GB2274174A - Optical fibre splice closure - Google Patents

Abstract

An optical fibre splice closure comprises a base 10, a removable cover 20 and means for mounting a plurality of stacks 11 of optical fibre splice storage trays 24 side-by-side on the base. Preferably the base 10 is formed with a cable entry port 12, an inner annular guideway 14 extending around the cable entry port, an outer annular guideway 15 concentric with the inner guideway, and a plurality of separator elements 16 disposed between the two guideways, for separating a bundle of fibres into a plurality of individual fibres or groups of fibres. <IMAGE>

Description

OPtical Fibre Splice Closure This invention relates to an optical fibre splice closure.

Optical fibres are widely used in telecommunications systems such as telephone networks. Typically a cable carrying a large number of optical fibres connects a particular subscriber area to an exchange. These cables are spliced to other cables in an optical fibre splice closure, these other cables being connected to other locations. Individual fibres or pairs of fibres are fed from the closure to subscribers.

These fibres are spliced inside the closure to the cable from the exchange. The splices between the optical fibres are stored in splice trays housed inside the closure. Unused fibres in the cables are also stored inside the closure.

United Kingdom Patent No. 2 225 442 discloses an optical fibre closure comprising a plurality a circular splice trays mounted in a stack, the trays being mounted at an acute angle to the longitudinal axis of the closure. With this arrangement, there is a limit to the number of trays which can be included in the stack, otherwise the closure would be undesirably long: the optical fibres enter the closure through a base at one end and substantial lengths of cable would be needed to connect to the uppermost splice tray. Fibres are carried in protective tubes of approximately 3mm in diameter, therefore a bundle of 96 tubes feeding 48 trays would be approximately 60mm in diameter. It will be appreciated that such a large bundle would be unmanageable inside the closure.

Splices between optical fibres are formed using a machine which fusion welds the ends of the fibres together.

It would be awkward for an engineer to splice fibres arranged in trays stacked in large columns: the engineer would have to stand and sit several times whilst holding the heavy machine, in order to splice cables in the uppermost trays.

When new subscribers are added to the telephone network, further splice trays or groups (modules) of splices trays need to be added. Hitherto, this has been achieved by providing long closures having spaces so that splice trays or modules can be added to the stack. However, as previously mentioned it is not desirable to have long stacks of splice trays.

In accordance with this invention as seen from a first aspect, there is provided an optical fibre splice closure comprising a base, a removable cover and means for mounting a plurality of stacks of optical fibre splice storage trays sideby-side on the base.

Thus, because the stacks of splice trays are arranged side-by-side, the length of the closure is small compared to conventional closures arranged to house a similar number of trays in a single stack.

Preferably the trays in each stack are supported on a member which extends upwardly from the base. Thus extra trays may be added by connecting new trays to vacant positions on the support member. Alternatively extra stacks (modules) of trays may be added alongside existing stacks, by connecting a new support member to the base.

Preferably the mounting means is arranged to mount the stacks of trays such that their axes extend parallel to a longitudinal axis of the closure.

Preferably the axes of the stacks are arranged on a cylinder which extends co-axially with the axis of the closure.

The splice trays are preferably mounted at an acute angle to the axis of their respective stack.

The upper surface of each splice tray is preferably directed radially outwardly of the closure, so that it is easy for an engineer to remove trays from any of the stacks.

Further because the height of the stack is small, then an engineer can mount the closure on a bench and perform splicing operations whilst he is sitting down. The size of the bundle of fibres to each stack (modules) is reduced compared to conventional closures because there are less trays in the stack.

Optical fibre splice closures comprising large numbers of splice trays contain large amounts of optical fibres. These optical fibres have to be securely and neatly arranged inside the closure so as to facilitate the maintenance and fitting of new fibres during the life of the closure.

Optical fibre cables entering the closure may be split or separated into single or pairs of fibres which connect to individual subscribers. It is important that the point at which such cables split can be easily identified so that fibres can be located and traced inside the closure. Furthermore cables and fibres entering and leaving the closure may have varying lengths, and it is important that the closure is able to accommodate such varying lengths of fibres.

Thus in accordance with this invention as seen from a second aspect there is provided an optical fibre splice closure comprising a base, a cable entry port formed in the base, an inner annular guideway extending around the cable entry port, an outer annular guideway concentric with the inner guideway and a plurality a separator elements for separating a bundle of fibres into a plurality of individual fibres or groups of fibres, wherein the separator elements are disposed between said inner and outer annular guideways.

Preferably the separator elements are spaced apart on a line which extends concentrically with said guideways.

Cables or portions of the cables entering the closure can be wound around the inner guideway and then deflected outwards to an adjacent separator element which divides the cable into single fibres or pairs of fibres. The portions of the divided cable are wound around the outer guideway and then branched up to a splice tray module. Inside the splice trays the fibres are spliced to other fibres entering the closure.

