Optical Coupler Wavelength Compensation for Polarization Multiplexing
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Solution Overview
Problem
In optical devices implementing polarization division multiplexing, the wavelength characteristic of the polarization synthesizer can lead to a decrease in optical power at the end of the operating wavelength band, potentially deteriorating the polarization multiplexed light.
Innovation Solution
The optical device incorporates an optical coupler with a wavelength characteristic that cancels out the wavelength characteristic of the polarization synthesizer, ensuring the optical power remains within specified limits by adjusting the waveguide widths and clearance gaps to maintain a balanced ratio of optical powers for the branched lights.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a polarization synthesizer is used to synthesize polarization multiplexed light, then the optical device can achieve polarization division multiplexing functionality, but the optical power decreases at the end portion of the operating wavelength band due to the wavelength characteristic of the polarization synthesizer
Solution Approach 1:
The patent applies preliminary anti-action by introducing an optical coupler with a specific wavelength characteristic that acts in advance to counterbalance the wavelength characteristic of the polarization synthesizer. The optical coupler is designed to have higher transmission characteristics at longer wavelengths, which pre-compensates for the power decrease that would occur at the end portion of the operating wavelength band after synthesis, thereby preventing the overall optical power from dropping below specification values
Solution Approach 2:
The patent applies parameter changes by adjusting the wavelength characteristic parameters of the optical coupler. Specifically, the optical coupler is designed with a coupling ratio and wavelength response that changes parameters to compensate for the polarization synthesizer's characteristics. By modifying the waveguide dimensions and coupling parameters of the optical coupler, the system achieves a balanced wavelength response that maintains optical power within specification values across the entire operating wavelength band
2Volume of moving object
If the optical coupler, polarization converter, and polarization synthesizer are mounted on a single substrate, then the optical device achieves downsizing, but the wavelength characteristic of the polarization synthesizer causes deterioration in polarization multiplexed light
Solution Approach 1:
The patent applies merging by integrating the optical coupler, polarization converter, and polarization synthesizer onto a single substrate. This consolidation reduces the overall device volume while maintaining the functional integrity of each component. The optical coupler is designed with specific waveguide dimensions and coupling gaps that enable it to provide wavelength compensation functionality within the integrated structure, ensuring that the merged device maintains both compact size and reliable polarization multiplexed light output
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 effectively prevents the deterioration of polarization multiplexed light by compensating for the wavelength characteristic of the polarization synthesizer, maintaining optimal optical power levels across the operating wavelength band.
Implementation Method 1
As the optical coupler and the polarization synthesizer, for example, directional couplers are used that perform optical coupling of two waveguides
Implementation Method 2
the direction of polarization of one branched light is changed using a polarization converter
Implementation Method 3
the branched light having the changed direction of polarization and the branched light having the unchanged direction of polarization are synthesized using a polarization synthesizer
Data Source
AI summary
An optical device includes an optical coupler that performs branching of the input light and outputs a first-type branched light and a second-type branched light; a polarization converter that changes the direction of polarization of the second-type branched light output from the optical coupler; and a polarization synthesizer that outputs a polarization multiplexed light by synthesizing the first-type branched light, which is output from the optical coupler, and the second-type branched light, which has the direction of polarization changed by the polarization converter. The optical coupler has the wavelength characteristic that cancels out the wavelength characteristic of the polarization synthesizer regarding the second-type branched light included in the polarization multiplexed light.