WO2014009708A1

WO2014009708A1 - Multiple occupancy building optical fibre routing

Info

Publication number: WO2014009708A1
Application number: PCT/GB2013/051806
Authority: WO
Inventors: David Stockton; Kim Samuel Howard Leeson
Original assignee: Miniflex Limited
Priority date: 2012-07-09
Filing date: 2013-07-09
Publication date: 2014-01-16
Also published as: GB201212188D0

Abstract

This invention relates to the routing of optical fibres (5) in a multiple occupancy building with individual optical fibres (55, 55') extracted from an optical fibre cable for routing into units at different locations within the building. The surface-mountable junction box (10) comprises a housing (12) with optical fibre mounts (18,18') and ports (9, 9') for routing into and out of the housing the optical fibre cable (4). A surface-mountable face of the housing has a pair of optical fibre routing apertures (31, 31'). The arrangement of the mounts (18, 18') and apertures (31, 31') is symmetric with respect to each other about a plane (32) that extends at right angles to a routing line (33) of the optical fibre cable (4) between the ports (9, 9') such that a length of optical fibre (55, 55') extracted from the optical fibre cable and/or protective tubing (37) for the extracted optical fibre can be routed through the mounts in one of two directions between the optical fibre cable (4) and out of one or the other of the optical fibre routing apertures (31, 31').

Description

Multiple Occupancy Building Optical Fibre Routing

BACKGROUND a. Field of the Invention

This invention relates to the routing of optical fibres in a multiple occupancy building comprising a plurality of units at different locations within the building, in which a bundle of optical fibres is carried within an optical fibre cable that extends around the building with individual optical fibres extracted from the cable at different locations for routing into the units. In particular, the invention relates to a method of routing optical fibres in a multiple occupancy building and also to a surface-mountable junction box associated with each unit inside of which at least one optical fibre is extracted from the cable. Furthermore, the invention also relates to a system of routed optical fibres in a multiple occupancy building having a plurality of units at different locations within the building. b. Related Art A multiple occupancy building, for example a multiple dwelling unit such as a block of flats or a business premises having a plurality of businesses under one roof, may be served by an optical fibre cable containing a plurality of individual optical fibres. In this specification, each such unit or premises will be referred to as a "unit". Each optical fibre will normally be physically protected by buffering or cladding to provide mechanical isolation, protection from physical damage. Such buffering or cladding can also be marked or coloured to allow for fibre identification. In this specification, the term "optical fibre" includes both bare optical fibres and buffered optical fibres. The cable itself will then normally comprise a number of protective layers to guard each of the buffered optical fibres inside the cable.

To minimise the number of splices that may be needed, one common way of routing the optical fibres is to open up the cable so that there is a cut-out in the cable protective outer covering, for example by cutting a slice through one side of the cable protective outer covering, which may be a sheath comprising multiple layers, in order to expose the optical fibres, and this is done at a plurality of locations throughout the multiple occupancy building where one or more individual optical fibres are to be connected to each unit. Each such location where the cable is opened up will be within a junction box which then provides protection around the opened cable and also helps to protect the optical fibres which have thereby been exposed.

It is necessary to provide a usable length of optical fibre inside each junction box, and during installation this is done by cutting the same optical fibre a subsequent location where the cable has been opened up, for example at the next junction box through which the cable has been routed around the building. The cut optical fibre is then pulled back through the cable to the location where the connection for that optical fibre is to be made within the unit at that location.

As is customary practise, although some of the pulled back optical fibre may then be cut off and discarded, a length of at least a metre may be retained and coiled up within the junction box, after an optical fibre connector has been terminated and joined to the end of the cut optical fibre. The optical fibre connector is then secured inside the junction box, for example in a clip fitting. It is then only a matter of routing an optical fibre cable between the location within the unit where the optical fibre is to be used and the junction box, where a mating optical fibre connector is connected to the connector at the end of the terminated optical fibre cable.

This system provides routing flexibility in many situations, but is inconvenient in a number of respects. It is necessary for the junction box to have space for the coiled spare length of optical fibre, and there is a limit to how tightly any optical fibre can be coiled without introducing excessive optical losses or risking damage to the optical fibre. This limits how small the junction box can be made. Space must also be provided within the junction box for the mated optical fibre connectors, and while this may not be an issue when just one optical fibre connection is provided to the unit, there will be a limit to how many of such connectors can be housed within the junction box when multiple optical fibre connections are to be provided to the unit. Even if only one connection is provided at the outset, it may be necessary to oversize the junction box to provide the capability to add new optical fibre connections in the future. Finally, to allow for future expansion for additional optical fibre connections, it may be necessary to provide a conduit from within the unit to the junction box which is large enough to accept passage of a terminated optical fibre having a connector at each end when the new connection is being made.

It is an object of the present invention to provide a method of routing optical fibres in a multiple occupancy building, and also to a junction box, which addresses these issues.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a surface-mountable junction box for use in the routing of optical fibres bundled in an optical fibre cable, the junction box comprising a housing and inside the housing a first mount and a second mount for holding an optical fibre extracted from the optical fibre cable and optionally also for holding protective tubing for said extracted optical fibre, the housing comprising:

a first port and a second port, for routing the optical fibre cable into and out of the housing, said first and second ports defining a routing line of the optical fibre cable between said first and second ports; and

a surface-mountable face on an external surface of the housing, said face having a pair of optical fibre routing apertures therein namely a first optical fibre routing aperture and a second optical fibre routing aperture, for routing out of the housing an optical fibre extracted from the optical fibre cable and optionally also protective tubing for said extracted optical fibre;

wherein the arrangement of said first and second mounts and said first and second optical fibre routing apertures is such that:

a length of optical fibre extending into the housing through the first port and extracted within the housing from the optical fibre cable can be routed through said first and second mounts in a first direction to exit the housing through the first optical fibre routing aperture; and

a length of optical fibre extending into the housing through the second port and extracted within the housing from the optical fibre cable can be routed through said first and second mounts in a second direction to exit the housing through the second optical fibre routing aperture, the first direction being opposite to the second direction between said first and second mounts.

