Optical Receiver Frequency Offset Estimation Using Pilot Symbols
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Solution Overview
Problem
Existing optical receivers face challenges in quickly and efficiently calculating the initial value of optical frequency offset due to the trade-off between calculation speed and circuit size, leading to potential errors or increased power consumption.
Innovation Solution
An optical receiver design that incorporates pilot symbols modulated with QPSK and data symbols modulated with 16QAM, allowing for rapid calculation of the initial optical frequency offset using a reduced number of symbols, thereby reducing power consumption and circuit size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional methods are used to calculate initial optical frequency offset, then calculation accuracy is maintained, but calculation speed decreases and circuit size increases
Solution Approach 1:
The patent divides the frequency offset calculation into two distinct phases: a coarse estimation phase using pilot symbols to obtain initial value, and a fine estimation phase using data symbols to refine the value. This segmentation allows each phase to use optimized algorithms appropriate to its precision requirements, improving overall calculation speed while controlling circuit complexity.
Solution Approach 2:
The patent applies partial action by using only pilot symbols for the initial frequency offset estimation rather than processing all data symbols. This partial processing achieves sufficient initial accuracy with reduced computational load, and then refines the estimate using a smaller subset of data symbols, thereby reducing circuit size while maintaining calculation speed.
2Measurement precision
If conventional methods are used to calculate initial optical frequency offset, then calculation accuracy is maintained, but power consumption increases
Solution Approach 1:
The patent segments the frequency offset compensation process into two stages: initial estimation using pilot symbols with lower computational requirements, and fine estimation using data symbols. This segmentation reduces the total computational load compared to conventional methods that process all symbols uniformly, thereby reducing power consumption while maintaining overall calculation accuracy.
Solution Approach 2:
The patent uses partial action by performing initial frequency offset estimation using only pilot symbols rather than all transmitted symbols. This partial processing significantly reduces the number of calculations required, leading to lower power consumption, while the subsequent fine estimation using a limited number of data symbols ensures the necessary accuracy is achieved.
3Speed
If pilot symbols are used for frequency offset calculation, then calculation speed is improved, but calculation accuracy may decrease
Solution Approach 1:
The patent segments the frequency offset estimation into two phases: a coarse estimation phase using pilot symbols for rapid initial value acquisition, and a fine estimation phase using data symbols for accuracy refinement. This segmentation resolves the contradiction by assigning different precision requirements to different phases, allowing fast initial calculation followed by accurate refinement.
Solution Approach 2:
The patent implements feedback by using the initial frequency offset estimate obtained from pilot symbols as the starting point for the fine estimation using data symbols. This feedback mechanism allows the system to build upon the rapid initial estimate and progressively refine it, thereby achieving both speed and accuracy in the overall calculation process.
Data Source
AI summary
An optical receiver includes a receiver to receive an optical signal that includes a plurality of data symbols and pilot symbols periodically inserted between the plurality of data symbols and that is modulated based on a multi-level modulation method, a first angle calculator to calculate a first phase angle to be used for calculating an initial value when compensating for an optical frequency offset, based on the pilot symbols, a second angle calculator configured to calculate a second phase angle of the plurality of data symbols based on a data symbol adjacent to the pilot symbol, an estimator to estimate an amount of the optical frequency offset based on a differential phase angle between the first phase angle and the second phase angle and amplitude of the data symbol, and a compensator to compensate for the optical frequency offset based on the amount of the optical frequency offset.