What do they do?
Octocouplers provide isolcation between high and low voltage circuits, preventing noise on delicate circuits such as ones controlled by microcontrollers.
Operation
Octocouplers rely on a light emitting diode (LED) and either a photodiode of phototransistor to detect the light. These components allow for the electrical signal to be transmitted via light, providing electrical isolation between the 2 circuits.
Octocoupler vs Standard Relay
Due to the solid-state nature of the octocoupler, it offers quieter and faster switching over a standard mechanical relay. On top of this, is is also less power hungry.