An optocoupler, also called an opto-isolator, is a component that transfers a signal using light while keeping two circuits electrically separated.
How an optocoupler works
Inside many optocouplers, an LED shines onto a light-sensitive transistor or detector. The input side controls the light, and the output side responds without a direct electrical connection.
Why isolation matters
Isolation can protect low-voltage control electronics from noise, high voltage, ground differences, or faults. Optocouplers are common in power supplies, motor controls, communication interfaces, and safety-related circuits.
An optocoupler is useful when a signal needs to cross a boundary but current should not.