Ultralow-dither automatic bias control on IQ modulators for optical single-sideband modulation via adaptive extended...

Area of Science:

• Photonics and Optical Communications
• Signal Processing
• Control Systems Engineering

Background:

• Optical carrier-suppressed single sideband (OCS-SSB) modulation is crucial for high-capacity optical communication systems.
• Traditional automatic bias control (ABC) schemes face challenges in balancing accuracy, complexity, and signal distortion.
• Minimizing dither signal amplitude is essential to reduce interference and improve suppression ratios in OCS-SSB modulation.

Purpose of the Study:

• To propose and validate an ultralow-dither automatic bias control (ABC) scheme for OCS-SSB modulation in IQ modulators.
• To enhance the optical carrier suppression ratio (OCSR) and optical sideband suppression ratio (OSSR) while maintaining low system complexity.
• To demonstrate the scheme's robustness, long-term stability, and ability to achieve directional sideband suppression.

Main Methods:

• Implementation of an enhanced correlation detection (CD) technology utilizing adaptive extended Kalman filtering (AEKF).
• Reduction of dither signal amplitude to 0.6% of the half-wave voltage (Vπ), significantly below conventional levels.
• Experimental validation of the AEKF-based ABC scheme's performance at a 20 GHz radio frequency.

Main Results:

• Achieved a 12.90 dB increase in OCSR by reducing dither amplitude, effectively suppressing dither interference.
• Attained high-accuracy stabilization with mean OCSR of 23.61 ± 0.18 dB and OSSR of 24.12 ± 0.26 dB.
• Demonstrated peak-to-peak fluctuation reduction by over 10 dB, long-term stability exceeding 9 hours, and robustness against environmental disturbances. Directional suppression of ±1st-order sidebands was achieved.

Conclusions:

• The proposed ultralow-dither ABC scheme effectively alleviates the trade-off between bias control accuracy and OCS-SSB signal distortion.
• AEKF enables high-accuracy stabilization and robust performance even with significantly reduced dither amplitudes.
• This scheme offers a practical solution for achieving high suppression ratios and stability in OCS-SSB applications, including novel directional sideband control.