Two cascaded Mach-Zehnder modulators´ harmonic distortion analysis in single side-band millimeter wave generation system

Two cascaded Mach-Zehnder modulators (MZMs) are utilized to generate optical single-side band millimeter wave signals. This modulation scheme is tolerant to fiber chromatic dispersion effect for long distance communication. Since, electrical voltage setting is critical to control the unwanted harmonics´ power, harmonic distortions analysis is necessary for the two cascaded MZMs. Second order (HD2) and third order (HD3) harmonic distortions due to the intrinsic nonlinear electric/optic transfer curve of the two cascaded dual electrode MZMs are mathematically obtained and analyzed. These dual electrode MZMs are used to generate OSSB 60-GHz sub-bands. In order to compare second and third order harmonic distortions´ effects on the mm-wave generation system, noise to signal ratio (NSR) curves are represented. HD2 and HD3 are studied in this article and the results represent the second order distortion should be regarded as a minatory factor for the system.