From: Shawn Bowen (shawn@xxxxxxxxx)
Date: Thu Apr 05 2001 - 01:12:13 GMT-3
Just to add to this, POS OC-48's have other options here. One is long reach
fiber and one is short reach, they run at ~1350nm and ~1540nm wavelengths.
The device you are referring to is commonly known as an Attenuator and they
basically turn a line that is +xDB (x=some number) into one that is 0DB or
whatever the receiving equipment is expecting. You have to be somewhat
careful with lasers at this frequency as they are NOT LED's that most folks
are used to, they are real lasers and will torch an eye. The typical use is
to light up dark fiber over long distances (dark fiber=non Telco private
lines). To run SM LX, LR, or SR over multimode you have to convert the high
output, high db laser into the proper DB and frequency by using an
attenuator that is tuned to the proper settings. MM Fiber is typically used
for much lower frequencies than SM fiber, and since the distances are vastly
different you could quite literally fry the receiving MM receiver with some
SM lasers.
Just my 2 cents,
Shawn
-----Original Message-----
From: Greg Ferro [mailto:gferro@netstarnetworks.com]
Sent: Wednesday, April 04, 2001 8:55 PM
To: ccielab@groupstudy.com
Subject: Fwd: Re: Gigabit ethernet distance limitation (off topic )
>Date: Wed, 04 Apr 2001 22:52:02 +1000
>To: Mohamed Heeba <MAHeeba@itqan.co.ae>
>From: Greg Ferro <gferro@netstarnetworks.com>
>Subject: Re: Gigabit ethernet distance limitation (off topic )
>
>Yes they can.
>
>Note that you should understand the physical layer. LX standard uses is a
>single mode laser, this means 9 nanometre aperture. SO to connect to MM
>you need to modify the aperture to 62.5 nanometre. This is done using a
>mode conditioning cable, its in the price list. This basically has a bit
>in the middle that diffuses the signal (apologies to the highly technical,
>but it will do) from SM to MM. You can drive this to 500 metres or so
>according to the standard. The real story is typically 1000 metres,
>depending on power loss as determined by cable quality and termination
>quality, YMMV.
>
>Note: Cisco charges an extraordinary sum for this cable, in Australia its
>about $1000 at RRP. You can find it at good cable suppliers for under
>$150. May have to order it in. Works fine.
>
>At 08:30 PM 4/04/2001, you wrote:
>>hi guys
>>anyone know if the LX modules can run over MM fiber ?
>>where can i get the distance limitation for this
>>
>>
>>thx
Regards
Greg Ferro | |
Senior Network Engineer, CCIE #6920, CCNP ||| |||
NetStar Australia Pty Ltd. .|||||. .|||||.
9 Mayneview Street, Milton, 4064 .:|||||||||:.:|||||||||:.
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