Lee
The information I am conveying is not on test boards. It is on real, living
designs using mid board optics with measurements of the far end eyes. Same
device and connector were used by multiple companies. There were multiple
board designs, some of which did not follow stated guidelines. Others where
Teraspeed Consulting was brought in to advise on the design.
Because these are customer designs, the results cannot be shared. You'll need
to trust me on this one.
Why are optical modules an issue, as opposed to large ICs, switch chips, FPGAs?
Because optical modules typically are desgned for the lowest power, and as a
result have little equalization, and no clock recovery. There is nothing to
clean up a signal. Jitter passes right through from the electrical domain to
the optical domain and back again.
Scott
Teraspeed Consulting - A Division of Samtec
Scott McMorrow, Technical Director SI/PI
Office 401-284-1827
www.teraspeed.com | www.samtec.com
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Lee Ritchey
Sent: Thursday, December 8, 2016 6:13 PM
To: dmarc-noreply@xxxxxxxxxxxxx; shlepnev@xxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: XTalk power flow in differential vias
I have already built dozens of test PCBs. I think the burden is on those
making the claims to show that this is a real problem with real boards rather
than visible on a test PCB.
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On ;
Behalf Of heyfitch (Redacted sender "heyfitch" for DMARC)
Sent: Wednesday, December 7, 2016 5:26 PM
To: leeritchey <leeritchey@xxxxxxxxxxxxx>; shlepnev@xxxxxxxxxxxxx;
si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: XTalk power flow in differential vias
You are free to design your own test board to convince yourself one way or
another. Right?
- VadimÂ
On Wednesday, December 7, 2016, 17:01, leeritchey <leeritchey@xxxxxxxxxxxxx>
wrote:
Cadin, I do design with hundeds of channels densely packed. Â There is no room
for "stitching vias'. Â These all work very well. Â You will find this the norm
with big iron.
Maybe stitching vias are over kill. To use them I would have to be shown that
their effect is significant rather than just visible .
Sent via the Samsung Galaxy S® 6, an AT&T 4G LTE smartphone-------- Original
message --------
From: heyfitch <heyfitch@xxxxxxxxx>
Date: 12/06/2016 8:36 PM (GMT-08:00)
To: leeritchey@xxxxxxxxxxxxx, shlepnev@xxxxxxxxxxxxx, si-list@xxxxxxxxxxxxx
Subject: Re: [SI-LIST] Re: XTalk power flow in differential vias
blockquote, div.yahoo_quoted {margin-left:0 !important;border-left:1px #715FFA
solid !important;padding-left:1ex !important;background-color:white;}Lee,In
fiber optics modules, for example, the density is so high that diff vias are
often right next to one another.
 The natural inclination is to have as few stitching vias as possible - to
have more routing channels. Â So, 2 stitching vias per a diff via is typical. Â
Yuriy's video clearly shows how the lower number of stitching vias result into
higher insertion loss.  This is a trade off consideration, imho. Also, it is
desired to have less than 40dB crosstalk between channels. That is another
consideration. Regards,Vadim Heyfitch
On Monday, December 5, 2016, 13:49, Lee Ritchey <leeritchey@xxxxxxxxxxxxx>
wrote:
Why are we worrying about differential vias?
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Yuriy Shlepnev
Sent: Monday, December 5, 2016 11:58 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] XTalk power flow in differential vias
Hello Everyone,
Last Friday I have uploaded visualization of crosstalk power flow in
differential vias - see #2016_13 at http://www.simberian.com/ScreenCasts.php
 -> How Interconnects Work (higher quality, but may be slow), YouTube version
is available at https://youtu.be/IyuQIl8T_uE The demo video illustrates two ;
ways for the crosstalk reduction. I was really fascinated with the power flow
view of the crosstalk :-) As always, I will appreciate any feedback.
Best regards,
Yuriy
Yuriy Shlepnev, Ph.D.
President, Simberian Inc.
2629 Townsgate Rd., Suite #235, Westlake Village, CA 91361, USA Office
+1-702-876-2882; Fax +1-702-482-7903 Cell +1-206-409-2368; Virtual
+1-408-627-7706
Skype: shlepnev
www.simberian.com
Simbeor - Accurate, Productive and Cost-Effective Electromagnetic Signal
Integrity Software
2010 and 2011 DesignVision Award Winner, 2015 Best In Design&Test Finalist
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