Effect of Nonlinear Phase Variation in Optical Millimetre Wave Radio over Fibre Systems

In this paper, we propose an optical millimetre wave radio-over-fibre (mm-wave RoF) system that uses a dual drive Mach Zehnder modulator (DD-MZM), which is biased at the maximum transmission biasing point, to generate an optical double sideband-suppressed carrier. The input to the DD-MZM are binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), 8-phase shift keying (8-PSK) and 16-qaudrature amplitude modulation (16-QAM) schemes at a carrier frequency of 5 GHz with a rate of 2 Gsym/s and a local oscillator of 15 GHz obtain an mm-wave RoF signal at 30 GHz. We evaluate the generation and performances of the proposed system in terms of the power penalty, the error vector magnitude and the bit error rate (BER). Impairments including the self-phase modulation, chromatic dispersion and attenuation are considered when modelling the single mode fibre (SMF) based on the symmetrical split step Fourier method. We show that the power efficiency improves in the optimum region on average by ~11 dB, ~11 dB, ~12 dB and ~18 dB for BPSK, QPSK, 8-PSK and 16-QAM, respectively for the same optical launch power over 10, 30 and 50 km of SMF compared to the linear and non-linear regions.