this post was submitted on 19 Aug 2025
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That's not true... There are different types of fiber with different throughputs depending on the class of the cable and the length of the installation.
It is true.
Multimode (what I think you're trying to reference) isn't used in distance applications at all, it’s only for short in-building links. Anything that your ISP would provide you would be single-mode. Carrier/Backbone is virtually 100% SMF as well. SMF (OS1 and OS2) don't really have a bandwidth cap. It's all transceivers not the fiber.
But the point is that fiber that ALREADY in the ground, you can upgrade simply by changing the transceivers. It doesn't matter the length, SMF/MMF, or anything else... you just get a transceiver rated for the length of run (power of the led/laser, and the optics). The length is irrelevant otherwise as the presumption is that the install in the ground has been shown to work in the past already.
Old standard ITU-G.652 single-mode has been made to push multi-petabit transfers in lab environments. The only change was the transceivers. And to be clear, ITU-G.652 was standardized in 1984. Nobody rips out the fiber from the ground (caveat is that the cable itself hasn't degraded). You just upgrade the optics/transceivers.
source: https://arxiv.org/abs/2108.01873
Your statement didn't specify an application!
The context of the discussion does...
SpaceX doesn't provide in rack or in-building connectivity.
SpaceX is an ISP. You wouldn't have an ISP running multimode.
ISP's absolutely run multimode. That's how you get fiber into a building or between buildings. Different types of fiber all play a role in a network deployment.
Broad statements are misleading. OM4 multimode won't push 10gb at 500meters no matter how good your hardware is.
Ignoring the context of the discussion is even more misleading. In the context of this conversation, ISPs providing consumer connections and obtaining grant money, my statement is 100% accurate.
You just said multimode can’t do significant speeds at distance, yet claim that buildings separated by distance would be connected with it? That logic doesn’t hold.
Intrabuilding or intrarack Yes, you’ll find multimode fiber occasionally. But even these rare cases are increasingly replaced by single-mode as costs drop and bandwidth needs rise.
Everything else (ISP deployments, backbones, FTTH) Single-mode fiber dominates. I haven’t seen a single ISP deploy multimode for consumer-facing services over a typical network radius (~hundreds of meters to kilometers). The only minor exception is MMF from the building network room to an apartment unit, which is irrelevant for this discussion and would be EXCEEDINGLY rare as most buildings would just copper line to the unit. But even in that case... the 20+km from the head end to the building counts for much more than the 20meters to the unit itself.
For all practical ISP purposes, single-mode fiber is what’s in the ground/on the pole, and upgrades are handled via transceivers, not ripping out the cable.
But just because you said it...
https://www.corning.com/catalog/coc/documents/application-engineering-notes/AEN075.pdf
https://www.fs.com/uk/blog/om4-multimode-fiber-faq-highspeed-connectivity-guide-9499.html
https://www.timbercon.com/resources/calculators/om1-om2-om3-and-om4-fiber/
You absolutely can run OM4 at 10gbps at or over 500m depending on your optics/laser.
But Multimode was never the point of discussion as the whole thread is based around broadband services (virtually none of it serviced by multimode, if any at all) and grant money for rural area coverage. Any fiber upgrade in this scenario will 100% be SMF with no qualifiers. In my past 30 years of IT career all buried and pole mounted fiber is SMF that I've ever seen for an ISP. I can tell you for certainty that ever fiber I've buried in the past 10 years for several companies has been SMF. I'm not even sure that I've touched MMF in the past 5 years even in intra-rack setups, I think I might have gotten some with a government auction win about 8 years ago I wanna say? With costs of SMF at near parity for the cable itself and getting closer every year in the modules... it's a dying form factor and was never really in use for ISP services to begin with.
My fiber ISP runs single mode to my home. And it means it's all single mode on the pole for the neighborhood.
Multimode just isn't used all that much anymore. We replaced all fiber links in our DCs with single mode recently. It's just cheaper, and as the other person said: Its far more future proof.
Technically that's true.
You just need to lay the 100Tb/s capable cable in the first place.