Researchers at Wits and the University of Bordeaux have taken another step towards making communication with satellites better and faster. They successfully sent information across a 270m open-air link between two buildings on the Wits West Campus, encoded so that atmospheric turbulence could not scramble it.

The work is published in Science Advances. The beam arriving at the receiver was badly distorted. The information it carried was not, because it was stored in the light's topology rather than in its shape.

The commercial point is what the experiment removes. Free-space optical links have always needed adaptive optics, expensive hardware that measures distortion and corrects for it in real time, or heavy computation to reassemble the signal afterwards. This approach skips both.

Professor Andrew Forbes, head of the Structured Light Lab, uses the standard analogy: a coffee mug and a doughnut look nothing alike, but each has one hole, and stretching either does not change that. The team encoded information using an optical structure called a skyrmion, and the topological value held across a wide range of turbulence strengths.

Four weeks ago, we covered the Wits lab result showing the same protection holds for entangled photons, and noted that a turbulence rig is not a link across Joburg. This is 270m of actual Johannesburg air. What is still missing, Forbes told MyBroadband, is fast encoding into topology, which requires a topological detector nobody has built yet.

MyBroadband reported Forbes's account of the work still to come, and his earlier claim that over a million patterns of light could be packed into a square millimetre of beam, each acting as an independent channel. Wits says the findings could support links to satellites and spacecraft, and improved connectivity in remote and underserved areas. ISPreview frames the telecoms significance as doing this without the complex correction systems free-space optics has always demanded.

Look at what South Africa has spent this month arguing about. Billions raised to trench fibre into townships, a wholesale 5G network switching on, and satellite licensing deadlocked in Parliament. All three are attempts to reach the same households.

Free-space optics has always been the cheap fourth option on paper and unusable in practice, because turbulence forced you to buy correction hardware costing more than the link itself. Wits has just removed that line item, on a campus, over 270m.

Nobody should write a business plan on this yet. There is no encoder, no detector and no product. But the constraint that kept this technology in the lab for two decades now has a solution, and it was found in Johannesburg.

You might also like our piece on why the SpaceX Icasa hearings leave satellite stalled in Parliament, the SA 5G coverage gap all of this is competing to close, and how Capitec home broadband plans to sell whatever gets built.

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