RE: Connector Return Loss
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?
From: Doug.Coleman@corning.com [SMTP:Doug.Coleman@corning.com]
Sent: Wednesday, April 11, 2001 9:23 AM
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?
Corning Cable Systems