European researchers build breakthrough long-distance fibre cable links

6 Jul 2018

The Chalmers University building at Lindholmen Science Park in Gothenburg, Sweden. Image: Albin Bolt-Hansen/Shutterstock

Researchers from Sweden and Estonia have demonstrated a 4,000km fibre optical transmission connection, but commercial use is still a long way off.

Scientists from Chalmers University of Technology in Sweden and Tallinn University of Technology in Estonia have published research into a major innovation in the fibre optic data transmission space. Improvements in fibre cable technology are crucial in our data-driven world.

The researchers together demonstrated a 4,000km fibre optical transmission link using ultra-low-noise, phase-sensitive optical amplifiers (PSAs). The teams said this is a reach improvement of almost six times what is possible using conventional optical amplifiers.

Advances in fibre cable technology

Demand for higher transmission capacity is being driven by increased cloud storage needs, video streaming and a variety of other online services. New technologies are being examined all over the world in order to significantly improve capacity.

The research, published in Nature Communications, highlighted several limitations in current fibre optical transmission links, such as noise accumulation originating from optical amplifiers within the link and signal distortion from non-linear effects in the transmission fibre. The use of PSAs can reduce both noise accumulation and signal distortion simultaneously.

The teams built an 80km-long test link, using standard single-mode optical fibre to simulate long-haul data transmission of a 10Gbps capacity signal. Results demonstrated that compared to conventional in-line erbium-doped fibre amplifiers (EDFAs), PSAs extended the reach of the link by 5.6 times to 4,000km.

Some challenges ahead

Prof Peter Andrekson is the optical communication research lead at Chalmers University of Technology, and he said: “While there remain several engineering challenges before these results can be implemented commercially, the results show, for the first time, in a very clear way, the great benefits of using these amplifiers in optical communication.”

Two weak lightwaves were used in the test link, called ‘signal’ and ‘idler’, which were then amplified by one or two high-power waves called ‘pumps’.

Polarisation tracking would be needed in real-world applications to align the waves – researchers manually tuned polarisation on the test link. A feedback system would also be needed to tune the frequency of so-called ‘slave lasers’ to match the incoming frequency from the pump wave.

The potential for marked improvement of future fibre optical communications systems is significant and other fields could also stand to benefit from these new PSAs.

Andrekson noted possible applications in the generation and processing of quantum states and spectroscopy, the latter of which is the study of the interaction between matter and electromagnetic radiation. Types of spectroscopy include x-ray, UV and gamma ray.

The Chalmers University building at Lindholmen Science Park in Gothenburg, Sweden. Image: Albin Bolt-Hansen/Shutterstock

Ellen Tannam was a journalist with Silicon Republic, covering all manner of business and tech subjects