I'm not saying from Home to ISP since its dedicated either
way.
But, its dedicated until the ISP only, once you cross the ISP,
both lines will still join together.
I think you have gotten it wrong.
All Internet connections come to Singapore via Submarine
Communications cable.
It will be connected to the ISP.
From the ISP, internet connection is split into 2
Fibre optics and Broadband.
Fibre optics and Cable modem are transported differently, thus
it will not affect each other.