Your calculation doesn't seem to account for the fact that light in fibre travels slower than in vacuum, 2/3 if memory serves, so it's a lot closer than you thi

Your calculation doesn't seem to account for the fact that light in fibre travels slower than in vacuum, 2/3 if memory serves, so it's a lot closer than you think. A lot of the latency will be due to the conversion between light and electricity for processing in routers/switches. If we had all optical processing that would probably bring the latency down close to the theoretical limit