Group velocity and third-order dispersion comparison in externally and directly modulated radio over fiber link
Radio over is an attractive solution for broadband wireless access. In this paper, the performance of externally and direct intensity modulated RoF links is analyzed in the presence of the group velocity dispersion and third-order dispersion of the optical fiber. An external modulation system with dual electrode lithium niobate Mach–Zehnder modulator (DE-MZM) and direct modulation system with vertical-cavity surface-emitting laser (VCSEL) are considered. Both modulation schemes are tested using Gaussian optical pulses. Simulations are performed with the same values for common global parameters for both schemes. Although external modulation is a generally considered more advanced, our simulations show that the direct modulation technique with VCSEL shows a more robust performance. The performances are compared using performance parameters like Q factor, eye diagram, BER and RF signal amplitude.
KeywordsGroup velocity dispersion (GVD) Third-order dispersion (TOD) Vertical-cavity surface-emitting laser Intensity modulation Lithium niobate Mach–Zehnder modulator
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