SFP break-out box? - Page 1
Forum section: electronics / beginners

author: borjam
author_rank: Unknown
timestamp: September 25, 2017, 03:07:51 pm
content: 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 SFPand a router. The router has a very high port density, so it's complicated to probe it properly and a sort of breakout box exposing the i2c lines would be great.Has anyone heard of anything similar?Thanks!

author: awallin
author_rank: Frequent Contributor
timestamp: September 25, 2017, 04:27:23 pm
content: There are SFP breakout boards like this:https://sincsquared.com/content/sfp-sma-breakout-boardbut 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.htmlSFPs are usually at 1Gbit or 10Gbit - sounds quite fast for i2c??

author: dmills
author_rank: Super Contributor
timestamp: September 25, 2017, 04:33:00 pm
content: 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.

author: borjam
author_rank: Unknown
timestamp: September 26, 2017, 07:23:20 am
content: ThanksThe 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.

author: borjam
author_rank: Unknown
timestamp: September 28, 2017, 02:31:45 pm
content: I found a reference, but seems to be obsolete.Avago's AFCT-5017ZI have only found one reference for the datasheethttp://manualzz.com/doc/21897054/application-note-5413-afct-5017z-sfp-extender-board

author: ildeu
author_rank: Newbie
timestamp: November 30, 2017, 01:46:59 am
content: Hi,See if this caters to you.https://github.com/SloMusti/sfpddm/blob/master/MC220Lmod.pdfRegardsIldeu

author: borjam
author_rank: Unknown
timestamp: December 04, 2017, 10:13:17 am
content: Quote from: ildeu on November 30, 2017, 01:46:59 amThanks!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 :/