Microwave photonic techniques, such as optical heterodyning of two correlated laser sources upon photo-detection, have been proposed to generate high purity millimeter wave (mmWave) signals. This approach is particularly suitable for RF frequencies where mmWave electronic are costly and difficult to implement. Additionally, radio-over-fiber allows an efficient remote delivery of the mmWave signal by transmitting the reference optical signal though low-loss high bandwidth optical fiber links. Laser characteristics, such as relative intensity noise and phase noise together with optical fiber characteristics are of maximum importance in such applications. In this paper, laser models with different degrees of complexity are discussed and compared to assess their suitability in the design of radio-over-fiber links and radar systems based on the optical heterodyning method.