I was going to do the "well akshually..." about HCFs because this article is so light on details. I used to work in a related field many years ago, and the attenuation of these fibers relegated them to niche applications (short-lengths that needed the odd properties of a hollow core, like ultra-high power transmission, low dispersion, low nonlinearity, etc.) They were orders of magnitude too lossy for long-haul telecommunications applications at the time.<p>But a quick search proved my knowledge was not up to date - here is the paper linked from the Laser Focus World blurb someone linked above. Looks like HCFs have achieved loss parity with traditional single-mode fused silica fibers, at least in the lab. Pretty amazing and cool if you ask me!<p><a href="https://eprints.soton.ac.uk/470034/1/OFC2022_PD_Jasion_submitted.pdf" rel="nofollow">https://eprints.soton.ac.uk/470034/1/OFC2022_PD_Jasion_submi...</a>