IP over Lasers
mikekohn.net27 points by xtoilette 2 days ago
27 points by xtoilette 2 days ago
They built a program they called (relay) that sends packets between a tun network device & a uart serial device
https://github.com/mikeakohn/small_projects/blob/main/ip_ove...
I .... wonder if they considered just using PPP/SLIP?
A while back I was doing some IP-over-UART shenanigans and it took me a surprising amount of research to discover the existence of SLIP. I think it's one of those things that at some point "everyone knew about" and ended up being poorly documented as a result.
SLIP is old and mostly forgotten for sure, but PPP was almost universal in dialup and unfortunately common in DSL. PPPoE was the bane of my existence as someone who had to support third-party routers on DSL. PPTP was also very common for small VPNs even well past when it should have been retired due to insecurity because it worked out of the box on Windows and Mac without a third party client.
Back when 10M ethernet was popular, it was pretty easy to wire up something like this with the transceiver (AUI) port... wire the tx to a laser and the rx to a photodiode (or whatever), ???, profit.
There's lots of commercial equipment in this space too.
When I studied our dorm was connected to the campus network via a laser uplink (and the Internet, with each room having a public IP address). I still remember the foggy daya when people, you normally did not see, gathered in the bars, because the network went unbearably slow. It was nice days with every CS student having a server rack in their closet. I had a VT520 hooked up to it be able to read emails and IRC chats bed without having to wait for my PC to boot.
Has to be the early to mid 1990's?
I was going to say, sounds like my college experience decades later. Still a very congested laser link, and I had a headless minitower instead of a rack (though I wasn't a CS student).
I dreamed of doing something like this growing up so that my neighbor and I could play StarCraft without the latency of dialup. I wish I knew then that it was that straightforward.
The AT tiny is not needed at all. You have a digital signal coming right out of the serial cable which can drive the laser using a buffer and a Schmitt trigger on the receiver.
Eliminating crosstalk is the tough part and requires some modulation to ensure the transceiver isn't accidentally listening to itself via reflections or picking up interference.
Look up point to point laser links. They have been around for quite some time.
Aren't regular fiber-optics just mass-deployed IP over lasers? (this message is brought to you by at least one, likely multiple, lasers in prod)
Yeah, but kinda cool making it from scratch.
Also this uses air as the medium.
Free-space optical transmission is a thing, though it's environmentally quite challenging. We tested some gear from https://www.koruza.net at the Internet Archive ~10 years ago or so (I've also built some 10G point-to-point links in my garage, though I'd hardly call them reliable). It is pretty cool to see a scratch build rather than using commercial transceivers
Doesn't Starlink do that already for sat2sat comms?
Not quite the same thing as doing it in an atmosphere.
There's not a huge amount of info I've seen on the specifics of Starlink's LISL setup, but there are a couple interesting bits in here: https://www.pcmag.com/news/starlinks-laser-system-is-beaming...
> Brashears also said Starlink’s laser system was able to connect two satellites over 5,400 kilometers (3,355 miles) apart. The link was so long “it cut down through the atmosphere, all the way down to 30 kilometers above the surface of the Earth,” he said, before the connection broke.
(the presentation that's being reported on, which I don't have access to: https://www.spiedigitallibrary.org/conference-proceedings-of... )
That's right, the beam pointing problem is far harder when everything is moving.
There's this thing called wind that can move your outdoor installations quite a bit ;)
I'd call it a wash, space is hard, but so are atmospheric interactions, weather, foliage, and all the side effects of human habitation (like someone building a house in the middle of your laser link, yes that happens.)
I don't know why, but I would have expected higher speeds. Maybe my mind just assumes "lasers = fast". It would be interesting to know which factors make this setup unreliable at higher speeds.
Really like seeing networks over whatever laser things. Very cool stuff. This thing always comes to mind. http://images.twibright.com/tns/1208.html
We had a laser link to the university 20 years ago. 10MBit/s for 300 people.
That thing was awful.. lol.
The link was dead during
- Heavy rain
- Fog in the early morning
- While snowing for days
- Pigeons building a nest within the optics
There are many long-range WiFi solutions. I wonder how these would have performed as alternatives.
Isn't this just fiber optics! Exciting turn of the century tech hitting HN boards in 2025
Every year new engineers and enthusiasts need to be exposed to cutting edge technologies through hands-on introductions like these.
Isn't fiber broadband exactly this?
It's shooting a laser through a fiber optic cable.
A typical computer is connected to the local network using either an Ethernet cable or WiFi. This project connects two computers together through lasers.
No mention of carrier pigeon? IPoAC has three RFCs!
Now try IP over electricity.
Powerline is sort of like that. Devices act like an L2 transparent proxies over electrical wiring.
Fun fact: large transmission lines use power line carrier communications for things like remedial action schemes and other system protection functionality (e.g. protective relay trip signals). The carrier can be a few hundred kV, so it tends to be outside the comfort zone of most casual experimenters.
I have UTP and DAC cables here at home. I even have a bit of 10base2 around here, although none of it’s running at the moment.
Photons vs electrons? Just rotate 90 degrees, seem to be swappable more easily than using neutrons or other particles, like tau/muon/electron neutrinos.
Oh wait, didn't fermilab even use neutrinos in 2012? That seems even harder, practically made for an April fools RFC.