[SI-LIST] Re: SFP+ (SFF-8431) Spec Confusion
- From: Gary Stein <garys@xxxxxxxxxxx>
- To: Gary Stein <garys@xxxxxxxxxxx>, "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
- Date: Thu, 11 Aug 2011 09:37:18 -0700
I'm designing a channel for a SFP+ interconnect, establishing the loss budget
to determine pcb material selection and allowable trace lengths.
SFF-8431 quotes a min allowable channel transfer of -6.5dB (Table 25).
The optics module receive output eye mask is spec'd at 150 - 425mV point C'
(Table 19).
The host receive input eye mask is spec'd at 150 - 425mV, point C" (Table 14).
The measurement points C' and C" are separated by the compliance test boards,
but these are spec'd to at most 1.5dB loss.
How can the two eye masks be virtually the same and yet the channel can allow
-6.5dB?
What assumptions have others made?
Gary Stein
Network Instruments
10701 Red Circle Drive
Minnetonka, MN 55343
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