I. Introduction
The radio over fiber (ROF) system is a promising technology for broadband wireless access application because of the many advantages of the optical fiber network, including low transmission loss and huge bandwidth. In these millimeter-wave (MMW) radio networks, the larger atmospheric attenuation of the radio signals enables architectures with improved frequency reuse capabilities to be implemented. However, since the wireless coverage area is smaller, the requirement for more base stations demands that the base station be functionally simple in design. For the reasons mentioned above, optical heterodyning (the transmission of two closely spaced optical frequency components) has attracted much attention [1]–[3].