Termination or break-out devices for optical fibre cables are well known.

International Patent Application WO 95/07481, for example, discloses a break-out device in which fibres can be passed from a larger guiding tube to a number of smaller guiding tubes without significant light loss. International Patent Application WO 00/72073 discloses a break-out device which allows tubes and/or fibre cables of various diameters to be used.

Detents for terminating optical fibres are disclosed in International Patent Application WO 00/75704. These known detents are designed in particular for optical fibre cables having a flexible strength member, for example a strength member made of KEVLAR4D.

The detent firmly clamps the strength member so any pulling of the fibre cable will not result in the relatively fragile optical fibre being pulled.

With the increasing number of optical fibres used in telecommunication networks there is an increasing need for miniaturisation. As modern optical fibre cables contain large numbers of relatively thin constituent cables or cable units (for instance so-called"pigtails"), large numbers of those cables have to be terminated in a relatively small space. There is, therefore, a need for smaller components. In addition, a large degree of flexibility is desired as the number of cables terminated in a certain component (e. g. fibre management rack) may be varied over its lifetime.

It is therefore an object of the present invention to provide a termination unit for optical fibre cables which is suitable for cable units having a small diameter. It is another object of the present invention to provide a termination unit for optical fibre cables which provides effective strain relief. It is a further object of the present invention to provide a termination unit for optical fire cables which is both flexible and economical.

Accordingly, the present invention provides a termination unit for terminating optical fibre cables, the unit comprising a base member and at least one detent member, the base member having at least one pair of upstanding walls defining a space for accepting detent members, the at least one detent member having a groove extending between a front face and a rear face for accepting an optical fibre cable, wherein the detent member has a protrusion extending substantially transversely of the groove and a recess for accepting a corresponding protrusion of another, adjacent detent member.

By providing at least one pair of walls between which detent members may be accommodated, a large degree of flexibility is obtained as detent members may be added or taken away.

By providing a protrusion on each detent member which can lock into an adjacent detent member, a vastly improved structural rigidity is obtained in an extremely simple manner. This structural rigidity is particularly useful for transferring axial pull forces from the strength member and the associated detent member onto the adjacent detent members and the base member. As the structure is simple, it is very suitable for miniaturisation.

In a preferred embodiment, the walls of the base member are provided with ribs protruding into the space for accepting detent members. These ribs can be used to engage the detent members and to transfer any axial pull forces from the detent members to the ribs.

The use of engaging ribs in addition to interlocking protrusions provides an enhanced structural rigidity. In addition, the ribs may assist in positioning the detents between the walls. Preferably the detent members have notches for accommodating the ribs.

Although an array of interlocking detents may extend between a pair of upstanding walls, parallel to the base member, it is preferred that the upstanding walls and the detent members are designed such that the protrusion of a detent member accommodated in the space defined by a pair of walls extends substantially parallel to those walls. In this way, each array of detent members constitutes a column, and a plurality of such columns may be located

on a single base plate, thus providing the possibility to terminate a relatively large number of optical fibre cables.

Preferably the said protrusion extends away from the base member. In this preferred embodiment it is advantageous when the base member has a protrusion which can be accepted in a recess of a detent member. Alternatively the base member may be provided with a recess for accepting the interlocking protrusion of the detent closest to the base plate, when the protrusions face towards the base member.

Optical fibre cables which are to be terminated and/or broken out into constituent cable elements usually have a cable sheath from which a certain length is removed to facilitate the termination, exposing the constituent cable elements and any strength member. As a consequence, the end part of the cable has a smaller diameter than the rest of the cable. In order to be able to suitably accommodate such a cable end it is preferred that the groove for accepting an optical fibre cable has a wider part near the rear face and a narrower part near the front face of the detent member. The actual width of the groove will of course depend on the particular type of cable to be terminated. In the preferred embodiment, however, the wider part of the groove has a width of less than 4 mm, said width preferably being approximately 2 mm To better contain any terminated cable, it is preferred that the detent member is provided with a hinging cover for covering at least part of said groove. To facilitate the application of the detent member and to minimise the number of parts it is preferred that the cover is integral with the detent member. In a preferred embodiment the cover when closed, covers only the wider part of the groove. This allows the cable to be contained by enclosing only the part having a relatively large diameter, leaving the smaller diameter end free for any handling and/or manipulation.

