A Guide to Multimode Fiber Types (OM1-OM5)

Written by Don Schultz, Senior Technical Marketing Specialist, Fluke Networks Certified Copper/Fiber CCTT, BICSI TECH, INSTC, INSTF Certified

Have you ever heard an installer exclaim “be careful with the fiber cable, it is glass and will shatter!” Any older installer/technician will likely have either said this, or heard it. Of course fiber optical cable (in general) is considerably more durable since this frantic refrain from the past, and has evolved over the years. We have seen many multimode (MMF) fiber types introduced, and technology has improved. Not only this, but from the beginning with OM1, to the most current OM5, there have been various improvements to the overall performance of the optical fiber, and multimode fiber has evolved with these needs too.

Please watch our video and then come back and finish reading this blog. Both mediums bring something to the table!

Where is Multimode Fiber Optical Cable Used?

Multimode fiber optical cable in enterprise LAN and data centers

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 typically has a 50µm (micron) core that enables multiple light modes to be propagated. Because of this, more light can pass through the multimode fiber core at a given time. Normally, this would be considered a good thing if we were not talking about fiber optical cable.

Multimode’s ability to allow multiple modes of light to transmit down the cable is precisely what holds it back from achieving extremely long distances due to what is called “Modal Dispersion”. Think of Modal Dispersion as junk, and your transmission equipment has to sort through the junk to get to the right light (called the mode).

Given this inherent limitation, multimode fiber optic cable is usually deployed at distances of 1,312 feet or less to handle 10 Gbps traffic (assuming OM4 or OM5) in backbone situations. In a large building, 1,312 feet may be considered a short distance!

Multimode fiber has become the fiber of choice to achieve 10Gbps speed over distances required by LAN enterprise and data center applications.

Multimode fiber optical cable in the home

ANSI/TIA 570-E (residential standard for communications cable) now recommends at least two fibers per outlet in new construction, along with Cat6A, in every room of your home except the bathrooms. Given the inherent distance limitations of multimode fiber optical cable, this type of fiber is perfect for any kind of home use, even underground backbone communications links between multiple outbuildings. Please see Fiber Optics In The Home - Why and When? for additional information and also see How To Use A Fiber Optic Media Converter In Your Network for a practical guide on how to deploy it!

As you noticed, I called out specific OM types like OM4 or OM1 when referring to speed and distances. That is where the practical difference lies between these multimode types. Let’s cover each one in some detail.

Differences Between OM1, OM2, OM3, OM4 and OM5

Starting in 1989 OM1 was introduced. The most recent is OM5 which came out in 2014. OM1 had a bigger core -- 62.5 micron and all subsequent versions use 50 micron.

50 micron vs 62.5 micron fiber core size difference

First up, below is a cross sectional view of the difference in core size of the early OM1 vs later OM versions.

Multimode Fiber Comparison OM1 through OM5

Below is a comparison chart showing the similarities and differences between the various multimode fiber types.

Handy multimode fiber comparison chart OM1 through OM5

Here are some additional points of difference between the various OM types. Please note that all performance data is at the 850nm (most common) mode.

OM1

• OM1 typically comes with an orange jacket
• Core size of 62.5 micron
• Supports 10 Gigabit Ethernet, but only up to 33 meters
• 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
• OM1 is officially obsolete per ANSI/TIA

OM2

• OM2 typically comes with an orange jacket
• Core size of 50 micron
• Supports 10 Gigabit Ethernet, but only up to 82 meters
• Like OM1, this fiber type commonly uses a LED light source
• Was seen installed for applications where long distances at 100 Mbps or 1 Gbps were required and copper twisted pair Category cable could not meet the need
• OM2 is effectively obsolete

OM3

• OM3 typically comes with an aqua jacket
• Core size of 50 micron
• Core and cladding are laser optimized for use with inexpensive and widely available VCSELs (Vertical Cavity Surface Emitting Lasers)
• OM3 supports 10 Gigabit Ethernet at lengths up to 300 meters
• OM3 also supports 40 Gigabit up to 100 meters and 100 Gigabit Ethernet up to 70 meters; however, 10 Gigabit Ethernet is most commonly used
• Installed for applications similar to OM1 and OM2 where distance was the priority, or for backbone applications where speed is the priority
• OM3 is still available, but falling out of favor for OM4

OM4

• OM4 is seen typically with an aqua jacket, but may have a erika violet jacket as well
• Core size of 50 micron
• Laser optimization is enhanced over OM3
• OM4 supports 10Gbps link distances of up to 400 meters and further extends 40 Gbps and 100 Gbps links up to 150 and 100 meters, respectively
• Installed for applications similar to all previous OM variations where distance was the priority, or for backbone applications where speed and distance are also priority
• OM4 is widely available and currently being deployed

OM5

• Outer jacket color is lime green
• OM5 is also known as WBMMF (wideband multimode fiber)
• Newest type of multimode fiber
• Same 50 micron core size as OM2, OM3, and OM4
• Designed for PONs (Passive Optical Networks)
• Further enhanced to support at least four WDM (wave division multiplex) channels at a minimum speed of 28Gbps per channel through the 850-953 nm window in PONs
• Outside of WDM data transmission, performance is identical to OM4 using conventional vertical cavity lasers

Singlemode (SMF) fiber vs multimode fiber

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

Please see more about the differences between singlemode and multimode fiber in Singlemode vs Multimode Fiber Optic Cable.

Frequently Asked Questions

What are the fiber optic jacket colors for OM1-OM5?

OM1 and OM2 share the same color, which is Orange. OM3 is aqua. OM4 can be Aqua or Erika Violet. OM5 is Lime Green.

Is multimode fiber optic cable extremely delicate?

Some types are more fragile than others, but fiber patch cords and indoor bulk distribution fiber are quite durable. The older fragile (easily shattered) glass construction is a thing of the past. New coatings and manufacturing techniques greatly reduce fragility. The latest innovation is a tight buffered bend-insensitive construction. See Top 10 Things You Should Never Do With Fiber Optic Cable for more.

What is the difference between OM3 and OM4 fiber?

Core sizes are the same so there are no issues in that respect, however the core and cladding (glass) of OM4 are further optimized for laser use. This results in OM4 having higher performance and distance potential at 10Gbps and above. trueCABLE recommends OM3 for existing installations that use it, but new installations should be installed with OM4.

Can you mix OM3 and OM4 multimode fiber?

Yes, but this can cause cabling performance issues in some cases. Depending upon the application, your fiber communication channel may be degraded to OM3 performance if you mix OM3 and OM4.

Conclusion

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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