Inter-BSs virtual private network for privacy and security enhanced 60Â GHz radio-over-fiber system

► VPN-based inter-BSs system is proposed for 60 GHz RoF to enhance its security. ► OCDM en/decoding technology is employed to configure inter-BSs VPN in 60 GHz RoF. ► A 58 GHz MMW is used as inter-BSs VPN, while a 60 GHz MMW is used as common CS-BSs. ► FWM in a SOA is to generate optical carriers for downlink, uplink and VPN link.