Evaluation of the influence of small deviations of the control signals of the Mach-Zehnder modulator on the optical and radio frequency spectra of the modulated signal

This article addresses a pressing issue in microwave photonics: the development and measurement of the characteristics of ultra-high-frequency optical modulation systems based on Mach-Zehnder modulators. Using ultrahigh-resolution optical spectrometers to measure the spectral composition of a modulator during operation allows us to identify features that cannot be measured after photodetection. Three types of control signal deviations are investigated: operating point setting accuracy, attenuation inequality in the modulator arms, and inequality in the absolute values of signal voltages on different arms of the modulator. The presented spectral compositions of the optical and radio-frequency spectra, obtained through numerical simulation and experiments on modulating radiation with a sinusoidal signal in different operating modes of a standard Mach-Zehnder modulator, allow us to evaluate the infl uence of these effects. It is shown that for deviations less than 1 %, the greatest contribution to spectral distortion is due to the accuracy of the operating point setting. Experimental evaluation methods are proposed for measuring deviation. The obtained results and conclusions provide new opportunities for assessing the manufacturing quality of standard modulators, as well as the accuracy of operating point control systems.

1. Wang C., Fang D., Zhang J. et al. Ultrabroadband thin-film lithium tantalate modulator for high-speed communications. Optica, 11(12), 1614–1620 (2024). https://doi.org/10.1364/OPTICA.537730 ; https://elibrary.ru/wfavkw

2. Kakolaki M., Bakhtafrouz A., Karimi P. Ultra-wideband (>1 THz) compact thin-film lithium niobate modulators using segmented coaxial transmission lines. Optic Express, 33(17), 35708–35722 (2025). https://doi.org/10.1364/OE.566284 ; https://elibrary.ru/iaxczh

3. Liu H., Li J., Zheng W., Chen Z. et al. High-Efficiency Lithium Niobate Electro-Optic Modulator with Barium Titanate Cladding on Quartz. Photonics, 12(2), 157 (2025). https://doi.org/10.3390/photonics12020157 ; https://elibrary.ru/qvimld

4. He M., Xu M., Ren Y., Ruan Z. et al. High-performance hybrid silicon and lithium niobate Mach–Zehnder modulators for 100 Gbit·s−1 and beyond. Nat. Photonics, 13, 359–364 (2019). https://doi.org/10.1038/s41566-019-0378-6

5. Huang X., Liu Y., Guan H. et al. High-efficiency, slow-light modulator on hybrid thin-film lithium niobate platform. IEEE Photonics Technology, 33(19), 1093–1096 (2021). https://doi.org/10.1109/LPT.2021.3106642 ; https://elibrary.ru/ariwbg

6. Valdez F., Mere V., Mookherjea S. 100 GHz bandwidth, 1 volt integrated electro-optic Mach-Zehnder modulator at nearIR wavelengths. Optica, 10(5), 578–584 (2023). https://doi.org/10.1364/OPTICA.484549 ; https://elibrary.ru/ywrpov

7. Zemtsov D., Pshenichnyuk I., Kosolobov S. Plasmon-Assisted Si-ITO Integrated Electro-Optical Rib-Shape Modulator. Journal of Lightwave Technology, 41(19), 6310–6314 (2023). https://doi.org/10.1109/JLT.2023.3283859 ; https://elibrary.ru/fbzopc

8. Nebavskiy V. A., Starikov R. S. Testing high-resolution optical spectrum analyzers for characterization analog optical links with external modulation. Izmeritel`naya Tekhnika, (12), 40–45 (2022). (In Russ.) https://doi.org/10.32446/0368-1025it.2022-12-40-45 ; https://elibrary.ru/vguklo

9. Li Y., Zhang Y., Huang Y. Any bias point control technique for Mach-Zehnder Modulator. IEEE Photonics Technology Letters, 25(24), 2412–2415 (2013). https://doi.org/10.1109/LPT.2013.2285184

10. Agruzov P., Parfenov M., Tronev A. et al. Electronic system of remote optical control of LiNbO3 Mach-Zehnder Modulator operating point. Electronics, 12(1), 206 (2023). https://doi.org/10.3390/electronics12010206 ; https://elibrary.ru/lpskhl