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RE: Connector Return Loss


The only thing that I would add is that there is a 25 dB return loss 
requirement for MM in 10BASE-F ( for 10BASE-FP (Passive Star). As 
we start to consider both passive splitter systems and single fiber systems 
in EFM return loss may again rear its ugly head.


At 11:02 AM 4/11/01 -0400, Kolesar, Paul F (Paul) wrote:

>Here are my views:
>The 20 dB level for MM connectors is historical in that that has been the
>spec used by previous generations of application standards and is in
>agreement with cabling standards.
>The 26 dB level for SM connectors initiated in Fibre Channel in the early to
>mid nineties. I believe this was at the request of 1300 nm transceiver
>vendors. It is also in agreement with cabling standards. It is interesting
>to not that Telcordia (formerly Bellcore) used 27 dB in the past, which I
>believe was in concert with SONET equipment standards.
>The use of isolators in the transceiver is a design choice and not dictated
>by IEEE 802.3. The receiver is specified with a minimum return loss level,
>the value of which has been the subject of debate.
>What type of testing are you referring to? Transceiver or cabling?
>Paul Kolesar
>Lucent Technologies
>         ----------
>         From:  Doug.Coleman@xxxxxxxxxxx [SMTP:Doug.Coleman@xxxxxxxxxxx]
>         Sent:  Wednesday, April 11, 2001 9:23 AM
>         To:  802.3ae
>         Subject:  Connector Return Loss
>         Does anyone know the history behind the connector return loss
>         proposed for 10 GbE?
>         The return loss for multimode connections shall be greater than 20
>         The return loss for single mode connections shall be greater than 26
>         Do the transceivers integrate isolators into them to address return
>         Has any testing be done to demonstrate compatibility?
>         Thanks
>         Doug Coleman
>         Corning Cable Systems