Researchers Show Differnt-Shaped Light Beams Could Increase Fibre Optic Capacity


Fibre optic cables have been the focus of research which seek to build the internet’s capacity. One such method led to the use of light with different wavelengths for the transfer of different signals over the same fibre cable. To compensate for the added traffic, each beam of light was required to be narrower. To ease the congestion caused by too many signals over one cable, researchers have experimented with light beams in different shapes which is attributed to orbital angular momentum. This is achieved by passing the light beam through filters which gives it a variety of shapes as it travels.

Previous research had indicated that after less than a meter, differently shaped light beams tend to fuse together. A research team has however discovered a way to increase the distance to 1.1 kilometers. The team made of members from Boston University and University of Southern California in LA built a 1.1 km long glass cable with a cross section of varying refraction index. Differently shaped light beams passed through the cable never got jumbled therefore giving matching results for the light input and output. Each light shape was affected uniquely by the varying refraction index, moving different shapes at different speeds through the cable.

Using four angular momentum modes at a single wavelength, the research achieved speeds of 400 Gbps transmission over the cable. With orbital angular momentum (OAM) modes over 10 wavelengths, a speed of 1.6 Tbps was achieved. These demonstrations suggest an additional degree of freedom for multiplexing data in future fibre cable transmissions. It will take sometime for the research to be translated to real world applications. An immediate focus The researchers’ however is to install cables that will carry twisted light over short distances between servers.

via Nature