This invention relates to communication systems and more especially it relates to such systems, which use optical TDM (Time Division Multiplex) switch cores.

TDM switch cores are now well known and such cores and systems/apparatus for use therewith are described in our co-pending Patent Application Numbers 2353157A and 2362280A to which attention is hereby directed. Accordingly, neither detailed switch core description, nor detailed optical back plane description is believed to be necessary herein.

In such known optical TDM communication systems, data packages are fed between subscribers via two stage routers coupled though an optical back plane. One stage of the two stage router is used to select in dependence upon frequency band or colour, data for onward transmission, which is returned to the backplane, and the other stage is used to select in dependence upon a label carried by each data package, data fed through the router to other routes. Labeling systems per se are in common use and for the internet for example, 32 bit packages are labeled IPV4, and 128 bit packages are labeled IPV6.

It is apparent however that this two stage router process, is somewhat inefficient since it uses both frequency band and labeling for routing, and it is an important object of this invention to provide a more efficient router.

According to the present invention, a communication system router comprises a number of optical backplanes which are arranged to feed a plurality of ingress lines, one for each ingress port, each of which lines utilises a plurality of TDM data slots, data packages being fed from the router via router egress ports, each data package being labeled in accordance with the line in which it traveled to the router and the TDM slot which it occupied, whereby the labels define for each package an address, each router comprising a lookup table which cross-correlates these addresses with egress ports, whereby each data package is routed to an appropriate egress port, as indicated by the lookup table, in dependence upon its label.

By labeling in accordance with both line and TDM slot, the provision of a much more efficient single stage system is facilitated in which data packages are routed as indicated by their label to any appropriate route, which may be to the backplane or to some other route.

The labeling operation of each data package may be effected within the router.

The lookup table may comprise a (Read Only Memory) ROM.

The routers may each include a buffer store for the temporary storage of data packages routed to the same egress port.

The processing which involves the lookup table may be electronic, optical data being fed to and from the routers and converted as necessary therein.

One embodiment of the invention will now be described by way of example only with reference to the accompanying drawing in which; - Figure 1, is a block circuit diagram of a known router system, and; - Figure 2, is a block circuit diagram of a TDM data router including a lookup table.

Referring now to Figure 1, a known data router system comprises an MPLS (Multi-Protocol Label Switch) router 1, and an OXC (Optical X-Connector) 2. The OXC 2, is fed with data from an optical backplane 3, data being routed in accordance with colour/frequency band, either via a line 4, to the MPLS router 1, or via a straight through path 5, for onward transmission through the optical backplane 3. The MPLS router 1, sorts data packages fed thereto in accordance with labels, which they are arranged to carry. This two stage router operation wherein data is first sorted by colour and then by label tends to be inefficient and so a single stage processor as shown in Figure 2, is proposed.

Referring now to Figure 2, in a communication system, TDM data is routed between a plurality of disparate routers, only one of which designated 6, is shown in Figure 2. Ingress ports 7, each of which is fed via one of input lines 7a, 7b, 7c, of the router 6, are fed from a number of optical backplanes 8. Egress ports 9, of the router shown, are arranged to feed data to other routes 10, via lines 9a, 9b, 9c. Data packages are fed to each of the ingress ports 7, in a predetermined one of 128 TDM slots and are labeled with an address determined in accordance with that line along which they were received, and the TDM slot which they occupy on that line. These addresses are correlated in a lookup table 11, with predetermined ones of the egress ports 9, and routed accordingly. In order to cater for a case where two or more data packages are routed to the same egress port at the same time, a buffer store 12, is provided for temporary storage.

It will be apparent that by using a lookup table as just before described to label data packages, single stage processing is facilitated which improves efficiency of operation.