Dual Preamble Insertion for Coherent PON Frequency Estimation
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Solution Overview
Problem
Simplified coherent receivers face challenges in extracting frequency and phase information due to limited data availability, making it difficult to correct frequency and phase errors in high-speed optical communication systems like 100 Gb/s PON, where traditional methods are not suitable.
Innovation Solution
Incorporating two preambles in the time-domain sequence of signals for frame synchronization and frequency correction, where the first preamble assists in coarse estimation of intermediate frequency and the second preamble facilitates fine correction of frequency and carrier phase recovery, without reducing optical power and with low computational complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional frequency and phase estimation schemes are used in simplified coherent receivers, then the method is well-established, but the receiver cannot extract sufficient frequency and phase information due to limited data availability
Solution Approach 1:
The patent inserts a dedicated preamble sequence before the actual data transmission. This preamble contains known training symbols that provide rich frequency and phase information in advance, enabling the simplified coherent receiver to perform accurate estimation before processing the actual data. The preamble acts as a preliminary action that prepares the receiver with necessary information that would otherwise be unavailable.
2Measurement precision
If preambles are inserted in the time-domain sequence for frequency correction, then frequency estimation accuracy improves, but inter-symbol interference may occur
Solution Approach 1:
The patent designs the preamble with specific local characteristics - using known training symbols with controlled amplitude and phase properties that are optimized for frequency estimation. The preamble section has different quality characteristics than the data section, with the training symbols specifically engineered to provide robust frequency information while minimizing interference effects on subsequent data symbols.
Solution Approach 2:
The preamble acts as an intermediary element between the transmitter and the actual data transmission. It provides a buffer zone with known characteristics that enables frequency correction without directly interfering with the data symbols. The preamble absorbs the frequency offset effects and provides correction information, protecting the actual data from inter-symbol interference.
3Measurement precision
If multiple preambles are used for both frame synchronization and frequency correction, then estimation accuracy improves, but device complexity increases
Solution Approach 1:
The patent designs a multi-functional preamble structure where the same preamble sequence serves multiple purposes: frame synchronization, coarse frequency offset estimation, and fine frequency/phase correction. By making the preamble universal and multi-functional, the system achieves high estimation accuracy without proportionally increasing complexity, as a single preamble element performs multiple tasks that would otherwise require separate structures.
Data Source
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AI summary
The objective of the embodiment of the present application is to provide a method and device for using preamble. The method of the embodiment of the present application comprises: inserting a first preamble and/or a second preamble in the time-domain sequence of a signal to be transmitted to an ONU device, wherein the first preamble is used for frame synchronization and coarse estimation of intermediate frequency, and the second preamble is used for fine correction of frequency and recovery of carrier phase; transmitting the signal containing the first preamble and/or the second preamble to the ONU device. The embodiment of the present application has the following advantages: by inserting two kinds of preambles in the time-domain sequence of a signal to be transmitted to an ONU device to assist the ONU device in frequency and phase estimation, the optical power of the effective signal will not be reduced with the way of inserting preambles in the time-domain sequence; the method according to this embodiment is easy to implement and has low computational complexity.