We discuss key device technologies for realization of an optical-fiber-network-connected distributed radar system in the millimeter-wave band using radio over fiber techniques. The radio over fiber technique is useful for precise signal generation and distribution over the fiber network. In the scenario, each millimeter-wave radar head is not necessary to be equipped with a precision radar signal source; low cost and low energy consumption radar head will be realized. For connection to the optical network, advanced high-speed optical/electrical converters are developed for signal conversion from/to optical signals in 90-GHz band directly in a central office and each radar head. A signal-to-noise power ratio of generated 90-GHz optical signal was achieved larger than 30 dB: enough quality to use in the radar system. An optical switching technique is useful not only for routing the optical signal to the radar heads but also for filtering unnecessary optical components. These device technologies are applicable for distributed millimeter-wave radar systems.