Data Center Design for 40/100G

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/ 100G Ethernet, Fibre Channel (32G and beyond) and InfiniBand (40G and beyond), the cabling infrastructures installed today must provide scalability to accommodate the need for more bandwidth in support of future applications.

The Need for Speed

1G and 10G data rates are not adequate to meet the future needs of high-bandwidth applications. The requirement for higher data rates is being driven by many factors. Switching and routing, virtualization, convergence and high-performance computing environments are examples of where these higher network speeds will be required within the data center environment. Additionally, Internet exchanges and service provider peering points and high-bandwidth applications, such as video-on-demand will drive the need for a migration from 10G to 40/100G interfaces.

IEEE 802.3ba 40G and 100G Ethernet Standard Ratified

The Institute of Electrical and Electronics Engineers (IEEE) 802.3ba 40/100G Ethernet Standard was ratified in June 2010. The standard provides detailed guidance for 40/100G transmission with multimode and single-mode fibers. The standard does not have guidance for CAT UTP/STP copper cable. OM3 and OM4 are the only multimode fibers included in the standard. Multimode fiber utilizes parallel optics transmission instead of serial transmission due to the 850 nm VCSEL modulation limits at the time the guidance was developed. Single-mode fiber guidance utilizes duplex fiber wave division multiplexing (WDM) serial transmission. 40/100G multimode fiber physical media dependent (PMD) variants continue to offer a significant value proposition compared to single-mode fiber PMDs for short length interconnects in the data center. Parallel optics transmission, compared to traditional serial transmission, uses a parallel optical interface where data is simultaneously transmitted and received over multiple fibers. The 40/100G Ethernet interfaces are 4 x 10G (Figure 1) channels on four fibers per direction and 10 x 10G (Figure 2) channels on 10 fibers per direction, respectively.

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