As data centres pack more computing closer together, the wires carrying data between chips become a bottleneck, losing signal and generating heat over distance. Photonic interconnects send that data as pulses of light through fibre instead of electricity through copper, carrying far more over longer distances with less loss.
Light does not heat the link the way a fast electrical signal does, which matters when thousands of connections run at once. The challenge is converting cleanly between electrical and optical at each end, but as data volumes grow, moving more of the path to light becomes increasingly worthwhile.