Dual-Polarization Optical Coding for Constant-Power High Data Rates
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Solution Overview
Problem
In optical communications, high data rate transmission using complex modulation formats like QAM leads to signal power variations and phase noise, while PSK formats offer constant modulus but result in higher bit-error rates due to shorter Euclidean distances.
Innovation Solution
The proposed solution involves an optical data coding method using X-polarization and Y-polarization constellation formats with circular grids and amplitude rings to encode symbols, ensuring constant signal power and improved bit-error rates by combining advantages of QAM and PSK formats.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If QAM modulation formats are used to increase data rate, then data rate is improved, but signal power variations and phase noise occur
Solution Approach 1:
The patent transitions from traditional 2D QAM constellations to 4D constellations by incorporating both X and Y polarizations with two amplitude rings each. This dimensional expansion allows encoding more bits per symbol (up to 8 bits) while maintaining constant modulus through the combined polarization-state representation, thereby increasing data rate without sacrificing signal stability.
Solution Approach 2:
The patent creates a composite modulation format that combines elements of QAM (multiple amplitude rings for high data rate) and PSK (constant modulus for reliability). The 4D constellation uses two amplitude rings per polarization with specific phase angle assignments, merging the high-capacity advantage of QAM with the noise-resistance advantage of PSK.
2Reliability
If PSK modulation formats are used to maintain constant modulus, then signal stability is improved, but bit-error rate increases due to shorter Euclidean distances
Solution Approach 1:
By expanding to 4D space with two polarizations and two amplitude rings, the patent increases the Euclidean distance between constellation points. The additional dimensional freedom allows spacing points farther apart while maintaining constant overall power, thereby reducing bit-error rate while preserving the constant modulus property.
Solution Approach 2:
The patent creates a hybrid constellation that combines PSK's constant phase angles with QAM's multiple amplitude levels across two polarizations. This composite approach maintains the phase stability of PSK while introducing amplitude variation in a controlled manner that increases Euclidean distance and reduces error rate.
3Reliability
If 4D-2A8PSK code is used to achieve constant modulus, then signal stability is improved, but implementation complexity increases
Solution Approach 1:
The patent divides the 8-bit symbol into two 4-bit subsets, with each subset mapped to a separate polarization (X or Y). Each polarization then uses a simplified 2A8PSK mapping with two amplitude rings and eight phase angles. This segmentation reduces the complexity of the overall mapping process while maintaining the constant modulus property through the combined 4D representation.
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
An optical data coding method includes at least steps of selecting a modulation scheme comprising an X-polarization constellation format having first and second amplitude rings with circular grids corresponding to predetermined phase angles and a Y-polarization constellation format having the first and second amplitude rings with the circular grids corresponding to the predetermined phase angles, arranging a first part of the symbol on a first circular grid of the first amplitude ring on the X-polarization constellation format, and arranging a second part of the symbol on a second circular grid of the second amplitude ring on the Y-polarization constellation format.