Optical Phase Difference Detection Using Lissajous Ellipsoid Analysis
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Solution Overview
Problem
In optical communication systems, phase shifts from the ideal 90° between in-phase (I-component) and quadrature (Q-component) signal light components affect the quality of the optical signal, and existing methods fail to accurately detect and compensate for phase differences caused by optical hybrids.
Innovation Solution
A device comprising a detector, compensator, and evaluator that couples signal light with local light to detect and compensate the I- and Q-components, using Lissajous figure analysis to determine phase differences, and compensates for power fluctuations by maintaining equivalent magnitudes and applying elliptic approximations to reduce errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional phase detection methods are used, then the detection process is simple, but the measurement precision of phase difference is poor with errors of ±1.3°
Solution Approach 1:
The patent applies preliminary action by performing power fluctuation compensation before phase difference measurement. The compensator normalizes the I and Q components by dividing by their respective power levels (|I| and |Q|), eliminating power fluctuation effects prior to Lissajous figure analysis. This preprocessing step reduces phase detection errors from ±1.3° to ±0.3° without significantly increasing system complexity
Solution Approach 2:
The patent implements feedback by using the detected phase difference and power levels to continuously adjust and compensate the I and Q components. The compensator uses real-time power measurement feedback to normalize the signal components, creating a closed-loop system that maintains accurate phase detection despite power fluctuations in the optical hybrid output
2Reliability
If power fluctuation compensation is applied, then the reliability of phase detection improves, but the device complexity increases due to additional compensator components
Solution Approach 1:
The patent replaces complex mechanical or hardware-based compensation mechanisms with mathematical signal processing operations. The compensator performs normalization using simple division operations on the I and Q components based on their power levels, achieving reliable phase detection without complex physical compensation devices. This substitution of mathematical operations for physical compensation reduces device complexity while maintaining reliability
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 effectively reduces phase difference errors from ±1.3° to ±0.3°, improving the accuracy and reliability of phase detection in optical communication systems by compensating for power fluctuations and phase shifts.
Implementation Method 1
The detector detects a positive element and a negative element of each of the I-component and the Q-component
Implementation Method 2
An optical communication system, in particular, the optical coherent system uses an optical hybrid that enables to generate the I-component and the Q-component of signal light input thereto
Data Source
AI summary
A device able to evaluate a phase difference between I-component and Q-component of signal light generated by an optical hybrid is disclosed. The device includes a detector, a compensator and an evaluator. The detector detects positive and negative elements of each of the I-component and the Q-component. The compensator generates a compensated I-component and a compensated Q-component so as to keep the sum of positive and negative elements of each of components in constant. The evaluator determines the phase difference via an ellipsoid drawn by the compensated I- and Q-components.