The hollow mold 1 is arranged on a fixed base 5. In the illustration according to FIG. 1, a two-part holder 6 is arranged to the right of the hollow mold 1, which in turn is fastened on a mounting table 7 which can move in all three spatial directions. An optical waveguide 8 is fixed in the holder 6 and contains a number of fibers 9 of the optical waveguide in a sheath 10.

On the side of the hollow mold opposite the holder 6

I a second assembly table 11 is provided, which can also be moved in all three spatial directions. The assembly table

II carries a first positioning device 12 and a second positioning device 13, which position the individual fibers 9 of the optical waveguide 8 as well as two dowel pins 14 with high accuracy.

The walls of the hollow mold 1, which on the one hand are adjacent to the holder 6 and on the other hand to the positioning device 12, each have a recess 15 or 16 at the separation point between the upper mold part 3 and the lower mold part 2. The recess 15, adjacent to the holder 6, is designed in cross section so that it can receive the optical waveguide 8 together with its cladding 10. The cross section is designed such that when the hollow mold 1 is closed, the recess 15 is essentially closed by the optical waveguide 8.

The recess 16 is adjacent to the positioning device 12 and is set up in such a way that it can accommodate the individual fibers 9 of the optical waveguide 8 at the intended spacing from one another, that is to say, for example, with a pitch of 250 μm from fiber to fiber. In addition, the dowel pins 14 are guided in the area of the recess 16 from the inside of the hollow mold 1 to the outside, so that they can be fixed in the positioning device 12 and in the positioning device 13. When the hollow shape is closed, the recess 16 is stalt that the fibers 9 and the dowel pins 14 are in the intended position, but that they have some play in the recess. The final and exact fixing of the fibers 9 and the dowel pins 14 relative to one another is carried out by the positioning devices 12 and 13. These positioning devices 12 and 13 are constructed essentially the same and fix the fibers 9 and dowel pins 14 with the required accuracy, ie in the case of single -Mode fibers with an accuracy of around 1 μm, as well as with the required axis-parallel alignment to each other. The assembly tables 7 and 11 can move the holder 6 on the one hand and the positioning devices 12 and 13 on the other hand into the intended position relative to the hollow mold 1.

FIG. 2 shows the hollow mold 1 with its lower part 2 and the upper part 3, the filling opening 4, the fibers 9, the dowel pins 14 and the recess 15 in a cross section, the viewing direction running in the longitudinal direction of the fibers 9 .

In the illustration according to FIG. 2 in conjunction with FIG. 1 it can be seen that the bottom 20 of the lower mold part 2 rises approximately pyramid-shaped from the outer sides to the center, the bottom 20 not tapering to a point, but in the middle with vertical walls and a flat surface a kind of base 21 is formed. The upper part of the mold has a corresponding design running parallel to the base 20 on the upper side of the mold interior, which essentially corresponds to the negative shape of the base 20 and the base 21.

The use of the device described so far is illustrated in FIG. 3 with the aid of 5 symbolic illustrations a) to e). In method step a), the optical waveguide 8, which is placed on one side over a length that corresponds approximately to the length of the dowel pins 14, is placed on the lower mold part 2 of the hollow mold 1. In this case, the covered area of the light waveguide 8 is placed on the holder 6, while the fibers 9 freed from the cover are introduced into the positioning devices 12 and 13 or placed there. The dowel pins 14 are then also introduced into the positioning devices 12 and 13 parallel to the fibers 9, so that they lie in one plane with the fibers 9.

As shown in b), the holder 6 is then closed around the optical waveguide 8 and the hollow mold 1 is joined by placing the upper mold part 3 in order to enclose a mold interior that corresponds to the geometric shape of the subsequent connector. Any deviation of the optical waveguide 8, the fibers 9 or the dowel pins 14 from the desired position can be eliminated at this time by moving the assembly tables 7 or 11.

In c) the hollow mold 1 is closed, the optical waveguide 8, the fibers 9 and the dowel pins 14 are fixed in their desired position. The interior of the hollow mold 1 is then filled with a casting compound, symbolically indicated at 30, so that the basic body of the plug connector, which surrounds the optical waveguide 8, the fibers 9 and the dowel pins 14, is formed in the mold interior of the hollow mold 1.

