Optical Multiplexing Device for OFDM Timing Control
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Solution Overview
Problem
Current optical OFDM systems face challenges in accurately controlling modulation timing between sub-carrier signals, leading to interference and reduced communication quality, especially at high symbol rates exceeding the processing capability of Digital Signal Processors (DSPs).
Innovation Solution
An optical multiplexing device that employs a controller to adjust modulation timing by sampling and minimizing the power of cross-point interference between sub-carrier signals, using a combination of optical branching units, nonlinear optical media, and a controller to ensure orthogonality and suppress interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high symbol rates are used to increase transmission capacity, then productivity is improved, but modulation timing control accuracy deteriorates due to exceeding DSP processing capability
Solution Approach 1:
The patent replaces the DSP-based electronic timing control system with an optical domain control system. By using optical branching units to extract sub-carrier signals and optical nonlinear media to generate timing error signals directly in the optical domain, the system achieves high-precision timing control at high symbol rates without being constrained by DSP processing capabilities.
Solution Approach 2:
The patent introduces optical nonlinear media as an intermediary element that converts optical sub-carrier signals into timing error signals through optical nonlinear effects. This intermediary mechanism enables direct optical-domain timing synchronization, bypassing the limitations of electronic processing and providing accurate timing control even at extremely high symbol rates.
2Productivity
If sub-carrier signals are densely multiplexed to maximize frequency utilization, then productivity is improved, but interference between sub-carrier signals increases
Solution Approach 1:
The patent implements a feedback mechanism where timing error signals are continuously generated from the multiplexed optical OFDM signal itself using optical nonlinear effects. These feedback signals are used to dynamically adjust and maintain precise timing synchronization between sub-carrier signals, ensuring that even when densely multiplexed, the orthogonality is preserved and interference is minimized.
Solution Approach 2:
The patent applies preliminary anti-action by proactively compensating for potential interference through continuous timing synchronization. By using the optical nonlinear media to generate timing error signals in advance and adjusting timing before significant interference occurs, the system prevents interference buildup that would otherwise result from dense sub-carrier multiplexing.
3Ease of operation
If DSP processing is used for timing control, then ease of operation is improved, but device complexity increases when higher processing power is required
Solution Approach 1:
The patent replaces complex DSP processing with simpler optical domain operations. By using optical branching units for signal extraction and optical nonlinear media for automatic timing error signal generation, the system achieves timing control without requiring high-power DSP processors, thereby reducing device complexity while maintaining ease of operation.
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 generates optical OFDM signals with reduced interference between sub-carrier signals, even at high symbol rates, by accurately controlling modulation timing and frequency, thereby enhancing communication quality and maximizing the utilization of optical fiber transmission bands.
Implementation Method 1
an optical branching unit that power-branches the multiplexed optical signal
Implementation Method 2
Cross Phase Modulation (XPM) that is a nonlinear optical effect in an optical fiber
Implementation Method 3
detecting a power of the optical components
Data Source
Figure 1~2
Figure 3~4
Figure 5A~5B
AI summary
An optical multiplexing includes: a monitor configured to detect power of an optical component including a frequency component of a cross point between spectra of a first sub-carrier signal and a second sub-carrier signal; and a controller configured to control a modulation timing of a data symbol of the second sub-carrier signal according to the power detected by the monitor, wherein the second sub-carrier signal is multiplexed to a carrier to be adjacent to the first sub-carrier signal multiplexed to the carrier so as to generate an optical Orthogonal Frequency Divisional Multiplexing (OFDM) signal in which an interference between the first and second sub-carrier signals is suppressed.