OPTICAL FIBRE CONNECTING MEANS

Abstract: The present invention relates to an arrangement for connecting a plurality of optical fibres from dwellings in a an apartment building to an external connection point, such as to a central unit. Optical fibres from the dwelling places are connected to the arrangement, which comprises a passive part and an active part. The arrangement is, in turn, connected to optical fibres extending to the external connection point, such as said central unit. The passive part of the arrangement includes cassettes (3) and an optical fibre organiser (5). The active part includes a cross-connecting unit (9), a current converter (10), and cooling means (12).

Description: OPTICAL FIBRE CONNECTING MEANS FIELD OF INVENTION The present invention relates to an arrangement for connecting several optical fibres to an external connection point, such as an arrangement for connecting several optical fibres from dwellings in an apartment block to an external connection point, said arrangement including a unit for switching optical signals transported by the optical fibres between said dwellings and said arrangement and between the arrangement and said external connection point. BACKGROUND OF THE INVENTION It is known to provide optical fibre networks for dwelling places, where individual apartments are connected by optical fibres to a central unit, for example a router. The central unit is then connected in turn to a transport network for the transmission of information from the individual apartments/dwelling places to said transport network, for instance the Internet. US005872644A teaches an optical fibre access system for optical subscriber communication between dwelling places and a central unit, where each dwelling place is connected by optical fibres to one of a number of optical transmitting modules (Tx) and to one of a number of optical receiver modules (Rx), said modules being connected to a communications switch. SUMMARY OF THE INVENTION There is provided a arrangement for the interconnection of optical fibres that can be placed centrally in an apartment building, for instance, such as in the basement thereof, with the intention of simplifying installation of optical fibre networks in, e.g.. offices, storerooms, terrace houses/town houses, detached houses or like places such as dwellings in an apartment building. There is provided in each dwelling, apartment/living space, an optical fibre connection point from which one or more optical fibres that have been pre-connected are blown or drawn down to the centrally located arrangement for connection thereto, wherewith the optical signals transported by the optical fibres can be switched and forwarded by the arrangement. The centrally located arrangement may have the form of a cabinet, a so-called capsulation cabinet, consisting essentially of two parts: a passive part and an active part. The fibre optic passive part is comprised of a transition from optical 5 fibres carried in ducts, so-called microducts, from the dwelling places to a fixed cross- coupling and a switch unit. The electrically active part is comprised of the switch unit and a converter. The cabinet is constructed on the concept of coupling the passive optical fibre part and the active electronic part together and to an optical fibre network that is capable of providing subscribers with 100 Mbps fibres (SX) lines, in a simple fashion and within a 10 small structural area. The active part and the passive part are each disposed in respective, adjacent smaller spaces in the encapsulating cabinet, with separate doors and keys. This minimises the risk of unauthorised access to the cabinet and to sensitive components housed therein, and also allows the functions to be separated. The cabinet may primarily be intended to be mounted on walls inside a building, and may be fastened to a wall 15 attachment by means of four screws, without needing to open the actual cabinet. The invention will now be described in more detail with reference to a preferred embodiment thereof and also with reference to the accompanying drawings. 20 BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates an optical fibre network connected to a subscriber. Figure 2 illustrates a switch unit for local switching of signals in the network shown in 25 Figure 1. Figure 3 is a perspective view of an encapsulating cabinet that includes a passive part and an active part in accordance with the invention and intended for use in the optical fibre network according to Figures 1 and 2. J 0 Figure 4 is a detailed illustrated in different views of an encapsulating cabinet organiser. DESCRIPTION OF PREFERRED EMBODIMENTS Figure 1 illustrates an optical fibre network for connection to a subscriber. The fibre network is comprised of a local switching unit 101 that connects pairs of optical fibres 103 to individual subscriber/dwelling places 105 with a local optical fibre loop 107. The local optical fibre loop 107 is, in turn, connected to a central unit 109 which, in turn, may be connected to a transport network 11 1, such as the Internet, in a conventional manner. The inclusion