[juliangmp]

> The most concerning limitation in the German market is the unavailability of native Glass Fiber modems, that can accept as input a Glass Fiber connection: at the moment, providers install their own Glass Fiber modem.

Im actually quite okay with that. Why should I have to pay for specialized hardware that won't be usable if I move and the new apartment uses DSL or docsis. Give me an rj45 (or sfp for some fiber connections) and let me put whatever Router I want behind it.

[perching_aix]

You say "why should I have to pay", but they really haven't said or suggested anything about how they'd rather you paid for anything. They're talking about having an option to supply one's own device, not about requiring so.

The common rationale behind this I'm aware of is that an ONT device is technically a computer with persistence, hosting arbitrary code and data that you cannot (or at least not supposed to) audit or alter, despite being on your premises, operated on your cost (electricity, cooling, storage), and specifically deployed for your use. These properties hold for SFP modules too in general, not just SFP ONTs (they're all computers with persistence).

The catch is that this is further true for all of these kinds of modems.

The counter-catch is that despite that, for DSL specifically, you could absolutely bring your own modem, hw and sw both.

The counter-counter-catch is that with DSL, you were not connecting to a shared media, but point-to-point. This is unlike DOCSIS and GPON, where a misconfigured endpoint can disrupt service for other people, and possibly damage their or the provider's devices and lines.

That's all the lore I'm aware of at least.

[LargoLasskhyfv]

There are other ONs, doing away with the sharedness of the GP. Giving you an exclusive ptp 'BIDI-link' into the ISPs next switch.

https://duckduckgo.com/?q=bidi+sfp looking like this:

https://www.fs.com/de/products/39196.html fitting to this interface specification from the ISP:

https://www.wilhelm-tel.de/schnittstellenbeschreibung which is AON also known as 1000BASEBX20-U.

Just have to watch out for the right wavelengths/colors for TX/RX(transmit/recieve/upstream/downstream)

[fL0per]

Very much indeed, a 'rogue ONT' can screw another nearly 63 users' acess in my area. Oversubscription is very noticeable, but just not problematic. 10G FTTH delivering 60~70% of the bandwidth is enough I guess. And latencies or jitter aren't a thing either.

[MarkusWandel]

The "glass fiber modem" is an inherent part of the GPON network. These are complicated. The "P" stands for "passive". Yours and and up to 127 other houses are all on the same "light domain" i.e. the downstream is passively split, and the upstream is passively combined, in optical boxes that don't even have electrical parts.

This needs crazy accurate timing for the upstream. The head end needs to know the exact delay to your particular box to give it a "grant" to transmit at exactly the right time so transmit bandwidth is not wasted by idle time or multiple boxes transmitting at the same time and corrupting each other.

You don't want brand X modems with dodgy configurations in this. Of course as a consumer you'd want "as little modem as possible" i.e. just give me an ethernet port running DHCP or PPPOE and let me do the rest.

[stephen_g]

They are complicated, but standardised and commoditised. Ubiquiti, for example, sells an ONT (fibre modem) in a SFP form factor for US$39 [1], or a little standalone unit with an Ethernet port for US$49 [2].

1. https://store.ui.com/us/en/category/fiber-gpon/products/uf-i...

2. https://store.ui.com/us/en/category/fiber-gpon/products/wave...

[direwolf20]

For comparison: you can bring your own DOCSIS modem to a cable network, even though all the houses on the street are connected to the same cable and you could jam it, or send a voltage spike to break everyone's modem.

[perching_aix]

Not very familiar with DOCSIS and cable; the story I'm getting from my nearest friendly LLM is that while you could bring your cable modem, it'd have to be a pre-approved model, and that the firmware and configuration would be under ISP control, unlike with DSL modems. Is that wrong?

[namibj]

In Germany it's wrong.

[perching_aix]

How does it work in Germany?

[fL0per]

Here in Spain it was common to get one of these to replace the ISP ONT:

https://eu.store.ui.com/eu/en/category/fiber-gpon/products/u...

Not that I had the need or anything, but it's similarly priced to the example in 2. Seems to me like maybe they're phasing it out soon?

[bobmcnamara]

I cloned mine into an SFP+ for a handful of microseconds of latency improvement.

[Fnoord]

Less W usage as well.