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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

32.0. "Single Mode Fiber Sizes?" by DWOVAX::LICAUSE (Al Licause) Wed Jan 24 1990 12:45

    I'm a bit confused about fiber sizes......at least for single mode.
    
    Our customer is telling us that they have a large multiple strand
    ring of 62.5 single mode fiber in place, currently used for T1's
    and voice multiplexing.
    
    In other notes I've seen reference to 5 and 10 micron single mode
    fiber.  Is there such a thing as 62.5 or a more general question:
    
    since we know the four basic sizes of multimode 50, 62.5, 85 and 100
    micron, what are all the known sizes of single mode fiber?
    
    Thanks,
    Al
T.RTitleUserPersonal
Name		DateLines
32.1not speaking as a fiber expertBAGELS::WILLIAMSBryan WilliamsWed Jan 24 1990 17:328
    Seicor's Catalog lists single mode fiber sizes of 8.3/125 and 8.7/125.
    
    Ask them for the vendor and the vendor part number of the fiber. From
    that, you should be able to obtain the specs for the fiber. If it's
    really 62.5, it's multimode (at least that's my understanding of
    fiber).
    
    Bryan
32.2Core diameter is not a single mode parameterBAGELS::LEVYWed Feb 07 1990 22:0119
    re: .0
    
    Bryan's right: If the core of the customer's fiber is indeed 62.5
    microns, it is definitely not a single mode fiber, at least as
    far as 1300nm light is concerned.                
    
    Core diameter isn't a very relevant parameter for single mode fiber.
    The light-carrying region is determined by the mode-field diameter,
    which is larger than the physical core diameter. Mode field diameters
    of 8 to 10 microns are typical.
    
    It's also worth noting that single mode fiber isn't single-moded at
    850nm, whereas multimode fiber is multimoded at both 850nm and 1300nm.
    The cut-off wavelength specifies the transition point in the spectrum
    where the single mode fiber will only propagate the primary mode.
    Cut-off wavelengths are typically in the 1100nm - 1300nm region. 
    
    So the parameters for specifying single mode fiber won't map
    one-for-one from multimode fiber's parameters. Unfortunately.