Issue link: http://www.epageflip.net/i/1043933
42 I ICT TODAY If looking beyond 100GBASE-SR4, IEEE 802.3cd (when published) will support 200GBASE-SR4 using the same number of fibers as 100GBASE-SR4 to again provide an easy transition. Looking even further ahead and targeted for data centers only, 400GBASE-SR4.2, found in draft IEEE 802.3cm, will also use the same number of fibers in a four-pair scheme that will leverage two wavelengths per fiber. When looking for a migration path with fewer connectivity components to be replaced or added when upgrading, a 24-fiber MPO system can simplify migration and reduces costs for both components and installation. For example, when a 24-fiber backbone trunk cable is installed in a 10GBASE-SR network, that backbone stays in place when upgrading to either a 40GBASE-SR4 or 100GBASE-SR4 network. A single 24-fiber MPO terminated cable with an appropriate cassette at each end can support 12 x 1000BASE-SX or 10GBASE-SR links, or 3 x 40GBASE-SR4 / 100GBASE-SR4 links, simplifying network upgrades immensely. When equipment is upgraded, only cassettes and patch cords are exchanged for the appropriate new MPO/MTP components. Non-IEEE-Based Applications Consider a scenario where there is duplex (two strand) multimode fiber in a network. If wanting to upgrade to a higher bandwidth, such as 40 and 100 GbE/s, the technician or installer would likely need MPO/MTP connections at some point. However, if not in the position to do that today, then there are some non-IEEE options available. The proprietary QSFP 40 Gb/s Bidirectional (Bidi) Transceiver, QSFP-40G-SR-BD, has a duplex LC connector interface using multimode fiber. Each BiDi transceiver consists of two 20 Gb/s transmit and receive channels, enabling an aggregated 40 Gb/s link over a two-strand multimode fiber connection using two wavelengths as shown in Figure 4. This transceiver transmits 850 nm at 20 Gb/s on one fiber, and then receives on that same fiber at 900 nm. This allows customers to reuse their existing duplex 10GBASE-SR infrastructure for migration to 40 Gb/s connectivity. FIGURE 4: Cisco 40 Gb/s BiDi, Bi-directional transmission over two wavelengths. In addition, non-IEEE versions defining 100 Gb/s over duplex have been released (Figure 5), extending the life of those older duplex installations. Support is only stated for OM3, OM4 and OM5. FIGURE 5: Cisco 100 Gb/s Bi-directional transmission over two wavelengths.