Semiconductor Laser Diode Algorithm for Extinction Ratio Stabilization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Semiconductor laser diodes exhibit significant temperature dependence in characteristics such as threshold current and slope efficiency, making it challenging to maintain average output power and extinction ratio independent of temperature in optical communication systems.
Innovation Solution
An algorithm that determines three modulation currents at different temperatures to maintain constant average power and extinction ratio, using an exponential function to relate modulation currents with temperature, and corrects for tracking errors through linear approximation, ensuring the extinction ratio remains stable across varying temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the bias current is controlled to maintain constant average power, then the average output power becomes independent of temperature, but the extinction ratio becomes dependent on temperature
Solution Approach 1:
The patent applies parameter changes by introducing temperature-dependent modulation current adjustments. Specifically, the modulation current is varied according to temperature conditions to compensate for LD characteristic changes, while the bias current remains controlled for average power stability. This selective parameter modification resolves the contradiction by allowing the extinction ratio to remain stable across temperature variations without affecting the average power control mechanism.
2Reliability
If the modulation current is adjusted to maintain constant extinction ratio, then the extinction ratio becomes independent of temperature, but the average power becomes dependent on temperature
Solution Approach 1:
The patent implements parameter changes by selectively adjusting the modulation current based on temperature conditions. The bias current is maintained for average power control, while the modulation current is specifically varied to compensate for extinction ratio drift. This targeted parameter modification allows the system to maintain both average power and extinction ratio stability simultaneously across different temperature conditions.
3Measurement precision
If tracking errors are present in the optical module, then the measured modulation current deviates from the actual value, but the extinction ratio can still be stabilized through correction
Solution Approach 1:
The patent applies feedback by implementing a correction mechanism that accounts for tracking errors. The system measures the modulation current, detects deviations caused by tracking errors, and applies compensatory adjustments to maintain accurate extinction ratio control. This feedback loop ensures that even when measurement errors occur, the extinction ratio remains stable through real-time correction.
Data Source
AI summary
An algorithm to drive a semiconductor laser diode (LD) is disclosed. The algorithm assumes that the modulation current to keep the extinction ratio in constant has temperature dependence represented by an exponential function under the average output power of the LD is kept constant by an auto-power-control (APC). When a tracking error exists and the approximation by an exponential function is turned out in failure, the algorithm adds a correction to the exponential function determined by a difference between a practically measured modulation current and another modulation current calculated from a value determined for a bared LD.