For internet uplink the access technology was changed from copper to fiber. As usual I wanted to use my own hardware with custom firmware / software with Deutsche Telekom AG as internet provider. Previously this was a fli4l sytem using a Draytek Vigor130 VDSL modem with 50MBit/s uplink. Getting an OEM router was not an option and so a SFP module (Zyxel PMG3000-D20B) for fiber access was ordered. The module is used in OEM ONTs so works on the uplink end. The module should be used with a Rack Matrix Noah 6 board running OpenWRT. Plugging the module into the SFP slot just resulted in the interface not coming up. This might be due to the power supply issue mentioned in [1] but has not been analyzed further and I switched to a backup solution temporarily.
The quick and dirty intermediate solution was using an EdgeRouter 6P with the Zyxel SFP module. As expected the interface came up directly during a dry run and the internal web interface could be accessed and was showing some stats about the GPON interface:
Internet access was configured using VLAN7 on the fiber interface. The modem ID was passed to the provider and the uplink came up promptly. Fiber access worked flawlessly but the issue was that download limit was obviously around 300 MBit/s while 1GBit/s was ordered. The statistics of the SFP module did not show any issues. RX level of -20dBm looks like being within the range of the specifications. As the module is used in OEM configurations the guess is that the SFP slot / hardware of the Edgerouter 6P is not capable of shoveling 1GBit/s between the interfaces.
Hack GPON (see [2]) lists a number of SFP module with some of them even tested with Deutsche Telekom AGs fiber access. There is even a number of parameters documented for the PMG3000-D20B module on [3] but the module came with recent firmware and blocked telnet access to the internals. The hack for enabling telnet did not work. In order to prevent hassling with changing modem IDs on the provider edge I ordered a LuLeey XS2510 aka. XPON Stick SFP. This module allows for configuring a number of parameters from its web interface. There even is a documentation on replacing the Zyxel PMG3000-D20B by the XS2510 under [4]. This describes how to pull all the relevant parameters / config from the telnet interface.
So the whole process boiled down to cloning the modem ID from the Zyxel to the LuLeey SFP module. The (modem) ID aka. PON SN can be found in the web interface:
This needs to be copied to the GPON SN field in the LuLeey SFP module:
In this case the ID was a 12-char string. PLOAM password and LOID are not needed in this case and are left blank. As the telnet interface on the Zyxel was not accessible I could not clone the other technical parameters as HW and SW versions so those were left at default. Connecting the fiber via the LuLeey SFP module worked like a charm. Simulaniously the router was switched to the Rack Matrix Noah 6 board with the module sitting in the SFP slot. Seems like the GPON SN is the only piece of information needed in this case and handing over a new modem ID to the provider was unnecessary. The fiber came up fine and in this case downlink speed reached almost 1BGit/s. Seems the SFP slot only supports 1G and no 2.5G so the missing bits are probably protocol overheads. Next attempt would be a piece of hardware with 2.5G SFP slot. But that is left for another day.
References
[1]: https://github.com/xvzf/zyxel-gpon-sfp/issues/10
[2]: https://hack-gpon.org/ont-zyxel-pmg3000-d20b/
[3]: https://github.com/xvzf/zyxel-gpon-sfp
[4]: https://dirkwouters.de/telekom-glasfaser-modem-2-durch-sfp-modul-ersetzen-luleey-ll-xs2510-im-test/