A circulator array is constructed in a planar substrate by forming a plurality of waveguide pair structures, each waveguide pair structure having first and second sections respectively coupled by first and second polarization multiplexers. A nonreciprocal polarization rotation element is positioned in the optical paths of the waveguide pair structures and is configured to rotate the polarization of light passing from the second sections of the waveguides to the first sections while leaving unchanged the polarization of light passing from the first sections to the second sections, such that optical signals received at one port of the circulator structure are routed along a predetermined path to another port of the circulator structure.