Issue link: https://www.e-digitaleditions.com/i/1066130
January/February 2019 I 41 FIGURE 2: This illustration shows the leaf-spine architecture used in newer data centers, comparing the use of MPO-24 to MPO-12 to MPO-8. There are even more options when using short wave division multiplexing (SWDM). With four wavelengths operating at 50 Gigs each, that goes to 200 Gb right away. Then, if more lanes or fibers are added, a move to 400 and 800 Gb can be achieved. From 50 Gb, the next step would be a 100 Gigabit lane rate. By using wave division multiplexing as well as parallel construction, it is possible to reach the terabit range on a multimode fiber infrastructure. As data rates increase, there will be a combination of duplex and parallel schemes used in topologies. To ensure the flexibility of being able to move between duplex and parallel solutions, the best strategy is to install MPO-based technology now. WHICH MPO TO USE FOR HIGH SPEED NETWORKS? When considering the selection of the MPO connector for the leaf-spine trunks, it is important to take into consideration the expected applications to be supported and the number of fibers required. Figure 2 shows some of the potential options for leaf-spine connectivity. Wherever possible, the industry is driving toward the use of fewer fibers for higher speeds (i.e., using multiple wavelengths to support 40 and 100G over a duplex infrastructure with BiDi and SWDM implementations). In terms of practical application, the three most common MPO connector options (Figure 3) are MPO-8, MPO-12 and MPO-24: • MPO-8 is a legacy standard for the QSFPs, coming out of the transceivers running 40 Gb or 100 Gb. It is used for both multimode and singlemode transceivers and breakouts. It offers the lowest density option, because there are more components for the MPO-8 when moving forward into higher speeds. • MPO-12 is the legacy embedded base. With the use of different modules and array fanouts, it can accommodate multiple configurations. • MPO-24 is the newest option and is used on the trunk cables and modules. MPO-24 is one way to future proof the network, because it provides the highest panel density, allows the use of fewer components, and may offer the lowest first installed cost. For example, a 24-fiber MPO link would require only one MPO-24 on each end, taking up only one port in each fiber shelf. A 24-fiber link using 12-fiber MPOs would require four MPO connectors, taking up two ports in each fiber shelf. A 24-fiber link using 8-fiber MPO-24 VS MPO-12 VS MPO-8 FOR MULTIMODE TRUNKS LC Duplex Patch Cord MPO-8 Patch Cord MPO-24 - 3xMPO-8 Break-out SPINE Leaf-Spine Applications on multimode fiber Application 10GBASE-SR 2 40G-SR4 8 100G-SR4 8 100G-SR2 4 200G-SR4 8 100G-BiDi (?) 2 200G-SR1.2 (?) 2 400G-SR2.4 (?) 4 400G-SR1.4 (?) 2 400G-SR4.2/4.4 (?) 8 40G-BiDi 2 40G-SWDM4 2 100G-SWDM4 2 #Fibers LEAF SPINE LEAF LC Duplex Patch Cord MPO-24 - 3xMPO-8 Break-out 1 x MPO-24 Trunk 1 x MPO-24 Trunk 2 x MPO-12 Trunk 2 x MPO-12 Trunk 3 x MPO-8 Trunk 3 x MPO-8 Trunk MPO-8 Patch Cord DUPLEX PARALLEL