OM2, OM3, OM4
Which upgrade is right for your network?

All Fifty-Micron Fiber Is Created Equal. Or is it?

Mike Palmer | Team Leader, Infrastructure Design Specialist

As a cable manufacturer, CABLExpress is presented with customers from all types of backgrounds. From small mom and pop shops looking for a single fiber jumper, to fortune 500 companies looking for robust structured cabling solutions – we see and hear it all.

Due to the variety of end user types in our wheelhouse, we’re tasked with answering questions from all across the board. Sometimes technical in nature, other times cost related - or a common question we are often fielding that combines both.

"If OM2, OM3, and OM4 are all 50 micron why wouldn’t I just buy the cheapest available?"

First, it’s important to note, OM1 isn’t in this discussion because we don’t want to mix core sizes. OM1, with a core size of 62.5 microns, should not be in the same link as 50-micron fiber. In general, if you can move away from OM1 you absolutely should be.

OM2 is an upgrade over OM1, largely because it is able to run 1gig of traffic, and is the first generation of 50-micron fiber jumpers. When the OM2 was first released it’s orange colored standard jacket made it very difficult for customers to differentiate from the OM1. The difference lies in it’s efficiency.  

What OM2 allows customers to do, is establish longer links than previous generations of multi-mode fiber. Multimode has always been viewed as more cost efficient than Singlemode due to the price of the transceivers used. With OM2 giving end users longer distances to work with, it became a great option to consider.

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This is new. When 1gig was surpassed by 10gig Ethernet speeds, the increased data bandwidth required another upgrade because of the fiber connections being used. Enter OM3 Multimode fiber. Standardized in 2002, the 50-micron core fiber jumper is recognized as the first “Laser Optimized Fiber.”

LED transceivers were on the decline as bandwidth needs started to ramp up. These transceivers couldn’t keep up with the rapid technology growth at the time and instead paved the way for a better type of transceiver to emerge.

This disparity lead to a new type of laser based Multimode transceiver that used a low cost laser known as VCSEL (pronounced VEX – EL). The VCSEL (Vertical Cavity Surface Emitting Laser) based transceivers were able to run high speed 10gig data efficiently as well as run 1gig data much further than OM2.

With the rise of laser-based transceivers, the multimode game was better than ever. From here, Laser Optimized Fiber was created as a fiber type that could move data faster than it’s OM2 predecessor.  

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Decisions, decisions. Changing the refractive index of the glass to decrease as it neared the outside of the channel, allowed the light to travel quicker on the edge of the Laser Optimized Fiber than other lanes. Increasing the speed for these lanes allowed for all light paths travelling down the fiber to arrive at their destination as close together as possible.

OM2 wasn’t able to do this because there was no grading in the end face of the fiber, proving to be difficult to keep up with the high 10gig of bandwidth.

Customers now had greater choices to leverage for what made sense to their network. A great approach was to leverage OM3 fiber wherever 50 micron could be used - even if 10gig wasn’t being run - so that it wouldn’t have to be replaced when the technology hardware of a network was due for an upgrade. This gave customers a migration path.

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Another upgrade? Of course, technology is an ever-growing creature and soon 10gig led way to 40gig for which the standard calls for OM4 Multimode fiber. OM4 fiber has been available since 2009 and allows customers access to another layer of technological capabilities.

As with the previous improvement, this fiber is capable of doing everything OM2 and OM3 could do, but better and at further distances. The price for OM4 fiber has come down considerably in recent years making it a much more logical purchase for multimode fiber needs.

With it’s capability to seamlessly work with both VCSEL based transceivers or older LED transceivers at the highest rate of performance, makes OM4 a very viable option for any fiber needs.

What to say when you didn’t read the all-employee email

Give me the CliffsNotes. In summary, OM2 became outdated when our multimode transceivers became laser based and bandwidth requirements approached 1gig. OM3 was able to work well with the laser based transceivers utilizing a graded refractive index to offer peak performance in a 10gig application.

The OM4 50 micron fiber type is recognized as the best performing multimode fiber type among those that have been standardized. It currently gives customers the longest migration path for their technology, working with 10/100, 1gig, 10gig, 40gig and even 100gig with the correct transceivers.

When looking for backbone runs, OM4 is something to highly consider because of its ability to withstand several generations of hardware upgrades where. OM2 on the other hand, fizzles quickly and would need to be replaced for 10gig applications.

Think of it like this. Buy OM4 once and grow - or buy OM2 once to later buy the OM4 and pay twice!


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About the Author

Michael Palmer is Team Leader for the CABLExpress infrastructure design specialist team. With more than two years of experience with CABLExpress, he is responsible for providing design support for all CABLExpress product lines and services, while maintaining data center cabling industry standards. Palmer is also the author of, Quality vs. Cost: The Threat of Low-Cost Cabling and featured in, Cleaning Up Your Closets - CABLExpress® Respect Layer One® #56.