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40 GbE and 100 GbE over Multimode Fiber

To support the changing and fast-growing bandwidth demands of data centers, the IEEE ratified standards for supporting 40 GbE (Gigabit Ethernet) and 100 GbE (Gigabit Ethernet), known as IEEE 802.3ba. Both 40 and 100 GbE can be deployed using the same cabling systems in use today. Multimode will employ parallel optics using MPO interconnects and require additional cable infrastructure depending on the system deployed while single mode fiber will employ serial transmission and use LC or SC connectors. Each has its own advantages and disadvantages. In this post, 40 GbE and 100 GbE over multimode fiber will be introduced.

40 GbE and 100 GbE Standard

IEEE published the IEEE 802.3ba standard for 40 Gigabit and 100 Gigabit Ethernet in June 2010. multimode optical fiber OM1, OM2, OM3 and OM4 have different capabilities of supporting different Ethernet applications. Only the laser optimized multimode fiber (grades OM3 and OM4) are capable of supporting 40G and 100G Ethernet. The next part will focus on the cabling requirements of 40 GbE and 100 GbE over multimode fiber. The table below shows 40GE and 100GE specifications.

40 GbE and 100 GbE Specifications

Implementing Parallel Optics

Traditionally, the Ethernet standard has relied upon duplex fiber cabling with each channel using one fiber to transmit and the other to receive. However, the 802.3ab standard requires multiple lanes of traffic per channel. To do this, the 40/100GbE standard uses parallel optics. The 802.3ba standard defines the parallel operation of four OM3/OM4 fibers for 40 GbE in 40GBASE-SR4 and the parallel operation of ten OM3/OM4 fibers for 100 GbE in 100GBASESR10. Two fibers have to be used per link because this arrangement is full duplex operation, i.e. simultaneous transmission in both directions. Therefore the number of fibers increases to eight for 40GBASE-SR4 and to 20 for 100GBASE-SR10. In the parallel optical link, the signal is split, transmitted over separate fibers and then joined again. That means the individual signals have to arrive at the receiver at the same time. Any skew in signal components has to be kept within tight tolerances. Trunk cables preterminated with MPO/MTP connectors are therefore the best choice for reliable transmission.

What Is 40 GbE and 100GbE over Multimode Fiber?

40G Ethernet and 100G Ethernet over multimode fiber uses parallel optics at 10 Gb/s per lane. One lane uses 1 fiber for each direction of transmission. 40G Ethernet requires 8 fibers. 100G Ethernet requires 20 fibers. The minimum performance that is needed to support 40 GbE and 100 GbE over multimode fiber is OM3 fiber for a distance of 100 meters. Cabling with OM4 fiber provides the capability to extend the reach up to 150 meters. Parallel optical channels with multi-fiber multimode optical fibers of the categories OM3 and OM4 are used for implementing 40 GbE and 100 GbE. The small diameter of the optical fibers poses no problems in laying the lines, and 802.3ba standard incorporated the MPO multi-fiber connector for 40GBASE-SR4 and 100GBASE-SR10, which can contact 12 or 24 fibers in the tiniest of spaces.


Optical fiber cabling is commonly deployed for backbone cabling in data centers for switch to switch connections and also for horizontal cabling for switch to server and storage area network connections. The use of pre-terminated optical fiber cabling can facilitate the migration path to 40G and 100G Ethernet in the future. Fiberstore can supply you with top-quality components for your 40 GbE and 100 GbE network, like 40G QSFP transceivers, and all kinds of QSFP+ cable choices, it also assists you competently with all questions involving planning, installation and maintenance.

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