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A team of researchers from the Indian Institute of Technology (IIT) Guwahati has developed a new optical communication system in free space for the transfer of information.
The team of researchers was led by Bosanta Ranjan Boruah, a member of the physics faculty of IIT Guwahati, and Santanu Konwar, an assistant professor in the physics department of Abhayapuri College, said in a statement from the IIT-G.
In free space communication, data in the form of voice, text or image is transmitted using light wirelessly rather than via fiber optics and represents the next generation of communication technology.
The results of this groundbreaking work were recently published in “Communications Physics (https://www.nature.com/articles/s42005-020-00468-1)“ a magazine published by Nature Publishing Group.
The past two decades have seen phenomenal developments in communication in free space.
Most free-space communication systems developed around the world so far use a type of light beam called a swirling beam to encode data, the statement says.
The problem with using the vortex beam is that it can be distorted by the turbulence that can occur in the propagation medium.
In fact, data transmitted wirelessly using light / laser beams can be damaged if transmitted through atmospheric turbulence such as wind.
To overcome this problem, IIT Guwahati researchers have, for the first time, used orthogonal spatial light modes called Zernike modes to encode data and transmit it robustly in the form of a phase profile of a laser beam.
“In our work, the transmitting station modulates the phase profile of a laser beam carrying the data, in terms of the strengths of certain Zernike modes. In the process, we also improve the information content per modulation cycle of the laser beam, “said Boruah.
At the receiving point, the laser beam with encoded user information is detected 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 user information can also be transmitted through a turbulent atmosphere resulting in negligible error in the receiving station.
“In addition to eliminating communication errors, our system is also isolated from hacking and interloping, because the receiver decodes the transmitted beam by measuring the phase and not the power of the light beam, with a prior knowledge of the strength and types of Zernike modes used, making it more secure than conventional wired and wireless forms of communication, ”Konwar said.
In addition, the transmission is strictly directed to the receiver, unlike other forms of wireless communication where information is transmitted in all directions, increasing the security of the communication.
The research team demonstrated the distortion-free transmission of text messages and images over a distance of one kilometer even in the presence of turbulence such as during a thunderstorm.
The communication system can therefore be used for high-speed and secure communications between two people located inside a building or outside.
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