How?
The prototyped mechanism involves a fresnel lens that concentrates sunlight into a fiber optic bundle. The lens has two degrees of rotational freedom and rotates with stepper motors (controlled by an arduino). Since the movement of the sun across the sky during different seasons / at different locations is well documented, there is no need for sensors to track the sun; a tabulated list of dates, times and angles is sufficient. We had a analog stick set up for demonstration.
The light can travel through the fibers with virtually no drop in brightness (attenuation). Market alternatives mainly use polished aluminum tubes for transmission, which is reasonable for short lengths but will reduce brightness as the light is attenuated with every bounce inside the tube.