Archived from groups: comp.dcom.lans.ethernet (
More info?)
"Daniel J McDonald" <djmcdona@fnord.io.com> wrote in message
news:sqGdnZ2dnZ06TePEnZ2dnftVuN6dnZ2dRVn-052dnZ0@io.com...
> In article <c72f9$43258705$3ec37582$20788@news.chello.nl>,
> M.C. van den Bovenkamp <marco@linuxgoeroe.dhs.org> wrote:
> >qazmlp1209@rediffmail.com wrote:
> >
> >> We have the following requirement for our LAN:
> >> - Maximum Distance between the terminals-> 2-3 kms and
> >> - Data rate -> 100 Mbps
> >> - Full Duplex
> >>
> >> As I am aware, 'Fast Ethernet(100baseFX)'(and not 'Gigabit Ethernet',
> >> as it supports the distance of only 200 m maximum)
>
> No, it's 385 meters or some such for SX over 62.5 micron fiber. Or 500
> meters if you have 50 micron fiber and LX optics.
this is the spec for Gig Ethernet on multimode rather than 100M (260m on
62.5 "typical" cable - cant remember the distance bandwidth product. good
stuff can do better).
Distance for 100 Base-FX is around 2 Km on multimode, but several
manufacturers used to support longer hops. i worked on some at an airport
that was running at between 4 and 5 Km.
There were also some single mode 100 Base fibre system, although i never
heard of a formal spec for it. This should be happy at 5 to 10 Km - but you
will need single mode. Single mode is the default for most telcos since the
distances supported make real life "last mile" links easier.
There has been a recent spec for 100 Base-BX which uses 2 different colour
on a single fibre - a lot of suppliers are pushing this at Telcos. These
things also come as GBICs, or the newer small version, SFP. Only switches
that understand variable speed GBICs work with them.
Also - SFP or GBIC based optics is probably an easier way to do this on
modern kit, since just about any recent enterprise based switch range will
support them, so you can mix optical link types on the same kit.
>
> >> can be used to
> >> fulfill this requirement.
> >
> >100Base-FX will do 2 km over multimode fiber, yes. Not 3, though (at
> >least not standard).
>
> But most 100baseFX optics will reach 3km, even if they are only spec'ed
> for two. But 100baseFX is much more cumbersome than Gigabit from an
> end-device perspective.
>
> >
> >> Is my understanding correct here? Do you suggest any alternative?
> >
> >1000BASE-LX will reach 5 km over single mode fiber.
>
> But nobody sells it. Almost every GBIC you can buy is LX/LH, which will
> reliably reach 15km and usually will make 20.
LX-LH is LX compatible, but more flexible. you can use it just about
anywhere that LX could be used.
only spec i saw talks about 10 Km distance, but once you need to go several
Km it is preferable to check power budgets and losses, since in metro type
environments the losses in splices and joints may be higher than that due to
fibre distance.
>
> "ZX" gbics are rated at 70km. They are spendy, but I've shot them 50km
> without any problems.
agreed - although the CWDM GBICs (intended for pushing up to 8 colours down
a single fibre pair) have a similar distance rating and seem to be cheaper.
Always nice to be able to add the passive glass muxes and put several more
lambdas down the same glass, esp as you can use it for fibre channel, SDH
and various other things.....
>
> > If you need 3 km and
> >100 Mbps or higher, that's probably easiest to do, assuming you have a
> >single mode fiber run available.
> >
> >If it's multimode, you probably need to look at range extenders of some
> >sort, as I'm not aware of any standard reaching 3 km over multimode.
>
> Champiom Computers (cctupgrades.com) sells a line of 2km and 4km mm
> gbics, as well as other distances for sm gbics. They have a 110km one I
> might have to use. They also have "single fiber" gbics that send and
> receive on the same glass.
>
>
>
>
> --
> Daniel J McDonald CCIE # 2495, CNX
> Visit my website:
http://www.austinnetworkdesign.com
--
Regards
stephen_hope@xyzworld.com - replace xyz with ntl
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