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Conference 7.286::fddi

Title:FDDI - The Next Generation
Moderator:NETCAD::STEFANI
Created:Thu Apr 27 1989
Last Modified:Thu Jun 05 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:2259
Total number of notes:8590

1156.0. "# of patch panels allowed smf/mmf" by 28809::GRIFFITH () Tue Nov 23 1993 16:29

    
    My customer has a smf point to point connection from a gigaswitch 
    smf-pmd through three patch-panels to a single-mode fiber US West 
    connection (10 miles), from the US West connection straight into
    a Fiber Host Synoptics Concentrator.  It states in the FDDI System
    Level Description on page 5-6 (Adapter Config guidelines) second
    bullet down - Maximum number of patch-panel connections between
    the concentrator and the adapter is two connections.  My customer
    needs a white paper explaining whether this is specifically for
    multimode or singlemode fiber or both.
    
    
    					Thanks in advance
    
    					       Deb Griffith
    
    
    
    Cross posted in both FDDI and Gigaswitch Notes Conferences.
T.RTitleUserPersonal
Name		DateLines
1156.1KONING::KONINGPaul Koning, B-16504Wed Nov 24 1993 11:1015
I'm surprised it would say that.

It makes perfect sense as a guideline, but it is NOT valid as a restriction.
If you want to build "straightforward" configurations, guidelines are helpful
in constructing valid networks without lots of analysis or measurement.  But
the actual rules are those defined in the ANSI standard, and those are
expressed in terms of distance, loss, and bandwidth.  

If the configuration meets the loss and bandwidth requirements (and distance,
in the MMF case, though that's specified primarily to help guarantee the
other two) then it is legitimate.  In particular, splices and patches are
sources of loss, so if you have a lot of them you MAY have a loss problem.
So measure it.  If the measurement says ok, it's ok.

	paul
1156.2Multivendor considerationsLEVERS::KIRKtis a gift to be simpleWed Nov 24 1993 14:0826
    You also have a multi-vendor situation to deal with in terms of
    understanding the limits of the power budget and system bandwidth.
    
    I called Synoptics (1-800-PRO-NTWK) and asked about the limits of their
    SMF product. They support 20 km maximum link lengths. We support up to
    40 km link lengths, so I believe there is no bandwidth limitation with
    this shorter distance of 10 miles (16 km).   The optical transmit 
    power of their device is -20 dBm (minimum) and the receiver sensitivity
    is -31 dBm (minimum).
    
    Using these values and the corresponding numbers for our product (-8
    dBm and -30 dBm), the worst case power budget occurs between their 
    transmitter (-20 dBm) and our receiver (-30),  providing 10 dB for a 
    loss budget.  If the customers installation has less than 10 dB of 
    loss, including fiber, patch panels, etc, then the link should work.
    
    We have an installation guide for our single-mode products that
    contains more detail. I think there is a note in this conference that
    points to on on-line location. If not, let me know and I'll post it.
    
    
    Richard Kirk
    Networks Engineering
    Optical PMD Project Leader
    LEVERS::KIRK
    DTN 226-7048