Fiber-Optic 60-GHz Wireless Downlink Using Cross-Absorption Modulation in an EAM

We demonstrate the 60-GHz radio-over-fiber downlink adopting the fiber-optic upconversion process. The cross-absorption modulation (XAM) in the multiple-quantum-well electroabsorption modulator (MQW-EAM) is incorporated for the fiber-optic upconversion. Error-free transmission of the 1.25-Gb/s and 622.08-Mb/s pseudorandom bit sequence data is achieved without critical power penalties after the fiber transmission up to 34 km followed by 1-m wireless transmission between the base station and the customer unit. The system performance is dependent on the bias voltage asserted to the MQW-EAM due to the bias-dependent modulation characteristics of XAM and absorption changes. The optimum performance is obtained at the bias of ${-}$0.8 V.