this guy from Tom’s hardware doesn’t have a clue what he’s talking about, so, go to the original :
https://interestingengineering.com/innovation/optical-fiber-for-brain-endoscopies
Single-mode fibers, used for long-distance communication, send only one light signal at a time, usually from a laser. Multimode fibers have a wider core and allow multiple light signals from LEDs to travel through them. However, these signals bounce off the fiber’s edges, which can scramble the data.

Scientists have ways to fix this problem, like using artificial neural networks or spatial light modulators, but these methods take time and use a lot of energy. They also require changing the light signals into electrical signals before processing them, which slows things down.

To solve this issue, researchers added tiny diffractive neural networks, about the size of a grain of salt, to the ends of ultra-thin multimode fibers. These networks can read and process light signals in real-time without needing complex computing power.