Dark fibre | Hacker News Reader

Dark fibre

en.wikipedia.org

19 pointspopcalc11 comments

One example of using dark fiber:

I help run an HPC environment that is spread across two data centers, one on-campus and one off-campus. The campus network is already spread across those two data centers, but the HPC environment also includes a couple of VLANs that are completely private.

So, our connection to the campus network is two 100 GbE campus-network ports in one data center, and I have two dark-fiber circuits (two fiber strands per circuit) from one data center to the other, which carry the private VLANs. One circuit is direct; the other goes via a third building.

The flexibility of the dark-fiber service means I can use the same 100GBASE-LR4 transceivers that I use for the connection to the campus network. I don't have to deal with weird transceivers (like single-strand single-lambda Bi-Directional 100 GbE), or custom wavelengths. UIT Facilities gives me a fusion-spliced and tested pair with an LC jack, and it Just Works™.

Ahh, this takes me back.

I started my career around the .com boom, and as a young (clueless) person with suddenly positive cashflow, I invested a bulk of my initial savings in Global Crossing (again, dumb for many reasons...) My thought process at the time was that there were gobs and gobs of .coms that would flameout (and they did - "fishing licenses online!" anyone?), but that Global Crossing and other telecoms had tons of real, valuable assets in the ground.

Of course, I didn't quite do the math on what happens if those assets become devalued when you're sitting on a mountain of debt (and you throw in some fraud for good measure) - "Wow, it really can go to zero and never come back" I discovered. The much bigger downside for me was that since this happened very early in my investment career, I took the wrong lesson and became much too conservative overall, becoming too wary about the stock market at just the wrong time (early '00s). Oh well, hope I can apply that lesson in the next life.

To some people, it makes a difference if the fibre is all yours or if you're sharing it with someone else.

What specific sharing are you talking about, the wavelength, the individual strand, the entire cable, the trench?

Dark fiber is unlit fiber where you can do whatever you want with it (eg. shoot your own light down it).

Leased fiber services are generally lit by the provider and may carry other customers' data on it, too. Albeit, this is still relatively secure, customers cannot see each other's data because the wavelengths are filtered.

I'm not sure why this Wikipedia link was submitted without question/comment, so I flagged it and encourage others to do the same.

>I'm not sure why this Wikipedia link was submitted without question/comment...

This is one of my pet peeves. I wish OP (in general) would comment as to why they're posting, what they found interesting. I don't flag these posts, but they do sometimes feel like a lazy karma-grab.

I have some which are literally fibre I've personally run (or asked my riggers to run), but on someone else's land. For me those tend to be sub-km length and usually temporary unless in building or between neighbouring buildings.

I have others which are fibre strands I pay another company to manage. They emerge as a single fibre at my location, and shine a powerful enough torch down and it comes out the other end. I'm sure that those strands go down cables with a few hundred strands on at some point though. These are mainly metropolitan range, but I've got a couple in the 100km+ range.

My company has some which are wavelength services, these are multiplexed at local exchanges and I assume the wavelengths might be shifted. I don't deal with these. In theory I guess I can shine a torch at a given wavelength and it pops out the other end

And then I've got ethernet circuits which are managed, I get an ethernet handoff at each end, but at its core it's just a packet service.

All of these can be tapped by advesaries, it depends on your level of paranoia. Best to encrypt.

The first 3 you can run say jumbo ethernet frames over. Or you can run non-ethernet traffic if you want.

Who would that be? I could imagine HFT maybe.

One difference is that you get to pick the optical equipment yourself instead of having to interoperate with whatever wdm scheme is deployed on the span.

Would recommend a dark fibre over a wavelength unless the price is very high. You can put your own wdm filter and run multiple wavelengths over it. And you aren't relying on the providers wdm system to work, just make sure you get two fibers with physical separation if you need redundancy.

This post is a great way to show who doesn't understand L1 topologies lol.

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