Big Data: Single-mode or Multi-mode in the Data Centre?
One of the biggest reasons for the huge demand for Big Data these days is the increasing use of the concept of the Internet of Things (IoT). IoT is today much more than just a concept – it is a part of everyday life and there are billions of “things” that are connected to the common network, or the Internet.
A number of applications have come up in recent years that are cloud-based and storage intensive, and increase the burden on data centres. There is a huge pressure on data centres, on various areas such as the core to the switch-to-switch backbone links and to the SAN or storage area network, to handle such vast volumes of data.
One of the major changes seen recently is that many switch-to-switch links have been migrated from 10 Gigabit per second (Gb/s) speeds to the significantly higher 40 and 100 Gb/s speeds. At these speeds, the data centres require optical fiber cabling to function properly. Moreover, more than just the high speeds, there are many more pieces of equipment and fiber links used these days, which has led to fiber connections of higher density.
There are now a range of fiber applications of different standards and based on a variety of technologies available. That’s why it is all the more important for data centre managers to truly get a sense of the current and future technological choices that are available to them. The fiber optics used in data centres these days have low latency, are easily scalable and are ideal for high bandwidth connections. Many data centres have wanted to modernise their whole backbone data centre cabling and are now required to choose between multi-mode and single-mode cables. There is an important distinction between them.
Single-mode cables provide much superior future proofing capability, but are more expensive than multi-mode cables. They can run for 10 km and have speeds of 40 to 400 Gb/s. But most datacenter backbone links feature short distances and don’t really need single-mode fiber cables. The maximum link length required by multi-mode equipment is only 100 meters. That explains why multi-mode fibers are the preferred choice for data centre backbone links.
Placing an order for the right multi-mode fiber is far more complex than it used to be in the past, because there is now a new third edition of the ISO/IEC 11801 standard in place, which includes a brand new variety of wideband multi-mode fibers classified as OM5. OM5 is different from the existing standard of multi-mode fibers – OM3 and OM4, which operate in the wavelength of 840 to 860 nanometer (nm), with the optimal wavelength being 850 nm.
The new OM5 standard fibers support a much higher range of wavelengths of between 840 nm and 953 nm, which is capable of handling the advanced wavelength division multiplexing (WDM) technology. The new WDM technology allows for multiplexing multiple signals into a single fiber and makes use of many different wavelengths. Now, OM5 is certainly a positive development as it reduces the fiber strand counts, but as of now there are no specific applications that have been developed under this standard under the Institute of Electrical and Electronics Engineers (IEEE) for operating through this medium.
What that means is there is not much information available on the strand count, data rate and link length necessary for the installation of this media. That is one reason why single-mode fiber applications could be a better option for those that are looking to future proof their connections over 400 Gb/s.
The IEEE P802.3bs (400GBASE-DR4) standard, which is still pending as of now, is meant to support 400 GB/s over a Single-mode fiber through a distance of 500 meters with 8-fiber MPO/MTP solutions. These applications will have four fibers working at the same time, transmitting at a speed of 100 Gb/s, with four fibers receiving the data at a speed of 100 Gb/s. Moreover, the IEEE P802.3cd (50GBASE-SR) standard, which is expected to be released in 2018 is expected to support speeds of 500 GB/s over single-mode fiber. This is an indication of the IEEE’s desire to develop applications with a much higher capacity over multi-mode fiber of the type OM3 and OM4.
Single-mode technologies that work over a much shorter reach of 500 meters or so are also being developed through the IEEE P802.3bs (200GBASE-DR4/400GBASE-DR4) and IEEE P802.3cd (100GBASE-DR), which is still pending. This is another reason for choosing single-mode fibers for making your fiber optic connections future proof.