Optical isolator
= Optical isolator
{wiki}
An <optical isolator> transmits <light> preferentially in one direction. An ideal <Faraday effect> device combines a $45^\circ$ rotator with <polarizers> at $0^\circ$ and $45^\circ$: forward <light> passes, while backward <light> acquires another $45^\circ$ rotation and reaches the entrance <polarizer> at $90^\circ$. See <Faraday rotation on a round trip>.