The present invention provides an optical time multiplexed space switch including a pulsed laser source, and means for producing from the laser source a plurality of wavelengths of pulsed radiation including means for providing permutable multi-wavelength pulse sequences from said multi-wavelength source and means for translating the input data pulses into the multi-wavelength pulse sequence. Each data pulse is subsequently guided through a wavelength selective structure, which may contain delay lines. In the case of time-slot interchange, the pulses are recombined in an interchanged sequence. In the case of tributary space switching different wavelength pulses are switched to generally different outputs and combine with pulses originating from different inputs. Alternatively, instead of or in addition to the means for providing permutable multi-wavelength pulse sequences from the pulsed source, means are provided for the permutation of the multi-wavelength data pulse sequence in reconfigurable wavelength selective structures.