Optical cable with regularly grouped optical fibres - which are in stacked strands with successive stack layers forming cable core

The invention relates to an optical cable having a plurality optical waveguides, each in groups to form ribbons are combined, wherein a plurality of such ribbons respectively forming a ribbon stack and several such tapes stack are provided in the region of the cable core and the Cable core is enclosed by an outer sheath.

From EP-A1 03 56 786 an optical cable is known, in the one provided with approximately rectangular chambers Kernele ment is provided. Such, as chamber Cable Marked designated structures are often together with ribbon cables used, that there are several optical waveguides to a Ribbon with approximately rectangular cross section summarized. Several such strips are ver a ribbon stack agrees, which stack on each approximately rectangular chamber formed by its likewise rectangular in Outer contour formed is adjusted. is within the chamber merely left a small gap to a certain Beweg sensitivity to ensure the ribbon stack, but to prevent it to a position change, ie a twist or an overturning of the ribbon stack can come.

As the number of ribbons within a stack The partition walls between the individual chambers by outside getting wider and receive an approximately wedge-shaped Cross-section. This existing space here is in accordance with the EP-A1 03 56 786 to a certain extent so available that there to outwardly open additional wells are attached (with approximately triangular cross-section), which, for other purposes For example, for the attachment of electrical conductors or like are usable. For the insertion of further light waveguide, for. example, in the form of ribbon stacks are these Cross-sections, however, not suitable because it relative to a are small and on the other hand essentially a triangular have shape.

The invention is based on the object aufzuzei a way gen, how easily a high packing density of Ribbons be achieved while ensuring chenstapel can that the optical fiber from unwanted high mecha African strains are protected. According to the invention this will in an optical cable of the type mentioned achieved in that the ribbon stack in a mehrschichti positioned gen assembly such in the cable core that the outer contour of the multilayer arrangement stepped ver is running and that the inner contour of the cable sheath is formed so that it consists essentially of the stepped outer contour of the more layered arrangement follows.

Since the internal contour of the cable sheath at the step-shaped Outer contour of the various layers of the ribbon stack matches is prevented that one of the ribbon stack about a Posi tion alternately performs so for example tip over, resulting in unwanted mechanical stresses of Lichtwellenlei would lead ter. At the same time is still ensured, that a certain mobility between the form of multilayer Assembly formed cable core on the one hand and the Cable jacket is ensured on the other side. any Gaps between adjacent bands or between stacks Ribbon stacks and the inner contour of the cable sheath are so small to choose that still sliding and a certain Mobility of the ribbon stack against each other and against the Outer shell remains possible during tipping so a Po is sitionswechsel a ribbon stack prevented.

The invention and its developments are to follow explained hand drawings.

Show it

<b>Fig.</b> 1 in cross section an optical cable according to the invention,

<b>Fig.</b> 2 in an enlarged view the structure of a ribbon stack and

<b>Fig.</b> 3 shows a further embodiment of a erfindungsge Maessen cable.

In <b>Fig.</b> 1 is an optical cable with OC1 referred to in whose Cable core arranged a variety of ribbon stacks BS1, BSs is. Each ribbon stacks BS1-BSs provides an inde ended unit represents, one possible configuration in <b>Fig.</b> 2 is indicated. There are four bands BD1-BD4 over stacked, each ribbon of four light contains waveguides LW1-PD4. The optical waveguides are within the ribbon in a soft plastic material is a embedded, which it controls the total band-shaped outer structure gives. Outside is a protective sheath SH1 mounted that about a rectangular, preferably square cross-section has. The protective sheath SH1 consists of extruded Ma material, the remaining spaces in the interior end, moderately with a lubricant (eg. as oily soft filling compound or powder) is filled. The structure of the protective sheath SH1 should be chosen so stiff that at a certain pressure externally there is no appreciable distortion. The Amount of pressure, which is taken as a basis in this case depends inter alia because of from which compressive stresses may in stranding occur.

It is also possible to work with individual bands stacks, the outside not have their own protective case. In this case it is expedient by other suitable means to a to ensure cohesion of the ribbon stack, for example, as by that the ribbon stacks BS1 (from the bands BD1-BD4) is wrapped with a thin film or that by soft elastic adhesive material interlayers between the individual NEN bands BD1-BD4 for the ribbon stacks BS1 a certain Cohesion is ensured.

When manufacturing the various ribbon stack are BS1-BSs deducted from corresponding supply reels and sammengeführt, being together - as shown by arrow PF angedeu tet - are stranded. It may be advantageous to the perform stranding the SZ process, ie with changing Lay directions. The outer contour of the stacks from the ribbon BS1-BSs existing cable core has a stepped, wherein in the present example, the individual stages as the Ab comprise measurements of half the ribbon stack. These steps arise from the fact that the successive layers, or Layers each similar to a masonry association with their butt are set against one another. This arrangement has the Advantage that the mobility guaranteed to a certain extent remains, the cable core as a whole, however, still a largely represents closed structure. Between each tome chenstapeln BS1-BSs can before small gaps or some play be seen, but only in the order of a few Pro producers of the external dimensions of a ribbon stack (example , between 1 and 5%). Thus, although the individual show Ribbon stack against each other a certain mobility, However, during a change of position, ie, tipping a represented individual ribbon stack in a currency other than the Position is prevented. It may be appropriate, between the each ribbon stack and between the cable core and the Outer shell, a lubricant (eg., In the form of a thixotropic Oil or a powder) to be provided.