According to a second aspect of the invention, there is provided a system of routed optical fibres in a multiple occupancy building having a plurality of units at different locations within the building, the system comprising a plurality of surface- mountable junction boxes including a first junction box and a second junction box, and an optical fibre cable having a protective outer covering and within said covering a bundle of said optical fibres, each junction box being located in proximity with and being associated with one of said units and the optical fibre cable being routed through the building and running through said junction boxes, wherein said first and second junction boxes are according to the first apect of the invention, and at least one optical fibre in the optical fibre cable does not extend between said first and second junction boxes, but is extracted from the optical fibre cable from within the first junction box and routed through said first and second mounts to exit the first junction box through the first optical fibre routing aperture.

According to a third aspect of the invention, there is provided a method of routing optical fibres in a multiple occupancy building using a plurality of surface- mountable junction boxes including a first junction box and a second junction box, each junction box having an external housing and said housing having a first port, a second port and a surface-mountable face, said surface-mountable face having therein at least one optical fibre routing aperture, and the building comprising a plurality of units at different locations within the building, the method comprising the steps of:

i) routing an optical fibre cable around the building, the optical fibre cable comprising a protective outer covering and within said covering a bundle of said optical fibres;

ii) running the optical fibre cable through said first and second ports of each of said junction boxes whereby the optical fibre cable passes through each of said junction boxes, each junction box being associated with one of said units and each junction box being mounted by means of said surface-mountable face on a mounting surface in proximity with said unit whereby said optical fibre routing aperture faces said mounting surface;

iii) exposing within each of said first and second junction boxes between said first and second ports the bundle of said optical fibres;

iv) selecting and cutting at least one of said optical fibres where said optical fibre is exposed at the second junction box;

v) at the first junction box where the bundle of said optical fibres is exposed, pulling back through the optical fibre cable said cut optical fibre to gain access at the first junction box to the intervening length of said cut optical fibre between the first and second junction boxes;

vi) routing the intervening length of said pulled back optical fibre out of the first junction box and into said unit, said intervening length of pulled back optical fibre passing through said optical fibre routing aperture; and

vii) terminating said intervening length of pulled back optical fibre within said unit. In the case where the surface-mountable face of the housing has a first optical fibre routing aperture and a second optical fibre routing aperture, step vi) may include passing said intervening length of pulled back optical fibre through either the first optical fibre routing aperture or the second optical fibre routing aperture depending on the direction in which the cut optical fibre has been pulled back from the second junction box.

The optical fibre may be exposed by providing a cut-out through the protective outer covering within each of the first and second junction boxes.

The method described above may optionally include the step of removing a removable cover over the optical fibre routing aperture prior to passing the pulled back optical fibre through the optical fibre routing aperture.

When each of the surface-mountable junction boxes is according to a first aspect of the invention the method may comprise, when the cut optical fibre has been pulled back from the direction of the second port, the step of routing the intervening length of pulled back optical fibre through the first and second mounts in a first direction to exit the housing through the first optical fibre routing aperture, which is preferably closer to the second port than to the first port. Alternatively, the method may comprise, when the cut optical fibre has been pulled back from the direction of the first port, the step of routing the intervening length of pulled back optical fibre through the first and second mounts in a second direction to exit the housing through the second optical fibre routing aperture, which is preferably closer to the first port than to the second port. In this case, the first direction is opposite to the second direction between the first and second mounts. Each optical fibre may optionally be provided with one or more protective outer layers, referred to as buffering. The term "optical fibre" as used herein therefore comprises any type of optical fibre both with and without such buffering.

By running the intervening length of the optical fibre into the unit, instead of cutting and terminating the intervening length for connection to an optical fibre connector mounted inside the junction box, it is possible to save a significant amount of time and cost during installation of the terminated optical fibre in the unit. The intervening length can then be routed to a convenient location within the unit where the optical fibre is terminated, for example with an optical fibre connector at the end of the intervening length (which may, optionally, be trimmed to a convenient length) or to an optical fibre connection socket, which may be inside a surface-mounted faceplate. At the same time, the junction box need not be so large as prior art junction boxes used with pulled back optical fibres, as it is no longer necessary to coil and store within the junction box a spare length of optical fibre as any spare length can be coiled and stored within the unit, nor is it necessary to provide mounts and space for a pair of mated optical fibre connectors within the junction box. This makes it easier to locate the junction box within the space that may be available within the building, and also makes any visibly mounted junction box, for example one that may be mounted in common areas such as corridors, less visibly noticeable.

The protective outer covering may comprise one or more layers, for example having a tough and relatively hard outer layer, which may have bend limiting properties, and a relatively softer and more flexible inner layer. The outer covering may also comprise an inner, low friction lining.

