[lstamour]

Can’t speak to this exact circumstance, but more generally: The ONT translates the SFP+ networking to fibre optic, but the modem is still somewhat necessary for logins if you use PPPoE as a wrapper for example. In telecom fibre optic, it often also assigns a particular vlan to internet packets and separate vlans for TV and phone. But I’m not an expert here, just explaining why I needed a modem function in my router as well as a media converter to house the ONT.

As far as I know, nobody uses separate boxes for the modem and router, that kind of thinking died when wifi became more widespread and included by default with ISP plans.

[vel0city]

I wouldn't really call that a "modem" though, it's not really doing modulation/demodulation work to convert between media types. The terminology I usually hear for the provider's box handling any final authentication and VLAN splitting is usually a "residential gateway", which can be configured to bridge to a client's equipment.

Definitely splitting hairs here though on terminology.

[kalleboo]

The component that does the PPPoE and VoIP VLAN is typically just referred to as a router (or a "residential gateway" for companies that want to sound less technical), I've never heard as it referred to as a modem, usually the ONT is referred to as a modem as it's MODulating/DEModulating the optical signal.