Optical Line Terminal Scheduling for Power Variation Reduction
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Solution Overview
Problem
In passive optical networks, the varying distances between optical network units (ONUs) and the optical line terminal (OLT) result in differing power levels of optical bursts received upstream, causing challenges for optical receivers due to phase and power variations, which can lead to incorrect data interpretation and increased settling times.
Innovation Solution
The OLT measures and adjusts for signal strength variations by scheduling transmission timeslots based on the power levels of optical bursts, using automatic gain control and clock/data recovery processes to optimize the order of transmission and minimize power differences between consecutive bursts, thereby reducing the settling time of the optical receiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ONUs transmit optical bursts asynchronously during allocated time slots, then bandwidth sharing and collision avoidance are achieved, but power level variations at the OLT receiver increase
Solution Approach 1:
The system performs preliminary actions by measuring signal strength of optical bursts before scheduling transmission timeslots. The OLT uses these measurements to determine a preferred transmission order that groups bursts with similar power levels together, thereby proactively minimizing power variations at the receiver without requiring real-time adjustments during transmission.
Solution Approach 2:
The scheduling of transmission timeslots is made dynamic based on measured signal strength variations. The OLT adapts the transmission order of ONUs according to their measured power levels, creating a dynamic scheduling system that responds to actual channel conditions rather than using fixed time slot assignments.
2Adaptability or versatility
If optical bursts with varying power levels are received, then upstream transmission from multiple ONUs is supported, but settling time of the optical receiver increases
Solution Approach 1:
The system measures signal strength of optical bursts in advance and uses these measurements to determine the preferred transmission order before actual data transmission begins. This preliminary characterization of power levels allows the system to pre-plan the transmission sequence to minimize receiver settling time.
Solution Approach 2:
The system changes the scheduling parameter (transmission order of timeslots) based on the measured power level parameter. By adjusting the transmission sequence according to power level similarities, the system optimizes receiver performance and minimizes settling time while maintaining support for multiple ONUs.
3Loss of time
If signal strength measurements are performed and transmission order is optimized, then receiver settling time is reduced, but system complexity increases
Solution Approach 1:
The system implements feedback by measuring the signal strength of optical bursts from each ONU and using these measurements to determine the preferred transmission order. The OLT continuously monitors power levels and adjusts the scheduling accordingly, creating a closed-loop system that optimizes performance based on actual channel conditions.
Solution Approach 2:
The system changes the scheduling parameters (transmission timeslot assignment and order) based on measured signal strength parameters. This parameter adaptation allows the system to reduce settling time while managing complexity through systematic optimization rather than complex real-time control mechanisms.
Data Source
AI summary
A signal strength corresponding to an incoming optical burst from each of a plurality of optical nodes is measured. The measurements can be performed at system start-up, configuration/installation of the optical nodes and/or at certain intervals of operation of the optical nodes. Signal strength information for the optical nodes based on the measurements is stored in memory. When scheduling the optical nodes for transmission, a preferred transmission order is determined in response to the stored signal strength information. In an embodiment, the preferred order is determined to reduce differences in signal strength levels between consecutive optical bursts.