On Wed, Nov 2, 2011 at 12:28 PM, Jeremy Nelson <[email protected]> wrote: > I may be missing something here, but if I'm reading this correctly, I > believe you're planning to buy multimode fiber.
We were actually planning on single-mode before I realized it was incompatible with all the fiber equipment we currently have. Now I'm just in the middle of trying to wrap my head around the implication of the choices, so we can pick the best for our needs. > Based on my experience, I > believe you're going to definitely want single mode, so that you can run 1G > for now, and 10G later by just swapping transceivers. I'm pretty certain > that if you put multimode under the golf course now, you're going to be > limited physically to 1G, no matter what transceiver you use. See, I'm nervous to go multi-mode because of just this possibility. But do you, or anyone, know this for a fact? I've yet to see this stated definitively anywhere—I only ever see the statement that there *are* no 10G transceivers, not that there never will be—and my brain just doesn't feel comfortable accepting it without some sort of corroborating explanation, as it clashes with both my pre-conceived notions and my ideal world. ;-) All the explanations I've read for why we're limited to 1 Gigabit only seems to explain "why multi-mode can't transmit the same bandwidth at the same distance as single-mode", not "why multi-mode can never reach a speed of 10G". Reading through theory of multi-modal dispersion, I can't find a concrete reason why 10G modules at this distance *can* never exist. I can also *imagine* (through a haze of ignorance) that at some point, when Fast Ethernet was expensive, that there were Fast Ethernet modules for fiber, and that maybe when Gigabit modules first came out, the general wisdom and all the documentation at the time said that if you used multi-mode fiber you would only be able to achieve Gigabit on short runs, so if you had a longish run that you might ever want to use for Gigabit, you should definitely get single-mode because otherwise you'd be limited to Fast Ethernet speeds. But, then times changed... Or is this a far cry from what actually happened? (Like I said, I'm brimming with ignorance, here) > Any time I undergo a fiber project, I always make sure I match up fiber, > transceivers, Ethernet standard, and my switches in advance. This may not > be an issue for you, but I've run into situations where I had a fiber and > transceivers to function with a particular standard, only to discover later > that while electrically compatible, the switch wouldn't support it. I've come across the issues of HP switches not recognising "generic" GBICs, and having to buy specifically ProCurve compatible ones. That's been our one weird mismatch. > So, for example, it sounds to me like you want: > Single mode fiber running 1000BASE-LX, with the ability to upgrade to > 10GBASE-LR later. That sounds possible; probably likely. If so, though, all the existing multi-mode infrastructure at campus B (fiber runs, patch cables, even GBIC modules...) becomes more or less obsolete/useless. > Hope that helps. > Jeremy Thanks for your thoughts. Simón _______________________________________________ Fwlug mailing list [email protected] http://mail.fortwaynelug.org/mailman/listinfo/fwlug_fortwaynelug.org This is a public list and all posts are archived publicly. Please keep this in mind before posting.
