BONNET construction work at the cable route to Endenich BONNET construction work at the cable route to Endenich

Upcoming Demolition work at the junction of the B56 and the BAB 565 (Endenicher Ei) by Autobahn GmbH made it necessary to relocate the university's cable routes in the immediate construction area at short notice. This affected several fiber optic cables between Poppelsdorf and Endenich, which form one of the main connections on the core network of the university network (BONNET). For the relocation, it was necessary to cut the existing cables (which consist of a total of around 350 optical fibers) in front of and behind the construction area and to re-route them via an alternative cable route, which was created together with Autobahn GmbH, and to reconnect them using so-called splice sleeves.

Autobahn GmbH specified a non-postponable time window from February 9 to February 23, 2024 for the relocation. Autobahn GmbH carried out preparatory construction work until February 9, 2024, and from February 23, 2024, the closure of the BAB 565 and subsequent demolition work on the "Endenicher Ei" bridge structure was scheduled. The challenge now was to organize and accommodate the extensive preparations, appointments with suitable service providers and the necessary material deliveries within the specified time frame.

Crucial data connections to Endenich were already and are still secured through path-redundant lines through the main building and the Römerstraße to Endenich.Non-redundant connections were switched to replacement lines via other cable routes as far as possible in order to keep outages in BONNET to a minimum. For a few connections, such as the fiber optic connection to the Klein-Altendorf campus, temporary interim solutions via other routes could not be made possible, so that an outage of one to two days had to be expected here. As part of the preparations, suitable points also had to be found for cutting the connection. The route shafts directly in front of and behind the construction area were not very suitable due to poor accessibility, which is also important for future work. In addition to good accessibility, the shafts must offer sufficient space to accommodate the splice sleeves and future extensions. Once suitable shafts had been found, route tests had to be carried out to ensure that the replacement cables could also be pulled through the routes to these shafts. The decision was also made in advance to pull so-called "speed pipes" into the routes instead of individual cables. These are thin empty conduits into which fiber optic bundles can later be blown over longer distances.  In the case of upgrades, this has the advantage that cables which are organised in distances  of 100 m, do not have to be lined in each shaft. This would always cause disturbances in public areas, which is why all attempts are made to avoid this. Blowing the optical fibers into existing speed pipes can be done over significantly longer distances, without having to open the shafts between the two ends of the route, which facilitates future works and upgrades at the connection to Endenich.

As part of the preparations, the distribution of the occupied and still free optical fibres across the various fibre bundles of the cable made it possible to carry out the splitting and re-splicing successively (12 fibres per fibre bundle). Compared to the logistically much simpler splitting and rerouting of the entire cable in one step, the successive splicing and in particular the simultaneous deployment of two splicing teams at both ends of the rerouting resulted in significantly minimised downtimes in BONNET.

On Friday, 16.02.2024 at 13:55, the time had come: the connection to the Klein-Altendorf campus was started and, thanks to the optimisation of the process, the changeover was completed in less than 15 minutes. The majority of critical fibres were then relocated on Saturday, 17.02.2024 between 07:00 and 15:00. Other, less critical fibres were relocated between 19 and 20.02.2024. As far as it could be integrated into the workflow, the necessary continuity measurements of the optical fibres were integrated into the splicing work, with a particular focus on the critical connections. Further measurements and the necessary follow-up work were then carried out over the following three weeks.