Digital Bias Voltage Control for Electro-Optic Modulators
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Solution Overview
Problem
Optical modulators are sensitive to environmental changes such as temperature and humidity, leading to shifts in their operating points and output curves, which existing analog-based bias voltage control technologies struggle to maintain stable operation.
Innovation Solution
A method and apparatus for digitally and automatically controlling the bias voltage of electro-optic optical modulators, involving scanning bias voltage output, signal acquisition and conversion, filtering, calculation of operating bias and dither parameters, and feedback loops to adjust the bias voltage based on harmonic analysis and error correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If analog-based bias voltage control is used, then the control process is simple, but the stability of operating point under environmental changes is poor
Solution Approach 1:
The patent implements a closed-loop feedback control system where the optical output signal is detected, converted to electrical signal, and processed to generate correction signals that adjust the bias voltage. The system continuously monitors the operating point and automatically compensates for environmental drifts through feedback mechanisms, achieving high stability without manual intervention.
Solution Approach 2:
The patent replaces traditional analog mechanical control systems with digital signal processing. Electrical signals are processed through digital algorithms to determine bias voltage adjustments, substituting mechanical adjustment mechanisms with electronic-digital control systems that offer higher precision and stability under environmental variations.
2Reliability
If bias voltage is continuously adjusted to compensate environmental changes, then the operating stability is improved, but the system complexity increases
Solution Approach 1:
The system performs self-diagnosis and self-correction by automatically detecting shifts in the optical modulator's transfer curve and generating appropriate bias voltage adjustments without external intervention. The control system serves itself by monitoring its own performance and making necessary corrections to maintain optimal operation.
Solution Approach 2:
The patent dynamically adjusts electrical parameters including bias voltage magnitude, dither signal frequency and amplitude, and filter characteristics based on detected operating conditions. By changing these parameters adaptively, the system maintains optimal performance across varying environmental conditions while using a unified control architecture.
3Measurement precision
If digital automatic control is implemented, then the precision of bias voltage control is improved, but the device complexity increases
Solution Approach 1:
The control system is divided into distinct functional modules: optical signal detection, optical-to-electrical conversion, signal filtering, harmonic analysis, bias voltage calculation, and actuation. Each module performs a specific function with well-defined interfaces, allowing the complex digital control system to be implemented through modular components that can be independently optimized and maintained.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach ensures stable operation of optical modulators by continuously correcting the bias voltage, reducing environmental interference and maintaining optimal performance across varying conditions.
Implementation Method 1
An optical modulator is used to modulate radio frequency signals onto an optical carrier output by a laser to form optical signals
Implementation Method 2
converting the first optical signal into a first electrical signal
Data Source
AI summary
A method and an apparatus for digitally and automatically controlling a bias voltage of an electro-optic optical modulator are disclosed. The method includes: outputting a scanning bias voltage; acquiring a first optical signal; converting the first optical signal into a first electrical signal; outputting a first direct current signal; calculating an operating bias voltage at each operating point and a half-wave voltage; calculating an error feedback coefficient and a dither amplitude; outputting an operating bias voltage and a dither signal with the dither amplitude; acquiring a second optical signal; converting the second optical signal into a second electrical signal; outputting a harmonic component; calculating a harmonic amplitude and a shift phase; calculating a new bias voltage; and using the new bias voltage as the operating bias voltage.