The protective outer covering may be manufactured and supplied for use in routing optical fibres around the building with the optical fibre bundle already inside the covering. Alternatively, the protective outer covering may be a hollow tube that is run through the building empty of optical fibres. In this case, the protective tube may itself have a low friction inner layer to facilitate later installation of the optical fibre bundle by pushing or blowing the fibre bundle down the length of the tubing. The protection tube could also have a pre-fitted pulling member to which the optical fibre bundle may then be attached and pulled through the protective tube. In any case, the optical fibres may be inserted into the protective tube after this has been installed in the building. Therefore, in steps i) and ii) of the method according to the third aspect of the invention, the invention is not limited to the installation of a fully assembled cable, prior to the cutting into the protective covering of step iii), but also extends to the case in which the optical fibre cable is not fully assembled at the time the protective covering is routed around the building and run through the junction boxes. Preferably, the intervening length of the pulled back optical fibre is inserted into an optical fibre protection tube, which may be a protective bend-limiting tube. The tube together with the inserted optical fibre is then routed from within the junction box to a convenient location within the unit through the optical fibre routing aperture.

In a preferred embodiment of the invention, the junction box has on the inside a first mount and a second mount, the first mount being sized to grip and hold the optical fibre and the second mount being sized to grip and hold the optical fibre protection tube. The pulled back optical fibre is then joined to or inserted into the first mount and the optical fibre protection tube holding the optical fibre is then joined to or inserted into the second mount. Each junction box has an external, or outer, housing with an optical fibre routing aperture being provided through the housing. A pair of ports is also provided in the housing into and out of which the optical fibre cable is run, both ports being separate from the optical fibre routing aperture. The method therefore comprises the step of routing the cut optical fibre out of the junction box through the optical fibre routing aperture.

In a preferred embodiment of the invention, the cutting through of the protective outer covering involves cutting a slice through part of the covering on one side of the optical fibre bundle, while leaving the opposite side of the bundle intact. A portion of the protective covering then extends continuously through the junction box between the pair of ports in the housing.

In a preferred a embodiment of the invention, the surface-mountable junction boxes may, for example, be for mounting on a wall surface of the building, each of the junction boxes having a surface-mountable face which has an optical fibre routing aperture therein. The first junction box is then mounted onto a surface of the unit such that the optical fibre routing aperture faces the mounting surface. Then, the pulled back optical fibre can be routed out of the junction box by passing this through the optical fibre routing aperture, following which the optical fibre is routed into the unit, for example through a passage through the mounting surface. When the optical fibre leaving the junction box is held within a protective sleeve, the protective sleeve may be passed through the mounting surface, for example a building wall, either inside a conduit provided for this purpose, or simply through a hole drilled through the wall.

Preferably, at least one of the first and second optical fibre routing apertures is provided with a removable cover for covering the aperture when not in use for routing said length of optical fibre out of the housing.

In general, the first and second ports will define a routing line of the optical fibre cable between the first and second ports. Preferably, the arrangement of the first and second mounts and the first and second optical fibre routing apertures is symmetric with respect to each other about a plane that extends at right angles to this routing line.

This symmetric arrangement provides several benefits in use. For example, the optical fibre cable may be routed either from left to right or from right to left (depending on the location of a connected network device), as viewed relative to a position in front of a surface (e.g. a wall surface) to which the junction box may be fixed. It is then not necessary to invert the orientation of the junction box depending of the left-right or right-left routing of the optical fibre cable. Each junction box can then be mounted the same way up, which makes it easier for the installer to get the job right the first time. A similar argument will apply to a vertically running cable. It is therefore not necessary to provide to the installer two types of junction box, one for each of the two possible orientations relative to the direction of routing of the optical fibre cable.

Alternatively, this symmetry of mounts and optical fibre routing apertures inside the housing means that the housing can be rotated 180 ° relative to the direction along which the optical fibre cable is routed, without changing the functionality of the junction box. It is therefore not possible to mount the junction box in an incorrect orientation, as long the ports in the junction box through which the optical fibre cable enters and exits the junction box are correctly aligned relative to the desired route of the optical fibre cable.

In a preferred embodiment of the invention, the junction box comprises inside the housing a third mount. The third mount is preferably positioned midway between the first mount and the second mount.

The third mount preferably has a recess with an engagement feature which is symmetric in both the first and second directions for holding the extracted optical fibre or for holding protective tubing inside of which is held the extracted optical fibre.

This third mount may be used as a further mount to stabilise or locate the optical fibre and/or protective tube surrounding the optical fibre, but preferably is used to secure an end connection on the protective tube, so that this tube cannot be inadvertently be pulled out of the junction box.

Preferably, each of the mounts has a first mounting portion and a second mounting portion, the first mounting portion being sized to grip and hold the extracted optical fibre and the second mounting portion being larger than the first mounting portion and being sized to grip and hold the protective tubing for the extracted optical fibre. A first one of the two mounts may be configured to hold the extracted optical fibre in the first mounting portion, and a second one of the two mounts may be configured to hold the protective tubing in the second mounting portion. Each of the first and second mounts may be provided in a post within the housing, the second mounting portion being provided in a first recess in a top end of the post and the first mounting portion being a second recess in a base of the first recess.

The first mounting portion may comprise an elongate slot for holding a plurality of the optical fibres extracted from the optical fibre cable.

The ports preferably define a routing line is along a straight axis of the cable as the optical fibre cable passes through the housing.

