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Mind the gap - the rising torrent of data and need for speed is leading to new choices in multimode fiber technology


The problem with most motorways is no matter how many lanes are built in the first instance, all too quickly they’re consumed and clogged by traffic. It’s similar with fiber optic infrastructure in buildings and data centers. As we speak, data volumes and data rates are being driven ever upwards by the growing impact of the Internet of Things and Big Data.

Add to this the plethora of next gen technologies such as Artificial Intelligence, Machine Learning and Virtual Reality and we have mixed a heady cocktail of new applications and on-demand services, where near instantaneous ‘real-time’ response times aren’t just nice to have, they’re absolutely expected. For good measure, there’s also the aggressive future development of Ethernet to throw in.


It’s abundantly clear the gap between the optimization of multimode fibers and the growth in transmission speeds is unlikely to be closing anytime soon - as we know, an increase in data rates almost always means a reduction in transmission length.

Unsurprisingly, all of the above presents an ongoing challenge for the fiber optic cabling industry, from those continually striving to bring affordable higher performance fiber optic solutions to market as quickly as possible, to systems integrators and installers planning immediate and future deployments.


For sure, singlemode fiber offers advantages in bandwidth and reach over longer distances, but multimode fiber continues to be the most cost-effective choice for enterprise and data center applications. Multimode technology has travelled a long way since its introduction nearly 40 years ago - initially as a long haul solution. And almost a decade ago it was the dramatic necessary increase in transmission speeds that spurred the introduction of OM4 multimode fiber in 2010. This immediately delivered bandwidth improvement over the by then 11 year old OM3, with maximum transmission lengths increasing to 550m for 10 Gbit/s.

For sure, OM4 is still alive and well today, but this is not the end of the journey. As the saying goes, “Necessity is the mother of invention” and this has never been truer than in the fiber optic network industry. Various innovative concepts have been put forward for addressing the market’s insatiable appetite for data and speed. One, for example, involves the multiplying of the number of fibers and the parallelization of data rates.


The birth of OM5

Another, and more viable option, has been the parallel transmission of multiple signals over one fiber. It was this approach which resulted in the development of WBMMF (Wideband Multimode Fiber) which provides optimized transmission parameters for the range 840 nm to 953 nm.

As the 5th incarnation of multimode fiber, it was designated OM5 in October 2016 by the ISO/IEC 11801. Now available, it delivers all the benefits of using multimode fiber in buildings and data centers while, like OM4, able to support all legacy applications. It’s also compatible with OM3 and OM4 cabling.


What makes OM5 different?

There are key differences with OM5 compared to OM4. Previously, the step up to the next higher OMx class has always been typified by a significant improvement in the quality of the fibers – in particular, the bandwidth-length – for a specific transmission window.

However, OM5 fiber is optimized over a larger range of wavelengths, allowing data transmission by means of wavelength multiplexing in the area around the first optical window. The actual use of these fibers, with its expanded transmission area, calls for a special transceiver and SWDM (short wave division multiplexing) has subsequently been adopted for enabling wavelength multiplexing over multimode fiber using VCSEL lasers.


In a nutshell, OM5 is designed to support at least four low-cost wavelengths in the 850-950 nm range, enabling optimal support of SWDM applications that reduce parallel fiber count by at least a factor of four. This allows 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.

The bottom line

While SWDM works with OM4 and OM3, the key performance benefit is in OM5’s support of SWDM applications in the wavelength range 850-953 nm - which are not possible with OM4, or indeed OM3.

Remember, it’s still relatively early days for OM5 in that the real advantages of using it are only available in combination with SWDM technology. SWDM applications on OM5 permit rapid upgrading without making modifications to the cable infrastructure. Right now, for instance, from 10 Gbit/s to 40 Gbit/s.

In addition to the SWDM4 multimode transmission standard, which has been known for several years, 400G BiDi is another useful application for the OM5 multimode fiber, because 400G BiDi as well as SWDM4 does not only work with 850nm wavelength, but also with 910nm and the OM5 fiber was explicitly developed for the transmission of the four SWDM4 wavelength 850/880/910/490nm. But for all other applications in the multimode sector, the OM4 fiber still remains the more obvious and practical choice.


Do you need more information about singlemode and multimode fiber optic cables? Then contact us directly - we will be glad to help you!