Multiple Ring Resonator for Stable Wavelength Control
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Solution Overview
Problem
Conventional variable-wavelength lasers for WDM transmission systems face issues with stability, mode jumps, high cost, and limited wavelength control due to complex structures and increased component count, making them unsuitable for practical use in ROADM systems.
Innovation Solution
A multiple resonator structure with three ring-shaped resonators of different light path lengths, connected via optical coupling, and an external resonator configuration using an etalon filter or Mach-Zehnder interferometer, which generates a vernier effect to maximize mode gain difference and ensure stable wavelength control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a DFB-LD with a diffraction grating is used to achieve stable longitudinal single mode oscillation, then oscillation stability is improved, but the variable-wavelength range is limited to approximately 3 nm
Solution Approach 1:
The patent divides the resonator into multiple sections with different diffraction gratings (first diffraction grating with period Λ1 and second diffraction grating with period Λ2). This segmentation allows each grating to contribute to different wavelength ranges, enabling the combined system to achieve a broader variable-wavelength range while maintaining stable single-mode oscillation through the composite grating structure.
2Adaptability or versatility
If a DBR-LD with a nonuniform diffraction grating is used to achieve a wide variable-wavelength range exceeding 100 nm, then wavelength tunability is improved, but the structure becomes complex and requires precise control of grating parameters
Solution Approach 1:
The patent applies local quality by creating a nonuniform diffraction grating where the grating period varies locally across different regions. The first and second diffraction gratings have different periods (Λ1 and Λ2) optimized for specific wavelength ranges, allowing the structure to achieve wide wavelength tuning while maintaining manageable complexity through localized grating characteristics rather than a completely complex uniform structure.
3Adaptability or versatility
If multiple DFB-LD products with different wavelengths are used to construct a WDM transmission system, then wavelength coverage is improved, but the number of components and shelf control cost increase
Solution Approach 1:
The patent creates a universal light source capable of operating across multiple wavelength ranges by combining diffraction gratings with different periods. This multi-functional resonator can tune to wavelengths corresponding to both the first diffraction grating (Λ1) and the second diffraction grating (Λ2), replacing the need for multiple separate DFB-LD products and reducing the quantity of components required for WDM transmission systems.
4Ease of operation
If a variable-wavelength mechanism is provided outside the laser element, then wavelength control flexibility is improved, but the device complexity and vibration resistance problems increase
Solution Approach 1:
The patent merges the variable-wavelength mechanism directly into the laser element by integrating multiple diffraction gratings within the resonator structure. This combination eliminates the need for separate external wavelength control mechanisms, reducing overall device complexity while maintaining wavelength control flexibility through the integrated multi-period grating system that can be controlled via current injection and temperature variation.
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 solution provides a high-reliability, low-cost variable-wavelength light source with improved stability and extended wavelength control, minimizing mode jumps and reducing the risk of oscillation frequency hopping, thus enhancing the operational reliability and flexibility of WDM systems.
Implementation Method 1
which generates a vernier effect to maximize mode gain difference and ensure stable wavelength control
Implementation Method 2
three ring-shaped resonators of different light path lengths, connected via optical coupling
Implementation Method 3
Multiple resonator and variable-wavelength light source used for an optical multiplexing transmission system
Data Source
AI summary
An external resonator which includes a multiple resonator with parameters which allow stable wavelength control, and a variable-wavelength light source includes such an external resonator are provided. The external resonator is a multiple resonator which is made up of first to third ring-shaped resonators, each having different light path length, and connected in series via optical coupling means. The parameters of the multiple resonator are characterized in that all the following Expressions <1>, <2> and <3> hold:L1={M1/(M1−1)}L0 <1>L2={M2/(M2−1)}L0 <2>M2−1=(M1−1)2 <3>where L0 is the light path length of the first resonator, L1 is the light path length of the second resonator and L2 is the light path length of the third resonator, and M1 and M2 are integers of 3 or greater.