Impact of Laser Mode Partition Noise on Optical Heterodyning at Millimeter-Wave Frequencies

This paper examines the impact of laser mode partition noise (LMPN) during optical heterodyning process. The system presented here employs a passively mode-locked laser diode (PMLLD) as a multimode source for millimeter-wave (mm-wave) generation. A comprehensive theoretical and experimental study of LMPN at low frequency and, for the first time, in mm-wave frequency band is demonstrated. Simulations are presented to investigate the distribution of mode partition noise across optical modes. LMPN appears as an impairment in performance on a radio-over-fiber (RoF) communication system by increasing the intensity noise when the number of optical modes detected by a photodiode (PD) is limited. The effect of LMPN for various number of modes is demonstrated by coherent and incoherent receivers, and it is shown that 25 dB degradation in signal power occurs due to noise when not all modes are detected.