Fabio Cavaliere, Luca Giorgi and Roberto Sabella
There are many factors that have contributed to the extensive use of fiber in telecom networks. As a result of the bandwidth and speed it can offer per dollar spent, the use of fiber is becoming more extensive being pushed deeper and deeper – particularly in the last mile. In a field trial carried out by Ericsson and Telstra, technologies to meet operator demand for seamless upgrade of networks were put to the test.
Fiber can carry information at very high data rates – terabit optical. With the application of additional technologies such as dense wavelength division multiplexing (DWDM) and optical amplification, capacities up to 800Gbps can be achieved on a single fiber over distances of 3000km without the need for signal regeneration.
However, with 1Tbps channels the race for terabit optical transmission speeds is on. Such data rates create challenges that are so difficult to overcome that terabit optical transmission capabilities have become a benchmark of technology leadership.
So what are these challenges? Better spectral efficiency is one of the key issues here, and one that is often treated using Nyquist-WDM. But this is not the ultimate solution for high-speed transmission over long distances. The Ericsson approach is to use time-frequency-packing (TFP) modulation. Together with Telstra, this solution was tested on 995km fiber link between Sydney and Melbourne and demonstrated the suitability of TFP to meet operator demand for seamless capacity upgrades.
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