Thermo-optic-based phase-shifter power dither for silicon IQ optical modulator bias-control technology

Area of Science:

• Photonics and Optical Communications
• Semiconductor Device Physics

Background:

• Silicon optical in-phase quadrature (IQ) modulators are crucial for modern coherent optical transmission due to their size and cost advantages.
• Maintaining optimal bias voltage is essential for stable modulation performance, but nonlinearities in silicon pose control challenges.

Purpose of the Study:

• To propose and validate a novel automatic bias-control scheme for silicon IQ optical modulators (SIQOM).
• To address the difficulty in achieving high-precision bias voltage control for SIQOMs.

Main Methods:

• Applying two sinusoidal power dithers to the I and Q channel biases of the SIQOM.
• Constructing orthogonal trigonometric functions synchronized with the dither signals.
• Utilizing cross-correlation integral operations to find the intersection of orthogonal-integral curves, identifying the optimal bias point.

Main Results:

• The proposed scheme accurately corrects bias errors for I, Q, and P channels.
• Vector amplitude error jitters are reduced to less than 1% for 128-Gb/s DP-QPSK and SP-16QAM formats.
• Demonstrated theoretical and experimental validation of the automatic bias-control method.

Conclusions:

• The novel automatic bias-control scheme effectively stabilizes SIQOM performance.
• This method enables precise bias voltage control, crucial for advanced optical communication systems.
• The scheme offers a robust solution for maintaining modulation integrity in high-capacity optical networks.