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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

834.0. "LCF-PMD status ?" by SOS6::GROSSETETE () Mon Jan 18 1993 04:39

    	Hi,
    
    	Could somebody explain LCF-PMD ? (Low Cost Fiber - PMD)
    
    What is the status of the standard ?
    What are the fiber's characteristics ?
    ...
    
    	Patrick
T.RTitleUserPersonal
Name		DateLines
834.1KONING::KONINGPaul Koning, A-13683Mon Jan 18 1993 11:4012
The standard is in development.

The name is somewhat misleading.  The "low cost" is no in the fiber, but in
the transceivers.  The fiber is the SAME as for regular multimode FDDI.
The difference is that the transmitter is somewhat lower power, the receiver
is somewhat less sensitive, and the connector is a lot smaller and cheaper.

The result is a PMD that will talk to the regular multimode PMD, but at
a reduced distance.  Think of it as a standardized version of the LC PMD
already available in several DEC FDDI products.

	paul
834.2Plastic fiber ?EVTAI1::GROSSETETEWed Jan 20 1993 06:319
    	Thanks Paul,
    
    	Since the goal is to reduce the cost, what kind of connector
    will be used ?
    
    	Is there any work to support "cheap fiber" ?
    
    	Patrick
834.3KONING::KONINGPaul Koning, A-13683Wed Jan 20 1993 13:3411
Plastic fiber has losses that are MUCH too high for FDDI.  850 nm (rather than 
1300 nm) devices were considered briefly, but that approach was dropped because
you get into compatibility problems -- you can't talk to "normal" devices if
you take that approach.  The one that was eventually picked gives you most of
the cost benefit with maximal compatibility.

As I understand it, there are two connectors defined: first choice is 
"duplex SC" (a small push/pull connector originally developed in Japan) and
second choice is ST (or "duplex ST"?  I don't remember).

	paul