New optical communication protocol overcomes modal distortion in noisy channels

Researchers at the University of the Witwatersrand (Wits) have introduced a novel optical communication protocol that utilizes spatial patterns of light for multi-dimensional encoding, overcoming the limitations posed by distortion in noisy channels. Published in Laser & Photonics Reviews, the study from the Structured Light Laboratory in the Wits School of Physics leverages a new property of vectorial light called “vectorness,” which remains unchanged when transmitted through a noisy channel.

Unlike traditional binary encoding (0 or 1), the researchers partitioned the vectorness range of 0 to 1 into more than 50 parts, effectively creating a 50-letter alphabet. As the vectorness is not distorted by the communication channel, both the sender and receiver can consistently agree on its value, enabling noise-free information transfer.

The key breakthrough achieved by the team was the utilization of light patterns in a manner that does not require their recognition, disregarding the natural distortion caused by noisy channels. Instead, by summing up light in specialized measurements, the invariant quantity of vectorness is revealed, unaffected by distortion.

Professor Andrew Forbes from the Wits School of Physics emphasized the significance of this advancement, stating that the ability to utilize a wide range of light patterns as an encoding alphabet is no longer limited by channel noise. The size of the alphabet is now determined solely by the quality of the detectors, rather than the noise in the channel.

Lead author Keshaan Singh, a Ph.D. candidate, expressed that the vectorness modulation can be implemented immediately in real-world scenarios using conventional communications technology, as it requires nothing more than existing equipment. The team has already conducted demonstrations in optical fiber and fast links across free-space, and they believe their approach can be extended to other noisy channels, including underwater environments.

Source: Wits University

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