New signal processing algorithms have been shown to help mitigate the impact of turbulence in free-space optical experiments, potentially bringing the ‘free-space’ Internet closer to reality.
The team of researchers, from Aston University’s Aston Institute of Photonic Technologies and the University of Glasgow, used commercially available photonic lanterns, a commercial transponder and a space light modulator to emulate turbulence. By applying a subsequent digital signal processing algorithm for interference suppression, they achieved record-breaking results.
The conclusions are published in IEEE Journal of Lightwave Technology.
Free-space optical technology wirelessly transmits data in the form of light through the air around us — called “free space” — for use in telecommunications or computer networks. Since free space optical communication does not require costly laying of fiber optic cables, it is considered an exciting development to bring communications to places where existing infrastructure is limited.
But since the data is sent as light pulses, weather conditions can cause problems. A sunny day or heavy fog can diffract or flicker the light beam, creating turbulence that causes data loss.
The researchers simultaneously transmitted multiple data signals using different spatially shaped beams of light using a photon lantern. Turbulence changes the shape of the beams, often losing signal if only a simple shape is transmitted and detected, but by detecting light with these shapes using a second lantern, more light is collected at the receiver and the original data can be decoded. This can greatly reduce the impact of the atmosphere on the quality of received data, in a technique known as multiple-input, multiple-output (MIMO) digital signal processing.
Professor Andrew Ellis of Aston University said: ‘Using a single beam, when a single beam was transmitted, turbulence similar to a hot sunny day destroyed the signal 50% of the time. By transmitting multiple beams of different shapes through the same telescopes and sensing the different shapes, we have not only increased availability to over 99%, but we have increased capacity to over 500Gbps, or over 500 ultra-fast pure fiber broadband links. “
A project investigating real-world applications of FSO technology is currently underway in South Africa, where researchers from Aston University and the University of Glasgow are working with the University of the Witwatersrand in Johannesburg to try to offer internet access to communities living in informal settlements and schools. in disadvantaged neighborhoods.
The Fiber Before the Fiber project aims to provide the Internet performance of a pure fiber connection without the need to install cables. It uses a free-space optical communication system that can connect to remote sites by using a wireless optical line of the site signal to connect to nearby fiber sources in richer suburbs.
Professor Ellis said: ‘Our role in the project is to examine the educational impact and benefits that free-space optics will have for school-age children who finally gain access to the Internet.’
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Material provided by Aston University. Note: Content can be edited for style and length.
