PON Scrambling Pattern Sync for Reliable Demultiplexed Upstream Data
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Solution Overview
Problem
In passive optical networks (PON) with increased line rates, such as 50G-PON, the physical separation of signal processing functions between distinct circuitries poses a challenge due to the need for high-bandwidth connections, leading to increased costs and uncontrolled demultiplexed data streams with undesirable bit sequences that can cause failure or suboptimal performance.
Innovation Solution
Implementing a scrambler and descrambler circuitry in optical network units (ONUs) and optical line terminals (OLTs) to scramble and descramble data streams using a periodic scrambling pattern, allowing for lower baud rate data exchange and adaptive control of scrambling patterns to avoid undesirable bit sequences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If physical separation of signal processing functions is implemented in high-line-rate PON systems, then functional flexibility and location optimization are improved, but bandwidth requirements and cost increase substantially
Solution Approach 1:
The patent divides the high-rate data stream into multiple lower-rate demultiplexed data streams. By segmenting the 50G PON signal into multiple lanes (e.g., four 10G streams or two 25G streams), the bandwidth requirement for each individual connection between distinct circuitries is reduced, thereby lowering cost while maintaining functional flexibility.
2Quantity of substance
If demultiplexed data streams are used to reduce bandwidth requirements, then cost is reduced, but undesirable bit sequences occur causing signal processing failure
Solution Approach 1:
The patent applies scrambling to the demultiplexed data streams before transmission between circuitries. This preliminary action modifies the bit sequences in advance to prevent the occurrence of undesirable patterns (such as long sequences of identical bits) that would cause clock recovery failure or signal processing issues at the receiving end.
Solution Approach 2:
The patent changes the parameters of the data stream by applying scrambling transformations. This modifies the statistical properties and bit sequence characteristics of the demultiplexed streams, ensuring they meet the requirements for reliable signal processing while maintaining the reduced bandwidth benefits of demultiplexing.
3Reliability
If scrambling is applied to demultiplexed data streams, then signal processing reliability is improved, but synchronization complexity increases
Solution Approach 1:
The patent introduces a reference sequence as an intermediary element that facilitates synchronization between transmitter and receiver scramblers/descramblers. This reference sequence acts as a mediator that carries synchronization information, allowing the receiving circuitry to properly align and descramble the data streams without requiring complex synchronization mechanisms.
Data Source
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AI summary
Example embodiments describe an optical network unit (210), ONU, configured to transmit data (232) to an optical line terminal (110), OLT, during upstream timeslots (201, 204, 206) within a passive optical network; wherein the ONU comprises a scrambler circuitry (220) configured to scramble (226, 227) at least one data stream (222, 223) according to a periodic scrambling pattern (228), and a descrambler circuitry (240) configured to descramble (243, 244) the at least one scrambled data stream (230, 231) according to the periodic scrambling pattern; and wherein the ONU further comprises at least one data channel (251, 252) for exchanging the at least one scrambled data stream between the scrambler circuitry and the descrambler circuitry; and wherein the scrambler circuitry is further configured to perform, during a period (203, 205) between the upstream timeslots: scrambling a predetermined reference sequence (221a, 221b) according to the periodic scrambling pattern, thereby obtaining a scrambled reference sequence; and sending the scrambled reference sequence to the descrambler circuitry over the at least one data channel.