Passive Optical Network Receiver Phase Estimation for CDR Initialization
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Solution Overview
Problem
In passive optical networks, the clock-and-data recovery process is hindered by initial phase errors, leading to inefficiencies and delays in synchronizing with incoming signals during burst-mode communication.
Innovation Solution
An optical receiver with phase estimation circuitry and clock-and-data recovery (CDR) circuitry that initializes with an estimate of the initial phase error by sampling at multiple positions within a unit interval, averaging temporal properties, and fitting a curve to determine the phase error, allowing for rapid compensation and synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the CDR circuitry is initialized with an arbitrary initial phase error, then the device complexity is reduced, but the synchronization time increases and communication efficiency deteriorates
Solution Approach 1:
The patent applies preliminary action by performing a quick phase estimation before the main CDR process to obtain an initial phase error estimate. This preliminary estimation uses a simplified method that samples the optical signal at multiple positions within unit intervals and fits a curve to determine the phase error, which is then used to initialize the CDR circuitry. This approach reduces the synchronization time without significantly increasing device complexity.
2Measurement precision
If multiple sampling positions are used to estimate initial phase error, then the measurement precision of phase error improves, but the processing time increases
Solution Approach 1:
The patent applies segmentation by dividing the unit interval into multiple smaller intervals and sampling at specific positions within each interval. This segmentation allows the system to obtain multiple samples at different positions (e.g., first sampling position, second sampling position, etc.) within each unit interval, which improves the accuracy of phase error estimation while keeping the overall processing time manageable through efficient curve fitting.
Solution Approach 2:
The patent applies parameter changes by varying the sampling positions and the number of samples collected at each position to optimize the balance between estimation accuracy and processing time. The system adjusts these parameters based on the specific requirements of the CDR process, using curve fitting techniques to efficiently determine the phase error from the collected samples.
Data Source
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AI summary
An optical receiver for a passive optical network, comprising a phase estimation circuitry and a clock-and-data recovery, CDR, circuitry, wherein the CDR circuitry is configured to be initialised with an estimate of an initial phase error between a received optical signal and a reference clock, and wherein the phase estimation circuitry is configured to estimate the initial phase error by: sampling a portion of an optical signal during consecutive unit intervals; wherein the sampling is performed in at least one of a plurality of possible sampling positions; wherein the sampling is performed such that a plurality of samples is obtained for each of the possible sampling positions; determining a temporal property in the respective sampling position at least from the plurality of samples corresponding to the possible sampling position; fitting a curve characterising the temporal property within a unit interval; and estimating the initial phase error from the fitted curve.