Preferably each separator element extends at an acute angle between the inner guideway and outer guideway, so that the fibres follow an optimum path as they pass between the inner and outer guideways.

Preferably the separator elements are curved so that fibres may be branched tangentially from the inner guideway and join tangentially the outer guideway.

The separator elements are preferably rotatably mounted so that their angle between the inner and outer guideways can be altered.

Preferably each separator element has means on its opposite ends for respectively receiving protective tubes of incoming and outgoing fibres.

Preferably the opposite ends of each separator element are provided with means for engaging said protective tubes so as to retain the tubes securely in place.

Preferably the central portion of each separator element is hollow so that incoming and outgoing fibres can be traced inside the element.

Preferably a transparent cover is provided for each separator element so that bare fibres inside the separator element are protected.

An embodiment of this invention will now be described by way of example only and with reference to the accompanying drawings, in which: FIGURE 1 is a perspective view of a optical fibre splice closure in accordance with this invention; FIGURE 2 is a plan view of the optical fibre splice closure of Figure 1, with its cover removed; FIGURE 3 is a sectional view along the line III-III of Figure 2; FIGURE 4 is a part side view taken in the direction of arrow A shown in Figure 3; FIGURE 5 is a sectional view along the line V-V of Figure 3; FIGURE 6 is a sectional view along the line VI-VI of Figure 5; FIGURE 7 is a simplified plan view of the base of the optical fibre splice closure of Figure 1; FIGURE 8 is a sectional view of a portion of the base of Figure 7; FIGURE 9 is a rear view of a separator element or manifold of the base of Figure 7; ; FIGURE 10 is a plan view of the manifold of Figure 9; FIGURE 11 is a front view of the manifold of Figure 10; FIGURE 12 is a sectional view along the lines XII-XII of Figure 11; FIGURE 13 is a sectional view along the lines XIII-XIII of Figure 11; FIGURE 14 is a sectional view along the line XIV-XIV of Figure 11; and FIGURE 15 is a sectional view along the line XV-XV of Figure 11.

Referring to Figure 1 of the drawings, there is shown an elongate optical fibre splice closure comprising a base 10 and a removable cover 20. Optical fibre cables enter and leave the closure through the base 10 via cable entry ports 12,13, to which they are sealed by heat-shrinkable sleeves or other means.

A plurality of splice trays are mounted in four modules 11 each containing a stack of e.g. 48 splice trays. The modules 11 are arranged side-by-side, with their axes on a cylinder which is co-axial with the axis of the closure.

Referring to Figures 2 and 3, each module 11 comprises a plurality of circular trays 24 mounted on a support. The support comprises an upright pillar 25 mounted to the base 10, from which a plurality of flexible leaves (not shown) project downwardly. The trays 24 are supported on respective leaves and are located and retained in place by projections (not shown) on the upper face of each leaf adjacent its lower edge.

A tray can be removed from the module 11 by pivoting the tray above upwardly so that the lower tray can be lifted over its retaining projections. The trays in each module 11 are inclined at an acute angle to the longitudinal axis of the closure so that their upper surfaces face radially outwards.

With this arrangement, a closure of a smaller diameter can be used than if the trays were oriented at 900 to the closure axis. A space is left between the modules 11 and the inner wall of the cover 20 so that fibre bundles 19 can pass from the base 10 to the modules 11. The trays 24 have fibre entry ports and means for securely mounting the fibre splices inside the trays.

The base 10 is generally circular in section and the cable entry port 12 projects downwardly from its centre. The smaller cable entry ports 13 are arranged circumferentially around the central port 12. In use, optical fibre cables 30, say carrying signals from a telephone exchange, enter the closure through the central port 12.

Referring to Figures 4 to 6, bundles 22 of e.g. 8 fibres emerge from the ends of the cables 30. Protective tubes (not shown) may be fitted over these bundles 22 in order to protect the fibres. However, in some instances the fibres may be contained in protective tubes within the cables 30. The bundles 22 of fibres are wound in one sense e.g. clockwise around the inner portion of the base, concentrically with the central cable entry port 12. The windings form an inner track 14 of fibres carrying input signals. Unused fibres 21 emerging from the input cable 30 may be stored along the axis of the closure.

