An optical circulator is a passive, non-reciprocal, multi-port optical device, typically featuring three or four ports, that routes incoming light signals sequentially from one port to the next in a single direction, thereby preventing backward propagation through the same path. Unlike optical isolators that block reflected light, a circulator routes optical signals in a specific order — typically Port 1 → Port 2 and Port 2 →. An optical circulator is a passive multi-port optical component characterized by its non-reciprocal property.