Cell Relay Archive

[ndowney@NET-CS.ucd.ie (Niall Downey)]

We have recently purchased a FORE ASX-200BX switch and we are trying to get it 
connected to our local Operator's site. The Operator recommends using a 
Single-mode interface, which is what they have or plan to purchase. We have a 
FORE card with one (short reach) single-mode interface and three multimode 
interfaces. However the existing fibre in the ground is multimode (I think 
62.5 microns). The distance is about 2 km between our site and that of the 
Operators. FORE and others think that we should be able to connect FC-PC 
connectors to the ends of the fibre and that it should work. Elsewhere in 
Dublin a similar attempt failed due, the Operator says due to the distance 
being too great (over 2 km). In addition there is at least 2 or 3 multimode to 
multimode joins (of unknown quality or type). 

My specifications for the interfaces on our switch give the following 
information:
the single mode interface has -8 to -15 dBm transmit power, -10 to -34 dBm 
receive sensitivity, 10 to 29 dBm path attenuation.
the multimode interfaces have -14 to -20 dBm transmit power, -14 to -30 dBm 
receive sensitivity, 0 to 10 dBm path attenuation

My questions are, has anyone any experience of such a configuration and what 
was the outcome ?. Also would it be better if we used one of the multimode 
ports rather than the single-mode port ?.

I have heard about an active device, for about $1500, which will allow a 
proper multimode to single mode interface.

Any information would be very welcome as I am having sleepless nights worrying 
about wether this will work.

Regards,

Niall Downey
Dept. Computer Science,
University College Dublin,
Ireland