How to Utilize OM3 & OM4 Optical Fiber for 40 & 100G Connectivity

As technology evolves and standards are completed to define data rates of 40G/100G, the cabling infrastructures installed today need to provide scalability to accommodate the need for more bandwidth in support of future applications. The most common multimode transmission fiber used in data center is currently OM3/OM4 which can transmit data rates for 10/40/100 Gbps. Since they provide an additional layer of performance that supports these applications at longer distances, how to utilize them for 40 and 100G connectivity is very essential in data center communications.

Data center bandwidth requirements increase due to requirements for additional switching and routing, virtualization, convergence, video-on-demand (VoD) and high performance cloud computing, the need for reliable and high performance cabling infrastructure to support these applications becomes more important. Ratified in June 2010, the IEEE 802.3ba 40G/100G Ethernet standard provides guidance for 40G/100G transmission with multimode and singlemode fiber. OM3 and OM4 are the only multimode fibers included in the standard.

In addition to the cable performance, the choice of physical connection interface is also important. Since parallel-optics technology requires data transmission across multiple fibers simultaneously, a multifiber connector is required. Factory terminated MPO/MTP connectors which have either 12 fiber or 24 fiber array, will support this solution. For example, a 10G system would utilize a single MPO/MTP (12 fiber) connector between the 2 switches. Modules are placed on the end of the MPO connector to transition from a MPO connector to a 12 fiber breakout LC duplex or SC duplex cable assembly. This enables connectivity to the switch. 40G and 100G systems require a slightly different configuration. Individual modules and subracks as well as various cable assemblies are available which provide an MPO/MTP interface and which also provide connectivity to LC, SC connectors. For instance, HP BladeSystem 455883-B21 compatible module from Fiberstore is with LC duplex interface and achieves link distance of 300m over OM3 multimode fiber.

In recent years, a kind of 40G cable assembly, namely the direct attach cable, is widely used in 40 Gigabit Ethernet. It includes passive and active direct attach copper cables and active optical cable (AOC). The QSFP+ passive or active direct attach copper cables are designed with twinax copper cable and terminated with QSFP+ connectors. For instance, Juniper QFX-QSFP-DAC-1M compatible QSFP+ to QSFP+ passive copper cable is suitable for very short distances and offer a very cost-effective way to establish a 40-gigabit link between QSFP port and SFP+ port of Juniper switches within racks and across adjacent racks. The main difference between passive QSFP+ DAC and active QSFP+ DAC is that the passive one is without the active component. AOC is used for short-range multi-lane data communication and interconnect applications. It uses electrical-to-optical conversion on the cable ends to improve speed and distance performance of the cable without sacrificing compatibility with standard electrical interfaces.

Cabling deployed in the data center today must be selected to provide support of data rate applications of the future. To achieve this purpose, OM3 or OM4 is a must. They provide the highest performance for today’s needs. With 850nm EMB of 2000 MHz∙km and 4700 MHz∙km, the fibers provide the extended reach required for structured cabling installations in the data center. Utilizing OM3 & OM4 optical fiber in 40 and 100G connectivity provides ways to migrate to multifiber parallel optic interface when needed.