[timrice]

This is not entirely true with PON (passive optical networks). The ONT is more than a media converter (optical -> copper), it facilitates the conversation with the OLT (Optical Line Terminal) further upstream. That connection is not an ethernet connection and needs specialized hardware that can communicate using the PON protocols.

The ONT is managed by the service provider and provisioned with their tooling. It typically holds the user profile of the customer, and contains information about the subscribers service level. It is not something that can reasonably be replaced by the end user with their own hardware.

[maratc]

This could be true in the general case, but in my specific case I was provided with the username/password combination that I fed into the PPPoE configuration page of my router.

[p_l]

Because the xPON ONT was provisioned to setup ethernet over PON for you, which in turn was used to setup PPPoE session to actual internet.

[maratc]

Again, I'm not certain of the entire stack beyond my house, but the device they brought for installation was sealed in the box that said "Media Converter" (not "ONT") on the box. It could still be the case that they somehow set it up remotely, or it could be that no setup was needed. For all I know, I tested my connection with PPPoE.

[p_l]

Yep, that's ONT.

They are provisioned remotely over network from controller run by ISP, which sets up appropriate timeslots (xPON is a time-division multiplexed network in practice, though DWDM - wavelength modulation - is also used).

  Internet -> ISP network -> PPPoE -> OLT (head unit) -> passive fiber network (and/or DWDM) -> passive splitter close to home (often in inside appartment buildings) -> ONT ->  ethernet to your router for PPPoE -> your systems

[maratc]

Can you please expand on how much of that chain can be qualified as "Ethernet" (or "TCP/IP") and how much is "neither at all", and how different that is from e.g. a classic "DSL with ATM" chain?

[p_l]

From OLT to ONT, and everything in between, is handled by non-ethernet/non-IP protocols over which you can tunnel whatever higher level protocol you want.

Technically that can continue to whatever hosts PPPoE gateway. Ultimately, OLT is "root node", and ONTs are "leaf nodes" of a passive optical network tree. What is distributed over it is less of interest to it. But that's why you often have ONTs called "media converters" - though they aren't exactly that. A typical ONT also includes xPON MAC component as well as all management functions necessary to login into xPON network, establish session, etc. and demux transported protocol to whatever is delivered on the other side (nearly always ethernet)