05 July 2018
| Alan Burkitt-Gray
A team from two European universities have found a way of extending the reach of repeaterless fibre by six times – potentially reducing the cost of subsea and terrestrial cables.
The researchers, from Chalmers University of Technology in
Sweden and Tallinn University of Technology, Estonia, say they
have developed new optical amplifiers that extend the range to
Professor Peter Andrekson, who leads the research on optical
communication at Chalmers University, said that the team used
ultra low-noise, phase-sensitive optical amplifiers.
"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," said
The team of five researchers published their research in Nature Communications, a peer-reviewed
They report that not only did they demonstrate "a reach
improvement of 5.6 times" using the new amplifiers, but there
was a significant increase in bandwidth. "The phase-sensitively
amplified link transmits two data-carrying waves, thus
occupying twice the bandwidth and propagating twice the total
power compared to the phase-insensitively amplified
There is a lot of research going on at the moment into ways of
improving the performance of fibre. Challenges include
amplifier noise and nonlinearities in the fibre, both of which
degrade the signal. These researchers have used phase-sensitive
amplifiers (PSAs) to counter some of the challenges.
The researchers used a recirculating loop, but they recognise
that "in order to realise a real transmission link with in-line
PSAs a few challenges remain to be solved".
They say the PSAs can provide a very significant reach
improvement over conventional approaches, and could potentially
improve the performance of future fibre communication
"Such amplifiers may also find applications in quantum
informatics and related fields, where generation and processing
of quantum states are of interest, as well as in spectroscopy
or any other application which could benefit from
ultra-low-noise amplification," said Andrekson.