optoisolator
/ˌɒptəʊˈʌɪsəleɪtə/Electronics
noun
A device consisting essentially of a current-dependent light source and a photodetector, which receives incoming electrical signals and transmits them optically over a short distance and can be used to provide electrical isolation between two parts of a circuit.
Origin
1970s; earliest use found in WESCON Technical Papers. From opto- + isolator.