Thread Links Date Links
Thread Prev Thread Next Thread Index Date Prev Date Next Date Index

RE: [EFM] PON timing parameters


Nice chart.

I just reviewed a spec sheet for a burst mode CDR. This company claims extremely low "lock times***." But, the delay through the chip is a couple of orders of magnitude greater than normal 1000BASE-X CDRs.

I don't understand how it can be done. But, if it is possible to trade "rapid lock" against latency or delay, there could be significant benefits. This presumes that this magnitude of latency is not of concern to EFM.

Is it possible to do this?


*** I note that there is no specification for jitter or BER. So, the low lock times might have nothing to do with the extreme latency.

| -----Original Message-----
| From: Gerry Pesavento [mailto:gerry.pesavento@xxxxxxxxxxxx]
| Sent: Thursday, December 12, 2002 1:07 PM
| To: FEffenberger@xxxxxxxxxxxxxxxxx; Vipul_Bhatt@xxxxxxxx;
| Subject: RE: [EFM] PON timing parameters 
| Attached is the timing parameter table, that is the result of the PMD
| conference call this morning.  As you can see, there has been
| significant progress, and two Options are currently on the table.  The
| OLT parameters are identical.  The remaining decision concerns the ONT
| laser on/off time (make large and settable, or make small and 
| fixed).  
| Fixed parameters in ONTs (option C) are attractive since it will not
| require the OLT to keep a table with on/off times per ONT. Settable
| parameters per OLT are almost mandatory (CDR time is 
| different with and
| without FEC, protocol delay may not be constant, etc).  As Frank
| mentioned, settable parameters means that during 
| initialization the OLT
| will broadcast a value that represents a number of idles that 
| ONT should
| transmit at the beginning of the burst.  This seems to be a simple and
| robust approach. 
| Glen/Gerry