3-port 1310nm Polarization Insensitive Circulator, one type is 1x2 that routes input signals from Port 1 to Port 2 and input Port 2 signals to Port 3 while blocking reflected light; The other type si 2x2 that routes input signals from Port 1 to Port 2, input port 2 to port 3, and input port 3 to port 4, while blocking reflected light. The device has high isolation, low insertion loss, high extinction ratio and excellent environmental stability.