Topology

In the Data Center, migration to 40 and 100-gigabit infrastructure deployment and flattened architectures are causing optical loss budgets to shrink.

Unfortunately, the loss values of many pre-terminated fiber solutions have only allowed for two mated pairs in a channel, which has limited the ability to deploy manageable, scalable and secure networks.

In fact, the current insertion loss of 0.75 dB per mated pair defined by TIA allows for just one mated pair in both 10- and 40-GbE fiber channels. Thankfully, new low-loss solutions allow Data Center managers to get back to the fundamental best practice of deploying multiple connection points that provide convenient cross-connects and zone distribution areas (ZDAs) to improve manageability, scalability and security.

How many connection points is optimum? Let’s take a look.

2-Point Topology

While less expensive in material, two mated pairs requires high-density patching at the core. This can cause difficult, unsecure access to critical switch ports, creating the risk of interrupting live traffic.

Installation is labor intensive with large numbers of cabling assemblies installed in long runs. Adding new equipment can also disrupt pathways as additional long trunk assemblies will need to be added. Many standard-loss solutions may also require Data Center managers to deploy more expensive OM4 fiber rather than OM3.

3-Point Topology

Using three mated pairs offers some improvement. With one point at the core and one at the access switch, an additional connection point can be added at a ZDA (i.e., End-of-Row or Middle-of-Row).

The same limitation of high-density patching exists at the core, but it does offer improved security. All of the cables from the core can be pre-installed to the ZDAs, eliminating the need for server teams to access critical switch cabinets. Adding new equipment involves running fewer cable assemblies short distances from ZDAs, rather than many cables all the way from the core.

Download our 10 Steps to Holistic Data Center Design white paper

4-Point Topology

This topology allows for a cross-connect at the core. High-density patching from core switches can be cross-connected to lower-density patching fields, making MACs easier while restricting access to switch cabinets. Unfortunately, long runs may still be required from the cross-connect to the equipment area.

5-Point Topology

Considered the pinnacle solution, a five-point topology allows for both a cross-connect at the core and ZDAs at each equipment row. This offers low-density, easy-access patching at the core and enables all cabling to be preinstalled from the core to the ZDAs.

5pointtopology

The core remains completely segregated from the equipment area. Adding new equipment requires only a short cable run from the ZDA for secure row-based “grow-as-you-go” scalability. 

While few vendors’ pre-terminated assemblies can even support four (or even three) mated connections, Belden offers the industry’s lowest loss connectivity (0.2 dB for MPOs and 0.15 dB for LCs) to support a four-point topology in 40 GbE channels using both OM3 and OM4 fiber, or a five-point topology in both 40 GbE and 16 Gb Fibre Channel applications using OM4.

For more information about what is driving the need for low loss connectivity, and a deeper analysis of the various connector topologies, consult my recent webinar Data Center Evolution: Prepare for change with Low-Loss Connectivity, or drop me a line in the comment box below.