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Nearly 100 percent of the fiber-optic cable we see in a data center consists of pre-terminated trunk assemblies. The data center, especially a hyperscale data center, is an ideal environment for this type of cable. We see cable trunk quantities in the 1,000s and fiber strands in the 100,000s. That is a lot of connectors to install at each end of every cable. The pre-terminated assemblies have the advantage of reducing the on-site labor cost and improving the quality and consistency of the connector polish.
Ordering pre-terminated cables can significantly improve the construction schedule, provided the cable assemblies can be ordered during the design phase or very early in the construction phase of the project. Manufacturers will say they can deliver a pre-terminated cable assembly in as little as two weeks or as much as six weeks. For hyperscale data centers, the schedule is much longer. This is due to the size of the cables ordered and the massive quantity of assemblies, with each assembly being a unique length. Within the order there will be cables of the same length but this is more of coincidence then of a desire to order cables of common lengths.
The key is to get every cable calculated to the correct length for the early cable order. Cables that are ordered too long quickly become a nightmare in trying to store the slack in the cable tray. To some extent, we already design the cable trays to handle a certain amount of slack, but just due to the massive quantity of cables that may enter a network room, too much slack can overwhelm the design capacity quickly. Cables that are too short can’t be used at all. Sure, they may be able to be used elsewhere in another phase of a build-out, but when it’s time to install the cable is not when you want to have to start a new order for longer cable trunks.
The solution is to use 3D CAD modeling software, such as Revit, to model every pre-terminated assembly. Once we lock down the location of the data center network rooms and the cable tray routing, the trunk cable assemblies can be laid out following a 3D route from one network rack to the other.
A small amount of slack is still designed into each trunk assembly. Although the bill of materials for the trunk assembly order may occur while the facility is still being designed, small adjustments can still be made in the tray design without impacting the cable order. The 3D model and BIM information allows us to see if any changes in the cable length are still within the amount of slack we designed.
During construction, however, it is critical that every cable tray is installed exactly where it was designed to be in the BIM model. Unlike in a commercial office facility, where it is not uncommon for the contractor to move the cable trays to avoid construction conflicts with other trades, for the hyperscale data center, the mentality has to be that the cable trays are monuments and cannot be moved. This is another value of designing the entire facility in a 3D model. It allows all engineering disciplines to design their systems to avoid conflicts in construction.
In extending the 3D model to include every trunk cable, we can assist in improving the accuracy of the cable order, reduce the amount of cable slack, and improve the construction schedule by ordering the cable lengths from an accurate model instead of waiting to measure cable lengths from the installed cable trays.
Still, if changes to the cable tray design need to be made in the 3D model, they can require significant time to make the thousands of corresponding edits to the cable connections. TEECOM’s Research and Development team has created a proprietary Revit plugin to accomplish this task and eliminate those six to 10 hours of engineering work. To continue the conversation about your hyperscale data center, use the Contact TEECOM form at the bottom of the page.