Is OM5 Fiber a Good Solution for the Data Center?

Wideband multimode fiber (WBMMF) is a new fiber medium specified in ANSI/TIA-492AAAE, published in June 2016. The ISO/IEC standards committee recently voted to use OM5 as the designation for WBMMF to be listed in the upcoming ISO/IEC 11801, 3rd edition. OM5 fiber specifies a wider range of wavelengths between 850 nm and 953 nm. It was created to support Shortwave Wavelength Division Multiplexing (SWDM), which is one of the many new technologies being developed for transmitting 40 Gb/s, 100 Gb/s, and beyond.

OM5 is being presented as a potential new option for data centers that require greater link distances and higher speeds. However, many enterprise IT and data center managers are increasingly adopting single-mode fiber systems to solve these challenges.

So, what are the reasons a data center might consider installing OM5?

"OM5 offers a longer cabling reach than OM4."
The difference is minimal.
For all the current and future multimode IEEE applications including 40GBASE-SR4, 100GBASE-SR4, 200GBASE-SR4, and 400GBASE-SR16, the maximum allowable reach is the same for OM5 as OM4 cabling. Based on application testing recently done with 40G-SWDM4 transceivers, it has been proven that OM4 could support about a 400-meter reach and OM5 a 500-meter reach. If a data center is using non-IEEE-compliant 100G-SWDM4 transceivers, they would see a 150-meter reach with OM5 — only 50 meters more than OM4. For most cloud data centers, if they have cabling runs over 100 meters, they will likely use single-mode for 100 Gb/s and greater speeds. 

"OM5 will reduce costs."
It won't.
OM5 cabling costs about 50% more than OM4. In addition, if you look at the cost of a full 40 Gb/s channel, including SWDM transceivers, the amount per channel is still 40% more than a 40GBidi/OM4 channel. The costs of single-mode transceivers have declined considerably over the past 12-18 months due to silicon photonics technologies and large hyperscale data centers buying in large volumes. When comparing the price of 100 Gb/s transceivers, 100G-PSM4 using single-mode fiber is the same price as 100GBASE-SR4 using multimode fiber.

"OM5 is required for higher speeds."
Not true.
All of the IEEE standards in development for 100/200/400 Gb/s will work with either single-mode (OS2) or multimode (OM4). The majority of these next-generation speeds will require single-mode. IEEE always strives to develop future standards that work with the primary installed base of cabling infrastructure so customers can easily migrate to new speeds. In addition, none of the these currently active IEEE standards addressing next-gen speeds (802.3bs or 802.3cd) will use SWDM technology.

"OM5 will create higher density from switch ports."
It won't.
It has been common for data centers using 40GBASE-SR4 to increase port density by breaking out 40 Gb/s ports into 10 Gb/s channels. This is also a benefit of new 100GBASE-SR4 modules, which use OM4 cabling. If a data center manager decides to use 100G-SWDM4 modules with OM5 cabling, they cannot break out into 25 Gb/s channels. This would become a real issue as the 25 Gb/s ecosystem fully develops and we begin to see more 25 Gb/s to the server.

Leviton does not see any good reason to currently recommend OM5 to large data center operators. For enterprise data centers looking at migrating to 40GBASE-SR4 or 100GBASE-SR4, OM5 offers no additional benefit over OM4 or OM4+. And larger cloud data centers are either already using single-mode or planning to move to single-mode in the near future for migration to 800 Gb/s and 1 Tb/s without changing out their cabling.

You can learn more about Leviton's multimode and single-mode solutions at Leviton.com/fiber.