Both the first and second mounts may lie on a first side of the routing line or axis and the first and second optical fibre routing apertures may both lie on a second side of the routing line or axis the optical fibre cable through the housing. The first side is then opposite to the second side relative to the routing line or axis. In a preferred embodiment of the invention, the optical fibre cable and/or its protective outer tubing, then loops first on one side of the routing line or axis away from the routing line or axis for connection to the first and second mounts, and optionally also the third mount, and then loops back towards the routing line or axis and then bends over the optical fibre cable and into one of the optical fibre routing apertures in the housing. An advantage of this arrangement is that the bend radius of the optical fibre cable can be kept within practical limits while at the same time limiting the lateral extent of the housing on both the first and second sides of the routing line or axis.

The housing may have a base and a cover, the base having the surface- mountable face, and the cover being secured to the base. In a preferred embodiment of the invention, the cover is removably fixed to the base, and the cover can be completely separated from the base when it is desired to gain access within the junction box. It would, however, also be possible for the cover to remain captive to the base when opened up, for example by means of one or more hinges between the cover and base, allowing the cover to pivot open when it is desired to gain access within the junction box. In a preferred embodiment of the invention, each port is provided in a seam between the base and cover. In a preferred embodiment of the invention, the protective outer covering of the optical fibre cable has a cut-out within each of the first and second junction boxes to expose the bundle of optical fibres. The cut-out may be provided using techniques which are known to those skilled in the art, such as by cutting through the covering, for example with a sharp knife or a tool specially designed to cut a limited depth into the covering so as to avoid inadvertent cutting of the optical fibre bundle. In a preferred embodiment of the invention, the extracted optical fibre extends continuously from within the junction box to within the unit with which the junction box is associated. The extracted optical fibre may then be terminated within said unit. As explained above, this may be achieved by cutting at least one of the optical fibres where the bundle is exposed within the second junction box, and then pulling back the, or each, cut fibre to the first junction box, and then using some or all of the intervening length of the, or each, optical fibre to run the, or each, optical fibre continuously from the bundle where this is exposed within the first junction box to the inside of the unit associated with the first junction box. There is then one or more optical fibres not cut at either the first or second junction boxes which extend continuously along the length of the optical fibre cable between the first and second junction boxes and which may therefore be routed within the optical fibre cable to third or subsequent junction boxes.

In this system, at least the first junction box, and preferably all of the junction boxes, are according to the first aspect of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described, by way of example only, and with reference to the accompanying drawings, in which:

Figure 1 is a schematic plan view of part of the interior of a multiple occupancy building having a plurality of units at different locations within the building, represented by doors, above which has been routed a surface- mounted optical fibre cable that extends through a plurality of surface- mounted junction boxes according to a preferred embodiment of the invention;

Figure 2 is a plan view of one of the surface-mounted junction boxes and the optical fibre cable of Figure 1 ;

Figure 3 is a side view of the surface-mounted junction box, taken along line Ill-Ill of Figure 2, showing also how an optical fibre protection tube containing an optical fibre exits the junction box and passes through a wall towards the unit;

Figure 4 is a plan view similar to that of Figure 2, but with a removable cover of the junction box having been removed to show how optical fibres are routed inside the junction box, and with an enlarged portion showing one of two similar mounts for holding either an optical fibre or a protective tube containing the optical fibre;

Figure 5 is a cross-section through a first one of the mounts of the junction box, taken along line V-V of Figure 4, showing how the optical fibre is held within a slot provided in a base of a recess at a top end of a post; and

Figure 6 is a cross-section through a second one of the mounts of the junction box, taken along line VI-VI of Figure 4, showing how the protective tube containing the optical fibre is held within the recess at a top end of a post.

DETAILED DESCRIPTION

Figure 1 schematically shows part of the interior of a multiple occupancy building, indicated by a dashed outline 1 , having a plurality of units at different locations within the building, which for convenience only are represented symbolically by doors 2, 2'. Above each door is routed a surface-mounted optical fibre cable 4. The exact location of the cable is not relevant to the invention, but the cable will most commonly be visible for much of its length, as opposed to being concealed in ducting, and may for reasons of convenience and economy be routed in communal spaces such as a corridor, particularly where optical fibres are to be extracted from the cable and routed inside different units 2, 2'.

The cable 4 is connected to a network device (N) 6, which may be part of any type of data storage or computer based network and which may be internal or external to the building, for example a file server or the public switched telephone network. The network device (N) 6 may be connected to one or more optical fibres at either end of the cable, i.e. at one of two locations, either a first location 7 or a second location 8. The second location 8 is shown in dashed outline in Figure 1 as the other drawings of Figure 2 to 6 relate particularly to the network device being at the first location 7. The optical fibre cable 4 extends through a plurality of similar surface-mounted junction boxes, two of which 10, 10' are shown. There may, in general, be other such junction boxes through which the cable runs on either side of the two shown. The junction boxes are each shown as being positioned on a mounting surface 20, which in this example is provided by a wall 30 above a corresponding door, and although this may be a convenient location in some buildings, for example a residential apartment block, Figure 1 is just a schematic representation to show that each junction box 10, 10' is associated with a particular unit, and the junction boxes may, of course, be mounted at any suitable location and on any suitable surface relative to the corresponding unit 2, 2'. A first one of the junction boxes 10 is relatively nearer the network device 6 shown in solid outline and a second one of the junction boxes 10' is relatively farther from this network device. As the junction boxes 10, 1 0' are preferably identical, only the first junction box 10 will be described in detail below, with reference to Figures 2 to 6.

