A Guide to Multimode Fiber Types (OM1-OM5)

Written by Ben Hamlitsch, trueCABLE Technical and Product Innovation Manager RCDD, FOI

At the end of this article, you should be able to identify each MM cable jacket in the image above.

Over the years we have seen many multimode fiber types. From the beginning with OM1, to the most current OM5, there have been various improvements to the overall performance of the optical fiber. In today’s ever expanding cabling systems, where higher bandwidth needs increase more and more, there has been a need to optimize the multimode fiber used for these applications.

Multimode fiber has become the fiber of choice to achieve 10Gbps speed over distances required by LAN enterprise and data center applications. There are several kinds of multimode fiber types available for high-speed network installations, each with a different reach and data-rate capability. With so many options, how do you know what multimode fiber type to use?

First, let’s explain what multimode fiber is and where it is commonly used. Multimode fiber is a kind of optical fiber mostly used in communication over shorter distances, for example inside a building or for the campus. Multimode fiber is also very commonly used in Data Centers. Multimode fiber cable has a larger core, typically 50 or 62.5 microns that enables multiple light modes to be propagated. Because of this, more data can pass through the multimode fiber core at a given time. The maximum transmission distance for multimode fiber cable is around 550m at the speed of 10Gbps. It can transmit farther at lower data rates, such as going about 2km at 100Mb/s.

A Closer Look at Each Type

Let’s take a closer look at each one of the multimode fiber types. Starting in 1989 with OM1 to the most recent OM5 which came out in 2014.

OM1 typically comes with an orange jacket and has a core size of 62.5 µm. It can support 10 Gigabit Ethernet at lengths of up to 33 meters. It is most commonly used for 100 Megabit Ethernet applications, where longer cable runs are needed and where copper cabling is unable to support those lengths. This fiber type commonly uses a LED light source.

OM2 also comes with an orange jacket and uses a LED light source, but with a smaller core size of 50 µm. It supports up to 10 Gigabit Ethernet at lengths up to 82 meters but is more commonly used for 1 Gigabit Ethernet applications.

OM3 comes with an aqua color jacket. Like the OM2, its core size is 50 µm, but the cable is optimized for laser-based equipment. OM3 supports 10 Gigabit Ethernet at lengths up to 300 meters. It can support 40 Gigabit and 100 Gigabit Ethernet up to 100 meters; however, 10 Gigabit Ethernet is most commonly used.

OM4 shares the same distinctive aqua jacket with OM3 fiber. Additionally, we are also seeing adoption of the violet OM4 fiber cabling. This newer addition has added benefits when cabling existing OM3 fiber and adding OM4 to your application. As we can see in the table below, there are advantages to OM4 fiber over OM3. However, the TIA/EIA continued with the same color aqua. This can cause cabling performance issue if the cabling is not carefully checked to make sure it is OM4 with OM4 or OM3 with OM3. Core sizes are the same so there are no issues in that respect, however cable construction and performance differences between OM3 and OM4 cable need to be considered in higher bandwidth cabling systems where longer lengths are required. OM4 was developed specifically for VSCEL laser transmission and allows 10Gbps link distances of up to 550m compared to 300m with OM3. And it’s able to run 40/100GB up to 150 meters, running multiple fiber in parallel or utilizing an MPO connector.

OM5, also known as WBMMF (wideband multimode fiber), is the newest type of multimode fiber. It has the same core size as OM2, OM3, and OM4. The color of OM5 fiber jacket was chosen as lime green. It is designed and specified to support at least four WDM (wave division multiplex) channels at a minimum speed of 28Gbps per channel through the 850-953 nm window.

Differences Between Fiber Types

So, what is the difference between all these multimode fiber types? The prime distinction between multimode fibers rests on physical difference. Accordingly, physical difference leads to different transmission data rates and distances.

Multimode fiber physical difference mainly lies in diameter, jacket color, optical source, and bandwidth, which is described in the following table.

Multimode fibers can transmit different distance ranges at various data rate. You can choose the one most suited according to your actual application. The max multimode fiber distance comparison at different data rate is specified below.

In today’s fiber applications singlemode fiber cabling systems are advantageous in terms of bandwidth and reach for longer distances. However, multimode fiber easily supports most distances required for enterprise and data center networks at a cost dramatically less than singlemode fiber.

Multimode fiber can transmit multiple signals at the same time in the same fiber cable. More importantly, the signals being transmitted carry very little to almost no loss. Therefore, the network user can send more than one packet in the cable at the same time, and all information will be delivered to their destination without any significant interference.

Multimode fiber can support many data transfer protocol, including Ethernet, Infiniband, and Internet protocols. Therefore, one can use the cable as the backbone of a series of high value applications.

With a larger fiber core and good alignment tolerances, multimode fiber and components are less expensive and often are easier to work with. In addition, fiber connector, fiber adapter, and multimode patch cords are less expensive to operate, install, and maintain than singlemode fiber cables. As fiber optics becomes more and more mainstream, and we see more adoption, overall cost will start to level out between multimode and singlemode fiber systems.

Due to its high capacity and reliability, multimode fiber is usually used for backbone applications in buildings. In general, Multimode cable continues to be the most cost-effective choice for enterprise and data center applications up to the 500–600-meter range. But it’s not to say that we can substitute singlemode fiber with multimode fiber cable. As for whether to choose a singlemode fiber patch cord or multimode patch cord, it all depends on applications that you need, transmission distance to be covered, as well as the overall fiber loss budget allowed.

HAPPY NETWORKING!

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