Subcarrier Polarization Control for PDL Mitigation
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Solution Overview
Problem
Optical communication networks face signal degradation due to polarization dependent loss (PDL) and nonlinear effects caused by cross talk among polarization components, leading to imbalanced optical signal-to-noise ratio (OSNR) and intensity variations.
Innovation Solution
A method and system that identify and modify the states of polarization of subcarriers in a multi-carrier optical signal before transmission to mitigate PDL, using a processor and polarization control system to align subcarriers with optimized states of polarization, reducing OSNR degradation and nonlinear phase noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polarization control is implemented to mitigate PDL, then signal quality improves, but system complexity increases
Solution Approach 1:
The patent applies preliminary action by modifying the states of polarization of subcarriers before transmission through the optical network. The transmitter proactively adjusts polarization states to compensate for anticipated PDL effects, eliminating the need for complex real-time feedback control systems while maintaining signal quality.
Solution Approach 2:
The patent changes the polarization state parameters of individual subcarriers to optimize performance. By modifying polarization angles and states as controllable parameters, the system achieves PDL mitigation through parameter optimization rather than complex hardware modifications.
2Reliability
If polarization states are modified for each subcarrier, then PDL mitigation improves, but processing complexity increases
Solution Approach 1:
The patent segments the multi-carrier signal into individual subcarriers and applies polarization control to each subcarrier independently. This segmentation allows targeted PDL mitigation for each frequency component, optimizing overall signal quality while maintaining manageable processing complexity through modular treatment of subcarriers.
Solution Approach 2:
The patent modifies polarization state parameters for each subcarrier to optimize PDL compensation. By treating polarization angles and states as adjustable parameters for each subcarrier, the system achieves effective PDL mitigation through parameter optimization rather than complex structural modifications.
3Reliability
If polarization alignment is optimized, then OSNR balance improves, but measurement and control difficulty increases
Solution Approach 1:
The patent optimizes polarization state parameters to achieve balanced OSNR across different polarization components. By treating polarization angles and states as controllable parameters, the system achieves OSNR balance through parameter adjustment rather than complex real-time measurement and feedback control.
Data Source
AI summary
Methods and systems for mitigating effects of polarization dependent loss (PDL) in an optical network transmitting a multi-carrier optical signal comprising a plurality of subcarriers may involve assigning and modifying a state of polarization to each subcarrier prior to transmission. An assigned state of polarization for each subcarrier may be modified for the subcarrier in the digital domain and/or the optical domain. Various specific assignment methods may be used, including individual subcarrier assignment, subcarrier set assignment, arbitrary subcarrier group assignment, random assignment, and/or combinations thereof. The assigned states of polarization may be selected based on a resulting minimum PDL-induced peak-to-peak power variation over a sum of the subcarriers for all orientations of a principal axis of PDL.