A huge demand for throughput capacity, its reliability and security are of great concern for telecommunication companies and the potential of fibre optic solutions has become one of the hottest topics for discussion. Anyone who has tried to deploy a new fibre-optic cable knows how difficult and expensive it is. This is why wavelength division multiplexing systems have been gaining more and more attention as this technology enables combining several independent data streams in a single fibre with the use of different wavelengths.
There are three types of WDM architecture: in type one, the second window band is separated from the third window band; type two bases on a CWDM system which provides 18 wavelengths with a step of 20 nm, starting from 1270 nm and ending with 1610 nm; type three bases on a DWDM system which offers 48 independent channels for a 100 GHz grid, and 96 independent transmission channels for a 50 GHz grid with a step of 0.8 and 0.4 nm.
The first of the above mentioned technologies is the least interesting for us from the perspective of its ability to multiplex a single fibre, as it can only double the fibre capacity.
The main advantage of a CWDM technology, especially for low speed transmission, is the cost of optical components for the system as it is even 80% lower in comparison to the cost of equivalent components in DWDM systems.
Such a huge difference in the price of optical elements determines the choice of CWDM solutions among those clients who start their adventure with WDM systems. Depending on the distance a given system is to work on, we can use 8 or 18 wavelengths from the available spectrum – this is caused by interference losses between the second and the third transmission window.
Regardless of the fact whether we consider building the first WDM system or whether we already have a system built in CWDM technology, we can multiplex its capacity by means of DWDM technology. Choosing DWDM solutions in a 100 GHz grid, we can upgrade the existing CWDM system by another 24 channels, while deciding on a 50 GHz grid, we can expand the system by another 48 independent transmission channels.
When you decide on implementing a CWDM technology in the first place, you can notice that the initial investment costs are lower than the costs of DWDM technology. This may help some operators to make the first step towards building their own infrastructure or increasing the potential of the existing one. On the other hand, dense wavelength multiplexing gives much greater possibilities as new services can be started on the existing infrastructure without any interruptions in its operation. This is a real architecture ‘Pay as you grow”.
It’s worth remembering that a typical CWDM band is able to transmit data with the speed of 14 Gbps in a single channel, while a DWDM technology can reach the speed of even 400 Gbps. This means that today when we decide to construct a CWDM system, which allows us to send approx. 100 Gbps, we leave open the possibility of sending even more than 19 Tbps over the fibres we own or lease, in the future.
Combining the best features of both CWDM and DWDM technologies enables us to meet the increasing demand for broadband and optimize the spending on investment at the same time. The major advantages of such an architecture are:
- Low costs of initial installation,
- Easy and uninterrupted network expansion when adding new channels,
- Network scalability from 100 Gbps to as much as 19 Tbps
- Pay as you grow architecture