Author Topic: SFP break-out box?  (Read 646 times)

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Offline borjam

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SFP break-out box?
« on: September 26, 2017, 01:07:51 am »
Hi,

Not sure where to ask, but the question doesn't really suit any of the other areas.

Does anyone know where to find a SFP break out box? I need to snoop the i2c communication between a SFP
and a router. The router has a very high port density, so it's complicated to probe it properly and a sort of break
out box exposing the i2c lines would be great.

Has anyone heard of anything similar?


Thanks!
 

Offline awallin

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Re: SFP break-out box?
« Reply #1 on: September 26, 2017, 02:27:23 am »
There are SFP breakout boards like this:
https://sincsquared.com/content/sfp-sma-breakout-board
but they are quite expensive..

or you could try just a "direct-attach-cable" which is essentially 4 pieces of small coax between two SFP connectors.
if you open up the cable you can connect the other end to a scope or logic analyzer.
http://www.fs.com/de/dac_cables.html

SFPs are usually at 1Gbit or 10Gbit - sounds quite fast for i2c?? ;)
 

Offline dmills

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Re: SFP break-out box?
« Reply #2 on: September 26, 2017, 02:33:00 am »
The I2C is not the high speed link, but instead connects to a virtual EEPROM in the module that contains some fixed data (Manufacturer, model number, some other bits) and some variable data (Rx power, Tx diode current, some other stuff).

This a direct attach cable will not get it done, because that only sees the high speed links, but you may be able to hack a spare SFP to break the relevant signals out on some kynar wire.

If your switch has a QSFP port, you could maybe use a QSFP -> SFP adaptor and break the I2C out on that?

Regards, Dan.


 

Offline borjam

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Re: SFP break-out box?
« Reply #3 on: September 26, 2017, 05:23:20 pm »
Thanks :)

The thing is: I know that the i2c is a control channel, not the actual data transmission channel. But, for some reason, the i2c bus in the router card seems to get stuck. It's not only read when the interface is initialized. The router monitors the temperature and other SFP parameters regularly.

So, what I need is the ability to observe the i2c exchanges while the router and the SFP are actually working. I thought there could be some sort of SFP breakout box which I could insert between the SFP and the router in order to capture the i2c traffic (initialization and the periodic polling). The port density is very high and it would be quite a pain in the ass to probe it.

 

Offline borjam

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Re: SFP break-out box?
« Reply #4 on: September 29, 2017, 12:31:45 am »
I found a reference, but seems to be obsolete.

Avago's AFCT-5017Z

I have only found one reference for the datasheet

http://manualzz.com/doc/21897054/application-note-5413-afct-5017z-sfp-extender-board

 

Offline ildeu

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Re: SFP break-out box?
« Reply #5 on: November 30, 2017, 12:46:59 pm »
Hi,
See if this caters to you.
https://github.com/SloMusti/sfpddm/blob/master/MC220Lmod.pdf

Regards
Ildeu
 

Offline borjam

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Re: SFP break-out box?
« Reply #6 on: December 04, 2017, 09:13:17 pm »
Hi,
See if this caters to you.
https://github.com/SloMusti/sfpddm/blob/master/MC220Lmod.pdf
Thanks!

The problem is, the card is a 16 port Gigabit Ethernet card for a Juniper router. It has a very high port density, no room inside to route cables properly and, given how expensive it is, I need a zero risk solution. Hence the break out box. Unfortunately it seems to be custom made now and I was quoted a rather insane price, like 500 dollars :/


 


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