Should I use OM3 or OM4 fiber for my 40/100G Network?

It is safe to say that 40 GB and 100 GB Ethernet are the future of fiber optic networks. They provide ultra-fast optic connections suited mostly for the biggest Datacenters and Service Providers in the world. Even though at the moment IT managers are only starting to implement the 10 GB Ethernet throughout their Datacenters, 40 GB and 100 GB Ethernet solutions are waiting right around the corner. These solutions have one main purpose: to provide stable high-bandwidth connection and to serve the new emerging technologies like cloud computing and server virtualization. These technologies are exhausting the current data rates and they are demanding more and more bandwidth in order for them to achieve maximum performance. They have been developed by the IEEE 802.3ba Task Force and they guarantee to support transmitting Ethernet frames at 40 and 100 Gigabits per seconds.

When it comes to Datacenters, they represent huge buildings which accommodate thousands of network components, servers, storages and a couple of kilometers of network cables. The leading Datacenters don’t want to disrupt their network architecture with unreliable components and they aim to build a solid ground for the newest of network technologies, the 100 GB Ethernet solution. Today 40 GB Ethernet can be safely deployed in the access and aggregation layer of Datacenters, leaving the 100 GB Ethernet to be the cherry on the top of the cake, serving the bandwidth thirsty, core layer in Datacenters and Service Providers.

When it comes to choosing the correct cables for these technologies it’s important to notice that quality will not keep you awake at night. Choosing quality cables will always prove to be the correct step on the long run. On one side we have the Single-mode fibers which with its smaller and centralized core, around 9µm in diameter, will transmit the light further, with very little power loss. As a result Single-mode fibers are used mainly for long distances, both indoors and outdoors. Because of their complex manufacturing process, Single-mode fibers are more expensive to manufacture and purchase.

In Datacenters every networking component must be connected with each other. This means that short range cables are needed. These cables are also called Multi-mode cables. They are characterized by their bigger core, which can be 62.5µm and 50µm in diameter. As a result they can accept larger volume of light, however the light is bouncing inside the cable resulting with high attenuation over long distance. Nonetheless, Multi-mode fibers are divided in four categories, each with its own characteristics: OM1, OM2, OM3 and OM4.

When thinking of deploying 40 GB or 100 GB Ethernet solution there is no option of using the cheaper OM1 and OM2 cables as they don’t support this kind of speeds. The only types of cables which can be used for short range connections are OM3 and OM4. Knowing the key differences between them is crucial.

The fact is that OM4 Multi-mode fibers provide higher network reliability and network design simplicity and flexibility, while allowing a reach of 150 meters. The original standardized specification by IEEE 802.3ba guarantees reach of up to 100 meters with OM3 Multi-mode fibers.

On the contrary, OM4 Multi-mode fibers would substantially extend the reach by at least 1/3 allowing for connectivity up to 150 meters. Even though new emerging network components play a huge role in this extended reach, the main reason for this is the greater Effective Modal Bandwidth compared to OM3 Multi-mode fibers. The Effective Modal Bandwidth, or EMB, is the maximum distance the cable could reach for a given signaling rate. This eventually gives the advantage to OM4 fibers to be chosen for Datacenter connections.

Multi-mode fibers are also available as parallel optics. As 40 GB and 100 GB Ethernet require multiple lanes of traffic, the parallel optics or MPO/MTP solution is capable of providing just that. This means that in order for 40 GB/s to be achieved on a Multi-mode fiber, a MPO/MTP connector type is used. This connector provides 12 fibers in a single connector. Out of the 12, 4 fibers are used for the transmission, 4 fibers are used for the receiving and 4 fibers remain unused. This is multiplied by two with the 100 GB/s standard, providing up to 24 fibers in a single connector (figure 1).

The deployment of these solutions would boost any network. With the 400 GB Ethernet on its way to be further developed, 40 GB and 100 GB solutions guarantee a solid ground for the future.