CDR Module Clock Stability in Multi-Rate PON Downlink Frames
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Solution Overview
Problem
In passive optical networks (PONs), the clock and data recovery (CDR) module on the user side often experiences instability when handling data streams with multiple rates in time division multiplexing mode, leading to potential loss of the uplink transmit clock.
Innovation Solution
A status control method is implemented to control the CDR module to remain in a specified state within a period where the data rate exceeds its working rate, using indication information in downlink data frames to manage the clock recovery, thereby preventing clock instability and uplink clock loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If time division multiplexing mode is used to send data of different rates in one data stream, then data transmission efficiency is improved, but the CDR module cannot recover the clock of data of each rate, leading to clock instability
Solution Approach 1:
The patent segments the downlink data frame into multiple rate partitions (e.g., 10G partition and 2.5G partition), with each partition containing data of a specific rate. This segmentation allows the CDR module to process each rate separately and recover clocks independently for each partition, resolving the clock instability issue while maintaining time division multiplexing efficiency.
Solution Approach 2:
The patent introduces indication information in the downlink data frame that provides advance notification about the rate and length of data in each partition. This preliminary information allows the CDR module to prepare and switch to the appropriate working rate before processing each data partition, ensuring stable clock recovery without compromising transmission efficiency.
2Measurement precision
If the CDR module traces the phase of high-rate data, then data synchronization is improved, but the clock on the ONU side becomes unstable and uplink transmit clock may be lost
Solution Approach 1:
The patent makes the CDR module dynamic by enabling it to switch between different working rates based on the indication information received in the downlink data frame. Instead of continuously tracing high-rate data that causes instability, the CDR module dynamically adjusts its operating rate to match the current data partition rate, maintaining synchronization precision while preventing clock instability.
Solution Approach 2:
The patent changes the operating parameter (working rate) of the CDR module according to the data rate indicated in the downlink frame. By adjusting the CDR module's working rate to match the current data partition rate rather than continuously tracking high-rate data, the system maintains precise synchronization while avoiding the clock instability that occurs when tracing exceeds the CDR module's capabilities.
Data Source
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AI summary
This application discloses a status control method, applied to an ONU or an ONT of a passive optical network (PON). The method includes: receiving a first downlink data frame, where the first downlink data frame includes data of N different rates and indication information, the indication information includes length information of data of each rate in the first downlink data frame, and N ≥ 2; determining length information of first data in the data of the N different rates, where a rate of the first data is higher than a working rate of a CDR module; and generating control information based on the length information of the first data, to control the CDR module to be in a specified state within a period of time corresponding to the length information of the first data. In technical solutions of this application, the CDR module may be controlled to be in the specified state within the period of time in which a rate is higher than a working rate of the CDR module, thereby preventing a clock on an ONU side from being unstable, and also preventing an uplink sending clock from being lost.