| The 2000m maximum when using MMF is mainly due to the pulse-widening or
distortion which will get gradually worse as the signal travels within
the MMF at various refraction angles. Components of the same signal
will arrive at the receiver at slightly different times in relation to
each other, in spite of having been launched onto the fiber all at the same
time.
That's why you must "reshape" the signal before it becomes difficult to
interpret it with confidence. If it were dependent on the budget only,
In SMF all components of the signal are forced to travel the same
straight line, hence this kind of distortion is virtually non-existant,
and you can travel 20Km.
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| A Much simpler route, would be to install an FDDI concentrator inside
ot the intermediate buildings, where the fiber enters, and (in your
current design) is patched back out again.
Instead of patching past the building, install a DECconcentrator 900MX
(in a DEchub One) with only two MOD-PMD's (both ANSI-MIC). This would
become in effect an FDDI repeater. I don't know your site's
measurements, but I would guess that any SINGLE SEGMENT is less than
2Km long, and your could insert an FDDI module in the line with little
difficulty.
****** BLATANT SALES PITCH ********
And by the way, I just happen to have an overstock in my warehouse (for
a limited time only) TODAY !! I have five Brand New (in the box,
with manuals and styrofoam and everything) DECconcentrator 900MX
modules, and 15 ANSI-MIC ModPMD's (and about seven UTP ModPMD's) that
I am getting ready to put onto DIAL. It would help me and my cost center,
if you would like to buy these for resale to your customer for this
very problem.
Such a Deal, no waiting!! It would solve this length issue, which as
the previous note states, WILL NOT WORK at distances of more than 2Km
between light sources over MMF.
******* END OF BLATANT SALES PITCH ******
Or you could change the fiber, and install single mode.
JR
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