Laser Modulator Bias Control via Open-Loop Scan
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Solution Overview
Problem
Existing bias control methods for laser modulators suffer from low convergence speed and long control times during startup, requiring several seconds or tens of seconds to achieve a stable operating point.
Innovation Solution
A linearly changing bias control voltage is input to the bias electrode during startup to scan the modulator's characteristics and determine a bias control voltage corresponding to a preset operating point, which is then used for closed-loop feedback control, thereby shortening the stabilization time and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional feedback control methods are used for bias control of laser modulator, then the bias control accuracy is maintained, but the convergence speed is low and control time is long (several seconds or tens of seconds)
Solution Approach 1:
The patent applies preliminary action by performing an open-loop scanning process before closed-loop feedback control to pre-locate the operating point. The microcontroller scans through a voltage range to identify the bias voltage corresponding to the desired optical output level, then uses this as a starting point for faster closed-loop convergence, significantly reducing overall stabilization time
Solution Approach 2:
The patent implements feedback control by continuously monitoring the optical output level through a photodetector and adjusting the bias voltage dynamically. The microcontroller compares the detected optical level with the target level and modifies the bias voltage accordingly, ensuring accurate long-term stabilization while maintaining fast response
2Measurement precision
If open-loop scanning method is used to find operating point, then the initial bias location is accurate, but the overall control time increases due to sequential processes
Solution Approach 1:
The patent merges open-loop scanning and closed-loop feedback control into a unified sequential process controlled by a single microcontroller. The open-loop scan quickly identifies the approximate operating region, and the closed-loop feedback immediately takes over to fine-tune the bias voltage, creating an efficient hybrid approach that minimizes total stabilization time while maintaining high accuracy
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 significantly reduces the time to achieve stabilization and enhances the accuracy of bias control, allowing for faster and more precise stabilization of the laser modulator.
Implementation Method 1
a photodetector to detect an optical output signal of the laser modulator
Implementation Method 2
phase shift occurs in an MZ (Mach-Zehnder) modulator based on LiNbO3 material as the operating point of such modulator is influenced by temperature, mechanical stress and the aging of components
Data Source
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AI summary
The present invention discloses a method and device for the bias control of a laser modulator. The method comprises: during startup of a laser modulator, inputting a linearly changing bias control voltage to the bias electrode of the laser modulator and obtaining the output optical power of the laser modulator so as to determine a bias control voltage corresponding to a preset operating point; then enabling a communication electrical signal to be input to the radio frequency electrode of the laser modulator, carrying out an amplitude modulation on the communication electrical signal by a low-frequency sinusoidal pilot signal, and inputting the determined bias control voltage to the bias electrode simultaneously; and sampling the output optical signals of the laser modulator, comparing the sampled optical signal with the pilot signal, and adjusting the bias control voltage input to the bias electrode according to the result of the comparison.