Optical Transmission Frequency Control via Signal Quality Feedback
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Solution Overview
Problem
Existing optical transmission systems face challenges in maintaining optimal frequency spacing between wavelength-multiplexed optical signals due to factors like aging of transmitters, wavelength dependency, and nonlinear effects in optical fibers, which vary with traffic and network conditions, leading to suboptimal transmission characteristics and increased apparatus costs.
Innovation Solution
A transmission apparatus that calculates signal qualities of frequency-division multiplexed subcarrier signals and controls the optical source frequency based on detected deviations, optimizing the spacing between adjacent signals to improve transmission characteristics without requiring expensive equipment like high-resolution optical spectrum analyzers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wavelength division multiplexing is used to transmit multiple optical signals, then transmission capacity is improved, but frequency spacing between signals becomes difficult to maintain optimally due to aging, wavelength dependency, and nonlinear effects
Solution Approach 1:
The patent implements a feedback mechanism where the reception apparatus measures signal qualities of multiple subcarrier signals, detects deviations from ideal signal quality distribution, and transmits control signals back to the transmission apparatus. The transmission apparatus adjusts the frequency spacing of optical signals based on this feedback, thereby maintaining optimal frequency spacing despite aging, wavelength dependency, and nonlinear effects in the optical fiber.
Solution Approach 2:
The system enables self-adjustment of frequency spacing through automatic detection and control. The reception apparatus autonomously measures signal qualities, detects deviations, and generates control signals without external intervention. This self-service mechanism allows the system to adapt to changing conditions (aging, temperature variations, nonlinear effects) and maintain optimal transmission characteristics automatically.
2Reliability
If frequency spacing is adjusted to compensate for nonlinear effects and wavelength dependency, then transmission characteristics are improved, but apparatus complexity and costs increase due to requirement of high-resolution optical spectrum analyzers
Solution Approach 1:
Instead of using expensive high-resolution optical spectrum analyzers to directly measure frequency spacing, the patent uses a copying approach: it measures signal qualities (electrical characteristics) of subcarrier signals at the reception end, which indirectly reflect the frequency spacing conditions. This substitution of measurement method reduces apparatus complexity while achieving the same control objective.
Solution Approach 2:
The patent replaces the need for complex optical measurement equipment (optical spectrum analyzers) with simpler electrical signal quality measurements. By substituting optical domain measurements with electrical domain measurements of subcarrier signals, the system achieves frequency spacing control with reduced apparatus complexity and lower costs.
3Productivity
If frequency spacing is reduced to increase multiplexing density, then transmission capacity is improved, but signal quality deteriorates due to increased crosstalk and nonlinear effects
Solution Approach 1:
The patent implements dynamic adjustment of frequency spacing based on actual transmission conditions. Rather than using fixed frequency spacing, the system continuously adapts the spacing between wavelength-multiplexed optical signals according to measured signal qualities and detected deviations. This dynamic approach allows the system to maintain optimal spacing that balances multiplexing density with signal quality, preventing excessive crosstalk and nonlinear effects while maximizing transmission capacity.
Data Source
AI summary
There is provided a transmission apparatus configured to receive a frequency-division multiplexed optical signal generated by modulating carrier light based on a plurality of frequency-division multiplexed subcarrier signals, the transmission apparatus including: a processor configured to: extract a plurality of subcarrier signals of the plurality of frequency-division multiplexed subcarrier signals from the frequency-division multiplexed optical signal; calculate signal qualities of the plurality of subcarrier signals; detect a deviation of the signal qualities between the plurality of subcarrier signals; and perform a frequency control of the carrier light generated by an optical source of a transmission apparatus configured to transmit the frequency-division multiplexed optical signal, based on the deviation of the signal qualities.