Optical Transmitter Time Skew Detection and Correction
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Solution Overview
Problem
Time skew between the in-phase and quadrature portions in optical M-QAM transmitters, originating from digital, analog, and optical domains, affects system performance and requires effective detection and correction methods, especially in pluggable photonics where in-factory calibration is not possible.
Innovation Solution
An optical transmitter system with an interferometric structure and a control module that calculates skew between the in-phase and quadrature portions, using training signals to detect and correct delays in both domains, minimizing skew to within the symbol unit interval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If in-factory calibration and correction of time skew is performed, then manufacturing precision is improved, but device complexity and assembly requirements worsen
Solution Approach 1:
The system performs self-calibration by automatically detecting and correcting time skew between I/Q tributaries using an interferometric structure and control module, eliminating the need for manual in-factory calibration and reducing assembly complexity
Solution Approach 2:
The calibration function is built into the system architecture beforehand, allowing automatic time skew correction to occur during operation without requiring pre-calibration during manufacturing
2Device complexity
If time skew is not corrected, then device complexity is reduced, but system performance and reliability worsen
Solution Approach 1:
The calibration function is extracted as a separate, dedicated module that can be independently implemented, allowing time skew correction without adding complexity to the main signal processing path
Solution Approach 2:
An interferometric structure serves as an intermediary mechanism that enables precise time skew detection and correction through interference pattern analysis, improving reliability without direct modification of the main signal path
3Measurement precision
If interferometric calibration structure is added, then time skew detection precision is improved, but device complexity worsens
Solution Approach 1:
The interferometric structure is designed to serve multiple functions including time skew detection, phase measurement, and calibration verification, justifying its addition through multi-functionality rather than single-purpose complexity
Solution Approach 2:
The system replaces complex mechanical adjustment mechanisms with an optical interferometric approach for time skew measurement, achieving high precision through optical phase detection rather than mechanical positioning
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 detects and corrects large and small amounts of time skew, ensuring optimal performance of the optical M-QAM transmitter system by minimizing I/Q skew to less than the symbol unit interval, thereby enhancing signal quality and system reliability.
Implementation Method 1
The interferometric structure can produce an output indicative of a skew between the in-phase portion and the quadrature portion
Data Source
AI summary
In some embodiments, an apparatus includes an optical transmitter system that defines an interferometric structure and has an in-phase portion and a quadrature portion. The optical transmitter system has a transmission configuration and a calibration configuration. The interferometric structure can produce an output associated with a skew between the in-phase portion and the quadrature portion of the optical transmitter system when in the calibration configuration. The skew is associated with a digital domain, an analog domain and an optical domain of the optical transmitter system.