Ultralow-dither automatic bias control on IQ modulators for optical single-sideband modulation via adaptive extended Kalman filtering-enhanced correlation detection

This work proposes an ultralow-dither automatic bias control (ABC) scheme for optical carrier-suppressed single sideband (OCS-SSB) modulation in IQ modulators. This scheme employs enhanced correlation detection (CD) technology through adaptive extended Kalman filtering (AEKF), maintaining low system complexity. It significantly alleviates the inherent trade-off between low bias control accuracy and distortion of OCS-SSB signals. Experiments demonstrate that reducing the dither signals' amplitude from 2.5% to 0.6% of the half-wave voltage (<i>V_π</i>) effectively suppresses dither interference, achieving an increase in optical carrier suppression ratio (OCSR) of 12.90 dB at a radio frequency of 20 GHz. Under this ultralow amplitude, AEKF enables high-accuracy stabilization: mean OCSR and optical sideband suppression ratio (OSSR) reach 23.61 ± 0.18 dB and 24.12 ± 0.26 dB, respectively, with peak-to-peak fluctuations reduced by 10.81 dB and 10.79 dB. Notably, the scheme exhibits long-term stability for over 9 hours and demonstrates robustness against external environmental disturbances. To the best of our knowledge, this work also achieves, for the first time, directional suppression of the ±1st-order sidebands. Overall, this scheme provides a low-dither disturbance, strong robustness, and high suppression ratios solution for various OCS-SSB applications.