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[802.3ae_Serial] 850nm eye mask and draft link model




Tomorrow, we hope to discuss an alternative eye mask for 850 nm serial.
Here is a straw man to focus the discussion in tomorrow's serial PMD call:
Please consider the scaled OC-12 mask which is a little more demanding than
the 10GE mask but not as much as the 1 GE mask.

     	| X1 	| X2 	| Y1 	|
10GE 	|0.3 	|0.4 	|0.25	|
OC-12	|0.25	|0.4 	|0.2 	|
1GE  	|0.22	|0.375|0.2 	|
The significant difference is that the OC-12 mask is 60% of the height of
the eye instead of 50%.  This forces faster risetime and/or lower jitter at
the transmitter, to allow for distortion from the multimode fibre.  (The
OC-1/3 mask is intermediate between OC-12 and 1GE.)

I have been updating the link model with a view to assisting the choice of
an eye mask for 850 nm serial.  The current file is too big to go through
the reflector.  There is a temporary file at
http://www.ieee802.org/3/ae/public/adhoc/serial_pmd/documents/10GPBud_tmp010
622a.xls but it only has a 1310 nm page.  I have a draft 850 nm page which I
can mail tomorrow to anyone attending tomorrow's meeting, or one can input
the 850 nm parameters to this temporary file.

Meeting coordinates at the bottom of the message below:

Piers

> -----Original Message-----
> From: DAWE,PIERS (A-England,ex1) [mailto:piers_dawe@agilent.com]
> Sent: 21 June 2001 16:30
> To: '802.3ae Serial'
> Subject: [802.3ae_Serial] From Serial PMD 19 June: 850nm eye mask, ORL
> spec, 1310serial ma x Tx power, ...
> 
> Eye mask for 850 nm
> -------------------
> 850 nm proponents, please notice that the serial ad hoc is 
> charged with
> producing a proposal for a 850-specific eye mask which would 
> preserve the
> transmitter integrity requirements of the current draft 
> standard but remove
> the need for rise time specification and measurement.  This 
> might be like a
> scaled OC-12 or 1GigE mask.  Please email and join next week's call if
> interested.
> 
> ORL
> ---
> We understand that ORL is total Optical Return Loss measured by
> disconnecting a transmitter from a link and measuring the link with a
> reflectometer.  The far end receiver remains attached.  
> Historically this
> has been a requirement of SONET but not of Ethernet.  It seems that it
> guards against multiple reflection effects (parasitic 
> etalons) in single
> mode links, where reflections that are individually within 
> spec combine to
> create a problem.
> 
> The following is a table (E&OE):
> 
> 		|   G.691  	|   10GE   	|
> Discrete	| 27 	| 27 	| 26 	| 26 	|
> Receiver	| 14 	| 24 	| 12 	| 26 	|
> ORL		| 14 	| 24 	|  - 	|  - 	|
> RIN test	|  - 	|  - 	| 12 	| 21 	|
> 
> If the ORL requirement is there to protect the transmitter from back
> reflection, 10G Ethernet could reasonably use the same 
> numbers for ORL spec
> as it uses for RIN test.  Input from the fibre and cabling 
> community on the
> merit of an ORL spec at 1310 and/or 1550 nm is needed: please 
> email or join
> next week's call!
> 
> Receiver overload
> -----------------
> Suggested re-calculating the Tx max mean power from current 
> likely Tx min.
> mean power + 5 dB for tolerances (keeping the 5 dB range we 
> started with).
> 
> How is stressed eye ISI value derived?
> --------------------------------------
> Thought to be calculated using a high receiver bandwidth 
> rather than the
> usual 7.5 GHz, and with TP3 DCD (6 ps) rather than TP4 (8 
> ps).  If this is
> right, to be recorded in "Notes" page of link model at next revision.
> 
> Jitter
> ------
> 0.015 UI sigma_RJ thought to be too small.  Obviously too 
> much causes an
> error floor, but maybe 0.025 UI would be in the right ball 
> park?  But we
> don't know what would cause Tx RJ apart from RIN, because 
> most oscillator
> phase noise is expected to be <4 MHz and tracked out by Rx PLL.
> 
> We have accounted for some DJ in the model with the DCD 
> factor.  We are
> still thinking in the range 0.3 to 0.35 UI.
> 
> Next meeting
> ------------
> Agenda items to include:
> 
> 850 nm mask proposals
> ORL spec
> Receiver overload
> Refining jitter DJ and RJ spec numbers
> 
> Usual coordinates:
> 
> 	15:15 GMT = 4:15 pm BST = 17:15 CET = 11:15 am EDT = 
> 8:15 am PDT,
> Tuesday
> 	+1(816)650-0631  Access code 39209
> 
> Piers
>