What about the fibre lenght? Is there a limitation?

Yes, the fibre length is limited by the amount of energy you can guide true a glass fibre. You have high-energy lasers and low energy density lasers. A low-density laser can have up to 100 m fibre. We produced a 2000 watt system with 100m fibre in 2021. You cannot avoid a quality change of your laser light after passing true 100 m of fibre. The power loss is very marginal, but the laser beam has lost a bit of its light quality. This will be seen as you try to focus this light at the end of the fibre.

The low-power systems ( but those are high density) will have 5-8 m as an absolute maximum for the moment.