Tunable Light Source Thermal Segmentation
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Solution Overview
Problem
When a ring oscillator and a wavelength filter are disposed on a single substrate and their characteristics are thermally controlled, heat interference occurs, leading to undesired characteristics and difficulty in maintaining a constant free spectral range (FSR) of the wavelength monitor, which affects the optical transmittance and wavelength control accuracy.
Innovation Solution
A tunable light source configuration where the wavelength of output light is controlled based on the optical transmittance of a wavelength filter and its corresponding transmittances at a target wavelength and control range limits, without directly controlling the light transmission characteristic of the wavelength filter, using a controller to generate control signals for the ring filter based on the transmittance data from power and wavelength monitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If both the ring oscillator and wavelength filter are thermally controlled on a single substrate, then the characteristics of both devices can be adjusted, but heat interference occurs between the two devices causing desired characteristics to be unattainable
Solution Approach 1:
The patent divides the thermal control system into separate independent control zones. The ring resonator and wavelength filter are equipped with separate heaters and control circuits, allowing independent temperature management. This segmentation prevents heat interference between the two devices while maintaining the ability to adjust characteristics of both, resolving the contradiction between adaptability and heat interference.
2Adaptability or versatility
If the wavelength filter is thermally controlled to adjust its characteristics, then the transmission characteristics can be tuned, but the free spectral range (FSR) becomes unstable affecting wavelength control accuracy
Solution Approach 1:
The patent implements a feedback control mechanism where the actual transmission characteristics of the wavelength filter are monitored and compared with target values. The controller adjusts the heating power dynamically based on this feedback to maintain the desired transmission characteristics while compensating for FSR variations, thus preserving wavelength control accuracy during characteristic tuning.
Solution Approach 2:
The patent changes the control parameter from direct temperature control to transmission characteristic control. By monitoring the actual transmission spectrum and adjusting the heater power based on the difference between actual and target transmission characteristics, the system can tune the filter characteristics while maintaining stable FSR and accurate wavelength control.
3Ease of manufacture
If thermal control is applied to both ring oscillator and wavelength filter, then both devices can operate on a single substrate, but the heat from one device affects the other device's performance
Solution Approach 1:
The patent segments the thermal management system into independent control units for each device. Each device has its own heater and control circuit, allowing independent temperature regulation. This enables single substrate integration while preventing heat interference, as each device can be maintained at its optimal temperature independently, ensuring reliable performance.
4Adaptability or versatility
If the FSR of the wavelength monitor changes due to thermal effects, then the optical transmittance varies, but this affects the accuracy of wavelength control
Solution Approach 1:
The patent uses feedback control to monitor the actual transmission spectrum of the wavelength filter and compares it with the target spectrum. When FSR changes cause deviations in optical transmittance, the controller adjusts the heater power to restore the desired transmission characteristics, thereby maintaining accurate wavelength control despite FSR variations.
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 configuration allows precise control of the wavelength of output light, independent of the FSR changes in the wavelength monitor, ensuring accurate wavelength control and reducing the interference issues caused by thermal control of both components.
Implementation Method 1
a wavelength filter that is disposed on the substrate, filters the output light, and outputs the filtered light
Implementation Method 2
the resonant wavelength of a ring resonator can be controlled by heating the ring resonator
Implementation Method 3
characteristics of both of the ring oscillator and the wavelength filter are thermally controlled
Implementation Method 4
light output from a light-emitting device such as a laser diode disposed on a substrate
Data Source
AI summary
A tunable light source includes a substrate; a light source; a wavelength selecting device that selects, according to a control signal, output light with a specific wavelength from light output from the light source; a wavelength filter that is disposed on the substrate, filters the output light, and outputs the filtered light; a light-receiving device that receives the filtered light from the wavelength filter; and a controller configured to generate the control signal based on an output transmittance corresponding to a quantity of the received light received by the light-receiving device, a first transmittance corresponding to a target wavelength, a second transmittance corresponding to a shorter-wavelength limit of a control range including the target wavelength, and a third transmittance corresponding to a longer-wavelength limit of the control range, and output the generated control signal to the wavelength selecting device.