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Everything You Always Wanted to Know About Optical Networking [pdf] (nanog.org)
116 points by walrus01 5 months ago | hide | past | web | favorite | 18 comments

Not long ago I was curious to see what it would cost to run fiber instead of copper in my home network, and it turns out that the fiber itself is cheaper (per meter) than copper, but the transceivers at each end and the equipment required to work with the fiber were much more expensive; which explains why much of the long-distance Internet links use it, but nearly no one uses it for their home network... yet?

There's also an interesting failure mode for fibers, known as "fiber fuse", which can happen when the power level is very high and an imperfection in the fiber causes the light to literally start burning it like a fuse:


> nearly no one uses it for their home network... yet?

Yeah, sorta. It's depressingly rare to find desktop motherboards with SFP ports, much less laptops. You end up converting back to copper anyway.

I have a fiber link in my home network, because I was sick of losing wifi routers every time a storm came through. I suspect the cable modem to be allowing badness to sneak in even past the grounding block (which doesn't ground the center pin, of course), so in addition to a UPS with a coax protector, I now also have the whole "outside" of the network isolated (the cable modem and a fiber media converter, on that one UPS, on its own circuit) by a few feet of glass, from the "inside" of the network (another media converter, wifi router, distribution switch, NAS, etc, on another UPS on a different circuit). There's now no electrical path between the cable HFC network and my inner sanctum, and I haven't blown up any more hardware yet!

Hah, in the EE space we call those optoisolators[1]. Super handy when connection questionable prototypes over USB. Never considered using it in a networking environment but that does the trick!

[1] https://en.wikipedia.org/wiki/Opto-isolator

Asking from a place of relative EE ignorance: Wouldn’t you worry about blowing a much more expensive optic transceiver with this setup?

Ubiquiti has some cheap(er) switches($200) that'll do two SFP[1] ports[2]. Pretty cool that you can swap the physical transceiver, however like you said not really worth the hassle with the price of cat6/5e these days.

[1] https://en.wikipedia.org/wiki/Small_form-factor_pluggable_tr...

[2] https://store.ubnt.com/collections/routing-switching/product...

MikroTik has a similarly-priced weird alternative in the 953GS-5HnT-RP: SIM slots, 3 Gigabit ports, 2 SFP cages, 3x3 MIMO. No PoE out tho.

Looking at one of these for an external garage where the existing conduit from the house has the electrical supply in it already; don’t want to dig a new trench or work out how to shield cat5/6

So fiber can transfer 20 Tbps+ ? Mind = blown. Great cursory read

Well, a single fiber pair and a rack's worth of expensive gear on both sides. The standard front panel ports on routers these day tends to go to 100G with 400 on the horizon.

Optical network surprises sometimes like when certain wavelengths on a cable will become unreliable due to damage but others work fine.

Do the transceivers work around this (similar to what happens with DSL) or do you have to replace the whole fibre?

Hmm no I don't think so, the goal with multiplexing is to keep the streams separate so you can untangle them at the end since you're running multiple customers on a fiber. Losing a wavelength means less streams you can fit on it.

heh ive used the phone camera trick heaps of times coming onto a site that has had a dodgy splicer who doesnt follow color standards to figure out which pair I was lighting up...quick and dirty but faster than pulling out the full tesy kit in a pinch

Related: a visualization of the wavelength assignment algorithm in optical networks : https://github.com/afourmy/swap

Ah, many of these slides are familiar to me! I used to work on the Cyan (now Ciena) Z-Series shelves way back. Got a chance to help develop some of Cyan's SDN routing tech to generate network routes through Z-Series 2, 4, and 8-degree ROADM cards.

The bandwidth and capabilities of fiber and ROADM still blow my mind long after leaving that industry.

I’ve been a contributor to GNPY as part of the Telecom Infrastructure Project. It’s essentially a route planning tool for planning optical networks.


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