Optical Receiving Apparatus Frequency Offset Estimation
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Solution Overview
Problem
In digital coherent systems for optical communication, estimating frequency offset in access networks with a wide estimation frequency range and short processing time is challenging due to the use of inexpensive light sources, leading to larger frequency variations and the need for frequent estimation in PON systems, where existing methods either limit estimation range or increase code sequence length, affecting communication efficiency.
Innovation Solution
An optical receiving apparatus that uses a training code sequence with multi-value phase modulation symbols and a fixed, repeated modulation phase difference pattern, allowing for precise frequency offset estimation by calculating averaged frequency offset amounts from multiple delay differential components, reducing the need for long code sequences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the code sequence length is increased to improve frequency offset estimation precision, then measurement precision is improved, but productivity deteriorates due to reduced communication efficiency
Solution Approach 1:
The patent segments the frequency offset estimation process by using multiple delay differential components with different delay periods. Instead of using a single long code sequence, the method divides the estimation into multiple smaller components that can be processed independently and then combined, reducing the required code sequence length while maintaining estimation precision.
Solution Approach 2:
The patent applies partial action by using only the necessary portion of the code sequence for estimation. By utilizing multiple delay differential components, the method achieves accurate frequency offset estimation without requiring the full length of traditional estimation sequences, thus improving communication efficiency.
2Device complexity
If a conventional frequency offset estimation method is used to simplify the estimation process, then device complexity is reduced, but measurement precision deteriorates due to limited estimation frequency range
Solution Approach 1:
The patent introduces dynamics by making the estimation process adaptable to different frequency offset conditions. The method uses multiple delay differential components that can handle a wide range of frequency offsets, allowing the system to maintain precision across varying conditions without increasing overall device complexity.
Solution Approach 2:
The patent changes the parameter of delay period in the differential components to create multiple estimation perspectives. By varying the delay periods and combining the results, the system achieves wide frequency offset estimation range and high precision without requiring complex device architecture.
3Measurement precision
If multiple delay differential components are calculated to improve frequency offset estimation precision, then measurement precision is improved, but use of energy increases due to additional calculations
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the delay differential components during the training signal period. This allows the frequency offset estimation to be performed efficiently during data transmission without requiring excessive real-time processing energy, as the heavy computational work is done in advance.
Data Source
AI summary
Upon receipt of a coherent optical signal that includes a training signal generated using a code sequence constituted by multi-value phase modulation symbols, in which a deviation angle of a vector average of a one-symbol delay differential component of a signal generated on the basis of the code sequence has a prescribed angle and a modulation phase difference between adjacent symbols has a fixed, repeated pattern, a reception training signal corresponding to a training code sequence for frequency offset estimation is detected within a reception signal acquired by converting the received coherent optical signal into an electric signal, a plurality of delay differential components are calculated on the basis of the detected reception training signal and at least two delay signals of the reception training signal, each delay signal having a different number of delay symbols, and an averaged frequency offset amount is calculated using the calculated plurality of delay differential components.