The cable 4 has a protective outer covering in the form of a sheath 3 inside of which is a bundle 23 of colour-coded buffered optical fibres 5, each of which may have an outer diameter of about 900 μιη. There will be a plurality of fibres connected to the network device 6, but the exact number is not pertinent to the invention. The protective sheath 3 may be 8 mm in diameter, in which case there will be about 4 to 6 buffered optical fibres inside the cable, or the protective sheath may be 10 mm in diameter, in which case there will be about 6 to 8 buffered optical fibres inside the cable, or the protective sheath may be 12 mm in diameter, in which case there will be between about 8 to 10 buffered optical fibres inside the cable.

Each junction box 10 has an external housing 12. The housing 1 2 is formed in two main parts, having a surface mountable base portion 14 and a cover 1 6 which is removably fixed to the base portion by means of three screws 17. The base portion 14 and cover 1 6 meet along a seam 15 which is interrupted on opposite left and right sides of the housing as drawn in Figure 2 by two semi-circular rims which together form a first port 9 and a second port 9'. Inside each port is a cylindrical rubber split sleeve 1 1 , 1 1 ' that holds the cable securely where this enters and exits the housing 1 2. This arrangement also provides some protection against water ingress.

The first port 9 is the port nearest the network device 6 at the first location 7 in terms of data transmission from and to the network device through the cable 4 and the second port 9' is the port furthest from the network device 6 at the first location 7 in terms of data transmission from and to the network device through the cable 4. In this detailed description and the drawings, similar features are identified with the same numerals and those features indicated with a numeral followed by the prime symbol are associated with features that are relatively nearer the second location 8 in terms of data transmission from and to the network device through the cable 4 as compared with the same features not followed by the prime symbol, which are relatively nearer the first location 7 in terms of data transmission from and to the network device through the cable 4.

As shown in Figure 3, the base portion 14 has a mounting side or face 21 which faces the mounting surface 20 of the wall 30 and which preferably has at least one mounting pad 22 that abuts against the mounting surface 20 when the junction box 10 is secured to the wall, for example by means of at least one screw 27 which passes through a corresponding through-hole 26 in the base portion 14. The base portion may, however, be offset from the mounting surface 20 if needed, for example, by a separate spacer element (not shown) between mounting face 21 and the mounting surface 20.

The base portion also has two optical fibre routing apertures, namely a first optical fibre routing aperture 31 and a second optical fibre routing aperture 31 ', each of which is provided in the mounting face 21 of the base portion 14 of the housing 1 2.

Inside the housing 12 of both the first and second junction boxes, 10, 10' part of the cable sheathing 3 is cut away at a cut-out 13, 1 3' on one side of the cable 4, preferably a lateral side relative to the mounting face 21 of the base portion 14. As shown in Figure 4, the cut-out may be at one of two locations, one of which 1 3 is proximate the first port 9 and is associated with the network device being at the first location 7 and is therefore shown in solid outline and the other of which 13' is proximate the second port 9' and is associated with the network device being at the second location 8 and is therefore shown in dashed outline.

The provision of the cut-out 13 nearest the first port 9, exposes the optical fibre bundle 23 inside the external housing 12 and is done in such a way so as not to damage or cut through any of the individual buffered optical fibres 5 inside the cable 4. During installation, at least one of the exposed buffered optical fibres 55 is exposed at a similar cut-out 13 in the second junction box 1 0' and then cut through so that the, or each, cut optical fibre can be pulled back through the cable to the first junction box 10. This step is represented schematically by the dot-dash arrow line 25 in Figure 4 and provides at least one intervening length of buffered optical fibre 55 at the first junction box, which is then routed out of the first junction box 1 0 without being cut or joined to an optical fibre connector so that this length of buffered optical fibre can be routed to extend out of the junction box and into the associated unit 2 without any breaks in continuity. Although there may be more than one buffered optical fibre extracted from the cable bundle 23, the following description will for the sake of clarity refer to this at least one buffered optical fibre in the singular. In the case of the cut-out 13' being nearest the second port 9', the same process is used to provide the exposed buffered optical fibre 55' (shown in dashed outline in Figure 4), except in this case the optical fibre 55' is exposed and cut through in a similar junction box (not shown) which would be to the left of the junction box 1 0 shown in Figure 1 .

Each of the optical fibre routing apertures 31 , 31 ' is for routing the exposed buffered optical fibre 55, 55' out of the housing 1 2 and into the associated unit, and is provided at the mounting face 21 of the housing in order to help to conceal the buffered optical fibre and any surrounding protective tubing, and thereby protect the buffered optical fibre from damage during the lifetime of the installation. The first optical fibre routing aperture 31 is proximate the second port 9' and the second optical fibre routing aperture 31 ' is proximate the first port 9. The choice of which of the two optical fibre routing apertures 31 , 31 ' to use depends on the direction in which the exposed buffered optical fibre 55, 55' exits the bundle from the cut-out 1 3, 1 3'. When the exposed buffered optical fibre has been pulled back from the direction of the second port 9', then the exposed buffered optical fibre 55 within the housing 1 2 extends generally in the direction of the second port 9' and so travels along a first direction or path to exit the housing through the first optical fibre routing aperture 31 . However, if the location of the network device 6 is at the second location 8, then the exposed buffered optical fibre 55' will have been pulled back from the direction of the first port 9, and so the exposed buffered optical fibre within the external housing extends generally in the direction of the first port 9 and so travels along a second direction or path to exit the housing through the second optical fibre routing aperture 31 '. The first and second paths, which may be straight or curved depending on the location of the mounts, overlap and extend along opposite directions between the first and second mounts. In this latter case, because of the left-right symmetry of the housing 12, the arrangement of the cable 4, the cut-out 13' and exposed buffered optical fibre 55' is a mirror image to the case when the network device 6 is at the first location 7.

