[LINK] Inexpensive GPON optical sniffing - a matter of time or already possible?

Glen Turner gdt at gdt.id.au
Fri Nov 30 02:54:26 AEDT 2012

> But of course I can´t even attemp to do this learning exercise if it
> involves buying the expensive "dedicated sniffer" box above.

By all means attach a 100Base-T ethernet switch in "span mode" to the UNI-D port on the customer side of the NBN Network Termination Unit.

However it is illegal to fiddle with the optical portion of the NBN network.

Your suggestion shows such a lack of understanding that it doesn't stand a hope of working (you don't preserve frequency, timing or OAM of the received packets when you retransmit them). Read the literature on "regeneration of EPON".

Your suggestion will in fact take out the other 30 subscribers on your fiber. Protecting those 30 people from "learning exercises" such as yours is exactly the point of the prohibition in the legislation. Not to mention protecting the privacy of those people's communications.

The relevant portions of the Telecommunications Act 1997 are Part 13 ("Protection of communications") and Part 21 ("Technical standards") with particular attention to Div 6A ("Connection permits authorising the connection of non-standard customer equipment and non-standard cabling"). And of course the Telecommunications (Interception and Access) Act 1979.

Most in-place optical sniffers use a design with a passive optical splitter feeding a optical amplifier to SFP in a network card. The transmitter is disabled either physically or in software. Inserting this equipment requires a good understanding of the optical loss of the line, and the sniffer may need to amplify the main line as well (whilst controlling the dispersion effects so that the main line receivers can still function). If conditions are perfect you may not need the amplifiers, in which case a passive optical splitter, GPON SFP and 1000Base-X SFP network interface card would be sufficient for a bespoke system. But the point here is that even using the correct solution (or a commercial product which conveniently packages that solution) can't be done without knowing the optical parameters of the network you are attaching to.

Not carefully that I am not saying that this cannot be done. I am saying that *you* should not do it, because you lack the technical knowledge to be successful and you lack the connection permit to be legal.

 Glen Turner <http://www.gdt.id.au/~gdt/>

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