Optical Frequency Offset Compensation in Signal Processing
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Solution Overview
Problem
In digital coherent transmission, accurately estimating and compensating for optical frequency offsets between light sources on the transmission and reception sides is challenging, especially when the offset exceeds a detectable range, leading to difficulties in setting initial tap coefficients for adaptive equalization processing.
Innovation Solution
A signal processing device that estimates the optical frequency offset using synchronization training sequence signals, generates multiple candidates for the compensation value, calculates the power of the optical signal compensated for the offset, and selects an initial compensation value based on the power to expand the estimable range of the optical frequency offset.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional adaptive equalization processing is used with standard initial value setting, then the processing can be performed, but the estimation range of optical frequency offset is limited and cannot accommodate large offsets
Solution Approach 1:
The patent segments the optical frequency offset compensation process into multiple stages: first estimating the offset using correlation processing with training sequences, then refining the estimation through power calculation and candidate selection. This segmentation allows the system to handle large frequency offsets by breaking down the estimation into manageable steps, expanding the overall estimation range while maintaining precision.
Solution Approach 2:
The patent changes the parameter approach by calculating power values for multiple candidate compensation values and selecting the initial value based on power comparison. This parameter change enables the system to adapt to different offset magnitudes by evaluating multiple possibilities and selecting the optimal one, thereby expanding the estimation range without sacrificing accuracy.
2Adaptability or versatility
If multiple candidates for compensation value are generated and power calculation is performed, then the estimation range is expanded, but the processing complexity increases
Solution Approach 1:
The patent implements feedback by calculating the power of the optical signal for each candidate compensation value and using this power information to select the optimal initial value. This feedback mechanism automatically guides the selection process, reducing the need for complex manual configuration while expanding the estimation range through systematic evaluation of multiple candidates.
Solution Approach 2:
The system performs self-service by automatically selecting the optimal initial compensation value based on power comparison without requiring external intervention. The processor autonomously evaluates multiple candidates and determines the best initial value, simplifying the overall process complexity while maintaining expanded estimation capability.
3Reliability
If accurate initial tap coefficient setting is achieved, then adaptive equalization performance improves, but the difficulty of detecting and measuring optical frequency offset increases
Solution Approach 1:
The patent introduces power calculation as an intermediary step between frequency offset estimation and tap coefficient setting. By calculating the power of the compensated signal for each candidate and using this as a selection criterion, the system creates a bridge that simplifies the detection process while ensuring accurate initial tap coefficient setting, thereby improving adaptive equalization performance without increasing measurement difficulty.
Data Source
AI summary
A signal processing device includes: a memory; and a processor coupled to the memory and configured to: compensate an electric field signal representing an electric field component in an optical signal input from a transmission channel for an optical frequency offset between light sources on a transmission side and a reception side of the optical signal based on a compensation value; calculate an estimated value of the optical frequency offset from data having a fixed pattern in the electric field signal; generate a plurality of candidates for the compensation value from the estimated value; calculate power of the optical signal compensated for the optical frequency offset based on each of the plurality of candidates; and select an initial value of the compensation value from the plurality of candidates based on the power of the optical signal.