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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

399.0. "RxTX must have same wavelength?" by SOLVIT::NNGUYEN () Wed Nov 20 1991 18:12

    	Hi,
    
    		Must the optical receiver have the same wavelength as the
    	transmitter? I think it must but my co-work says it does not
        matter. The specific case is transmitter has 1550 nm and the
    	receiver is 1300 nm. Can they work together reliably? Even with
    	mismatched wavelength?
    
    		Thank you for your answer.
    
    								Neil
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399.1Depends!!LEVERS::J_HILLThu Nov 21 1991 19:3036
    First,
         Why are you asking?  Is this something that a customer is asking
    for, or is this a, "For your information," type question.  Also in what
    context is the question being asked?
    
         As it stands now, DIGITAL stands by the products that were
    designed for 1300 nM operation, for use at 1300 nm operation only.
    So in this sense the answer is, "NO."
    
         As to whether or not a 1300 nm receiver will work with a 1550 nm
    transmitter is uncertain.  Issues such as PIN diode structure will
    determine responsivity variations due to wavelength.  While it is
    true that text books show that specific compounds have good
    responsivity over a wide range of wavelegths, I CANNOT make a
    blanket statement.
    
         The next obvious question is how the 1300 nM station transmitter
    is going to talk to the 1550 nM station receiver.  FDDI has data
    flowing bi-directionally, so I gather that your 1550 nM system will 
    want to receive as well as transmit?
    
         Why is this person using 1550 nM, is there a specific need for it?
    
         Are there any other issues that you may have not thought of?
    Systems running 1550 nM are often long haul, using dispersion shifted
    single mode fiber.  Clearly a 1300 nM transmitter may not be able to meet
    the loss budget of such a system.
    
         Is the customer using single mode fiber?  How much?  Whats the
    link loss at each wavelength?
    
         If someone really needs to know then we can probably get an answer
    but otherwise the answer is, "NO."   Please let us know more about
    the circumstances.
                                                    Jonathan