100G & 400G Data Center TOPICS

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.