Methods, systems, and apparatus for optical wavelength selective switching. One 2×2 wavelength selective switch array includes a plurality of optical input ports configured to receive one or more optical input beams, and a plurality of optical output ports configured to receive one or more one or more optical output beams wherein the plurality of optical input ports and optical output ports form an array of 2×2 optical port pairs; one or more optical conditioning and wavelength dispersion elements; a polarization modulator array having a plurality of polarizing modulation cells, each cell configured to independently change a polarization orientation of an optical beam passing through the cell and associated with a particular wavelength channel; and a polarization-selective beam-routing optical element configured to route each particular input beam to either a first output port or a second output port according to polarization orientation.