If you have to run more fibre, there is no point. Because the main cost of running fibre is the work, not the material. And it's so thin you can run as many as

If you have to run more fibre, there is no point. Because the main cost of running fibre is the work, not the material. And it's so thin you can run as many as you want. So, if you're going to run new fibre anyway, just run 10x as much as you need. In fact this is pretty standard procedure with most telcos. Not sure about the polarisation by the way, when I was working with this it was not yet a thing but it's decades ago.