Dark fibre is essentially an optical fibre infrastructure that is not in use. The term “Dark” referring to the fact that data is not being transported, so there is no light.
Dark fibre networks arise because when laying down network infrastructure, operators and utility companies will often overestimate the amount needed, future proofing their growth and cost, but this means that there could be thousands of miles of fibres across the globe which are not being used.
Mobile operators use leased lines to connect their masts and demand is increasing as we consume more data on the move. The introduction of next-generation 5G mobile networks in the next few years is expected to further expand the market as operators plan to build more masts.
Adding wavelength division multiplexing (WDM) to a dark fibre network, doubles capacity on a single fibre, helping to achieve high connectivity, while keeping costs down.
WDM – CWDM and DWCM
Put simply, WDM adds multiple signals to the same fibre pair, using different colours of light. CWDM (course wavelength division multiplexing) and DWDM (dense wavelength division multiplexing) solutions allow multiple channels, travelling in either direction, to be simultaneously combined over a single fibre, meaning signals can be multiplexed into existing infrastructure, reducing the number of dark fibres needing to be leased.
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