In order to ensure even outdoors that none of the some extent against each movable else but location moderately fixed ribbon stack changes its position, ie For example, tipping is the inner contour of the cable sheath MI designed so that it by the outer contour of the tapes stack BS1-BSs formed cable core follows. Again, in again be provided Outside a small gap (z. B. in the order of 0.5 to 1 mm, or between 1 and 5% the external dimensions of the ribbon stack, whereby these Gap or this game must be set so that an order tilt or a position change of a ribbon stack in Outside is avoided. The cable core, which by the Ribbon stacks BS1-BSs is formed, then does not require Other facilities for holding together. It can only be useful in the preparation may - if not a continuous manufacturing process is applied - possibly outside a slight retaining spiral in the form of a thin plastic film or provide similar to the material forming the cable core bundle from the ribbon stack positionally in the desired order and to keep structure until the cable sheath is applied.

For the optical cable OC1, any kinds of outdoor mantles are used; in the present case is assumed, that the outer shell is constructed in two layers namely an outer cladding layer MA and an inner cladding layer MI having. In between can pull and / or support elements ZE be provided - - for example, a layer of aramid fibers. The inner cladding layer MI and the outer cladding layer MA are conveniently prepared by extrusion, wherein the are conveniently prepared by extrusion, wherein the Extrusion process it must be ensured that also stepped, matched to the structure of the cable core inside outline, is that achieved with corresponding gradations. Furthermore, it must be ensured that during the extrusion process, the soft extrudate of the inner cladding layer MI not to Ribbon stacks BS1-BSs adheres. This can, for example, through the use of appropriate lubricants in the range of reaches the ribbon stacks BS1-BSs existing cable core , whereby the lubricant as the separating layer between the Inner surface of the inner cladding layer and the MI Bändchensta PelN BS1-BSs acts and at the same time a corresponding gap results. Should be worked without overlay, then the mechanical separation between the extrusion process still hot inner wall of the inner cladding layer and MI Ribbon stacks BS1-BSs z. B. by applying a thin Film can be achieved on the outer contour of the cable core. At the Down stretching the stretching cone, the inner cladding layer MI forms, is then obtained by a corresponding pressure this film without additional further effort shaping the inner contour corresponding to the gradations, as used in the present outer contour of the cable core. Another manufacturing possibility consists in the use of profile extruders and Although with an extrusion die with stepped (corre accordingly the inner contour of MI) designed exit slit.

In <b>Fig.</b> 3 is a modification of the embodiment according to <b>Fig.</b> represented 1 wherein even the inside of the (here only single-shown) casing IM2 of optical Ka bels OC2 analog gradation having as <b>Fig.</b> 1, ie in accordance with the gradations of the respective ribbon stack, z. B. BS31-BS3m the only schematically drawn as squares are. For stiffening the entire structure and to a better Guide the ribbon stack are two approximately perpendicular kreu WA1 and WA2 provided collapsing between walls or webs, so that four sectors SE1-SE4 are formed. Overall, therefore, can 4-m-ribbon stack are housed. Such Struk ture is similar to that of a "chamber cable", which is why also beneficial way in the middle of a high tensile element CE in the field of Stege is shown WA1 and WA2. The at right angles kreu collapsing bridges WA1 and WA2 form the core element of Kammerka bels, the sector-shaped chambers SE1-SE4 longitudinally seen the cable helically extend. Each of these sectors SE1-SE4 in the preparation so ge with ribbon stacks fills that an outer contour is produced, while about the a circumscribed circle corresponds, but continuously ge classifies runs. The manufacturing process of such a cable structure proceeds as the preparation of a chamber cable, ie it is first selected from the two walls WA1 and WA2 and the central element CE existing core member by extrusion produced. Then the 4-m-ribbon stack are in the four sectors SE1-SE4 inserted in such a way that the already described stepped outside contour arises. The thus resultant structure is in a second operation, the cable coat or the innermost layer of the cable jacket by IM2 applied extrusion, said extrusion operation carried out is that the inner contour of the cladding layer to IM2 the stepped contour of the ribbon stack applies without me mechanically using this to connect. be a further possibility stands by profile extrusion. The covered with filling compound Bänd chenstapel are grouped together and sent directly to Spray head introduced. By appropriate design of the Ex trusionswerkzeuges is simultaneously the cable described creates cross-section. For regulier cables are required in the Extrusion line rotating off and winding provided. at SZ stranding is the exchange spin at fixed up and Unwinding generated by one or more Tristen.

The advantage of the arrangement according to <b>Fig.</b> 3 also in the fact that there is here by the web-like walls WA1 and WA2 an additional Liche guide for the respective multiple layers of the bands stack z. B. BS31-BS3n is ensured.