Dynamic Laser Diode Compensation for Optical Power Errors
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Solution Overview
Problem
Laser diode operating characteristics are not time-invariant, leading to variations in optical power due to factors like age and temperature changes, causing errors in optical energy delivery, especially with short pulse durations and finite rise/fall times.
Innovation Solution
A dynamic compensation method using basis functions and weighted summation to adjust desired optical power values, accounting for time-varying nonlinearities, which includes generating compensation values based on past data and measured optical power to correct for errors in pulse durations and rise/fall times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an inverse laser model is used to linearize the relationship between desired optical power and output optical power, then the linearity is improved, but the system fails to account for time-varying characteristics such as temperature changes and aging
Solution Approach 1:
The patent transitions from a static inverse laser model to a dynamic model that incorporates time-varying basis functions. The compensated desired optical power is calculated using a sum of basis functions with time-dependent coefficients, allowing the system to adapt to changing temperature, aging, and pulse duration effects while maintaining linearity.
Solution Approach 2:
The patent changes the parameters of the compensation model by introducing time-varying coefficients for basis functions. These coefficients are determined based on measured optical power data and system state, enabling the model to adapt to changing operating conditions while preserving the linearization function.
2Productivity
If short pulse durations are used, then productivity is improved, but errors in optical energy delivery increase due to finite rise and fall times
Solution Approach 1:
The patent applies preliminary compensation by calculating correction values based on pulse duration and rise/fall time characteristics before generating the drive signal. The compensated desired optical power incorporates predictions of energy delivery errors, allowing the system to pre-correct for the effects of short pulse durations and finite rise/fall times.
Solution Approach 2:
The patent uses feedback from measured optical power data to refine the compensation model. By comparing actual optical power output with desired values and adjusting the basis function coefficients accordingly, the system continuously improves accuracy for short pulse operations.
Data Source
AI summary
A laser drive circuit compensates for laser diode dynamics. A compensation value is determined from a sum of weighted basis functions. The basis functions may be a function of current desired optical powers and/or past desired optical powers. The weights may be updated periodically based at least in part on accumulated basis function outputs and measured optical powers.