Optical Coupling Adjustment Using Merged Photocurrent Signals
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Solution Overview
Problem
The optical coupling adjustment in optical integrated circuits faces challenges in accurately guiding lenses to optimal positions, leading to misalignment and deterioration of optical characteristics due to the monitoring of photocurrent from a single electrode, which maximizes at a misaligned position.
Innovation Solution
The method involves measuring the sum of optical power along multiple waveguides by detecting photocurrents from electrodes, adjusting the optical focusing spot position to maximize the sum of photocurrents, and determining the optimal position for optical components to ensure accurate alignment with the core center of the waveguide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If optical coupling adjustment is performed by monitoring photocurrent from a single electrode, then the adjustment process is simple, but the alignment precision deteriorates because the photocurrent maximum occurs at a misaligned position
Solution Approach 1:
The patent combines the photocurrent signals from multiple electrodes (at least two electrodes positioned at different locations along the waveguide) into a single monitoring signal. This merging of signals allows the adjustment process to maintain simplicity while achieving accurate alignment, as the combined signal provides a more reliable indicator of optimal coupling position than any single electrode alone.
Solution Approach 2:
The patent makes the optical coupling adjustment method applicable to various waveguide configurations and electrode arrangements by using a universal approach of monitoring combined photocurrent from multiple electrodes. This multi-functional monitoring strategy can be applied regardless of the specific waveguide geometry or electrode positions, making the adjustment process universally applicable while maintaining high alignment precision.
2Ease of operation
If optical focusing spot position is adjusted to maximize single electrode photocurrent, then the adjustment is easy to perform, but optical loss increases due to misalignment from core center
Solution Approach 1:
By merging photocurrent signals from multiple electrodes, the patent creates a composite monitoring signal that accurately indicates when the optical focusing spot is properly aligned with the waveguide core center. This approach maintains operational simplicity while eliminating the misalignment-induced optical losses that occur when relying on single electrode photocurrent maximization.
3Difficulty of detecting and measuring
If single electrode photocurrent monitoring is used for alignment, then the measurement process is simple, but measurement precision deteriorates due to wavelength dependency and higher order mode generation
Solution Approach 1:
The patent combines photocurrent measurements from multiple electrodes to create a more robust and precise alignment measurement. This merged measurement approach reduces the wavelength dependency and higher order mode generation issues that plague single electrode monitoring, thereby improving measurement precision while maintaining relative simplicity.
Solution Approach 2:
The patent uses the combined photocurrent signal from multiple electrodes as feedback during the alignment process. This feedback mechanism provides more accurate real-time information about the optical focusing spot position relative to the waveguide core, enabling precise alignment measurements that are less susceptible to wavelength variations and mode generation effects.
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 enables more precise adjustment of the optical focusing spot position to the core center, reducing optical loss and wavelength dependency, thereby improving the quality of the optical signal and suppressing the generation of higher order modes.
Implementation Method 1
photocurrents detected by the electrodes can be observed, the photocurrents enabling monitoring of optical power propagating along each of the waveguides
Data Source
AI summary
In the adjustment method of optical coupling for an optical integrated circuit according to the present disclosure, the optimal adjustment position of optical coupling is determined on the basis of, for example, a sum of a plurality of photocurrents at electrodes on arm waveguides respectively formed on the plurality of MZIs in the polarization-multiplexing IQ modulator. According to the maximum value of the sum of the plurality of photocurrents, the light condensing spot position is adjusted to the center position of the end face core of the optical waveguide of the integrated chip. Typically, the light condensing spot position is adjusted to the center of the end face core by displacing the two input lenses.