Dear Jonathan,
There are couple of examples on the circulators in OptiSystem Example Library that could be found at the following link, which would provide guidance to you. Also, please click on the Help of the component properties popup window to access the datasheet of any component. Please find attached a file describing the ports.
C:\Users\USER NAME\Documents\OptiSystem 17.1 Samples\Component sample files\Passives Library\Optical\Circulators
Regards,
Ahmad
