ACPL-054L Dual-Channel Digital Optocoupler Broadcom ACPL-054L dual-channel 1MBd digital optocoupler uses an insulating layer between the LED and an integrated photon detector to provide electrical insulation between input and output. Separate connections for the photodiode bias and output transistor collector increase the speed up to a hundred times over that of a conventional photo-transistor coupler by reducing the base-collector capacitance.