Optical Network Link Protection via Constellation Distortion
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Solution Overview
Problem
Optical transport networks face challenges in quickly rerouting traffic without incurring long service interruptions or excessive overcapacity when link failures occur, due to the time-consuming reconfiguration required for adapting modulation and coding schemes in multi-rate multi-format transponders.
Innovation Solution
The method involves partitioning traffic into priority classes, mapping higher priority traffic to more resilient bit positions within a constellation diagram, and applying a predetermined distortion to ensure reliable transmission over both working and protection links, allowing for rapid switching without reconfiguring the transponders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the transmission format is adapted by reconfiguring transponders to maintain transmission quality over protection links, then reliability is improved, but service interruption time increases significantly
Solution Approach 1:
The patent applies preliminary action by pre-configuring multiple constellation diagrams with different distortion levels before any failure occurs. When a link failure is detected, the system immediately switches to a pre-calculated constellation diagram suitable for the protection link conditions, avoiding the need for real-time reconfiguration. This prepares the system in advance with multiple ready-to-use modulation formats that can be instantly activated.
Solution Approach 2:
The patent implements dynamics by making the constellation diagram selection dynamic and adaptable based on real-time link conditions. The system dynamically chooses among multiple pre-configured constellation diagrams with varying distortion levels, allowing the modulation format to adapt to different protection link qualities without requiring physical reconfiguration of the transponder hardware.
2Reliability
If all protection paths are constrained to support the same throughput as working paths, then reliability is improved, but network overcapacity requirements increase tremendously
Solution Approach 1:
The patent applies local quality by assigning different constellation diagrams with different distortion levels to different priority classes of traffic. High-priority traffic is mapped to bits in the constellation diagram that are more resilient to distortion, while lower-priority traffic can tolerate higher distortion. This allows each portion of traffic to receive the appropriate level of protection locally, rather than uniformly across all traffic.
Solution Approach 2:
The patent implements parameter changes by varying the constellation diagram distortion level based on traffic priority and link conditions. Instead of maintaining a fixed modulation format, the system changes the constellation parameters (distortion level) to match the required service level, allowing protection links to support variable throughput levels without requiring excessive overcapacity for all scenarios.
3Reliability
If constellation distortion is applied to map high-priority traffic to resilient bit positions, then reliability of high-priority traffic is improved, but complexity of the modulation scheme increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing multiple constellation diagrams with different distortion levels and bit mappings before operation. The mapping of high-priority traffic to resilient bit positions is predetermined in the pre-configured constellation diagrams, eliminating the need for complex real-time calculations during failure scenarios. The system simply selects and applies the appropriate pre-prepared constellation diagram.
Data Source
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AI summary
Enclosed herewith is a method for protecting a link in an optical network configured for transmitting digital data employing a predetermined modulation format which comprises a number of symbols in a constellation diagram. A binary address is associated with each symbol. The modulation format allows for a constellation distortion, according to which the relative positions of constellation points in the constellation diagram are varied in a predetermined way by a predetermined degree. The method comprises the steps of: A) partitioning the traffic in two or more priority classes, B) mapping higher priority traffic to predefined bit positions within the binary symbol addresses, C) evaluating the quality of a predetermined protection link, D) determining a degree of distortion such that a desired transmission quality for the transmission of the traffic of the highest priority class or classes via said predetermined protection link and a desired transmission quality for the full traffic via said given link are simultaneously ensured, and E) employing said distorted constellation diagram for transmission of digital data over said given link.