As others already noted: you need a VoIP-to-POTS gateway to connect your plain old phone. ISPs usually provide ONT/router devices which include one, none of MT devices does. Another possibility is to fetch a VoIP phone and then properly configure router to pass VoIP (usually it’s a separate VLAN). This part then becomes very similar to passing IPTV.
But I wish you good luck replacing ONT with a 3rd party SFP module. There’s a lenghty thread about this very topic and it doesn’t seem to be a smooth ride: http://forum.mikrotik.com/t/usage-gpon-module-sfp-in-spain/104807/1 The problem serms to be two fold:
- finding a GPON module that actually works with any particular MT device model is a hard thing. ROS support for 3rd party modules is less than satisfactory (to put it mildly). GPON modules in particular need additional support (to set GPON-specific paraneters) which is not offered in ROS either.
- getting correct settings required by your GPON provider … ONT devices are considered as termination point of provider’s network and replacing that piece of equipment is considered as invasion into (if not breach of) their network by network operators. And as such it doesn’t fall into “free choice of customer’s equipment” category, protected by (EU) laws.
So I guess the best you can do is what @anav mentions: use ISP’s gadget to terminate FO (ONT function) and deliver phone and IPTV services. Try to put it into “bridge mode” for data service and use your own router as router and firewall.