Optical circulator is 3 or 4 port passive fiber optic element. Its main feature is to send signal between ports in one direction and to isolate it back forward.
Due to such capabilities it finds broad usage in different optical networks.

3 or 4 ports

different vaiants of cover (patchcord, LGX, splicecassette)

connectors SC, FC, E2000, LC version PC and APC

available waves - 1310nm and 1550nm