GPON SFP options

General discussion
#1

Looking forward to the Turris Enterprise! :partying_face:

An idea for an “add-on” to this would be a MAC-less GPON SFP stick, if that’s technically viable for the device.

At least here in Germany where I’m located, GPON fibre infrastructure is being massively built out, but there are no MAC-less GPON SFP sticks available (there’s one for AVM Fritz!Boxes named “Fritz!SFP GPON”, but that only works on that HW platform).

GPON SFP sticks commonly found on the market today, like the one I currently use in my Omnia, are actually full (very outdated, receiving no updates) OpenWrt Linux hosts that pass the traffic through and do OMCI signalling. In other words: That’s quite bad. (On the other hand, your ISP-provided ONT device may not get any updates either, and using a MAC-ful GPON ONT SFP is probably still the more energy- and space- efficient option).

I’m currently a user of the FS.com GPON ONT SFP stick, so it does work, although having another OpenWrt instance running on the stick is not ideal.

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Turris Omnia 2022
Supported SFP modules
#2

IIRC on those Fritzboxes there is a dedicated GPON chip on the main board and the optic is indeed just a passive transceiver, but without that additional chip there will be no GPON…

#3

I’m no HW expert, but I’d think no dedicated chip is required. As I understand it, the OMCI signalling stuff could be done on CPU, too. It’d be important however that the SFP port has a dedicated MAC chip, which should be the case at least for the WAN port (also already on Omnia).

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#4

Found this on the devicetree ML, but it doesn’t look like it went anywhere: What is inside GPON SFP module? (Was: Re: Unsupported phy-connection-type sgmii-2500 in arch/powerpc/boot/dts/fsl/t1023rdb.dts) — Linux Device Tree

#5

There is no open GPON stack as far as I know… unless you write one you will have to get a complete ONT from a 3rd party…

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#6

You could “bake” your own … https://www.flexoptix.net/

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#7

So how could I use this to replace an ONT from my ISP?

#8

This might be completely different stories - my ISP (Deutsche Glasfaser) completely refuses to hand out PPPoE-credentials to use an own SFP-module (you might file a law case against this, but I do not have the energy to do so atm).
But this might be only the case for retrograded German providers.

You first need technical data of the connection (wavelength etc) from your provider, the respective SFP module can then be ordered tailored to your needs e.g. from fs.com. But that only works for AON connections, not for GPON.

#9

With a Turris Omnia, you need a GPON ONT SFP stick.
That’s the part that can technically replace the ISP-provided ONT.

These sticks mostly run another OpenWrt instance internally, which is energy-inefficient, but certainly no worse than using another dedicated ISP-provided ONT/ONU. And it’s certainly the more space-efficient option.

#10

Oh, I thought they did that by now at Deutsche Glasfaser. There are plenty of testimonials on forums online, also for folks using a FritzBox Fiber, so it might be worth re-requesting those credentials?

Alas, it’s far from perfect in Germany currently. At my current ISP PYUR, it was quite a pain to get them to onboard my GPON SFP (by allow-listing the MAC addr, no PPPoE or such). I have the one from FS.com and it’s been working great.

Since you mention it, I usually request the technical interface spec (“Schnittstellenbeschreibung”) from the ISP. Their response to that is a litmus test for their readiness (or willingness) to allow your own device in.

#11

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