Optical Modulator Bias Control via Drive Signal Amplitude Detection
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Solution Overview
Problem
Conventional optical transmitters face challenges in maintaining high-quality optical signal generation due to changes in drive signal amplitude caused by modulation format changes and pre-equalization, leading to inadequate bias control of optical modulators.
Innovation Solution
An optical transmitter system that includes a drive signal generator, an optical modulator, a superimposer for reference signals, a detector for monitoring signal intensity and phase, and a controller to adjust bias voltage based on detected signals, allowing for adaptive bias control schemes depending on drive signal amplitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the modulation format or pre-equalization amount is changed during operation, then the transmission system can adapt to different communication requirements, but the drive signal amplitude changes causing bias control to become inadequate
Solution Approach 1:
The patent implements dynamic bias control by detecting drive signal amplitude and selecting different control schemes based on the detected amplitude. The controller dynamically adjusts the bias voltage control method according to current operating conditions, transitioning from static to adaptive control that maintains reliability across varying modulation formats and pre-equalization settings.
Solution Approach 2:
The system changes the control parameter from fixed bias voltage to adaptive bias voltage based on detected drive signal amplitude. By monitoring the actual drive signal characteristics and adjusting the bias control strategy accordingly, the system maintains optimal performance across different modulation formats and pre-equalization amounts.
2Device complexity
If a fixed bias control method is used, then the control scheme is simple, but it cannot maintain high-quality optical signal generation when drive signal amplitude changes
Solution Approach 1:
The patent implements feedback control by detecting the drive signal amplitude and using this information to adjust the bias control strategy. The detector monitors the actual drive signal characteristics, and the controller uses this feedback to select the appropriate control scheme, ensuring high-quality optical signal generation while maintaining reasonable system complexity.
Solution Approach 2:
The system performs self-adjustment by automatically detecting drive signal amplitude and selecting the appropriate bias control scheme without external intervention. The optical transmitter self-regulates its bias control based on its own operating conditions, maintaining signal quality across varying conditions.
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
The system effectively controls bias voltage to maintain high-quality optical signal generation even with changes in modulation format and pre-equalization, ensuring optimal performance across varying drive signal amplitudes.
Implementation Method 1
The optical modulator 12 has intensity modulation characteristics in which an intensity of output light periodically changes with respect to an applied voltage
Implementation Method 2
The photo detector 14 converts the modulated optical signal output from the optical modulator 12 into an electric signal
Data Source
AI summary
An optical transmitter includes: a drive signal generator configured to generate a drive signal from input data; an optical modulator configured to generate an optical signal corresponding to the drive signal; a superimposer configured to superimpose a first reference signal on the drive signal and superimpose a second reference signal on a bias voltage of the optical modulator; a detector configured to detect the first reference signal and the second reference signal included in the optical signal, and generate a first monitor signal indicating intensity and a phase of the detected first reference signal and a second monitor signal indicating intensity and a phase of the detected second reference signal; and a controller configured to control the bias voltage of the optical modulator in a control scheme determined based on the first monitor signal and the second monitor signal.