Light in fiber moves at about 0.66c due to bouncing off the walls of the fiber trillions of times in a short distance.
It moves at that speed because the index of refraction of glass is about 1.5. In single-mode fiber the light doesn't really bounce off the walls.
Also significant latency is imposed by the network architecture vs the choice of bearer, and by shared vs single user. My guess is that the main driver is actually to get a private channel with qos guarantees and as few retransmission hops and security bumps as possible.
Fiber optics are slower than microwave, and the routes aren't as straight.
I'm being pedantic but microwave just has lower latency. Bandwidth is definitely down compared to fiber.
I wondered about that, but since microwaves in air are 50% faster moving than the light through fiber it seemed correct.
Probably should have said "Light through fiber optics is slower than microwaves in air".