The increase in travel time comes from: extra path length from bouncing between the sides of the inner fibre (depends, maybe 20%?) and from refractive index slo

The increase in travel time comes from: extra path length from bouncing between the sides of the inner fibre (depends, maybe 20%?) and from refractive index slowdown (about 70%). But then you have to worry about the greater total path from going into space, and also mux/demux/boosting delays.