Optical Transmission Module Wavelength Drift Detection
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Solution Overview
Problem
Existing wavelength monitors in optical communication systems fail to accurately detect wavelength drifts due to deterioration or failure of the laser source, leading to erroneous detection and potential communication failures.
Innovation Solution
An optical transmission module that includes monotonous and periodical variation amount detection means to accurately detect wavelength drifts by combining temperature and transmittance data from multiple sensors, ensuring accurate detection even when the wavelength significantly deviates from the target.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If only an etalon filter is used for wavelength monitoring, then the device complexity is low, but the measurement precision deteriorates when wavelength drifts significantly from the target wavelength
Solution Approach 1:
The patent combines two different detection methods into a unified wavelength monitoring system: (1) etalon filter-based periodic transmittance variation detection, and (2) monotonous transmittance variation detection using a long-pass filter. By merging these two approaches, the system achieves high measurement precision across the entire wavelength range while maintaining reasonable device complexity through shared optical components and integrated control logic.
Solution Approach 2:
The patent segments the wavelength detection function into two complementary detection paths: one path uses an etalon filter for high-precision detection near the target wavelength, while the other path uses a long-pass filter for detecting significant wavelength drifts. This segmentation allows each detector to optimize its performance for specific wavelength conditions, improving overall measurement precision without requiring a single complex detector to handle all scenarios.
2Reliability
If temperature monitoring is used to stabilize wavelength, then the reliability improves for small drifts, but it fails to detect significant wavelength drifts caused by laser deterioration
Solution Approach 1:
The patent introduces optical filters (etalon filter and long-pass filter) as intermediary components between the laser source and the detection system. These filters convert wavelength information into transmittance variations that can be precisely measured. The etalon filter provides periodic transmittance variations for detecting small wavelength changes, while the long-pass filter provides monotonous transmittance variations for detecting significant drifts, thereby enabling reliable detection across the full range of wavelength variations.
Solution Approach 2:
The patent changes the detection parameter from direct temperature measurement to optical transmittance measurement. By monitoring how the transmittance of light through the filters changes with wavelength, the system can detect wavelength drifts more accurately. The combination of periodic transmittance variation (etalon filter) and monotonous transmittance variation (long-pass filter) provides complementary information that improves both reliability for small drifts and detection accuracy for significant drifts.
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
The module effectively detects wavelength drifts without errors, preventing communication failures by utilizing a combination of temperature and transmittance data from multiple sensors, enhancing the accuracy and reliability of wavelength monitoring.
Implementation Method 1
The etalon filter is an optical filter having such a characteristic that the transmittance periodically increases and decreases with respect to the wavelength (frequency)
Implementation Method 2
a second optical filter which is a long-pass filter having a characteristic that light with a wavelength longer than a predetermined wavelength is transmitted and light with a wavelength shorter than the predetermined wavelength is blocked
Implementation Method 3
monitoring the laser temperature by a temperature detector such as a thermistor
Data Source
AI summary
To detect a wavelength drift of laser light with no error, an optical transmission module (10) includes: a laser diode (20); a laser temperature calculation section (52) for detecting the temperature of the laser diode (20) that monotonously increases with respect to a wavelength of the laser light; a wavelength calculation section (44) for detecting a transmittance of the laser light incident on an etalon filter (36) whose transmittance periodically varies with respect to the wavelength of the incident light, and a laser wavelength corresponding to the transmittance; and a wavelength error obtaining section (54) for detecting a wavelength error (wavelength drift), from a target wavelength, of the laser light output from the laser diode (20), based on the temperature detected by the laser temperature calculation section (52) and the laser wavelength detected by the wavelength calculation section (44).