Mike (et
al):
We missed you at the
last meetings. I hope all is well with you and that you will "meet me in
St.
Louis".
We had a very
interesting discussion about return loss at the last meeting
(Santa
Rosa),
although no attempt was made to change the specifications, only to rename
them.
There appear to be
four parameters of interest in a link, all confusingly named and specified,
IMHO. My attempt to rename these parameters more descriptively and call them
out explicitly by these new names met with enough resistance that it didn't
get approved, although everyone appeared to think it was a "good" idea. Some
present felt it was too much change and that it would invite comments to
rename these parameters, but due to the amount of churn already present in the
clause, let me try again:
- Optical
Return Loss Tolerance (ORLT): Looking out of the transmitter,
the maximum reflectance it can tolerate during
operation.
- Transmitter
Reflectance (TR): Looking into the transmitter,
the maximum reflectance observed.
- Receiver
Reflectance (RR): Looking into the receiver, the
maximum reflectance observed.
- Maximum
Discrete Reflectance (MDR): Looking into the fiber plant,
the maximum reflectance of any point along that optical fiber (usually a
connector).
I won't play around
with the sign of the numbers right now, but here's how I think these are
specified currently for each link type:
ORLT TR
RR
MDR
10GBASE-S: 12
-
-12
-20
10GBASE-L: 12
-12
-12
-26
10GBASE-E: 21
-26
-27
-26
-
indicates not
specified
Comments? Suggestions? I really want to make this as clear as
possible, so I am going to recommend that: ORLT, TR be listed in each PMD's transmit parameters explicitly, and RR in each PMD's receive parameters, and that MDR be listed
explicitly as such where it is now. In addition, if it is appropriate, we can
include a measurement technique referencing appropriate other standards for
any specifications we deem appropriate.
Cheers,
Dave
------
David
Kabal
Sr.
Technology Planner
Picolight
e-mail:
david.kabal@xxxxxxxxxxxxx
Main:
303-530-3189 x7498
Direct:
303-527-7498
Fax:
303-527-4961
-----Original
Message-----
From:
owner-stds-802-3-hssg-serialpmd@xxxxxxxxxxxxxxxxxx
[mailto:owner-stds-802-3-hssg-serialpmd@xxxxxxxxxxxxxxxxxx] On Behalf Of Mike Dudek
Sent: Monday, February 25,
2002 7:17
PM
To: Christensen, Benny
Cc: Serial PMD Ad Hoc Reflector (E-mail)
(E-mail)
Subject: Re: FW:
[802.3ae_Serial] 12 dB return loss for
transmitter?
This is all good information, however
returning to the original question. The 12dB return loss for the
transmitter is as Ron said a specification on the transmitter, not the cable
plant. It is measured by injecting an optical signal into the Tx and
measuring how much light is reflected back. It was included to keep
Interferometric noise to a low level. This noise is generated when there
is a triple path (ie reflection from the Rx which then gets reflected back by
the Tx with a single mode source.). It would be nice to remove the
specification, but a significant amount of work was done in the serial Ad Hoc
to show that the specification is needed unless the return loss on the Rx is
tightened.