Optical Wavelength Multiplex Signal Preemphasis
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Solution Overview
Problem
Existing methods for preemphasizing optical multiplex signals in WDM transmission systems face challenges due to wavelength-dependent gain in amplifiers, leading to performance differences between channels, especially at small channel separations, and require complex noise power measurements that are time-consuming and impractical for dynamic networks.
Innovation Solution
A method that sets new power levels for optical multiplex signals by determining mean gain values and attenuations across amplification sections, allowing for autonomous preemphasis without the need for signal-to-noise ratio measurements or planning tools, using only power level measurements at the transmitter and receiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If OSNR measurement methods are used to determine channel power levels, then signal-to-noise ratio leveling can be achieved, but measurement time increases significantly and the method becomes too slow for dynamic networks
Solution Approach 1:
The patent extracts only the necessary measurement information (total power levels at transmitter and receiver) from the complex OSNR measurement process. By removing the need to measure noise power separately and performing only power level measurements, the method achieves the essential preemphasis function without the time-consuming OSNR measurement steps, reducing measurement time while maintaining sufficient precision for power level optimization.
Solution Approach 2:
The patent uses power level measurements as a simplified copy or proxy for the full OSNR characterization. Instead of measuring the complete signal-to-noise ratio, it measures only the power levels at key points (transmitter input/output and receiver input) and uses these copied measurements to calculate and optimize the preemphasis parameters, achieving comparable results with much faster measurements.
2Measurement precision
If separate measurements for channel power levels and ASE power levels are performed, then accurate OSNR distribution can be determined, but the measurement process becomes too complex and slow for dynamic networks
Solution Approach 1:
The patent merges the separate measurement processes for channel power levels and ASE power levels into a single integrated power level measurement approach. By combining these measurements and using the relationship between total power, signal power, and noise power, the method determines the necessary preemphasis parameters with a single measurement set, reducing system complexity while maintaining measurement accuracy.
Solution Approach 2:
The patent introduces total power level measurements as an intermediary that connects the transmitter and receiver characteristics. By measuring total power levels at key points and using these intermediary measurements to calculate the preemphasis parameters, the method avoids the need for direct separate measurements of channel and ASE powers, simplifying the measurement system while preserving the ability to optimize OSNR distribution.
3Reliability
If iterative OSNR-based preemphasis methods are used, then channel power levels can be optimized, but the process requires expensive planning tools and is too slow for dynamic network adjustments
Solution Approach 1:
The patent performs preliminary measurements of total power levels at the transmitter and receiver before the preemphasis optimization process. By having these measurements ready in advance and using them directly to calculate the preemphasis parameters without iterative adjustments, the method achieves fast preemphasis setup that is suitable for dynamic networks, while still ensuring reliable transmission quality through accurate power level optimization.
Solution Approach 2:
The patent enables the preemphasis system to self-adjust using locally available power level measurements without requiring external planning tools or iterative OSNR measurements. The system uses the measured power levels to automatically calculate and apply the appropriate preemphasis parameters, making the process independent, fast, and suitable for dynamic network conditions while maintaining transmission quality.
Data Source
AI summary
Methods are described for preemphasizing an optical multiplex signal that comprises a plurality of signals having different wavelengths, which are transmitted by a transmitter to a receiver. Power levels for the signals are set at the transmitter and measured at the receiver. A mean power level for the transmit-side signals is ascertained. New signal power level values are ascertained from the current power levels of the signals at the transmitter and at the receiver and set on the transmit side such that signal-to-noise ratios for all signal are approximately equalized at the receiver. In order to make more precise settings for the preemphasis, mean gain values and mean attenuations are ascertained from the sum power levels for the multiplex signal measured at the input and at the output of each amplification section and incorporated together with an effective noise figure into the process of ascertaining the new signal power level values. The preemphasis is thus performed autonomously without there being any need for further planning resources for control purposes.