Therefore, as shown in Figure 4, the length of buffered optical fibre 55, 55' passes out from the junction box 10 through one of two apertures, either the first optical fibre routing aperture 31 or the second optical fibre routing aperture 31 '. The length of buffered optical fibre 55, 55' outside the housing 12 is then routed into the associated unit 2 by means of any convenient path, the choice of which is not germane to the invention, for example through a hole or conduit 24 provided in the wall 30 or other body to which the junction box 10 is mounted.

Preferably the intervening length of optical fibre 55, 55' is also protected by a tube 37, 37' into which the optical fibre is loosely inserted. The protective tube preferably extends through one of the optical fibre routing apertures 31 , 31 '. In the case of the buffered optical fibre 55 extending from the cut-out 13 nearest the first port 9, the tube 37 is shown in detail in solid outline, and in the case of the buffered optical fibre 55' extending from the cut-out 13' nearest the second port 9', the tube 37' is shown in dashed outline only. By extending through one of the optical fibre routing apertures 31 , 31 ', the continuous length of extracted optical fibre 55, 55' is continuously protected along its length from within the housing 12 to within the associated unit 2. In this example, the protective tube is a bend-limiting tube having a series of alternating circumferential ridges 41 and circumferential grooves 42, which may be installed prior to mounting of the junction box to the mounting surface 20, in which case the intervening length of optical fibre 55, 55' may be inserted or blown down the protective tube 37, 37' into the associated unit 2.

The cable 4 need not be surface mounted along its full length to the mounting surface 20 but preferably extends parallel with or is mounted to the same surface to which the junction box 10 is mounted at least where the cable 4 is routed in to or out from the junction box.

Although not illustrated, once inside the unit 2, the end of the, or each, intervening length of optical fibre 55, 55' may be cut to the desired final length, if necessary, and then terminated for use, for example with an optical fibre connector or within an optical fibre socket. The pulled back optical fibre 55, 55' and preferably also the bend-limiting tube 37, 37' surrounding a portion of the optical fibre which exits the housing 12, are secured in position by means of a first mount 1 8 and a second mount 1 8', which apart from their location within the house are identical with each other. The first mount 18 is provided by a first recess 38 in a top end of a first post 28 and the second mount 18' is provided by a second recess 38' in a top end of the second post 28'. Preferably, each of these posts and recesses is identical in form with the other.

Between the first and second mounts 18, 18' is an optional third mount 19 which holds a collar 35 affixed to an end of the bend-limiting tube 37, 37'. This provides further protection against the tube from being pulled out of the housing 12. The third mount is provided by a recess 39 in a top end of a third post 29.

Each of the mounts 18, 1 8', 19 has the same general shape, with each post 28, 28', 29 extending upwards from the base portion 14. Once the cover 1 6 is fitted to the base 14, the cover contacts the top of each post to cap each of the recesses 38, 38', 39 so that the optical fibre 55, 55', the protective tube 37, 37' and the collar 35 cannot come out of the respective recesses. As shown in Figure 4, the junction box 10 is symmetric in the sense that the left and right halves of the junction box on either side of a plane 32 at right angles to a cable routing line or axis 33 through the junction box, are mirror images of each other. In this example, the routing line 33 is straight and extends along an axis of the cable, however, it would be possible to introduce some bend into the line of the cable between the first and second ports 9, 9' without departing from the scope of the present invention as set forth in the claims, as long as such a bend was within the mechanical and optical performance limits of the optical fibre bundle 23. This mirror symmetry, and the arrangement of the first and second mounts 18, 18' and the first and second apertures 31 , 31 ' relative to the optical fibre cable routing line or axis 33, ensures that the intervening optical fibre 55, 55' may be pulled back from a junction box on either side relative to the cable routing direction 33. Both possible arrangements are shown in Figure 4, one in solid outline and the other mirror image arrangement in dashed outline where features are reversed left-to- right as drawn.

The first mount 18 of Figure 4 is shown in detail in Figure 5 and the second mount 18' of Figure 4 is shown in detail in Figure 6. Each of these mounts is identical to the other. In the base of each recess 38, 38' is a first mounting portion being sized to hold and grip an optical fibre, which in this example is a slot 36, 36' through the post 28, 28' with a width suitable for holding gently the buffered optical fibre 55, 55'. The slot 36, 36' is deep enough so that it may, if desired, hold in a stacked formation more than one such intervening length of buffered optical fibre, if more than one such optical fibre is to be routed into the associated unit 2. The protective tube 37, 37' has an inner diameter sufficiently large to hold at least two of such buffered optical fibres 55, 55'. The location of one of such additional buffered optical fibre 155 is shown in dashed outline in Figure 6. The recesses 28, 28' of the first and second posts 28, 28' each have a second mounting portion being sized to grip and hold the protective tubing 37, 37', which in this example is an enlarged upper portion 45, 45', that has a width too large to engage with the buffered optical fibre 55, 55', but which has two pairs of corresponding ribs 48, 48', each pair extending along opposite sides of the recess to engage with opposite sides of corresponding grooves 42 on the outside of the bend-limiting tube 37, 37' when the bend-limiting tube is press-fitted into one of the recesses to secure the bend-limiting tube from being pulled out of the respective mount 18, 18'.

The collar 35 has a single circumferential groove 43 which is engaged with a corresponding pair of ribs 49 that extend along opposite sides of the recess 39 within the third post 29 of the third mount 19 when the collar is press-fitted into the recess to secure the collar from being pulled out of the third mount.

