Programmable Clock Recovery Bandwidth for Dense Optical Channels
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Solution Overview
Problem
In optical communication systems, particularly in gridless deployments, increasing channel density is hindered by interchannel interference and clock jitter due to spectral energy leakage from adjacent channels, which affects the integrity of the extracted data clock and limits the ability to synchronize data recovery.
Innovation Solution
The proposed solution involves a clock recovery circuit with a programmable bandwidth that decouples the clock recovery bandwidth from the receiver's phase noise suppression, using a phase rotator or adjustable reference clock to optimize clock recovery and reduce adjacent channel interference, thereby improving phase estimation accuracy and synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If channel density is increased in gridless optical systems, then bandwidth utilization is improved, but interchannel interference increases due to spectral energy leakage from adjacent channels
Solution Approach 1:
The patent segments the frequency spectrum by introducing guard bands between adjacent optical channels. This segmentation isolates spectral energy leakage from one channel from affecting adjacent channels, thereby reducing interchannel interference while maintaining high channel density in gridless optical systems
Solution Approach 2:
The patent dynamically adjusts the bandwidth parameters of individual channels and the width of guard bands based on traffic requirements and interference conditions. By changing these parameters adaptively, the system optimizes bandwidth utilization while maintaining adequate isolation between channels to prevent interchannel interference
2Productivity
If guard bands are reduced to increase channel density, then channel spacing is improved, but clock recovery integrity deteriorates due to spectral energy leakage affecting the extracted data clock
Solution Approach 1:
The patent introduces guard bands as intermediary frequency regions between adjacent data channels. These guard bands act as mediators that absorb and isolate spectral energy leakage, preventing it from reaching the excess bandwidth regions where clock recovery is performed, thus protecting clock integrity while enabling tighter channel spacing
Solution Approach 2:
The patent addresses the clock recovery problem by operating in the frequency domain rather than solely in the time domain. By analyzing and managing spectral distribution across frequency dimensions, the system can identify and protect the excess bandwidth regions critical for clock recovery, even when channels are densely packed
3Reliability
If excess bandwidth is used for clock recovery at the receiver, then synchronization is improved, but adjacent channel interference increases as leaked energy affects the excess bandwidth area
Solution Approach 1:
The patent converts the harmful spectral energy leakage into a beneficial structure by designating specific frequency regions as guard bands. What would otherwise be interfering energy is channeled into controlled regions that do not overlap with the excess bandwidth used for clock recovery, thereby transforming potential interference into a protective mechanism
Solution Approach 2:
The patent extracts the clock recovery function from the main data channel spectrum by utilizing the excess bandwidth region separately. This extraction allows the system to dedicate specific frequency resources to clock synchronization while isolating them from data transmission frequencies, reducing mutual interference
4Productivity
If channel width is increased in fixed grid systems, then bandwidth utilization is improved, but device complexity increases due to the need for precise spectral management
Solution Approach 1:
The patent implements dynamic spectral management where channel widths, guard band widths, and frequency allocations are not fixed but can be adjusted in real-time based on traffic demands and interference conditions. This dynamic approach allows the system to optimize bandwidth utilization while adapting to changing conditions without requiring overly complex static configuration
Data Source
AI summary
Techniques and circuits are proposed to increase averaging in the clock recovery band based on an amount of channel overlap in receivers using excess bandwidth for clock recovery, to mitigate the impact of spectral energy leaking into an active channel of interest from an adjacent active channel and to improve the accuracy of the phase estimate of the received transmitted clock.