Swiss scientists working out of EPFL, part of Switzerland’s Federal Institutes of Technology, have found another way to boost the performance of existing fibre optic networks by shortening the distance (space) between pulses of laser light. Better yet the solution is said to be “highly flexible and can be easily integrated” into existing communication systems.
So far scientists have already discovered a variety of different ways to improve the performance of fibre optic networks, such as by twisting the light signals into a vortex, using hollow fibre optic cables or harnessing the different colours of light to transmit more data. Many other methods have also been developed.
Now a team of EPFL researchers have also tested a way to reduce the amount of space required between the pulses of light that transport the data. This has previously been very difficult to achieve because if the pulses get too close then they interfere and the information becomes corrupted.
The solution they devised involves changing the shape of the spectrum to be more rectangular (Nyquist sinc pulse), which means that the pulses can still interfere with one another but the point at which you actually read the data remains clear. The end result is that the distance between each pulse can be significantly reduced and thus more data carried.. ten times more.
Camille Brès, Photonics Systems Laboratory (PHOSL), said:
“These pulses have a shape that’s more pointed, making it possible to fit them together, a little bit like the pieces of a jigsaw puzzle lock together. There is of course some interference, but not at the locations where we actually read the data.”
The Nyquist sinc pulse method was first proposed earlier this year but the paper has only just recently been published by Nature, which provides extensive detail about the solution. But the method isn’t perfect and slight deviations from the ideal sinc shape can be expected in the implementation because of some practical limitations, such as the “laser linewidth or the chirp induced by the modulators“.
Never the less these pulses are usually “more than 99% perfect” and there’s always room for improvement in the technology (e.g. using Brillouin lasers). But the real bonus is the way that such pulses can be produced by using only a simple laser and modulator.