Optical waveguides – Accessories – Plug/termination device
Reexamination Certificate
2001-02-09
2003-08-12
Bovernick, Rodney (Department: 2874)
Optical waveguides
Accessories
Plug/termination device
C385S137000, C385S060000, C385S066000, C385S078000, C385S084000
Reexamination Certificate
active
06606445
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a method for producing a holding configuration for at least one sheathed optical fiber conductor.
Such holding configurations are used, for example, for connecting an optical fiber conductor end to an electrooptical module, or for coupling to corresponding plug connectors. Holding configurations, as an end piece which can be coupled, can directly terminate the optical fiber conductor, which is sheathed by a protective sheath, or can surround a section of the optical fiber conductor located in front of the end, so that the optical fiber conductor runs on both sides of the holding configuration. In each case, the holding configuration has at least one end (which is called an outlet opening in the following text) of a through-channel for holding the optical fiber conductor, from which end the optical fiber conductor emerges.
U.S. Pat. No. 4,984,865 discloses a holding configuration for an optical fiber conductor which emerges from a cable sheath end together with ends of a strain relief device in the form of strands (aramide fibers). The cable sheath end is inserted into a plug connector housing, which is filled with a thermoplastic. It is not possible for unacceptably small bending radii of the optical fiber conductor to occur in the case of that known holding configuration, since the optical fiber conductor is completely surrounded by the thermoplastic and runs in a fixed manner within the holding part.
German Patent DE 27 11 670 C2 discloses a holding configuration in the form of a detachable plug connector, in which two optical fibers to be coupled are each bonded by their end region into a centering insert. The latter is inserted into one end of a tube, which is used as a guide body and can be inserted with the corresponding coupling partner into an adjustment capillary, in order to make contact at the end.
In the case of the holding configuration of the type mentioned initially, which is known from German Published, Non-Prosecuted Patent Application DE 43 03 737 A1, corresponding to U.S. Pat. No. 5,574,819, a cable end, which has been freed at the end of its cable sheath revealing strain relief device ends and two optical fiber conductor ends which are sheathed by one protective sheath (buffer) in each case, enters an inlet opening of a receptacle. A spreading sleeve is inserted into the cable sheath end and expands the sheath beyond the inlet opening width. The optical fiber conductors pass through a through-channel which runs from the inlet opening to an outlet opening, and leave the receptacle with radial freedom of movement. The receptacle is partially filled with a fixing compound. That surface of the cured fixing compound which is close to the outlet opening (filling level) is located vertically at a distance below the outlet opening in the longitudinal axis direction when the configuration is oriented vertically.
If the cable end, once it has been provided with the holding configuration, is handled incorrectly or carelessly in the rest of the production or assembly process, there is a risk of the optical fiber conductors being bent over the comparatively sharp-edged contact line to the surface of the fixing compound.
That problem is exacerbated if fixing compounds are used which raise up the optical fiber conductors due to adhesion effects and capillary forces. Specifically, in practice, it has been found with through-channels having a cross section which is dimensioned to be only slightly greater than the cross section of the sheathed optical fiber conductor, that the fixing compound, when in the flowing state, rises to an undesirably high extent above the desired filling level due to capillary effects, and consequently forms sharp edges which lie against the optical fiber conductor, closely underneath the outlet opening. On one hand, if optical fiber conductors are bent beyond their critical bending radii, they can be irreversibly damaged. Such damage may temporarily remain concealed by the protective sheath in a disadvantageous manner, and not be detected until final inspection or initial operation. On the other hand, comparatively narrow through-channels are desirable in order to achieve adequate adhesion forces, the necessary amount of fixing compound and its curing time.
In order to overcome that problem, production and assembly have until now had to be carried out extraordinarily carefully, with the optical fiber conductors temporarily being fixed in appropriately constructed production holders at least until additional, permanent structural elements (for example separate kink protection elements) or appropriate housings with guides were fitted.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method for producing a holding configuration for at least one sheathed optical fiber conductor, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type and which, even immediately after fitting and curing of a fixing compound, and without any additional apparatuses, ensure reliable protection of the sheathed optical fiber conductor against unacceptably small bending radii.
With the foregoing and other objects in view there is provided, in accordance with the invention, a holding configuration, comprising a fixing compound; a receptacle for receiving the fixing compound, the receptacle having an inlet opening for receiving an end of an optical fiber cable stripped at the end to expose an optical fiber conductor, and the receptacle having an outlet opening through which the optical fiber conductor emerges with radial freedom of movement and free of the fixing compound fixing a section of the optical fiber conductor; and a spreading body at least partially inserted into an end of a cable sheath of the optical fiber cable, the spreading body bounding a through-channel expanded from a first cable section closely surrounding the optical fiber conductor to a second cable section opening into the outlet opening, the second cable section having a cross section dimensioned relative to a cross section of the optical fiber conductor for maintaining the fixing compound in the second cable section substantially free of capillary forces.
While capillary force effects on the fixing compound are achieved in the first, narrower section, in order to fix the optical fiber conductor safely while using little material, as long as the fixing compound is still a low-viscosity liquid, the deliberate expansion of the through-channel results in the capillary effects in the second section being suppressed in a defined manner. On one hand, the amount of fixing compound to be introduced can thus be considerably reduced in an advantageous manner since it is necessary to fill only a comparatively narrow gap between the optical fiber conductor and the wall of the first section. Since, on the other hand, the expansion reliably prevents the fixing compound, which can still flow, from flowing on or rising undesirably in the direction of the outlet opening, the amount of fixing compound can be dimensioned and introduced without so much care being required in particular with regard to capillary effects. The amount of fixing compound is preferably dimensioned in such a way that the optical fiber conductor remains largely free of fixing compound in the second section. In consequence, the optical fiber conductor has radial mobility even at the start of the expanded section, and that has a positive influence on the bending geometry, which is governed by the last fixing point, close to the outlet opening, of the optical fiber conductor. The expansion allows the distance between the fixing point and the outlet opening to be set as planned, and to be easily controllable.
The maximum angles or bending radii of the optical fiber conductor which occur during the production and assembly processes (without deliberate overbending) are automatically kept comparatively gentle in conjunction with rounding of the rims or edges of the outlet opening whic
Bovernick Rodney
Greenberg Laurence A.
Infineon - Technologies AG
Kang Juliana K.
Locher Ralph E.
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