Ethernet requirement for Data rate:100 Mbps, Distance:2-3 km

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) can be used to fulfill this requirement. Is my understanding correct here? Do you suggest any alternative?

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Ethernet, over twisted pair, has a maximum distance of 100 M per segment. To go the distances you want, you'll need fibre or some broadband technology. Further, if that distance involves cable passing over public roads, you'll have to get the connection from a telecommunications company or other utility that has "right of way" over public roads. You might be able to use a microwave system, without having to worry about right of way.

Reply to
James Knott

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.

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.

But nobody sells it. Almost every GBIC you can buy is LX/LH, which will reliably reach 15km and usually will make 20.

"ZX" gbics are rated at 70km. They are spendy, but I've shot them 50km without any problems.

Champiom Computers ( 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.

Reply to
Daniel J McDonald

This sounds like different buildings :)

You will need some fiber!

-- Robert

Reply to
Robert Redelmeier

Well, a quick Google search shows that while it is "broadband", it fails on both bandwidth and distance requirements.

Reply to
James Knott

100Base-FX will do 2 km over multimode fiber, yes. Not 3, though (at least not standard).
1000BASE-LX will reach 5 km over single mode fiber. 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.



Reply to
M.C. van den Bovenkamp

In article , James Knott wrote: :Ethernet, over twisted pair, has a maximum distance of 100 M per segment. :To go the distances you want, you'll need fibre or some broadband :technology.

Is Cisco's "Long Reach Ethernet" a "broadband technology" under the hood? I've encountered a few long-range ethernet devices recently, but I haven't happened upon any information about how they work.

Reply to
Walter Roberson

We have a fairly large deployment of Cisco's LRE on our campus. It is basically a variant of DSL. I am thinking Cisco told us it was prestandard VDSL.

It works pretty well, but we only run it at 4Mb/s down and 1Mb/s up. It is very difficult to get the link to come up and stay up at Cisco's advertised 15Mb/s. Beware of all kinds of funky cable plant issues with this technology. If you do not know your copper plant really, really well, you might be in for a ride.


Reply to
Michael Roberts

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.

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.

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.....

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