Tunable Laser Calibration Using Internal Photodiode Feedback
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Solution Overview
Problem
The calibration of tunable lasers is a time-consuming and costly process due to the need for multi-dimensional searches and the use of expensive equipment like optical spectrum analyzers and digital sampling scopes, which increases manufacturing time and labor.
Innovation Solution
A method and system for calibrating external cavity semiconductor tunable lasers that aligns filter output peaks, etalon output peaks, and cavity modes with a target wavelength grid using a built-in photodiode and temperature control, eliminating the need for external analyzers and scopes by using a controller with non-transitory memory to store calibration parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional calibration equipment (optical spectrum analyzer, digital sampling scope) is used to measure output modulation amplitude and extinction ratio, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the measurement function from external expensive equipment and relocates it to an internal photodiode detector within the laser device itself. This eliminates the need for external optical spectrum analyzers and digital sampling scopes, reducing device complexity while maintaining measurement capability through the use of existing internal components.
Solution Approach 2:
The internal photodiode is made to serve multiple functions: it acts as both the laser's output detector and the calibration measurement instrument. This multi-functionality eliminates the need for separate dedicated measurement equipment, reducing overall system complexity and cost while maintaining measurement precision.
2Manufacturing precision
If multi-dimensional search calibration method is used, then calibration accuracy is improved, but calibration time increases
Solution Approach 1:
The patent applies preliminary action by using the internal photodiode to perform preliminary measurements of output modulation amplitude and extinction ratio during the calibration process. This preliminary data guides the multi-dimensional search, allowing the system to converge faster on the optimal calibration parameters without sacrificing accuracy, thereby reducing overall calibration time.
Solution Approach 2:
The internal photodiode provides real-time feedback on output modulation amplitude and extinction ratio during calibration. This feedback mechanism allows the calibration algorithm to iteratively adjust parameters and converge to the optimal solution more efficiently, reducing calibration time while maintaining manufacturing precision.
3Reliability
If multiple external measurement devices are used for calibration, then measurement comprehensiveness is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent merges the measurement function into the laser device itself by incorporating an internal photodiode. This combination of the laser source and detector into a single integrated device eliminates the need for multiple separate external measurement devices, simplifying the calibration process and making the device easier to manufacture while maintaining measurement comprehensiveness.
Solution Approach 2:
The laser device performs its own calibration measurements using the internal photodiode, making the system self-sufficient. This self-service capability eliminates the need for complex external measurement setups, simplifying manufacturing and calibration procedures while maintaining reliable and comprehensive measurement data.
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 reduces the time and cost of calibration by enabling self-calibration of tunable lasers, improving manufacturing throughput and reducing the need for expensive equipment, while maintaining precise alignment and performance.
Implementation Method 1
shifting a filter output peak defined by a tunable optical feedback filter of the tunable laser in an optical spectral domain to align with a target etalon output peak
Implementation Method 2
shifting the spaced output peaks defined by the etalon to align a target etalon output peak with a target wavelength of an output wavelength grid
Implementation Method 3
shifting a cavity frequency grid defined by cavity modes of the tunable laser to align a target cavity mode of the cavity frequency grid with the filter output peak
Implementation Method 4
monitoring an optical output of the tunable laser using a photodiode of the laser
Data Source
AI summary
A method of calibrating a tunable laser includes shifting a filter output peak defined by a tunable optical feedback filter of the tunable laser in an optical spectral domain to align with a target etalon output peak of a plurality of spaced etalon output peaks defined by an etalon of the tunable laser. The method also includes shifting a cavity frequency grid defined by cavity modes of the tunable laser to align a target cavity mode of the cavity frequency grid with the filter output peak and shifting the spaced output peaks defined by the etalon to align a target etalon output peak with a target wavelength of an output wavelength grid. The method includes modifying a bias current and a modulation current of a gain section of the tunable laser to achieve a defined output modulation amplitude and a defined extinction ratio.