Enhancing the spectral quality of the signal without varying the extinction ratio is a challenge for millimeter (MM) wave generation. Here, we propose a novel extinction ratio tolerant frequency 8-tupling technique using two Mach-Zehnder modulators (MZMs) with optimal splitting ratio in parallel configuration. Although the proposed technique is not affected by extinction ratio, a high quality MM wave is still obtained with complete unwanted sideband suppression. Two non-ideal MZMs with π/2 and π phase shifter realize MZM with optimal splitting ratio, which acts as a high extinction ratio modulator. The 80 GHz MM wave with 62 dB optical sideband suppression ratio (OSSR) and 54 dB radio frequency sideband suppression ratio (RSSR) is generated from 10 GHz local oscillator signal at 2.403 6 modulation index (MI). Performance of the present work has been evaluated using various MIs, phase drifts and extinction ratios. Sideband suppression ratio (SSR) greater than 10 dB is reported in a wide MI ranging from 2.36 to 2.47. Further, both the SSRs are tolerant towards MZM extinction ratio. The work is ideal for wavelength division multiplexing (WDM) applications due to its filterless characteristics.