How to get 1 or 2Km of optical fiber?

Steve Alligood steve at
Mon Mar 18 10:13:31 MDT 2013

On Mar 18, 2013, at 9:47 AM, Lloyd Brown wrote:

> When working with fiber lengths, you *always* want to consult the
> specifications of your optics modules.
> For example, we use a lot of hardware from Force10 Neworks here (They've
> been bought out by Dell, which is advantageous for us, for other
> reasons).  My spec sheet for their 10GbE SFP+ optics modules says 300
> meters on multi-mode using 850nm wavelength (10GBASE-SR), as long as
> it's OM3 or OM4 spec, but I don't have lengths for OM1 or OM2 MMF (I
> vaguely recall it was 150m, but I don't know for sure).

It's actually 33 meters and 82 meters, respectively.  Even worse is FDDI grade (26 meters).  It has a massive center defect, so you probably have to have a mode conditioning patch cable (shift the light slightly off-center) to even get that 26 meters.  You can tell if is it OM1 or FDDI from the size (62.5 microns) where OM2 and later is all 50 microns.

>  For the
> 10GBASE-LR (1310nm), you use single-mode for up to 10km.  For the
> 10GBASE-ER (1550nm) you use single-mode for up to 40km.
> In general, you can use 850nm on multi-mode, and 1310nm and 1550nm on
> single-mode.  There are a few applications (eg. 10GBASE-ESR), which pair
> 1310nm with multi-mode, but they're rare and will probably be more
> expensive than you want to pay.
> And of course everything changes when you're talking about faster
> speeds, eg. 40GBASE or 100GBASE.

Actually, the general spec for these use 4 and 10 distinct fibers.  Basically, 10GBASE across multiple strands to get 40 and 100 GBASE.  To go long distances, you have to put all 4 or 10 channels across a DWDM on 4 or 10 colors.

There *is* a 40GBASE spec that uses a single pair of fiber, but it is limited to 2 km.

> TLDR: At the lengths you're talking about, it's going to depend on what
> the optics vendor will support.

He is totally right.  Figure out what you need, then research what will do it.

one gig is relatively easy.  10 gig gets a little more complicated and pricey, but not bad.  And forget 40G and 100G for now.

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