• • • DATA CENTRE MANAGEMENT • • •
Connecting modern data centres with DWDM technology
With the rapid advancement of telecommunications, two or more data centres can be connected in a versatile and cost-efficient way using Dense Wavelength Division Multiplexing (DWDM) technology, says Marcin Bala, chief technical officer at telecommunications networks specialist Salumanus
T
raditionally, data centres were seen as compartmentalised facilities that did not offer much flexibility to companies. If a company
wanted to expand its data capabilities, it had to invest in acquiring more server space in the data centre, but this did not address security concerns, as all data was stored in only one location. European data centres attracted approximatively
£23.5 billion worth of investment in the first half of 2020, despite the impact of Covid-19, according to The Knight Frank Data Centre Report. This is an impressive increase from only $2bn investment volumes in 2019, and companies such as Amazon, Facebook and Google are continuously expanding their hubs. As the size and number of companies choosing
to host their information in data centres grows, so does the demand for stronger capabilities and higher bandwidth. Data centres can host data from giant corporations like Google together with the assets of smaller companies, meaning that they must meet the needs of a small business that
needs 1GbE or 10GbE connectivity, as well as a multinational corporation with needs of 100GbE or even 400GbE connectivity. They also need to be interconnected
geographically to minimise the risk of external threats on customers’ networks, as well as to increase their backup capabilities. Strong encryption protocols with strict accessibility rules are also required to avoid costly data breaches. To respond to companies’ demand for capacity,
distance and security, data centre operators can use Wavelength Division Multiplexing (WDM) technology, which allows data centres to virtually multiply their existing fibre backbone infrastructures and meet their customers’ demand for bandwidth.
CWDM or DWDM? The traditional solution used by data centres is Coarse Wave Division Multiplexing (CWDM), which is a convenient and low-cost technology that allows up to 18 channels to be connected over a
fibre pair. However, although the 18 channels will work efficiently for distances of up to 40 kilometres, only 8 will function properly for up to 80 kilometres. The channels are transmitted through a single
optical fibre at the same time, with a distance of 20 nanometres between the central wavelength of each channel. Because of the large distance between the channels, CWDM cannot be amplified. Due to technology limitations, the speed of data transmission is around 10 Gigabit Ethernet and 16Gb Fibre Channel. Unlike CWDM, DWDM connections can be
amplified using an optical amplifier, and therefore can be used for transmitting data at a much longer distance, even a few thousand kilometres. DWDM is capable of supporting anywhere between 40 and 160 separate wavelengths. To support 48 channels for a 100GHz grid, there is 0,8 nanometres spacing, while the spacing to obtain 96 channels for a 50 GHz grid is 0,4 nanometres. This means that enormous amounts of data can be transmitted
18 ELECTRICAL ENGINEERING • JUNE 2022
electricalengineeringmagazine.co.uk
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