[SI-LIST] Re: Questions concerning DC-block Caps and coaxial optical packages ( ROSA/TOSA)
- From: 张胜利 <zhangshengli@xxxxxxxxxx>
- To: bharris@xxxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Thu, 19 Jan 2006 10:16:50 +0800
Bernard,
I think you are devolepling the 2.5Gb/s SFP optical module. In the
design, the srandard X7R capacitor is already enough for AC coupling.
As to the interfacing to coaxial optical, you can mounting on the edge
of the board or connecting them with flexible PCB, but i prefer to the former.
Best Regards
> packages,
----- Original Message -----
From: "Bernard Harris" <bharris@xxxxxxxxxx>
To: <si-list@xxxxxxxxxxxxx>
Sent: Wednesday, January 18, 2006 4:59 PM
Subject: [SI-LIST] Questions concerning DC-block Caps and coaxial optical
packages ( ROSA/TOSA)
> Hi All,
>
> I would appreciate recommendations on layout for series DC block capacitors,
> so as to minimize the impedance mismatch. The signal is 2.5Gb/s, 100 ohms
> differential, with nominal 80ps rise and fall times and is fairly short -
> only a few centimetres. I would prefer to use 0402 size caps. Do the caps
> have to be special RF type or can standard X7R or NPO caps be used?
>
> In addition, I would like to use the point where the series caps are
> connected for a dual layout option - top layer to one device and bottom
> layer to an alternative device. Is this a risky choice ? I've seen it on an
> eval board from our device vendor, but I'd like some insight from the
> experts.
>
> Also does anyone have some guidance on interfacing to coaxial optical
> packages, such as ROSA/TOSA/TO45 CAN. Our application requires mounting
> parallel to the board, but the packages are through hole, vertical mount. I
> suspect that the interfacing to the leads is not straightforward to get a
> decent impedance match. I thought that it may be possible to mount on the
> edge of the board, with leads soldered above and below.
>
> Thanks,
> Bernard Harris
> Lynx Photonic Networks
>
>
>
>
>
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