Optical Coherent Receiver Frequency Offset Estimation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current optical coherent receivers face challenges in accurately and efficiently estimating frequency offsets within a wide range (-5 GHz to +5 GHz) due to high computational complexity and limited range, which is critical for stable and precise optical communication systems.
Innovation Solution
A frequency offset estimating apparatus comprising a phase offset calculating section, a phase offset change calculating section, an ambiguity deciding section, and a loop filtering section, which reduces computational complexity by eliminating the need for complex number multiplication and provides a wider range of frequency offset estimation through ambiguity removal and weighted averaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex number multiplication and quartic calculation are used for frequency offset estimation, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts and removes the ambiguous phase component from the frequency offset estimation process. By separating the phase offset calculation from the frequency offset calculation, the method eliminates the need for complex quartic calculations while maintaining estimation precision through the use of phase offset change rate instead of direct phase analysis
Solution Approach 2:
The patent replaces complex mathematical operations (complex number multiplication and quartic calculation) with simpler differential operations. The frequency offset is obtained by calculating the time derivative of the phase offset, which involves only basic differentiation and filtering operations rather than complex algebraic manipulations
2Device complexity
If the frequency offset estimation range is limited to [-Br/8, +Br/8], then device complexity is reduced, but the usable frequency offset range becomes insufficient for actual optical communication systems
Solution Approach 1:
The patent changes the fundamental parameter used for frequency offset estimation from direct phase analysis to phase offset change rate. This parameter transformation allows the system to handle larger frequency offsets because the derivative operation naturally scales with the frequency range, removing the artificial limitation of [-Br/8, +Br/8] and enabling coverage of [-5 GHz, +5 GHz] and beyond
3Device complexity
If phase offset change is calculated without ambiguity removal, then device complexity is reduced, but measurement precision deteriorates due to phase wrapping ambiguity
Solution Approach 1:
The patent introduces a feedback mechanism where the calculated frequency offset is used to compensate for phase wrapping ambiguity in subsequent measurements. By continuously tracking and correcting for phase discontinuities, the system maintains high measurement precision without requiring complex ambiguity resolution algorithms
Data Source
AI summary
The present invention discloses an optical coherent receiver, and a frequency offset estimating apparatus and a frequency offset estimating method for use in the optical coherent receiver. The optical coherent receiver includes a front end processing section for changing an optical signal into a base band digital electric signal. The frequency offset estimating apparatus comprises a phase offset calculating section, for calculating a phase offset in said base band digital electric signal; a phase offset change calculating section, for calculating a change of said phase offset, namely a phase offset change, in accordance with the phase offset calculated by said phase offset calculating section; an ambiguity deciding section, for deciding whether there is ambiguity in said phase offset change calculated by said phase offset change calculating section, and outputting the phase offset change having no ambiguity; and a loop filtering section, for acquiring a weighted average of the phase offset change outputted by said ambiguity deciding section.