Optical Network Unit Synchronization Using Psync and FEC Checks
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Solution Overview
Problem
In passive optical networks (PON), the process of entering a synchronization state is inefficient due to the need to search for specific synchronization sequences in consecutive data streams, which takes a long time and is prone to errors at high bit rates.
Innovation Solution
The method involves determining a pre-synchronization state by verifying a physical synchronization sequence (Psync) and a superframe counter (SFC) in the data stream, followed by decoding forward error correction (FEC) codewords to enter the synchronization state, utilizing multiple FEC codewords between Psyncs for efficient state transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ONU searches for synchronization sequences in consecutive data streams to enter synchronization state, then the synchronization can be achieved, but the time required to enter synchronization state becomes too long
Solution Approach 1:
The patent segments the synchronization process into two distinct states: pre-synchronization state and synchronization state. The pre-synchronization state uses a simplified verification method (checking only one Psync sequence) to quickly achieve preliminary synchronization, while the full synchronization state verification is performed later. This segmentation allows the system to trade off some verification completeness for significantly reduced synchronization time.
Solution Approach 2:
The patent implements preliminary synchronization action by entering a pre-synchronization state before full synchronization. In this preliminary state, the ONU performs basic Psync sequence verification to quickly establish initial synchronization without waiting for the complete verification process (which would require finding multiple Psync sequences separated by data frame intervals). This preliminary action dramatically reduces the time to enter synchronization state.
2Reliability
If the ONU uses traditional synchronization sequence searching method, then the synchronization state can be entered, but the process is prone to errors at high bit rates
Solution Approach 1:
The patent performs preliminary verification of the Psync sequence in the pre-synchronization state before committing to full synchronization. This preliminary action allows the system to detect and reject erroneous sequences early, preventing error propagation. The ONU can verify basic properties of the detected Psync sequence (such as its format and initial validation) before entering the pre-synchronization state, reducing the likelihood of incorrect synchronization at high bit rates.
Solution Approach 2:
The patent implements a feedback mechanism where the ONU continuously monitors the validity of the Psync sequence and SFC values. If verification fails or errors are detected during the pre-synchronization or synchronization state, the system can transition back to the pre-synchronization state or reset the synchronization process. This feedback loop ensures that erroneous synchronizations are detected and corrected, improving reliability at high bit rates.
Data Source
AI summary
A data processing method and a device, the method including determining, by an optical network unit, in a received data stream, after the optical network unit enters a pre-synchronization state, a position of a forward error correction (FEC) codeword boundary in the data stream based on a position of a physical synchronization sequence (Psync) field, performing an FEC codeword decoding check, where the Psync field is a field that matches a preset Psync, in the data stream, and entering, by the optical network unit, a synchronization state in response to an FEC codeword among N consecutive FEC codewords in the data stream passing the decoding check, where N is an integer greater than or equal to 1.