Each bundle 22 of fibres within the inner track 14 has to be separated into single fibres or pairs of fibres to feed subscribers: for this purpose a plurality of separator elements or manifolds 16 are spaced apart along a concentric line around the central cable entry port 12. The manifolds 16 are rotatably mounted on respective pins 31, and are arranged for movement along their respective pins 31. The fibre bundles on the inner track 14 are spiralled radially outwards through an adjacent manifold 16. It will be appreciated that fibre bundles 22 of different lengths can be accommodated inside the casing by winding them around the inner track 14. Short bundles 22 may be fed directly to a manifold 16 and longer bundles 22 may be wound several times around the inner track 14 before being fed to a manifold 16.The manifolds 16 may separate fibre bundles 22 into any number of fibres or pairs of fibres 33. The output fibres 33 from the manifold 16 are contained in protective tubes which are wound in the same sense around an outer track 15. The pivotable mounting of the manifolds 16 allows the fibres to pass from the inner track 14 to the outer track 15 along an optimum path, to avoid exceeding the maximum bending radius of the fibres. The fibres 33 in the outer track 15 are fed up in bundles 19 to respective modules 11 of splice trays. Inside the splice trays 24, the fibres are spliced to fibres which feed to subscribers. These subscriber fibres are also contained within the bundles 19 and the inner and outer tracks 14,15. Cables feeding to subscribers may be connected to the smaller cable entry ports 13 arranged around the central port 12.The manifolds 16 may combine several subscriber fibres from various splice trays into one cable.

Of course, the input or subscriber fibres may pass between the inner and outer tracks 14,15 without being connected via a manifold 16.

The manifolds will now be described in greater detail with reference to Figures 7 to 15 of the drawings. Each manifold 16 comprises an arcuate body 43 mounted vertically on a pin 31. The pins 31 extend upwardly from a frame 34 mounted to the base 10. The body 43 of each manifold 16 is provided with a vertical mounting hole 36 having a diameter larger than that of the pin 31, so that the manifold 16 is free to rotate about or slide along the pin 31. Several manifolds 16 may be mounted on each pin 31, and a retainer 32 may be fitted to the pin to prevent the manifolds 16 from being dislodged. An aperture is formed in an end wall of the manifold 16 for receiving the fibre bundle 22 to be split. The body 43 is tray-like in section so that the fibres can splay out inside the body.The opposite end wall of the body 43 is formed with a plurality of apertures through which the split fibres 33 leave the manifold 16. Internal dividing walls 41 diverge from the centre of the body towards the end wall having a plurality of apertures. The dividing walls 41 serve to separate the fibres e.g. 40 inside the manifold 16. The apertures in the end walls preferably taper towards the outside of the body, so as to retain the protective tubes disposed around the fibres 22,33 entering and leaving the manifold 16. The tubes are preferably provided with tapering ends 42 which engage into the tapering apertures. However it will be appreciated that the tubes have to be pre-assembled to the manifolds before the fibres are fitted.

A transparent cover 37 fits onto the outside curved surface of the body 43, so as to enclose the fibres e.g. 40 inside the manifold. The cover 37 may be fitted by way of fastenings 38 disposed at each corner of the manifold.

Alternatively the cover may be self-adhesive so that it can be adhered to the body.

The arrangement of the fibres inside the closure makes it easy for an engineer to identify and trace cables through the closure.

Whilst the trays 24 have been described as housing splices between fibres, some of them may include optical splitters (i.e. feeding a signal from one fibre into two or more branches).

Claims (12)

1) An optical fibre splice closure comprising a base, a removable cover and means for mounting a plurality of stacks of optical fibre splice storage trays side-by-side on the base.

2) An optical fibre splice closure as claimed in claim 1, in which the mounting means comprises a plurality of members, one for each said stack, extending upwardly from the base and arranged to support a plurality of said trays.

3) An optical fibre splice closure as claimed in claim 1 or 2, in which the mounting means is arranged to mount the stacks of trays such that the axes of said stacks extend parallel to a longitudinal axis of the closure.

4) An optical fibre splice closure as claimed in claim 3, in which said mounting means is arranged to mount the stacks of trays with the axes of said stacks on an imaginary cylinder coaxial with the axis of the closure.

5) An optical fibre splice closure as claimed in any preceding claim, in which the mounting means is arranged to mount the trays at an acute angle to the axis of their respective stack and such that the upper surface of each tray is directed radially outwardly of the closure.

6) An optical fibre splice closure comprising a base, a cable entry port formed in the base, an inner annular guideway extending around the cable entry port, an outer annular guideway concentric with the inner guideway, and a plurality of separator elements for separating a bundle of fibres into a plurality of individual fibres or groups or fibres, the separator elements being disposed between said inner and outer annular guideways.

7) An optical fibre splice closure claimed in claim 6, in which said separator elements are spaced apart along a line extending concentrically with said guideways.

8) An optical fibre splice closure as claimed in claim 6 or 7, in which each separator element extends at an acute angle between the inner and outer guideways.

9) An optical fibre splice closure as claimed in claim 8, in which each separator element is curved so that fibres may be branched tangentially from the inner guideway and join tangentially the outer guideway.

10) An optical fibre splice closure as claimed in any one of claims 6 to 9, in which each separator element is rotatably mounted about a vertical axis.

11) An optical fibre splice closure as claimed in any one of claims 6 to 10, in which each separator element is arranged at its opposite ends for receiving respective protective tubes of incoming and outgoing fibres.

12) An optical fibre splice closure substantially as herein described with reference to the accompanying drawings.