Optical Transmission Mapping Control for Jitter Reduction
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Solution Overview
Problem
Conventional optical transmission networks using asynchronous accommodating methods generate low-frequency jitter due to frequency differences between client and server signals, limiting the reduction of jitter components.
Innovation Solution
An optical transmission apparatus that includes a mapper unit and a mapping control unit to determine the number of client data pieces and their timing for mapping, allowing random insertion into the payload portion, thereby controlling the stuffing and de-stuffing processes to reduce low-frequency jitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If asynchronous accommodating method is used to accommodate client signals in server signal, then data loss is prevented through stuffing operation, but low-frequency jitter (WTJ) is generated due to frequency difference between client and server signals
Solution Approach 1:
The patent applies dynamics by making the stuffing threshold variable rather than fixed. The threshold is randomly changed over time, which transforms the static stuffing operation into a dynamic process. This dynamic adjustment prevents the regular periodic stuffing that causes low-frequency jitter, while still maintaining data integrity through adaptive stuffing control in the elastic store memory
Solution Approach 2:
The patent changes the parameter of stuffing threshold from a constant value to a randomly varying value. By randomly changing the threshold, the stuffing operation timing becomes unpredictable, which converts low-frequency jitter components into higher frequency components that can be filtered by the PLL, thus reducing WTJ while maintaining reliable data accommodation
2Stability of the object's composition
If stuffing operation is performed with low cycle due to small frequency difference, then data synchronization is maintained, but low-frequency jitter components cannot be removed because PLL bandwidth is limited
Solution Approach 1:
The patent introduces dynamics into the stuffing operation by randomly varying the threshold. This causes the stuffing cycle to vary dynamically rather than occurring at fixed low intervals. The random variation transforms the spectral characteristics of the jitter, moving energy from low frequencies into higher frequencies that the PLL can filter, while still maintaining synchronization through adaptive control
Solution Approach 2:
The patent uses a form of periodic action with random variation in the stuffing threshold. By periodically updating the threshold with random changes, the system creates an irregular stuffing pattern that avoids the problematic low-frequency periodicity. This approach maintains synchronization while transforming jitter spectral content to be removable by the PLL
3Object-affected harmful factors
If de-stuffing timing is made random to reduce jitter amount, then low-frequency jitter is reduced, but the stuff and de-stuff settings are restricted by the OTU frame structure
Solution Approach 1:
The patent applies local quality by introducing randomness specifically in the stuffing threshold parameter within the elastic store memory, while maintaining the overall OTU frame structure intact. The randomization is localized to the threshold value that controls stuffing timing, allowing jitter reduction without disrupting the global frame synchronization and structure required by the OTN system
Data Source
AI summary
An optical transmission apparatus that accommodates client signals in a line signal, includes: an OPUn mapper unit that receives and maps the client signals; and a mapping control unit that determines the number of pieces of client data to be mapped to a payload portion and determines the timing to insert client data and information on the number of pieces of client data into the payload portion to control mapping performed in the OPUn mapper unit.