Because the first and second mounts 1 8, 18' are the same, either or both can be used to secure the intervening optical fibre 55, 55' after this leaves the cable bundle 23 and similarly, if a bend limiting tube 37, 37' is provided, either mount can be used to secure the bend-limiting tube before this leaves the housing 1 2. The junction box 1 0 can therefore be used in any orientation relative to the cable routing axis 33, for example with the cable cut-out 13 being either below the cable axis 33 as shown in Figure 4, or with the junction box being rotated 180 ° about an axis perpendicular to the plane of the drawings of Figure 4 so that the cable cut-out 13, 13' is above the routing line 33 of the cable.

A further advantage is that there is no need to provide space inside the housing for coils of spare buffered optical fibre or for optical fibre connectors or for optical fibre splices. As a result, the junction box is relatively compact in terms of its height (i.e. the direction transverse to the cable routing line 33 and parallel to the plane of the drawing of Figure 4), being in this example 140 mm long in the direction of the cable axis 33, 60 mm high and 27.5 mm deep in the direction perpendicular to the plane of the drawing of Figure 4.

As can be seen in Figure 5, it should be noted that the slot 36, 36' through each post 28, 28' is raised above the level of the optical fibre bundle 23 relative to the mounting face 21 of the surface mountable base portion 14. The exposed buffered optical fibre 55, 55' is therefore raised as it exits the bundle 23 at the cut-out.

As can be seen from a comparison of Figures 5 and 6, the enlarged upper portion 45, 45' of each recess 38, 38' is raised above the level of the slot 36, 36' through each post 28, 28' relative to the mounting face 21 of the surface mountable base portion 14. The exposed buffered optical fibre 55, 55' is therefore raised as it traverses from the slot 36, 36' in which the buffered optical fibre is engaged to the enlarged upper portion 45, 45' where the surrounding tube 37, 37' is engaged.

Although not illustrated, the collar 35 holds the buffered optical fibre 55, 55' at an intermediate height relative to the mounting face 21 of the surface mountable base portion 14, so that the height of the buffered optical fibre is steadily increased away from the cut-out 13, 13'. This is done to increase the distance between the buffered optical fibre 55, 55' and the mounting face 21 so that the optical fibre and tube 37, 37' can cross over the side of the cable 4 that is opposite the mounting face 21 of the surface mountable base portion 14, and so that the optical fibre and tube can then curve towards the mounting face 21 and through the corresponding optical fibre routing aperture 31 , 31 ' in the base portion, while still maintaining an acceptable minimum bend radius, in this example, of no less than 25 mm ± 1 mm.

Finally, because there is no coiling of the optical fibre within the housing, and because the extracted buffered optical fibre can be protected within a bend-limiting tube even within the housing, it is possible to save cost in the type of optical fibre cabling which is used. With the conventional approach in which extracted optical fibre is coiled within the housing, it is necessary to use bend-limiting optical fibre, for example according to the standard ITU-T G.657A or ITU-T G.657B. The invention does not require that the optical fibre be bend-limiting, and so it is possible to use less expensive optical fibre cable, for example containing buffered optical fibre according to the standard ITU-T G.652D.

There is also no need to provide a low friction coating on the buffered optical fibres, as bend-limiting protective tubing is commercially available having a low friction coating on the tube inner surface. Therefore, the optical fibres may be buffered with a less expensive acrylate resin rather than a more expensive low friction material. This again allows less expensive optical fibre cables to be used with the invention.

It should be noted that, because only one of the optical fibre routing apertures 31 , 31 ' will be used at any one time, the unused aperture may be covered over by a removable cover 131 , for example a removable rubber plug or a rupturable membrane. Through-holes 26 in the base portion 14 that remain unused for mounting the base portion 14 to the supporting surface 20 may also be covered over by removable cover 126, which may be of a similar form to that for the unused optical fibre routing aperture. In this way, the housing 1 2 can remain substantially closed or sealed, although there will in most cases be no need that the housing should be water-tight or hermetically sealed. Therefore, in the context of the present invention, the term "aperture" extends to any passage between the inside and outside of the housing, even if closed by a removable cover.

The invention therefore provides a convenient and economical method of routing optical fibres in a multiple occupancy building, and also a surface-mountable junction box for use in the routing of optical fibres bundled in an optical fibre cable, and also a system of routed optical fibres in such a building using such a junction box.

Claims

1 . A surface-mountable junction box for use in the routing of optical fibres bundled in an optical fibre cable, the junction box comprising a housing and inside the housing a first mount and a second mount for holding an optical fibre extracted from the optical fibre cable and optionally also for holding protective tubing for said extracted optical fibre, the housing comprising:

2. A surface-mountable junction box as claimed in Claim 1 , in which at least one of said first and second optical fibre routing apertures is provided with a removable cover for covering said aperture when not in use for routing said length of optical fibre out of the housing.

3. A surface-mountable junction box as claimed in Claim 1 or Claim 2, in which said first and second ports define a routing line of the optical fibre cable between said first and second ports, the arrangement of said first and second mounts and said first and second optical fibre routing apertures being symmetric with respect to each other about a plane that extends at right angles to said routing line.

4. A surface-mountable junction box as claimed in any preceding claim, in which said first and second ports define a routing line of the optical fibre cable between said first and second ports, and said first and second mounts both lie on a first side of the routing line of said optical fibre cable and said first and second optical fibre routing apertures both lie on a second side of the routing line of said optical fibre cable, said first side being opposite to said second side relative to the routing line of said optical fibre cable.

