Optocouplers have most commonly been used to provide safety
isolation for compliance with domestic and international
regulatory requirements. In this capacity, they have been very
effective at isolating lethal high voltage potentials from low-
voltage, user-accessible circuitry in equipment such as power
supplies. Furthermore, they have proven to be a cost-effective
solution by saving PCB space. In addition to safety isolation,
however, optocouplers also provide another benefit that is often
overlooked: isolation from electrical noise. The devices can be
used to reduce the effects of noise at both the board and system
level. Optocouplers separate noisy circuitry from more sensitive
circuitry by allowing signals to cross boundaries without
requiring the sensitive circuit to share a common ground
reference with the offending circuit’s noisy ground plane. The
ability to easily and effectively separate sections of PCB
boards can greatly reduce the design risks in systems that
require sub-circuits of varying levels