Originally, laser beams in optic fibres carried information in pulses of light; data signals were impressed on the beam by rapidly turning the laser on and off, and the resulting light pulses were carried through the optic fibres.
However, to meet the increasing demand for bandwidth, communications system engineers are now adopting a new method of impressing the data on laser beams that no longer requires this “on-off” technique.
This method is called coherent phase communication.
The digital electronic bits carrying video, data, or other information are converted at the laser into these small delays in the otherwise rock-steady light wave.
But the number of possible delays, and thus the data-carrying capacity of the channel, is fundamentally limited by the degree of spectral purity of the laser beam.
The findings were published in the journal Proceedings of the National Academy of Sciences.
This purity can never be absolute, but with the new laser, Yariv and his team have tried to come as close to absolute purity as is possible.
