Noise-Canceling Twin-Beams based Fast Optical Fiber Communication

A simple, neat and elegant solution to noise cancellation has been applied for the first time to fiber optic communication speeding up the data transfer rate by a whopping 400% (compared to the best commercially available speed) over a distance of 12,800 km - much longer than any of the existing intercontinental fiber links.

The idea is not new as it is already in use in many of the active noise cancellation headphones. In general terms, when faced by an evil, better have a pair of them - pit one against the other and come out clean through them.  

In headphones, unwanted ambient noise is cancelled out by using microphones placed near the ear. The microphones pick up the ambient acoustic noise which is then used to generate anti-noise signal.  The noise in the headphone speaker is combined with this anti-noise signal (destructive interference).  Noise gets cancelled out and one is left with pure blissful music!

This simple idea was recently applied to fibre optics communication by Xiang Liu and his team at Bell Labs, NJ, USA. 

In this case, a pair of light beams (instead of the usual one), one phase conjugate of the other (crest and trough interchanged) has been used.  At the receiving end the two beams are combined together. the noise in the two beams cancel each other out leaving just the clear original signal.

A simple idea doing wonders!