Which Optical Fiber Should You Use: OM4+ or OM5 Fiber?

Since the TIA ratified the specification for OM5, a wideband multimode optical fiber (WB-MMF), customers that are thinking about upgrading their existing infrastructure, or building out new, are asking a question: Should they deploy OM5 fiber?

I’ll get to the answer in a bit.  First, let’s talk about what OM5 is.

OM5 is essentially an OM4 fiber that has an additional bandwidth specification at 953nm.  Both OM4 and OM5 have bandwidths specified as 4,700MHz•km at 850nm, and OM5 has a bandwidth specification of 2,450MHz•km at 953nm.  OM4 does not have a bandwidth specified at 953nm.

OM5 was designed to be used with optical modules that employ Shortwave Wavelength Division Multiplexing (SWDM).  These new SWDM modules use four wavelengths that span from 850nm through 953nm, to implement 100Gbps links.

Each wavelength is modulated at 25Gbps and by multiplexing them together, one attains 100Gbps.  See figure 1.  Given what wavelengths are used in SWDM optical modules, it is easy to see why the OM5 standard was developed.

OM5 signature core fiber

OM5 was designed to be used with optical modules that employ Shortwave Wavelength Division Multiplexing

Figure 1 – Implementing SWDM

Back to the question.

You only need to consider using OM5 if you plan on deploying 100Gbps links using SWDM optical modules AND need to reach out past 100m.

The interest in using SWDM optical modules is that they allow deploying a 100Gbps link over duplex MMFs, rather than taking up eight parallel fibers required when using 100GBASE-SR4.  SWDM allows reusing the existing duplex fiber infrastructure.

However, there are many more ideal alternatives for deploying 100Gbps over duplex fibers, such as 100G BiDi, or using PAM4 modulation to achieve the higher data rate.

The other alternatives do not suffer from SWDM’s shortcomings, such as higher cost, higher operating temperatures, and the inability to support breakout applications.  If you still are thinking about using SWDM 100G optical modules, and the reach is under 100m, then one would be better off using standard OM3 or OM4, as it is less expensive than OM5.

If extended reach is needed, say for 40G BiDi, the better alternative to OM5 fiber would be our OM4 Signature Core MMF.  Our OM4 Signature Core MMF can reach out to 200m using 40G BiDi, while OM5 will only reach out to 150m, the same as OM4.

That is because at the wavelengths used by BiDi modules, OM5 fiber is no better than OM4.  In fact, OM4 Signature Core has outperformed standard OM5 fiber in several head-to-head competitions conducted at end-user sites.

If the decision is to use 100G SWDM modules AND you need to reach longer than 150m, the better fiber to use would be our OM5 Signature Core MMF.  Our OM5 Signature Core MMF uses the same reach-enhancing technology as our OM4 Signature Core, so you can take advantage of reaches greater than the standard by 20%.

For an in-depth explanation on how our OM4 Signature Core and OM5 Signature Core MMFs are able to achieve extended distances, please visit our Signature Core landing page, where you will find everything you need to know about Signature Core MMFs.

Better yet, view the recorded webinar, Where Do We Go From Here? A Fork in the Road for Multimode Fiber, presented by Robert Reid, our senior technical manager with our Data Center business unit.  In the webinar, not only does Robert talk about our Signature Core MMF, but also OM5, SWDM, and other topics surrounding multimode optical fiber and modules.

Finally, you can download our ebook for a comparison of the various fiber type.