of the local switching unit 101 affords a number of advantages over a conventional optical fibre network for subscriber connection (Fibre To The Home/FTTH). For example, there is no need to draw to the central unit pairs of optical fibres from respective individual subscribers. This results in a smaller number of optical fibres that need to be drawn to the central unit, since the total conductor length will be shorter. Moreover, it simplifies the connection of new subscribers, since a new optical fibre need only be drawn from the individual subscriber to the switching unit, which can be placed much closer to the subscriber, for instance in the basement of an apartment block, instead of needing to draw optical fibres all the way to the central unit. The local switching unit will preferably be housed in a robust casing that can be placed in a basement or in a loft or attic of a building without risk of damage to the electronic components. Moreover, switching is effected on a local level, meaning that the traffic load to the central unit will be reduced since all traffic transmitted between subscribers connected to the same switching unit need never be sent to the central unit 109. Figure 2 shows the switching unit in more detail. Thus, the switching unit may include a CPX 201 for cross-connection of signals to/from different subscribers connected to the switching unit. CPX 201 is connected to a PIN diode array 203 and to a VCSEL laser array 205. The PIN diode array receives signals arriving at the switching unit and the VSCEL laser array 205 transmits signals from the switching unit. The PIN diode array and the VSCEL laser array are each connected to a respective optical fibre ribbon. These fibre ribbons are cross-connected in the CPX, so as to form receiver/transmitter pairs. Each individual pair is then connected to a given subscriber. The PIN diode array 203 is connected to an amplifier 207, which is connected in turn to a conventional packet-handling unit 209. The packet-handling unit 209 is connected to a block 211 that includes a distribution selector, appropriate filters, and preferably also support for handling a VLAN (Virtual Local Area Network). The block 21 1 is connected to a packet switch 213. The packet switch 213 is connected to a buffer 215 in which a packet outputted from the packet switch is stored while waiting to be transmitted from the switching unit. The buffer will preferably have support for handling different priorities relating to the transmitted packets. The buffer 215 is then connected to a conventional packet manager 217 and an amplifier 219, which, in turn, are connected to the VCSEL laser 205. In a preferred embodiment of the invention, the switching unit will include filters for preventing information sent to/from an individual subscriber from being received by another subscriber connected to the same switching unit. Filtering of information is also effected to prevent one subscriber disturbing another subscriber connected to the same switching unit. Moreover, different subscribers can be given different connection qualities, providing so-called virtual networks (Virtual Local Area Network/VLAN). When the switching unit includes a cross-connection facility, switching on local levels can be carried out, i.e. traffic to/from subscribers connected to one and the same switching unit can be cross-connected in the switching unit on local levels. Figure 3 shows an example of a so-called encapsulating cabinet IA and IB which includes a passive part and an active part and which is constructed in accordance with the invention for enclosing the switching unit showΗ in Figure 2, among other things. The cabinet IA and IB is shown with open doors/covers 2 A and 2B, and also in a partially separated view. The cabinet is preferably made of 1.5 mm lacquered steel plate and aluzinc plate, and may be painted in structured coral white. The passive components, such as eight cassettes 3 for handling 96 optical fibres/48 fibre ribbons and an organiser, this number of optical fibres and fibre ribbons being a maximum at present. Incoming multiduct cables and/or microducts carrying optical fibres from different apartments in an apartment block, for instance, shall be capable of being installed in the cabinet in accordance with a particular installation plan. Holes 4 are provided in the back piece of the cabinet for the insertion of ducts/pipes carrying optical fibres from said apartments. The ends of the various ducts/pipes are then placed in the organiser 5 (see Figure 4) such as to place the optical fibres in the ducts/pipes in order and to enable said fibres to be handled more easily at the transition of the fibres from the ducts/pipes to the cassettes. As shown in Figure 4, the organiser 5 may comprise a combined ladder-like holder for individual pipes or pipe-ends, where the pipe-ends can be placed parallel one above the other in recesses 17 on both sides of the holder. Optical fibres blown into/drawn by suction into respective ducts/pipes by means of the FTTH (Fibre To The Home) technique or by means of the FFTH (Fibre From The Home) technique