In the case of d) the potting compound 30 has solidified or hardened within the hollow mold 1, the upper mold part 3 can be lifted off the basic body of the plug connector formed, and in e) the plug connector is demolded from the lower mold part 2. The dowel pins 14 have been treated with a release agent before casting and can now, after the men of the connector, are pulled out of the base body 31. This results in cylindrical cavities in the base body 31, into which corresponding coupling elements can be introduced, the alignment and positioning of which satisfy the accuracy described above.

The fiber ends of the fibers 9 emerging from the end face of the base body 31 are now separated and the end face of the plug connector which is penetrated by the fiber ends and which forms the subsequent contact area is polished by methods known per se.

FIG. 4 shows various positioning devices 12 which can be used to fix the fibers 9 of an optical waveguide 8. A first, two-part positioning device 30 with an upper part 31 and a lower part 32 has V-shaped grooves into which the fibers 9 can be inserted. The upper part 31 and the lower part 32 are constructed essentially the same and are used facing V-shaped grooves. The fibers 9 are clamped into the spaces formed between the grooves, the clamping force being applied by the elastic deformation of the material of the positioning device 12 itself.

A second positioning device 12 is made in one piece and has a comb-like structure 40 which is provided with tines 41. The tines 41 have an arc in their course, two tines being arranged in pairs in such a way that the arcs point away from one another and form a space between them in the radius suitable for receiving the fibers 9. At the free end, the respective pair of tines is chamfered so that an insertion bevel for the respective fiber 9 is formed. The clamping force required for the exact positioning of the fiber 9 between two tines 41 is required, is applied by the spring elasticity of the tines.

A further, two-part clamping structure 50 likewise has the interstices, which are required for the clamping of the optical fibers 9, through mutually facing, V-shaped cutouts. In this case, each fiber 9 is enclosed in a V-shape on all sides, similar to the device 30, but the spring force is applied in the transverse direction by the plate-shaped spring elements 51 arranged in the front view due to their spring elasticity.

A two-part positioning device 60 can be compared in terms of its geometric arrangement to the positioning device 30, but the spring elements 61 surrounding the fiber are not solid, but thin-walled with an inner hollow chamber 62, the walls of which in turn are spherically deformed under pressure. This deformation results in the elasticity required for the individual fibers 9 to be held firmly but without damage.

Finally, a one-piece positioning device 70 shows an embodiment which surrounds the fibers 9 on all sides, but which nevertheless has a certain elasticity in the transverse direction of FIG.

Finally, FIG. 5 shows an end view of a plug connector 80, which was produced by means of the device according to FIG. 1 and FIG. 2 using the method according to FIG. 3. The fibers 9 of the optical optical waveguide emerge from an end face 81. In addition, two positioning openings 82 are formed on the end face, which are provided for inserting dowel pins serving as coupling elements are. Thanks to the positioning device 12 of the device according to the invention, the relative position of the individual fibers 9 to one another and to the positioning openings 82 is defined with a high degree of accuracy, for example better than 1 μm absolute.

This accuracy is achieved in that the positioning devices 12 and 13 are produced, for example using the structures illustrated in FIG. 4, by means of a highly precise microtechnology, for example by UV lithography or X-ray lithography with subsequent galvanic molding or by anisotropic Silicon etching. The positioning device used in each case, which is not arranged within the mold space of the hollow mold 1, but is used externally in the immediate vicinity of the hollow mold, is not affected by the actual molding process of the connector. The microstructure used for the positioning of the fibers 9 and the dowel pins 14 or the positioning openings 82 produced therewith can therefore be used repeatedly, practically as often as desired, for producing a plug connector. In this point, the device according to the invention is advantageous compared to the previously known connectors or devices for the production of connectors because only the optical waveguide 8 itself and the molding material 30 used for forming the base body 31 are used to produce the connector. The microstructure is retained for further production steps, whereas previously a corresponding, elaborately manufactured and very precise microstructure had to remain in the connector for each connector.

