Impact of Amplitude Noise in Millimeter-Wave Radio-Over-Fiber Systems

In this paper, a complete theoretical and experimental study of amplitude noise impact on performance of radio-over-fiber (RoF) communication system in millimeter-wave (MMW) frequency band is presented. A simulation method is also presented, using which one can determine the origin of the amplitude noise which has the most impact on error vector magnitude (EVM). This method is based on analyzing the trends of EVM versus received optical power. The impact of different optical and electrical noise such as relative intensity noise, shot noise and thermal noise on EVM is precisely studied employing experimental and theoretical analysis. In the proposed RoF system, two techniques are used to generate MMW signal, and the EVM results are compared from amplitude noise viewpoint. In the first technique, two independent distributed feedback lasers are used to generate MMW signal at the output of a photodetector, and the second technique is based on a passively mode-locked laser diode. Impact of optical sources phase noise on performance of the system is removed using a noncoherent down-conversion method based on envelope detector. Using this method, a very good matching between the experimental and the simulation results is observed.