Four-port circulators have two stages of the Faraday rotator-beam splitter combination, enabling light circulation between four fiber ports. Isolating optical sources from reflections in fiber optic networks. This means that if light enters port 1 it is emitted from port 2, but if some of the emitted light is reflected back to the circulator, it does not come out of port 1 but. Faraday circulators (or less specifically optical circulators) are a kind of non-reciprocal optical devices. Unlike optical isolators that block reflected light, a circulator routes optical signals in a specific order — typically Port 1 → Port 2 and Port 2 →. The optical circulator is a fundamental device, acting as an advanced traffic controller that provides strict directional control over light signals within the network architecture.