@Clive_A I'm aware of possible hardware incompatibility, I just wanted to explore the easy solutions first. The gpon module can operate in different modes, depending on what the host supports. It is...

@Clive_A All of those steps has been tried allready. The problem seems to be the router disconnecting the sfp module before the module has had any chance to initialize, and thus gets stuck in this...

I have one of those chinese "RTL960x based xPON ONU Stic" SFP module which works fine in my old MikroTik router, but my new TP-Link ER7206 seems to be unable to connect to it. The SFP lamp lights up...