How Does Multimode Fiber Realize 40G/100G Ethernet Migration?

Updated on Aug 29, 2022 by

100G Network

Most data centers are migrating their network to 40/100G to support high-speed transmission, thanks to the cloud, Big Data, and IoT deployments.

The core technologies of 40 GbE are quite mature, and upgrading from 10G to 40G can be more convenient. However, rapidly growing enterprises and data centers that need even higher bandwidth and expanded networks go for 100G and beyond. This article delves into the critical components of a successful 40/100GbE network migration, examining the roles of transmission media, media-dependent interfaces, and fiber optic transceivers. Continue reading to gain valuable insights into optimizing your high-speed network deployment.

40G/100G Transmission Media

Whether migrating to a 40G or 100G network, you’ll need to choose a transmission media that supports the transmission speed and distance you want. 40G Ethernet supports three media systems:

  • 40 GbE over copper cable for short transmission distance.

  • 40 GbE over four short-range multi-mode fiber cables.

  • 40 GbE over four wavelengths carried by a long-distance single-mode fiber cable.

It’s worth noting that copper is cheaper but only supports 40G transmission for shorter distances. For a 100 GbE network, fiber optic cables are commonly used, except within the same server rack where direct-attach copper cables may be used.

Single-mode fiber cables support 40G and 100G transmission up to a distance of 10 km/6.2 miles. On the other hand, multi-mode fiber cables support short-distance transmission. Only OM3, OM4, and OM5 cables support 40G and 100G transmission. OM3 cable can support 40/100 GbE for a maximum of 100m, while OM4 and OM5 support a maximum distance of 150m for both transmission standards.



Media Dependent Interface (MDI)

Media dependent interface is an Ethernet port connection that connects network devices such as switches and hubs without using a null-modem or crossover cable. A suitable MPO (multi-fiber push-on) adapter is often used as the MDI for multimode fiber cables. The benefit of using an MPO connector is that it can support up to 24 fibers in one ferrule. With the 40 GbE transmission, a 12-position MPO connector is used. Only four transmit fibers are used on each side of the MPO connector, leaving the middle four unused.

MPO Connector

For 100 GbE transmission, a 24-position MPO connector with 12 fibers in each row is used. But only ten fibers on the top and another ten on the bottom rows are used, leaving the middle four unused. Besides MPO connectors, you can also use LC connectors. The LC connector comes with one fiber in each ferrule but supports wideband multimode fiber technology for higher transmission speeds of up to 400GbE.

LC Connector

As fiber optic density increases, field termination and splicing become much more complicated. You can save time & energy by choosing custom cable lengths and pre-terminated MPO and LC connectors.


Fiber Optic Transceiver

Every fiber optic network needs photoelectric conversion to ensure effective conversion between different optical and network signals. Fiber optic transceivers are responsible for this photoelectric conversion and are a critical part of the network during migration. Commonly used transceivers for 40G/100G transmission are the CFP, QSFP+, and CXP transceivers.

QSFP+ is popular in 40G applications, while CFP supports 40 and 100GbE. CXP targets high-density, 100 GbE and works well with multimode fiber for short-distance deployments.

When choosing a transceiver, ensure it is switch compatible. Several third-party transceivers are compatible with popular high-end switches. Choosing them instead of the original brand transceivers will save you a lot of money. Just ensure the transceiver is from a reputable manufacturer to avoid quality and interoperability issues down the line.


Migration Path for 40/100 GbE

A practical and seamless migration to a higher Ethernet speed ensures minimal disruption with little to no replacement of existing connectivity components and fiber optical cabling. The latter is often deployed for the switch to switch connections, switch to server, and SAN connections.

Some components needed during migration include modules, harnesses, adapter plates, and trunks. 40/100 GbE migration uses nearly the same components except for the MPO connectors. Using pre-terminated optical fiber cabling is often preferred as it eliminates rework and testing and minimizes cost during installation. It also allows for convenient replacement or the addition of new connections in the future.

When choosing between 12 and 24-fiber trunks, always pay attention to the network density and congestion. Generally, high-density connectivity needs more active equipment, but the space could be limited. 24-fiber cabling will work best as it will allow for more connections without increasing the number of ports. It also reduces the cables needed compared to a 12-fiber model, translating into a lighter load, convenient management, and reduced cooling costs.



As the demand for high-speed connectivity increases, large corporations, and data centers are moving from the legacy 1G/10G to the faster 40GbE and 100 GbE networks. There are obvious benefits of migrating to a higher networking standard. And considering the rate of technological evolution and adoption, the decision to upgrade the enterprise network is just a matter of time.

A successful migration path for a 40G/100G network is more about understanding the required components and working with the right IT professionals. An excellent place to start is to pick the right transmission standard based on your current and future data and networking needs. You’ll then choose a suitable transmission media, media-dependent interface, and a fiber optic transceiver—the rest are more technical, and your IT technician will handle them.

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