Please advice which SFP module to choose

Hi. I would like to replace my Dasan H640GW device with a SFP module (I know that MikroTik’s modules were tested and are supported), as asson as I get my new Omnia. I’m a beginner in fiber networking (although quite experienced in “copper” networks). Please advice.

More info about the device here: http://dasannetworks.eu/en/gpon-ont---h640gw-02/19/