I/Q Separated Dual Multicarrier Coherent Optical Transmission
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Solution Overview
Problem
Coherent optical transmission systems face performance degradation due to RF time delay errors between in-phase (I) and quadrature (Q) components, leading to high device complexity and cost, especially in multicarrier-based systems where phase coherence is critical.
Innovation Solution
The system generates multicarrier signals using Hermitian symmetry and independently modulates input data for I and Q components, inserting a separate RF tone to compensate for phase variations at the reception side, thereby reducing time delay and phase differences between the components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If coherent optical transmission is used to enhance transmission capacity, then transmission distance and capacity are improved, but RF time delay errors between I and Q components cause performance degradation
Solution Approach 1:
The patent segments the optical carrier into independent in-phase (I) and quadrature (Q) components, each modulated with separate multicarrier signals. This segmentation allows independent optimization of each component's transmission characteristics, enabling the system to achieve high transmission capacity while maintaining signal stability by preventing time delay errors between components.
Solution Approach 2:
The patent changes the modulation parameters by independently modulating I and Q components with different multicarrier signals having specific frequency relationships. This parameter change enables the system to maintain phase coherence and reduce RF time delay errors while enhancing transmission capacity through efficient use of optical carrier properties.
2Ease of operation
If I and Q components are separated with 90-degree phase difference, then coherent detection is enabled, but RF delay causes critical performance degradation
Solution Approach 1:
The patent segments the modulation process into independent I and Q component modulation, allowing each to be optimized separately. This segmentation enables coherent detection to be maintained while reducing the impact of RF delays by ensuring that time delay errors do not critically degrade performance through independent signal generation.
Solution Approach 2:
The patent incorporates feedback mechanisms through the receiver that estimates and compensates for phase and time delay errors between I and Q components. This feedback enables the system to maintain manufacturing precision requirements while preserving coherent detection capability.
3Productivity
If multicarrier signals are modulated on optical carrier, then transmission capacity is enhanced, but device complexity and cost increase
Solution Approach 1:
The patent uses a universal optical carrier that can be independently modulated with multiple multicarrier signals for both I and Q components. This multi-functionality allows a single optical carrier to carry multiple transmission streams, enhancing capacity while avoiding the need for separate carriers and reducing overall device complexity.
Solution Approach 2:
The patent optimizes transmission capacity by changing modulation parameters such as signal frequency and phase relationships between I and Q components. These parameter changes enable high capacity transmission using standard optical components, avoiding the need for complex specialized devices.
Data Source
AI summary
Provided is an apparatus and method for in-phase (I)/quadrature (Q) separated dual multicarrier transmission in a coherent optical transmission system. A multicarrier transmission apparatus includes a carrier generator configured to generate a plurality of multicarrier signals; and a modulator configured to independently modulate input data with respect to an I component and a Q component of an optical carrier using the generated plurality of multicarrier signals.