Modulator bias optimization of radio over fiber links considering noise figure and RF gain

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Optimum bias level for Mach-Zehnder modulator is important for the performance of radio over fiber links. This paper proposes a method to optimize the bias point of the external modulator of a radio over fiber system considering both RF gain and noise figure. In suboctave systems, there is a trade-off between these parameters. RF gain first nonlinearly increases and then decreases with the bias voltage while, the noise figure has an inverse relationship with the bias voltage. Therefore, a figure of merit is proposed in this paper that takes into account gain, noise figure and spurious-free dynamic range. Simulation results show that an optimal bias point can be obtained by using this figure of merit.