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[8023-10GEPON] change in sync pattern (preamble)



Dear Task Force members,

 

Recently it has been proposed to change the sync pattern (Preamble) from the periodic 101010 …  pattern to a non-periodic “data-like” pattern. I am afraid that this might affect negatively one of the main purposes of having a preamble, clock recovery, as well as its associate parameter:  the locking time.

 

As was pointedly stated in 3av_0805_effenberger_3.pdf, the periodic 101010… pattern  is the “golden” pattern for clock recovery and it also has the advantage that it does not discriminate between any specific implementations, neither present nor future, which is a very good feature for a Standard.

 

Changing to a “data-like” pattern preamble will clearly affect the locking time which will become longer, since the number of transitions (or updates for the phase-locked-loop)  will be less. In some situations, where the BER (before FEC) might be marginal, it might even lead to catastrophic failure of the clock recovery system.

 

Regards,

 

Jaime Kardontchik

Kawasaki Microelectronics