Burst-mode Optical Receiver Phase Estimation for PON Synchronization
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Solution Overview
Problem
Burst-mode communication in passive optical networks (PONs) is hindered by significant communication overhead due to clock-and-data recovery (CDR) processes, which are critical for synchronizing with incoming optical burst signals but can be excessive, especially when dealing with non-idealities such as jitter and frequency offset.
Innovation Solution
An optical receiver is equipped with a phase estimation circuitry that performs a quick phase estimation to determine an initial phase estimate, which is used to correct the CDR process, reducing the need for extensive synchronization overhead by compensating for phase errors and allowing faster convergence to a synchronized clock phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If clock-and-data recovery (CDR) is implemented to synchronise with incoming optical burst signals, then data extraction reliability is improved, but communication overhead increases
Solution Approach 1:
The patent applies preliminary action by performing phase estimation before the full CDR process to obtain an initial phase estimate. This initial estimate is then used to seed the CDR process, reducing the time needed for synchronization while maintaining reliability. The phase estimation circuitry provides a head start on the synchronization process, avoiding the need to search for phase alignment from scratch each time a burst is received.
2Measurement precision
If extensive synchronization is performed to handle non-idealities like jitter and frequency offset, then synchronization accuracy is improved, but processing time increases
Solution Approach 1:
Phase estimation is performed as a preliminary action to obtain an initial phase estimate that accounts for non-idealities such as jitter and frequency offset. This initial estimate is then used to seed the CDR process, reducing the time needed for subsequent synchronization while maintaining accuracy in handling these non-idealities.
Solution Approach 2:
The system uses feedback from the phase estimation process to continuously refine the synchronization. The initial phase estimate obtained from phase estimation is fed back into the CDR process as a seed value, and the CDR process continuously adjusts based on actual signal conditions, creating a feedback loop that maintains synchronization accuracy while reducing processing time.
3Manufacturing precision
If phase estimation is performed for each burst signal, then phase error compensation is improved, but device complexity increases
Solution Approach 1:
The patent segments the synchronization process into two distinct functional blocks: phase estimation circuitry and CDR circuitry. The phase estimation circuitry handles the preliminary phase estimation and error compensation, while the CDR circuitry handles the main synchronization and data recovery. This segmentation allows each block to be optimized independently, managing overall device complexity while improving phase error compensation.
Data Source
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AI summary
An optical receiver, configured to receive optical burst signals in a passive optical network, PON; wherein the optical receiver comprises a clock-and-data-recovery, CDR, circuitry configured to synchronise a reference clock signal with a received optical burst signal starting from a configurable initial clock phase, thereby obtaining a synchronised data signal and a synchronised clock phase; wherein the optical receiver further comprises a phase estimation circuitry configured to estimate a phase of a received optical burst signal with respect to the reference clock signal and wherein the optical receiver is further configured to: receive a first optical burst signal; determine a phase estimate correction; receive a second optical burst signal; and obtain a corrected phase estimate; and, synchronise the reference clock signal with the corrected phase estimate as the configurable initial clock phase.