Large signal analysis on microwave photonic generation using an asymmetric dual‐drive Mach–Zehnder modulator and with different modulation indices

Abstract

This paper proposes an exact closed‐form frequency domain analytical solution for large‐signal conditions to analyze a microwave photonic signal generator that employs external electro‐optic intensity modulation and direct detection. The detected power of the generated microwave signal was used to evaluate the effect of an asymmetric dual‐drive Mach–Zehnder modulator with finite extinction ratio and using different modulation indices. Considering these effects simultaneously, a full analysis of different bias and phase shifts is also theoretically investigated. The optimum modulation index that maximizes a desired generated microwave frequency is shown here. For a given generated harmonic, the modulation index increases by around 40%. Comparing with the ideal situation, that is, symmetric modulator and using equal modulation indices, for the same harmonic, there is a reduction of around 0.2 dB in the power level and an increase of around 10% in the modulation index to achieve maximum power.

Advancing microwave signal generation: frequency quadrupling using dual-drive Mach-Zehnder modulator

“…Several methods for generating quadrupling-frequency optical millimeter-wave signals are discussed in the range of literatures. These methods include the utilization of double sideband (DSB) modulation as described in references [3][4][5], optical carrier suppression (OCS) as discussed in references [6][7][8], and single sideband (SSB) modulation as mentioned in reference [9]. The DSB optical mm-wave system has two primary obstacles: the occurrence of fading and the temporal displacement of codes, which is mainly caused by chromatic dispersion of the fiber [10].…”