Inea Agreement: Using Asus RT-N16 with Tomato Firmware & Compatible Optical Modem with TV Output

Hello.
I am moving and in the new place I will have internet with TV provided by INEA.
I received an Alcatel-Lucent G-241W-A wifi router from them
I would prefer to use my own router on which I have tomato (asus rt-n16)
But it's not that simple because Alcatel has a TV output and an optical modem.
Does anyone know if I could buy, for example, an optical modem with a TV output to which I would connect the TV and my router and could work like that?
Am I stuck with this unknown device?

The provider's modem must remain in place. What you connect to it is up to you.

This is a terrible bowel because it is probably impossible to switch the provider's router into bridge or "modem only" mode and use your own router.

---EDITION---
I found. The router can work in BRIDGE mode. You can turn it on in the settings. So I connect it in this mode to my router and that's it.