5. A surface-mountable junction box as claimed in Claim 3 or Claim 4, in which said routing line is along a straight axis of the cable.

6. A surface-mountable junction box as claimed in any preceding claim, in which the junction box comprises inside the housing a third mount, the third mount being positioned midway between the first mount and a second mount, the third mount having a recess with an engagement feature which is symmetric in both said first and second directions for holding said extracted optical fibre or for holding protective tubing for said extracted optical fibre.

7. A surface-mountable junction box as claimed in any preceding claim, in which each of said first and second mounts has a first mounting portion and a second mounting portion, the first mounting portion being sized to grip and hold said extracted optical fibre and the second mounting portion being larger than the first mounting portion and being sized to grip and hold protective tubing for said extracted optical fibre, such that, in use, a first one of said first and second mounts is configured to hold said extracted optical fibre in the first mounting portion, and a second one of said first and second mounts is configured to hold said protective tubing in the second mounting portion.

8. A surface-mountable junction box as claimed in Claim 7, in which the first mount and the second mount are each provided in a post within the housing, the second mounting portion being provided in a first recess in a top end of the post and the first mounting portion being a second recess in a base of the first recess.

9. A surface-mountable junction box as claimed in Claim 7 or Claim 8, in which the first mounting portion comprises an elongate slot for holding a plurality of said optical fibres extracted from the optical fibre cable.

10. A surface-mountable junction box as claimed in any preceding claim, in which the housing has a base and a cover, the base having said surface- mountable face, and the cover being secured to the base, wherein each of said first and second ports is provided in a seam between the base and the cover.

1 1 . A surface-mountable junction box as claimed in Claim 10, in which the cover is removably fixed to the base.

12. A system of routed optical fibres in a multiple occupancy building having a plurality of units at different locations within the building, the system comprising a plurality of surface-mountable junction boxes including a first junction box and a second junction box, and an optical fibre cable having a protective outer covering and within said covering a bundle of said optical fibres, each junction box being located in proximity with and being associated with one of said units and the optical fibre cable being routed through the building and running through said junction boxes, wherein said first and second junction boxes are as claimed in any preceding claim, and at least one optical fibre in the optical fibre cable does not extend between said first and second junction boxes, but is extracted from the optical fibre cable from within the first junction box and routed through said first and second mounts to exit the first junction box through the first optical fibre routing aperture.

13. A system of routed optical fibres as claimed in Claim 12, in which the protective outer covering of the optical fibre cable has a cut-out within each of said first and second junction boxes to expose the bundle of said optical fibres.

14. A system of routed optical fibres as claimed in Claim 12 or Claim 13, in which said extracted optical fibre extends continuously from within the junction box to within the unit with which said junction box is associated.

15. A system of routed optical fibres as claimed in any one of Claims 12 to 14, in which said extracted optical fibre is terminated within said unit.

16. A method of routing optical fibres in a multiple occupancy building using a plurality of surface-mountable junction boxes including a first junction box and a second junction box, each junction box having an external housing and said housing having a first port, a second port and a surface-mountable face, said surface-mountable face having therein at least one optical fibre routing aperture, and the building comprising a plurality of units at different locations within the building, the method comprising the steps of:

vii) terminating said intervening length of pulled back optical fibre within said unit.

17. A method as claimed in Claim 16, in which said surface-mountable face of the housing has a first optical fibre routing aperture and a second optical fibre routing aperture, and step vi) includes passing said intervening length of pulled back optical fibre through either the first optical fibre routing aperture or the second optical fibre routing aperture depending on the direction in which said cut optical fibre was pulled back from the second junction box.

18. A method as claimed in Claim 16 or Claim 17, in which the bundle of said optical fibres is exposed by providing a cut-out through said protective outer covering within each of said first and second junction boxes.

19. A method as claimed in any one of Claims 1 6 to 18, comprising the step of removing a removable cover over said optical fibre routing aperture prior to passing said pulled back optical fibre through said optical fibre routing aperture.

20. A method as claimed in any one of Claims 16 to 19, comprising the steps of inserting said intervening length of pulled back optical fibre into an optical fibre protection tube, for example a protective bend-limiting tube and routing said tube and said inserted optical fibre from within the first junction box to within said unit through said optical fibre routing aperture.

21 . A method as claimed in Claim 20, in which the first junction box has therein a first mount and a second mount, the first mount being sized to grip and hold said pulled back optical fibre and the second mount being sized to grip and hold the optical fibre protection tube, the method comprising the steps of inserting said pulled back optical fibre into the first mount and inserting the optical fibre protection tube into the second mount.

22. A method as claimed in any one of Claims 16 to 20, in which the first junction box has therein a first mount and a second mount, the method comprising the step of using said mounts to hold said pulled back optical fibre and optionally also to hold protective tubing for said pulled back optical fibre.

23. A method as claimed in Claim 21 or Claim 22, in which each of said surface-mountable junction boxes is as claimed in any one of Claims 1 to 1 1 , the method comprising:

when said cut optical fibre has been pulled back from the direction of the second port, then routing said intervening length of pulled back optical fibre through said first and second mounts in a first direction to exit the housing through the first optical fibre routing aperture; or, alternatively,

- when said cut optical fibre has been pulled back from the direction of the first port, then routing said intervening length of pulled back optical fibre a length of optical fibre through said first and second mounts in a second direction to exit the housing through the second optical fibre routing aperture, the first direction being opposite to the second direction between said first and second mounts.