¡Que siga la fiesta!
They're an interesting technology, but the system costs more than my turntable at the moment. Rather than use a moving magnet, moving iron or moving coils to electromagnetically generate the output signal, the DS Audio optical cartridges use a mirror attached to the end of the cantilever that reflects the light of two tiny LEDs inside the cartridge. That signal is then sent back to the phono stage where it's converted to an audio signal. Having heard an earlier model, they have excellent tracking ability, better than just about anything I'd heard. But they are cost prohibitive...