Optical Frequency Conversion for Millimeter-Wave Ultra-Wideband-Over-Fiber Systems

This letter investigates all-optical frequency conversion of ultra-wideband (UWB) signals for UWB-over-fiber up-link and down-link systems. An electrooptical Mach-Zehnder modulator is used in nonlinear regime to realize frequency up and down conversion of UWB rectangular pulse and monocycle. All-optical frequency up-conversion of rectangular pulse at 18 GHz generates undesired local oscillator centered in the up-converted UWB spectrum, whereas up-conversion of monocycle waveform exhibits a power spectrum density optimally fitting the UWB emission mask. Up and down conversions of UWB monocycle, using the same UWB-over-fiber system, have shown low distortion induced by the optical mixing process on the UWB monocycle.