The advertising at Heathrow Central and T4 previously was in the form of static illuminated posters, scrolling illuminated posters and tunnel-mounted posters. The scrolling posters could only cycle through three different advertisements at a time. The posters had to be physically replaced in order to change the advertisements. The scrolling posters contributed significantly to the amount of noise in the stations.

J C Decaux wished to replace the existing scrolling signs with large format LCD displays. These screens are automatically updated from a central server with each screen being provided with a PC to drive the images.

Firstco have provided the Ethernet connectivity from each of the new displays back to the central server. The central server is located within the Heathrow Central B4 equipment room where it will be connected to an Ethernet switch.

A 24-core fibre cable was installed in a resilient fibre optic ring in the T5 B4 Level (UPE) to provide connectivity between the active ethernet switches required to feed the media displays. The fibre cable was installed as a ring topology. This method maximised the resilience of the network due to primary and secondary routing of the fibre cable and ensured diverse routing at all times.

The topology was configured with point-to-point connections between the core and edge switches. At each location a number of fibres are presented for use, with the rest being spliced straight through. This reduced the physical amount of cable required and the subsequent installation time and cost. At any given time the system can operate on two cores, with the other six providing a high degree of resilience.

This is done for the following reasons:

• A redundant fibre-optic circuit is always available via a resilient route
• A core switch port failure will only disrupt the service to a single switch, not all of the downstream switches
• Overall circuit latency is reduced, mitigating the risk of broadcast storms associated with the Ethernet frame round trip delay

A fibre network of this style represents the current state-of-the-art LAN fibre performance, significantly increasing the longevity of the system and the flexibility with respect to the number of protocols that will operate over it.

Upon completion the network was fully tested and the results documented and presented to J C Decaux.