Wavelength Tunable Laser Diode Thermal Control
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Solution Overview
Problem
Wavelength tunable laser diodes (LDs) in wavelength division multiplexing systems face challenges in precisely tuning emission wavelengths due to the complexity of thermal systems with multiple heaters, which can lead to instability and self-oscillation, making it difficult to align reflection and gain peaks simultaneously.
Innovation Solution
A method involving a controller that detects wavelength differences and evaluates power to be supplied to micro heaters in both the chirped sampled grating distributed Bragg reflector (CSG-DBR) and sampled grating distributed feedback (SG-DFB) regions to shift the emission wavelength to a target wavelength, ensuring even power distribution and concurrent control of both regions to stabilize the tuning process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple heaters are used in CSG-DBR and SG-DFB regions to tune emission wavelength, then wavelength tuning capability is improved, but system stability deteriorates due to thermal complexity and self-oscillation
Solution Approach 1:
The patent divides the wavelength tuning function into two independent segments: CSG-DBR region heaters for controlling reflection peaks and SG-DFB region heaters for controlling gain peaks. Each heater is independently controlled to adjust its respective region's refractive index, allowing separate optimization of each segment's contribution to the overall wavelength tuning while maintaining system stability.
Solution Approach 2:
The patent applies local quality by providing different heating control strategies for different regions. The CSG-DBR region and SG-DFB region each have their own heaters with independently evaluated power requirements. This allows each region to be optimized locally for its specific function (reflection or gain) while contributing to the overall wavelength tuning goal.
2Device complexity
If conventional single heater control is used, then device complexity is reduced, but wavelength tuning precision deteriorates due to inability to independently control reflection and gain peaks
Solution Approach 1:
The control system is segmented into multiple independent heater control channels. Each heater (in CSG-DBR and SG-DFB regions) has its own control loop that independently evaluates the power required based on the detected wavelength difference. This segmentation enables precise control of each region's contribution to the emission wavelength.
Solution Approach 2:
The patent changes the control parameter from a single heater power setting to multiple independently adjustable heater power levels. By evaluating and controlling the power supplied to each heater separately based on the wavelength difference detection, the system achieves higher wavelength tuning precision through multi-parameter control.
3Adaptability or versatility
If heaters provide unequal power to shift wavelengths, then individual region optimization is improved, but overall wavelength tuning stability deteriorates causing wavelength hopping
Solution Approach 1:
The patent implements a feedback mechanism where the emission wavelength is continuously detected and compared with the target wavelength. Based on the detected wavelength difference, the controller evaluates and adjusts the power supplied to each heater in real-time. This closed-loop feedback ensures that unequal power distribution to different regions does not cause wavelength hopping, as the system continuously corrects to maintain stable tuning.
Solution Approach 2:
The system dynamically changes heater power parameters based on detected wavelength deviations. By evaluating the required power for each heater independently and adjusting these parameters in response to wavelength feedback, the system achieves both region-specific optimization and overall wavelength stability without hopping.
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 allows for precise and stable tuning of the emission wavelength without wavelength hopping, enhancing the response time and reducing heat consumption, while maintaining stability and precision in aligning reflection and gain peaks.
Implementation Method 1
The wavelength tunable LD provides two regions each having at least one micro heater to modify refractive index of the regions
Implementation Method 2
A wavelength tunable LD in an arrangement thereof provides an active region put between optical gratings each having a specific diffracting wavelength different from others
Data Source
AI summary
A method to tune an emission wavelength of a wavelength tunable LD is disclosed. The wavelength tunable LD includes two regions each providing micro heaters to modify the refractive index of micro regions provided with power. The method periodically detects a difference between the emission wavelength and the target wavelength. This wavelength difference is converted into power next supplied to respective micro heaters independently.