ONT Automatic Self-Disabling System for Optical Collision Prevention
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Solution Overview
Problem
In passive optical networks, Optical Network Terminals (ONTs) lack a reliable mechanism to recognize unsynchronized states, leading to disruptions and service losses, as they continue transmitting outside assigned time slots, causing collisions and service disruptions to other ONTs, and existing solutions require costly hardware implementations for detection.
Innovation Solution
An automatic self-disabling system for ONTs that recognizes an uncontrolled state after a programmed number of ranging attempts with an optical signal, disabling transmission until a valid handshake signal is received from the OLT, allowing for automatic adjustment and self-resetting without human intervention, using firmware or hardware to manage time slots and handshake messages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ONTs continuously send handshake signals at random times to resume service after loss, then the ONT can attempt to re-establish connection, but this causes optical collisions and disruption of service to other ONTs
Solution Approach 1:
The ONT monitors downstream traffic from the OLT and uses this feedback to determine when to transmit handshake signals. By listening to the downstream optical traffic and detecting the absence of OLT signals, the ONT can safely resume transmission without causing collisions, thus maintaining service restoration capability while eliminating harmful optical collisions.
Solution Approach 2:
The ONT performs preliminary listening to downstream traffic before transmitting handshake signals. This preliminary action allows the ONT to assess the current network state and determine the appropriate timing for resumption, ensuring that transmission only occurs when the OLT is ready to accept handshakes, thereby preventing collisions while maintaining reliability.
2Ease of operation
If ONTs transmit outside assigned time slots to resume service, then the ONT can attempt to re-establish connection, but this disrupts the PON and causes service loss to other ONTs
Solution Approach 1:
The ONT uses feedback from downstream traffic monitoring to dynamically determine the optimal time for resumption. By continuously observing the optical traffic and detecting OLT presence, the ONT can safely resume service at the appropriate moment without disrupting the time-division multiplexed network, thus maintaining both operational flexibility and service continuity.
Solution Approach 2:
The system dynamically adjusts the resumption timing based on real-time downstream traffic conditions. Rather than using fixed or random transmission schedules, the ONT adapts its transmission timing based on the actual network state detected through downstream monitoring, allowing flexible service resumption while preserving network reliability and time slot discipline.
3Reliability
If hardware components like watchdog timers are introduced to detect excessive laser use, then the system can prevent disruptions, but this increases device complexity and cost
Solution Approach 1:
The ONT performs self-monitoring of downstream traffic and automatically determines when to resume transmission without external intervention. The system uses its own existing downstream reception capabilities to detect OLT presence and timing opportunities, eliminating the need for separate watchdog timers or external monitoring hardware, thus achieving disruption prevention while maintaining simplicity.
Solution Approach 2:
The ONT's downstream reception function is used for multiple purposes: normal operation monitoring and service resumption detection. By making the existing downstream monitoring capability serve dual functions, the system avoids adding specialized hardware for disruption prevention, thereby maintaining reliability while minimizing device complexity.
4Difficulty of detecting and measuring
If power level variation detection is used to identify uncontrolled ONTs, then the system can detect disruptions, but this requires costly hardware implementation and complex processing
Solution Approach 1:
The ONT uses feedback from downstream traffic monitoring to detect OLT presence and determine appropriate transmission timing. This feedback mechanism provides direct information about network state without requiring complex power level analysis or additional sensing hardware, thus simplifying the detection of uncontrolled transmission while maintaining accuracy.
Solution Approach 2:
The system replaces complex power level variation detection with a simpler optical traffic monitoring approach. Instead of measuring power level changes to identify disruptions, the ONT directly monitors the presence and timing of downstream optical signals from the OLT, providing a more straightforward and less resource-intensive method for detecting network state and preventing disruptions.
Data Source
AI summary
A system, method and computer readable medium comprising instructions for sending a message from an Optical Network Terminal (ONT) to an Optical Line Terminal (OLT), if the ONT does not receive an expected OLT action or an expected OLT response to the message within a period, considering the non-receipt of the expected OLT action or the expected OLT response a failure, and if a certain number of consecutive failures have occurred, considering by the ONT that it has entered an uncontrolled state.