To terminate a large number of optical fibre cables it is advantageous when the pairs of upstanding walls are arranged in at least two staggered rows. The staggered arrangement allows cables terminated in the front row of detent arrays to pass between the detent arrays

of a back row. Each array (preferably stack) of detent members may comprise 2,3,4,5 or even more detent members, although arrays of 3 detent members are preferred.

To guide the optical fibre cables to the detent members the base member may be provided with additional upstanding walls which are curved and have a bend radius which is equal to or greater than the minimum bend radius of the optical fibre cables.

The present invention further provides a kit-of-parts for providing a termination unit as defined above, a detent member for use in such a termination unit, and an organizer for optical fibres provided with such a termination unit. The base member of the termination unit may advantageously be integrated in a base member of the organizer.

The present invention will be further explained with reference to an exemplary embodiment illustrated in the accompanying drawing, in which: Figure 1 schematically shows, in perspective, a termination unit according to the present invention; Figure 2 schematically shows, in perspective, the termination unit of Fig. la as seen from the back; and Figures 3 a and 3b schematically show, in perspective, a detent member for use in the termination unit of Figure 1.

The termination unit 1 shown in Fig. 1 merely by way of non-limiting example has a base member 2 on which a plurality of detent members 3 is accommodated. The base member 2 shown in Fig. 1 has four pairs of upstanding walls 4. Each pair of walls 4 defines a space in which a number of (in the example shown: three) detents 3 are accommodated. A rib 12 protrudes from each wall 4 into the said space to engage the detents.

Each detent 3 has a groove 7 which extends in its longitudinal direction, from a front face 8 to a rear face 9 (see Fig. 3a). A hinging cover 14 covers part of the groove 7 to contain an optical fibre cable (not shown) accommodated therein.

According to an important aspect of the present invention, each detent 3 has a protrusion 10 which serves to interlock with another detent. As shown in Fig. 1, the protrusions or locking pins 10 extend in the same direction as the walls 4, away from the base member 2, transversely of the direction of the groove 7. This arrangement ensures that any pulling forces exerted on the strength member of an optical fibre cable accommodated in a groove 7 will be at least partially absorbed by any adjacent detents of the same stack. As a result, any strain is distributed over the detents of the stack. In addition, the interlocking protrusions 10 maintain the orientation of the detents.

Optical fibre cables (not shown) are guided in their paths towards the detents 3 by guide walls 16 which maintain a minimum bend radius. In the embodiment shown, the guide walls 16 and the walls 4 are integral parts of the base member 2.

In the embodiment shown, four stacks of detents 3 are accommodated in the base member 2, in two rows. The stacks of the back row are not positioned immediately behind those of the front row but are shifted over about half their widths. This staggered arrangement allows optical fibre cables terminated in the back row to pass between the stacks of the back row.

The view of Fig. 2 clearly shows the guide walls 16 for guiding any optical fibre cables (not shown) towards the grooves 7 in the rear faces 9 of the detents 3.

The detent 3 of Fig. 3 a is shown to have a longitudinally extending groove 7 for accommodating an optical fibre cable (for example a so-called"pigtail"). The groove 7 has a wider part 7a in which the sheathed part of the cable can be fitted and a narrower part 7b for accommodating that part of the cable from which the sheath has been removed. The groove parts 7a and 7b are separated by a transverse groove 17 in which the strength member of the cable can be accommodated. Preferably, the strength member emerging from the sheath in the wider groove part 7a is wound, through the transverse groove 17 (for example from left to right in Fig 3a), one or more times around the detent and then passed longitudinally through the narrower groove part 7b or over the (closed) cover 14.

Figures 3 a and 3b clearly show the notches 13 which serve to accommodate the ribs 12 shown in Fig. 1 and thereby to engage the walls 4. These notches 13, which allow the detents to slide up or down between the walls 4 while maintaining their engagement, transfer any pulling forces to the walls 4. In addition, the protrusions 10 transfer any pulling forces to other detents. To this end, the detents are provided with a recess 11 for accommodating the protrusion of another detent, as shown in Fig. 3b.

The cover 14 is shown to be integral with the detent 3, connected by so-called"living hinge"15. It is, of course, possible for the cover 14 to be hinged by a releasable hinge, or not to be hinged at all.

It will therefore be understood by those skilled in the art that the present invention is not limited to the embodiments shown and that many additions and modifications are possible without departing from the scope of the present invention as defined in the appending claims.