As data centers scale to ever larger sizes in recent years, the demand for great bandwidth and higher speed is growing too. Recently, OM5 has been approved to be a new type of multimode fiber (MMF) for high speed data center applications. And various discussions about its characteristics and features attract much attention. This article will illustrate some frequently asked questions to help you get a clear view on OM5 fiber optic cable.

What Is OM5 Fiber Standard?

Telecommunications Industry Association (TIA) initiated a workgroup in October 2014 to develop guidance for a wide band multimode fiber (WBMMF) 50/125 μm standard to support short wavelength division multiplexing (SWDM) transmission. The TIA-492AAAE Standard was published in June 2016. The IEC WB MMF standard is anticipated to be completed by early 2017.

What Is Different about OM5 Fiber?

OM5 is designed to support at least four low-cost wavelengths in the 850-950 nm range, enabling optimal support of emerging Shortwave Wavelength Division Multiplexing (SWDM) applications that reduce parallel fiber count by at least a factor of four to allow continued use of just two fibers (rather than eight) for transmitting 40 Gb/s and 100 Gb/s and reduced fiber counts for higher speeds.

What Is SWDM?

Shortwave data center connections are usually powered by VCSELs operating near a wavelength of 850 nm. Shortwave wavelength division multiplexing (SWDM) is a technology that uses four wavelengths across the 850 to 950 nm range. SWDM transceivers were designed to use 2-fiber connectivity into the transceiver with OM5 multimode fiber.

Will Field Channel Loss Measurements Be Required at Both 850 and 953 nm?

No. Compliant 850 nm field channel loss measurements can be used to demonstrate 953 nm channel loss conformance.

Can SWDM Be Used over OM3/OM4?

Yes. SWDM transceivers are compatible with OM3/OM4/OM5 optical connectivity solutions.

What Are the Expected SWDM Data Rates and Distances?

According to SWDM4 MSA technical specifications, the 40/100GbE expected maximum operational distances are given in the table below.

What Are the Specified OM5 Cable Effective Modal Bandwidth (EMB) Values?

EMB ≥ 4700 MHz・km at 850 nm EMB ≥ 2470 MHz・km at 953 nm

How Do OM3/OM4 EMB Values Compare to OM5 Cable?

EMB is specified only at 850 nm for OM3 fiber at 2000 MHz・km and OM4 fiber at 4700 MHz・km respectively. OM5 EMB values are specified at both 850 and 953 nm.

Is OM5 Fiber Compatible with Existing OM3 and OM4 Fiber?

Yes. OM5 cabling supports all legacy applications at least as well as OM4, and is fully compatible and intermateable with OM3 and OM4 cabling.

Is OM5 Specified in Optical Transmission Standards such as Ethernet and Fibre Channel?

There are no transmission standards that specify OM5 or SWDM. Transmission standards typically include only one multimode fiber variant that is selected based on economic, commercial, and technical criteria. Parallel transmission is the default multimode fiber variant for data rates ≥ 40G.

Is OM5 Multimode Fiber Compatible With Existing Optical Transceiver?

In fact, OM5 fiber does not support existing optical transceiver. Usually, 40G and 100G SWDM4 optical transceiver can be used with OM5 fiber. The SWDM4 transceiver uses a complex short wavelength division multiplex (SWDM) technology. Signals at four wavelengths (850nm, 880nm, 910nm and 940nm) are transmitted over one fiber. And only two fibers are required for bidirectional transmission.

What Cable Jacket Color Will Be Used for OM5 Multimode Fiber?

TIA has specified lime green as the official cable jacket color for OM5.

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

Actually, for all current and future multimode IEEE applications including 40GBase-SR4, 100GBase-SR10, the maximum allowable distance 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 fiber, 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.

Does OM5 Multimode Fiber Costs Less?

As the matter of fact, OM5 cabling will costs about 50% more than OM4. Besides, with the considerably declined costs of single-mode transceivers 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.

Is OM5 Multimode Fiber Really Required for Higher Speeds?

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.

Will OM5 Create Higher Density from Switch Port?

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.

OM5 Multimode Fiber Vs. Single Mode Fiber: Which to Choose?

Although the price of single mode fiber (SMF) is reducing recently due to new technologies application, the cost of pluggable optics still limits the implementation of SMF in data centers. Compared to that, OM5 can multiplex four wavelengths spaced in the range of 850nm to 953nm, increasing data capacity by a factor of four as well as reducing fiber cost. Furthermore, MMF has more advantages on installation, troubleshooting, cleaning and overall maintenance, which makes it a better choice in data centers. However, the problem for MMF is distance. And the maximum distance will decrease as the data speed grows. Therefore, multimode fiber has higher value to network owners for distance up to 500m and OM5 allows for migration to 400Gbps at the distance up to 150m. For applications beyond 500m, single mode fiber should be chosen.

Can FS Provide OM5 Multimode Fiber?

Yes. At presnt, FS can offer LC-LC and LC-SC OM5 fiber for 1m, 2m, 3m and 5m. For specific applications, custom service can also be provided.