are preferably numbered or marked in accordance with a prescribed numbering or marking system, for instance using marking tabs or like devices to ensure simple and precise handling ofthe optical fibres. Six 2-fibre ribbons on the subscriber side can be joined/spliced to, e.g., 12-fibre ribbons on the switching side, in each cassette 3. Single-mode joins/splices for so-called upstream traffic may be made in the uppermost and the last cassette. Holes 6 for upstream traffic out to the central unit 109 are provided on the front of the left-hand cabinet part. The cabinet part A is sealed by means of a sealing strip 7 provided around the edges of the lid 2A. Fastened to the underside of the cabinet part 1 A is a bar 8 by means of which the cabinet can be secured to a supportive surface, such as a basement wall or some technically equivalent structure. The right-hand cabinet part 1 B houses the active components, such as the switching unit 9 described above with reference to Figure 2, a DC converter 10, a current supply network cable 11, and fans 12 for cooling enclosed components. In this case, the door opening is provided with especially made, conductive silicone packings 13, and all other openings are optimised to stop electromagnetic radiation so that the unit will satisfy so-called EMC requirements. When suitably designed, the switching unit 9 can be fitted readily in the cabinet without requiring the use of tools to this end, for instance by exerting a light pressure on a pivotal locking clip. A cross-connection unit 14, a so-called CPX, can be fitted to the switching unit 9 in the form of long 12 fibre ribbons with tension force relieving means on a front panel of the switching unit. For instance, eight CPX pigtails having a length of 1.8 m may extend from the switching unit to the cassettes 3, and two or four single mode pigtails for upstream traffic may extend to an external connection point. All pigtails may be drawn through one or more holes in an intermediate member between the passive part and the active part, preferably through a hole 16 having a diameter of 5 mm so as to fulfil EMC requirements. The intermediate member may comprise at least one side of one of the cabinet parts. By marking all pigtails with predetermined identification means, for instance with marking tags or the like, positioning can be facilitated with respect to intended places in respective fibre joining/splicing cassettes. A bar 15 may be fastened to the underside of the cabinet part IB for attachment of the cabinet to a support surface, such as a basement wall or some technically equivalent structure. The cable seals will preferably be made of rubber and the internally fitted jointing cassettes may, for instance, be made of modified PPO with fire protection class UL 94 VO. It will be understood that the invention is not restricted to the aforedescribed and illustrated embodiment and that modifications can be made within the scope of the accompanying Claims.

Claims: CLAIMS 1. An arrangement for connecting a plurality of optical fibres to an external connection point, for instance connecting optical fibres from several dwelling spaces to an external connection point, wherewith the arrangement includes a unit for switching optical signals transported by the optical fibres, characterised in that the arrangement is comprised of two parts: a passive part (1 A) and an active part (IB); and in that said parts are connected to one another. 2. An arrangement according to Claim 1, characterised in that the passive part includes cassettes (3) and an optical fibre organiser (5). 3. An arrangement according to Claim 1 or 2, characterised in that the active part includes a cross-connecting unit (14), a switching unit (9), a current converter (10), and cooling means (12). 4. An arrangement according to any one of Claims 1-3, characterised in that said two parts are parts (IA, IB) of an encapsulating cabinet, where the cabinet part (IA) is intended as the passive part, and the cabinet part (1 B) is intended as the active part. 5. An arrangement according to Claim 4, characterised in that each part (IA, IB) of the cabinet is provided with an openable lid or cover (2A, 2B). 6. An arrangement according to Claim 5, characterised in that each lid or cover (2 A, 2B) is provided with sealing means (1, 13) that function to ensure the impermeability/tightness of said cabinet parts. 7. An arrangement according to any one of Claims 1-6, characterised in that said arrangement is adapted so as to enable it to be placed centrally in a building. 8. An arrangement according to any one of Claims 1-7, characterised in that the arrangement is adapted so that it can be placed vertically.

Inventors: EKLUND HANS, HOLMBERG JOHAN, RADOJEVIC GOJKO, SJOELINDER SVEN, EKLUND, HANS, HOLMBERG, JOHAN, RADOJEVIC, GOJKO, SJOELINDER, SVEN
Applicants: EKLUND HANS, ERICSSON TELEFON AB L M, HOLMBERG JOHAN, RADOJEVIC GOJKO, SJOELINDER SVEN, EKLUND, HANS, HOLMBERG, JOHAN, RADOJEVIC, GOJKO, SJOELINDER, SVEN, TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)
Application year: 2001
Main classification: G02B6
IPC codes: G02B6