May 4, 2017

FAQs About OM5 Fiber Optic Cable

Data centers everywhere are moving quickly to manage ever-increasing bandwidth demands. And the emergence of cloud computing has acted as catalyst for driving even faster adopting of new network technology and higher bandwidth. Speeds as high as 40G and 100G Ethernet have already become mainstream in data centers, and the industry is working collaboratively on next-generation Ethernet development, such as 200G and 400G Ethernet. In this high speed migration, multimode fiber (MMF) plays an important role. As everyone knows, OM1/OM2/OM3/OM4 are commonly used multimode fibers in networking field, especially OM3 and OM4 are proven to be the future-proofing MMF. And now, a new types of MMF fiber medium—OM5, specified in ANSI/TIA-492AAAE and published in June 2016, is introduced. OM5 is being presented as a potential new option for data centers that require greater link distance and higher speeds, however, is it really a good solutions for data centers? This post will deal with this question from some FAQs about OM5.

Q: Does OM5 Offer a Longer Transmission Distance than OM4?

A: Actually, for all current and future multimode IEEE applications including 40GBase-SR4, 100GBase-SR10, 200GBase-SR4, and 400Gbase-SR16, the maximum allowable reach is the same for OM5 as OM4. According to a recently done application testing with 40G-SWDM4 transceivers, it shows that 40G-SWDM4 could reach 400 meters over OM4 cable, while over OM5 cable, the module can achieve link length up to 500 meters. Besides, if a data center is using non-IEEE-compliant 100G-SWDM4 transceivers, it proven that OM5 can support 150-meter reach—only 50 meters more than OM4. In addition, for most data centers, when transmission distance over 100 meters, IT managers will choose single-mode fiber.

transmission distance of OM4 and OM5 in 100G

Q: Does OM5 Costs Less?

A: As the matter of fact, OM5 cabling will costs about 50% more than OM4. Besides, with the considerably declined costs of single-mode transceivers over the past 12-18 month due to silicon photonics technologies and large hyperscale data centers buying in large volumes, more and more users will be pone to choose single-mode transceiver modules. For example, 100GBase-PSM4 using single-mode MTP trunk cable that can support 500-meter reach is only $750.

Q: Is OM5 Really Required for Higher Speeds?

A: All of the IEEE standards in next-generation 100/200/400G Ethernet will work either with SMF and MMF, but in most situations, these next-generation speeds will require single-mode fiber, since IEEE always strives to develop future standards that work with the primary installed base of cabling infrastructure, so customers can easily upgrade to new speeds. Besides, none of these current active IEEE standards addressing next-generation speeds will use SWDM technology.

Q: Will OM5 Create Higher Density from Switch Port?

A: As we all know, it is common in data center using 40GBase-SR4 to increase port density by breaking out 40G to 10G with MTP breakout module or MTP breakout cable. This is also a benefit of new 100GBaes-SR4 modules, which use OM4 cabling. However, if data center manager decides to use 100G SWDM4 modules with OM5 cabling, they cannot breakout into 25Gb/s channels, which will become a real issue as the 25Gb/s ecosystem fully develops and we begin to see more 25G to the server.

Summary

According to the questions we have discussed above, it is apparent that OM5 is not suitable for large data centers. As far as I’m concerned, for current high-speed network applications, OM3 and OM4 is still the most recommended multimode fibers.

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