With the continued requirement for expansion and scalability in the data center, cabling infrastructures must provide reliability, manageability and flexibility. Deployment of an optical connectivity solution allows for an infrastructure that meets these requirements for current and future data rates. A key factor when choosing the type of optical connectivity is scalability. Scalability refers to not only the physical expansion of the data center with respect to additional servers, switches or storage devices, but also to the scalability of the infrastructure to support a migration path for increasing data rates. As technology evolves and standards are completed to define data rates such as 40- and 100-Gbit Ethernet, 32-Gbit and higher-speed Fibre Channel, and 40-Gbit and higher-speed InfiniBand, the cabling infrastructures installed today must provide scalability to accommodate the need for more bandwidth in support of future applications.
As 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. The IEEE 802.3ba 40G/100G Ethernet standard provides guidance for 40G/100G transmission with multimode and singlemode fibre. OM3 and OM4 are the only multimode fibres 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 fibres simultaneously, a multifibre connector is required. Factory terminated MPO MTP connectors which have either 12 fibre or 24 fibre array, will support this solution. For example, a 10G system would utilise a single MPO/MTP (12 Fibre) connector between the 2 switches. Modules are placed on the end of the MPO connector to transition from a MPO connector to a 12 Fibre 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.
Factory-terminated MPO solutions allow connectivity to be achieved through a simple plug & play system. To meet the needs of today’s serial Ethernet applications, MPO-terminated backbone/horizontal cabling is simply installed into preterminated modules,panels or harnesses (Figure 1).
Cabling migration from 10G to 40G to 100G in an MPO-based system is a simple and easy deployment. Starting with 10G, a 12 fiber cable is deployed between the two 10G switches. Modules are used at the end to transition from the 12-fiber MPO to LC duplex. This enables connectivity into the switch (Figure 2).
When the switches migrate to 40G, the module is removed and is replaced by a 12-fiber MPO adapter panel. The use of a 12-fiber MPO jumper is needed to establish connectivity between the switches (Figure 3).
Insertion loss is a critical performance parameter in current data center cabling deployments. Total connector loss within a system channel impacts the ability of a system to operate over the maximum supportable distance for a given data rate. The 40G and 100G Ethernet standard specifies the OM3 fiber 100-meter distance maximum channel loss to be 1.9 dB, which includes a 1.5-dB total connector loss. The OM4 fiber 150-meter distance maximum channel loss is 1.5 dB, which includes a 1.0-dB total connector loss budget. The insertion loss specifications of the MPO connectivity components should be evaluated when designing data center cabling infrastructures. With low-loss MPO connectivity components, maximum flexibility can be achieved with the ability to introduce multiple connector matings into the connectivity link such that structured cabling architectures can be supported.
Cabling deployed in the data center today must be selected to support data rate applications of the future, such as 100G Ethernet, Fibre Channel ≥32G and InfiniBand ≥40G. To do this, OM3 or OM4 fiber is a must. In addition to being the only multimode fibers included in the 40G and 100G Ethernet standard, OM3 and OM4 fibers provide the highest performance as well as the extended reach often required for structured cabling installations in the data center.
Multiple loss-performance tiers are available for MPO connectivity solutions. Just as connector loss must be considered with current, deployed applications such as 10G Ethernet, insertion loss is also a critical factor for 40G and 100G Ethernet applications. For example, IEEE 802.3ae defines a maximum distance of 300 meters on OM3 multimode fiber for 10G Ethernet (10GBase-SR). To achieve this distance, a total link loss of 2.6 dB is needed with a maximum total connector loss of 1.5 dB. As the total connector loss in the channel increases above 1.5 dB, the supportable distance decreases the channel loss increases. When extended distances or multiple connector matings are required, low-loss performance modules and connectivity may be necessary. OM3 is bandwidth-limited beyond 300 meters.
As the network migrates to 100G, the link-loss requirements are the same as 40G. In this scenario, two 50-meter links are connected from the MDA to the HDA. 100G switches are deployed, and the link loss is calculated from the HDA to the MDA and from one HDA to another. In this case, both links are below the 1.9-dB maximum for 100G on OM3 fiber.
To best meet the needs of the future, MPO-based connectivity using OM3 and OM4 fiber is the ideal solution in the data center. With inherent modularity and optimization for a flexible, TIA-942-compliant structured cabling installation, MPO-based optical fiber systems can be installed for use in today’s applications, while providing an easy migration path to future high-speed technologies such as 40G and 100G Ethernet.