The connector 80 shown in FIG. 5 has an extension 83 on its upper side which corresponds to the negative of the upper part 3. A cavity which is complementary to this approach is on the underside of the connector 80, inwards molded, not visible in Figure 5. With this approach 83, a plurality of plug connectors can be arranged one above the other by pressing them onto each other.

The optical connection between two connectors takes place in a manner known per se in that two connectors 80 are pressed against one another with their end faces 81 together with two suitable dowel pins 14, for example using an emulsion gel, which adjusts the optical transition between two coaxially opposed ones Fibers 9 promotes. Because the position of the fibers 9 relative to the positioning openings 82 and thus also relative to the dowel pins 14 used together is very precisely defined with respect to the accuracy of the microstructures of the positioning devices 12 and 13, two fibers 9 to be coupled are each coaxial and axially parallel opposite, so that the attenuation of the optical transition remains small.

Claims

claims

1. Device for producing connectors for optical fibers (8) with several fibers (9), the connectors having a base body with a contact area (81) each containing the free ends of the fibers (9) and an An¬ holding the optical fiber (8) have the closing area, the coupling area also having coupling elements, for example Fitting bores (82) or pins (14) are assigned, characterized in that at least one microtechnically manufactured positioning device (12, 13) is provided for the fibers (9) and the coupling elements (14, 82) is.

2. Device according to claim 1, characterized in that the positioning device (12, 13) comprises a centering device for the fibers (9) and / or the coupling elements (14, 82).

3. Device according to one of the preceding claims, da¬ characterized in that the positioning device

(12, 13) is assigned to the side of the mold (1) which delimits the contact area.

4. Device according to one of the preceding claims, da¬ characterized in that the device comprises a mold (1) with a cavity for casting the base body and that the positioning device (12, 13) is arranged outside the cavity.

5. Device according to one of the preceding claims, da¬ characterized in that the positioning device

(12, 13) is at least in two parts, a separation point being provided in the plane of the optical fibers (9) and essentially at right angles to the contact area (81).

6. Device according to one of the preceding claims, da¬ characterized in that the positioning device

(12, 13) can be moved relative to the mold (1) at least in the plane of the contact area (81).

7. Device according to one of the preceding claims, da¬ characterized in that the positioning device

(12, 13) is produced by means of UV lithography and subsequent electroplating or by the LIGA process by means of X-ray lithography and subsequent molding.

8. Device according to one of the preceding claims, da¬ characterized in that the positioning device

(12, 13) by means of microstructuring of plastics or by means of anisotropic or isotropic etching of a material, preferably silicon.

9. Device according to one of the preceding claims, da¬ characterized in that the positioning device

(12, 13) in the use position of the device, the fibers (9) and the coupling elements (14, 82) in the plane of the contact area with a repeatable accuracy of better than 5 µm, preferably better than 2.5 µm, in particular specifies better than 1 μm.

10. Device according to one of the preceding claims, da¬ characterized in that the fibers (9) Lichtwellenlei¬ ter of the single-mode type and / or optical fibers of the multi-mode type and / or electrical conductors.

11. Method for producing multiple connectors for optical fibers with the following steps:

- Inserting an optical waveguide into a hollow mold which has a molding space in such a way that the individual fibers of the optical waveguide penetrate a side wall of the molding space;

- Detecting the individual fibers of the optical waveguide in a positioning device;

- Introducing coupling elements in such a way that they protrude into the mold space and also penetrate the side wall penetrated by the fibers;

- Detection of the coupling elements in the same positioning device in which the fibers are detected;

- Pouring or injection molding the molding space with a hardenable or solidifiable molding compound; such as

- De-molding of the molding compound after hardening or solidification.

12. A method for producing multiple connectors for optical fibers according to claim 11, characterized ge indicates that an insert made of a ceramic or metallic material is used, which remains in the connector.

13. Multiple plug connector for optical fibers, produced by means of a device according to one of claims 1 to 10 or by the method according to claim 11 or claim 12.