An Analytical Solution for Fiber Optic Links with Photonic-Assisted Millimeter Wave Upconversion Due to MZM Nonlinearities

Photonic-assisted technique employed in the generation of stable and high-purity signals in the millimeter wave band has been investigated using dual-parallel Mach-Zehnder modulator. Indeed, this type of generation performs a high order RF multiplier, whose operation principle steams out from the nonlinear characteristic of the external modulators. Its application in direct-detection fiber optic link was investigated based on an exact formulation that properly takes into account both the dispersion of a single mode fiber and the modulator nonlinearity. Analytic expression for the link transfer function dependence with respect to both modulator bias point and modulation index were obtained. It is worthwhile to mention that RF tuning is enabled since no optical filtering is required. As an illustration of the modeling usefulness, it is analytically shown that a 60 GHz millimeter signal, generated by photonic quadruplicating a 15 GHz signal using dual-parallel Mach-Zehnder modulator, can be transmitted through a 80 km link of standard single mode fiber with less than 0.1 dB deviation with respect to ideal flat response. This performance is much better than previously published results.