Hollow core had a good week in English. I spent it reading three Chinese write-ups from one forum in Shenzhen, and they are more specific about the technology than anything I have read on it this year. Same stage, 11 September, three speakers, all three write-ups published within half an hour of each other. The buyer first. Han Liuyan of China Mobile's research institute calls anti-resonant hollow core a complete disruption of optical communications, and says loss reduction is essentially finished and now sits far below the solid-core limit. Then he lists what is not finished. CO2 absorption badly hurts transmission and the two known fixes, sealing and positive pressure, are in his words neither an ultimate solution. The loss spectrum is rougher than solid core and degrades after transmission. Hollow-core fibres with different cladding unit counts have high connection loss and are not suited to being mixed at random. He had good news too: two years of monitoring on the Wuxi line, gas evenly diffused, fibre and splice loss stable, without purging. Then the standards body. Ao Li, a vice president of CAICT, listed five engineering problems. The first is the one I keep coming back to. A single preform draws less than 100 kilometres. Lifetime cannot yet be assessed. In live networks splice time is long and loss is high, and construction and maintenance norms do not exist yet. Then the toolmaker, which is the part nobody covers. Fujikura's Zhao Lin: hollow core has an internal microstructure, so splicing needs rotational alignment and the structure must be kept from collapsing. Conventional four and six-motor splicers align cladding or core only. Hollow core needs an eighth motor. That is a specialist machine, and it is not what is in the vans. Now put the preform number next to the volumes. CAICT puts global hollow-core demand at 800 thousand fibre-km in 2030, from a market it says is still at pilot stage. At under 100 km a preform, that is more than 8,000 preforms. Microsoft's 15,000 km is more than 150, and more again if that figure is route rather than fibre. That one line explains something I had filed as a curiosity: why the most motivated hollow-core buyer on earth stopped trying to scale the company it bought and hired Corning and Heraeus instead. Corning draws it in North Carolina. Then the clock. ITU-T opened its first hollow-core project in July, two months ago, and its scope covers interoperability, deployment and maintenance, which are precisely what the buyer and the standards body flagged. For calibration, the multicore items opened in March 2025 and are expected to publish in 2028. So here is what I take from it. Between now and a standard, the money in hollow core is not in the fibre design, because the design is the part they say is working. It is in preform and draw capacity, and in the splicer. Corning is paid on both new-fibre routes at once, drawing Microsoft's hollow core in Carolina and co-founding the four-core group in March alongside Sumitomo Electric, Fujikura and TeraHop. The disruptor is paying the incumbents to industrialise it. What would change my mind is a preform length. If anyone shows a draw well past 100 km at usable yield, five problems collapse to two and the timeline moves in. Until then I read hollow core as a datacentre and campus product, where runs are short and splices are few, and not yet as a long-haul one. $GLW $MSFT

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