[c-nsp] SX GBICs - too close?

[Deepak Jain]

Jay Ford wrote:

> On Sun, 8 Aug 2004, Deepak Jain wrote:
> 
>>Can someone point me to a quick reference about distances that might be
>>_too close_ for SX transceivers? (say 6" or 12") I have a few GBICs
>>ports that take 5-10 minutes to "recognize" the other end, and if I do a
>>"clear int" on one of the interfaces it goes away for between 5 minutes
>>and an hour or two. It can only be bad hardware or a bad installer. :)
>>
>>Saturating the receiver is what I am hoping for because I'd rather blame
>>the latter. heh
> 
> 
> It shouldn't be possible to saturate the receiver with SX.  According to
> http://www.cisco.com/en/US/products/hw/modules/ps872/products_data_sheet09186a008014cb5e.html
> the allowable transmit range is -4 to -9.5 dBm & the receive window is 0 to
> -17 dBm.
> 
> You actually have jumpers as short as 6-12"?  You're not supposed to use
> jumpers shorter than 2 m (6.5').  I've gone as short as 1 m in bench testing
> with no obvious trouble, but no shorter.

Ahh, there's a rub... Why aren't you supposed to go shorter than 2m? I 
had a 15ft cable that had a small SC-MMJ? converter on it, the converter 
is about 6" of cable or so and a coupler. So anyway, I ripped it out and 
connected the converter only. It works, but probably doesn't solve the 
brain-dead interfaces issue. So if you can't saturate the receiver, 
what's the problem with a short cable?

I guess that means its probably flakey hardware even though each device 
has multiple GEs on it, and multiple combinations have been tried 
between the ports with no success.

Hmmm.

thanks,

DJ