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RE: Connector Return Loss (1550 nm versus 850/1300 nm)

the Telcordia spec is not wavelength specific. Your points are valid, but
not in the same context as mine. I was referring to Ethernet in the First
Mile (EFM) not 10GbE.

	From:  gwinn@xxxxxxxxxxx [SMTP:gwinn@xxxxxxxxxxx]
	Sent:  Thursday, April 12, 2001 11:27 AM
	To:  Kolesar, Paul F (Paul); 'Geoff Thompson'
	Cc:  802.3ae
	Subject:  RE: Connector Return Loss (1550 nm versus 850/1300 nm)

	Paul and Goeff,

	The Telecordia 40-dB return loss requirement may be intended for
	1550-nanometer systems.  There was a discussion of these issues at
	Tampa 10GbE meeting in 2000, mostly revolving around what the
	return loss should be.  Basically, 850 and 1300 nanometer links are
	(1 Km or less) and are build by connecting randomly-chosen parts
from bins,
	while 1550 nanometer links are long (tens of Km) and are
	engineered.  Use of optical isolators was discussed as well, but
this is a
	transmitter design issue, and thus should not be required.  The
	agreement was to leave the connector return loss specs as they were,
	for 1550 only tighten the receiver loss, and the RIN specs and
	would be how the transmitter was specified.  A tranmitter with an
	sensitive laser might require an isolater, but this is not for the
	to say.  If memory serves, the return loss spec was changed from 12
dB to
	20 or 26 dB; the current draft should tell the story.

	Anyway, we may wish to use Telecordia optical specs across the board
	1550 nanometer links, but 1300 and 850 nm links are a different


	At 10:24 AM 1/4/12, Kolesar, Paul F (Paul) wrote:
	>Good point on passive splitter systems. Similar concerns exist for
	>bi-directional transmission on the same fiber at the same
wavelength. For
	>EFM, both of these systems will probably be only on singlemode
fiber and use
	>singlemode connectors. While outside the scope of Structured
	>Standards, the improved return loss performance that may be
required for SM
	>connectors is found elsewhere. For example, Telcordia now requires
at least
	>40 dB return loss for singlemode connectors. Fortunately, products
	>that easily meet this performance level.