Semiconductor Laser Testing Device Dispersion Matching
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Solution Overview
Problem
Current laser testing methods fail to accurately evaluate the data transmission properties of semiconductor lasers due to the disregard of optical fiber dispersion variations across different wavelengths, leading to incorrect classification of defective and non-defective products.
Innovation Solution
A method and device that select the length of an optical fiber based on the test wavelength to match a reference dispersion condition, ensuring accurate evaluation of bit error rate and eye pattern by using a combination of main and sub optical fibers with adjustable lengths, controlled by optical switches and a variable attenuator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed-length optical fiber is used for all wavelength tests, then the testing device is simple to operate, but the dispersion amount does not match the actual transmission conditions leading to inaccurate evaluation
Solution Approach 1:
The optical fiber length is made dynamically adjustable based on the test wavelength. The system switches between different optical fiber lengths (e.g., 10km, 80km, 100km) depending on whether the laser wavelength is shorter than, equal to, or longer than the reference wavelength, allowing the dispersion conditions to match actual transmission scenarios for accurate evaluation
Solution Approach 2:
The optical fiber path is divided into multiple segments with different lengths. By combining a main optical fiber with selectable sub-optical fibers of different lengths, the system can configure the total fiber length to match the required dispersion conditions for each wavelength test, enabling accurate evaluation without requiring a completely different fiber setup for each wavelength
2Measurement precision
If the optical fiber length is adjusted to match dispersion conditions for different wavelengths, then accurate evaluation is achieved, but the testing procedure becomes more complex
Solution Approach 1:
The system automatically determines the appropriate optical fiber length based on the measured laser wavelength. The wavelength measurement unit provides the wavelength value, and the control unit automatically selects and configures the corresponding optical fiber length without requiring manual intervention, making the complex procedure transparent to the operator
Solution Approach 2:
The system uses feedback from the wavelength measurement to automatically adjust the optical fiber configuration. The measured wavelength feeds back to the control unit, which then selects the appropriate fiber length from available options, creating a closed-loop system that adapts to each laser's specific wavelength
3Reliability
If a single optical fiber length is used for all lasers, then the testing process is simple and fast, but defective products may be misclassified due to dispersion mismatches
Solution Approach 1:
The system performs preliminary wavelength measurement and determines the required optical fiber length before conducting the actual bit error rate test. This preliminary configuration ensures that the dispersion conditions are already optimized for the specific wavelength, preventing misclassification and ensuring reliable product evaluation from the start
Solution Approach 2:
The system changes the optical fiber length parameter based on the laser wavelength parameter. By adjusting the fiber length to match the dispersion characteristics of each wavelength, the system ensures accurate evaluation of transmission performance, preventing both false positives and false negatives in product classification
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 evaluation of data transmission properties by matching the optical fiber length to the test wavelength, thereby accurately determining the semiconductor laser's performance and preventing misclassification of defective products.
Implementation Method 1
the dispersion amount of laser light having passed through the optical fiber 102 is enlarged when the laser device outputs a wavelength longer than a reference wavelength
Data Source
AI summary
A testing method of a semiconductor laser emitting a wavelength under a test different from a reference wavelength in a given wavelength range includes: a first step of obtaining a length of an optical fiber under the test satisfying a reference dispersion condition at the wavelength under the test, based on the reference dispersion condition for the test and a unit dispersion amount of the optical fiber; and a second step of inputting a modulation signal that is a modulated laser light of the semiconductor laser having a wavelength as the wavelength under the test into an optical fiber having substantially the same length as the length obtained in the first step and evaluating an output of the optical fiber.