An integrated circuit has an optical waveguide configured to carry a plurality of optical channels, which in a particular embodiment are optical clock signals generated by an optical clock generator. The integrated circuit includes an optical crossbar having a first output, a second output, a first optical ring resonator, and a second optical ring resonator. In a further embodiment, the optical crossbar is an optical crossbar switch and an output path in the optical crossbar switch includes another tunable optical ring resonator and an intermediate waveguide, which allows isolating the output from any optical channel on the on-chip optical waveguide by tuning the first ring resonator to a first wavelength, and tuning the other ring resonator to another wavelength.