Optical circulator structure principle

Basically it consists of a Faraday Rotator and two polarizing prisms on either side. When polarized light passes through a Faraday rotator, its polarization plane can be rotated by 45° under the action of an external magnetic field. As long as the optical axes of the two polarizing prisms are arranged at an appropriate angle to each other, the insertion loss of the inter-connected optical paths can be very low without the isolation of the inter-connected optical paths being large.

The optical circulator can also be formed by utilizing the characteristics of the single-mode fiber that produces the Faraday rotation effect under the action of an external magnetic field.

The insertion loss and isolation of the polarization-independent optical circulator are independent of the polarization state of the incident light.