IIT Guwahati researchers develop free-space optical communication system for info transfer

Most free-space communication systems developed so far all over the world use a type of light beam called the ‘vortex beam’ to encode the data. “The problem in the use of a vortex beam is that it can be distorted by turbulence that may occur in the medium of propagation," Bosanta Ranjan Boruah, Department of Physics, IIT Guwahati said.

Researchers at the Indian Institute of Technology, Guwahati have developed a novel free-space optical communication system for information transfer. According to the team, in free-space communication, data in the form of 'voice, text or image' is transmitted using light wirelessly rather than through optical fibres, and it represents the next generation of communications technology.

The results of the path-breaking work has recently been published in Communications Physics, a reputed journal belonging to the Nature Publishing Group. "The past couple of decades have seen phenomenal developments in free-space communication. Most free-space communication systems developed so far all over the world use a type of light beam called the 'vortex beam' to encode the data.

"The problem in the use of a vortex beam is that it can be distorted by turbulence that may occur in the medium of propagation," Bosanta Ranjan Boruah, Department of Physics, IIT Guwahati said. "In effect, data transmitted wirelessly using light or laser beams, can become corrupted when transmitted through atmospheric turbulence such as wind. To overcome this problem, the IIT Guwahati researchers have, for the first time, used orthogonal spatial light modes called Zernike modes to encode the data and to transmit the same robustly in the form of the phase profile of a laser beam," he said.

Explaining the technicality of the research, Baruah said the transmission station modulates the phase profile of a laser beam that carries the data, in terms of the strengths of a few Zernike modes. "In the process we also enhance the information content per modulation cycle of the laser beam. At the point of reception, the laser beam with encoded user information is sensed by a specially designed wavefront sensor that decodes the user information.

"In this communication system, a unique mechanism has been implemented that can compensate for the effect of atmospheric turbulence, so that the user information can be transmitted even through turbulent atmosphere resulting in negligible error at the receiving station," he said. The team claimed that the research has demonstrated the distortion-free transmission of text messages and images over a distance of one kilometre even in the presence of turbulence such as during a stormy weather.

"The system can thus be used for high speed and secured communication between two individuals located either inside a building or outside," Baruah added. PTI GJS SRY

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