[EFM],[EFM-P2P] Pave, OMA, Extinction ratio diagram

["Meir Bartur" <Meir@zonu.com>]

In the upcoming EFM meeting we will need to pay attention to PMD specification approach that is applicable for the multiple PMD currently being worked out. 

The basic question is whether to specify according to the one of two options:
Option 1    ExR_MIN, ExR_MAX, Pavg_Min, Pavg_MAX  (currently the 1000Base-LX)
Option 2    OMA_MIN, Pavg_MAX, ExR_MAX 
Note: I added ExR < 20dB to avoid duty cycle distortion, working too close to the laser threshold

Option 1 enables simple power measurements in the field for link troubleshooting
Option 2 simplify and relaxes the PMD specification (and potentially reduces cost) 

The enclosed slide tries to explain the pending issue graphically.  It refers to the dual fiber 100Mb/s baseline proposal but similar concept applies for all (with potential limited refinements for the P2MP PMD).  The existing baseline is depicted in blue.  For an operator with a power meter it provides about 2 dB ambiguity on OMA while measuring average power without ExR knowledge.

From a transceiver producer point of view, the benefit of specifying OMA is the additional red area (or parts of the red area) on the graph, that, according to some claims, offers significant simplification (with no penalty of link budget - assuming no AGC effects for the TIA).  Obviously, at the expense of rendering average power measurements useless.

Informed discussions will result in better decision process in Edinburgh.


Meir

100MbsTxPowerSpace20020425.pdf.ppt