Flexible Grid Spectrum Power Control via Segmented Resolution Bandwidth
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Solution Overview
Problem
In flexible grid DWDM optical networks, measuring and controlling signal power becomes difficult due to spectral overlap and limited resolution of Optical Channel Monitors, leading to inaccurate power measurements and erroneous control, especially when signals are closely spaced in Nyquist-spacing.
Innovation Solution
A method and apparatus that utilize a control bandwidth close to the center frequency of optical signals, allowing for accurate power measurement and control by defining a control bandwidth less than spectral occupancy but equal to or greater than the measurement device's resolution bandwidth, enabling adjustments to actuators within and outside this bandwidth based on measured and target powers, and applying a relative bias for precise power control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If optical signals are spectrally squeezed in Nyquist-spacing to improve spectral efficiency, then spectral efficiency is improved, but measurement precision of per signal power deteriorates due to power contributions from neighboring signals
Solution Approach 1:
The patent divides the spectral occupancy of each optical signal into multiple resolution bandwidth (RBW) segments. By measuring power in each RBW segment separately and summing them, the system can isolate the power contribution of individual signals even when spectrally overlapped, thereby maintaining measurement precision while achieving high spectral efficiency through Nyquist-spacing.
Solution Approach 2:
The patent applies different measurement resolutions to different parts of the spectrum. By using fine RBW segmentation specifically at the edges of spectral occupancy where signal overlap occurs, while using coarser measurement in the center, the system achieves accurate power measurement without requiring uniformly high resolution across the entire spectrum, thus balancing measurement precision with spectral efficiency.
2Measurement precision
If conventional fixed grid DWDM is used to ensure signals are spaced far apart for accurate measurement, then measurement precision is improved, but spectral efficiency deteriorates
Solution Approach 1:
The patent transitions from the static fixed grid approach to a dynamic measurement approach. Instead of relying on fixed spatial separation, the system dynamically segments the spectrum into RBW portions and adaptively measures power contributions, allowing signals to be closely spaced in frequency while maintaining measurement accuracy through computational separation of power contributions.
3Measurement precision
If high-resolution Optical Spectrum Analyzers are used to measure closely spaced signals, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies the principle of partial measurement by using moderate-resolution OCMs that measure only specific RBW segments of the spectrum rather than requiring full high-resolution coverage across the entire spectral occupancy. This partial measurement approach achieves sufficient precision for power control without the complexity and cost of high-resolution OSAs.
Data Source
AI summary
Systems and methods to control optical signals in a spectrally overlapped, flexible grid spectrum system include receiving measured power within a control bandwidth for an optical signal, wherein the control bandwidth is less than a spectral occupancy of the optical signal and equal to or greater than a resolution bandwidth of a measurement device configured to measure the measured power; and controlling the optical signal based on the measured power and a target power within the control bandwidth. The optical signals can include Nyquist spaced or super Nyquist spaced signals in a media-channel.