An optical switch fabric includes horizontal optical waveguides including a first set and a second set, the first set is configured to receive a first plurality of wavelengths from the one or more external switches and the second set is configured to send a second plurality of wavelengths to the one or more external switches; wavelength-selective drop optical switches associated with the first set, wherein the wavelength-selective drop optical switches are each configured to drop a selected wavelength from a horizontal optical waveguide of the first set to an associated vertical optical waveguide of vertical optical waveguides; and controllable optical switches associated with the vertical optical waveguides, wherein the controllable optical switches are each configured to direct a selected wavelength from a vertical optical waveguide to a horizontal optical waveguide of the second set.