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Enhancing Burst Mode Capabilities in OLT and ONT: A Comprehensive Discussion Document

Explore the historical perspective, suggested path forward, and complexity considerations related to improving burst mode capabilities in OLT and ONT technologies. Learn how thoughtful design and loose maximum values can optimize efficiency.

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Enhancing Burst Mode Capabilities in OLT and ONT: A Comprehensive Discussion Document

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  1. Burst Mode Timing Ad-HocInitial Discussion Document Frank EffenbergerHuawei Technologies Co. Ltd

  2. Topics • Burst mode capabilities • Historical perspective • Suggested path forward

  3. Burst mode capabilities • OLT and ONT burst mode quality is highly dependent on technology used • Reuse of continuous mode parts yields rather poor timing (microseconds) • Use of specially customized circuits can yield quite fantastic timing (10’s ns) • However, such circuits are hard to get at first • Thoughtful design can obtain anything in between • The choice is generally a matter of cost and other pragmatic issues

  4. Historical Perspective • IEEE side: Loose specification of both • ONT got much better • OLT got somewhat better • But recovering the lost time is an issue • ITU side: Tight specification on both • ONT was never a problem • OLT was very hard, and eventually needed to be loosened • This caused a market delay

  5. What we’ve already agreed • Draft already captures the agreement: • To specify a “loose” maximum value of Ton and Toff (512ns) • ONU to report actual values via MPCP • OLT can thereby recover efficiency • Why not extend this concept to the OLT timing?

  6. Suggested path forward • Loose maximum values of Tagc and Tcdr are specified (400ns each) • Optionally, informative ‘suggestions’ on better values could be added: 200ns each for “AC coupled” designs, 50ns each for “dynamic coupled” designs • OLT is free to do better, of course • OLT broadcasts its burst-mode overhead requirements in the downstream • How long a series of 0x55 is needed • What amount of rise-time control is needed

  7. Complexity consideration • A downstream broadcast is not complicated • There is no negotiation • There is not much of a state machine impact • ONU must simply wait until it hears a verified “Downstream overhead” message • Once received, the ONU: • Sets the required parameters • Proceeds with the remainder of the activation state machine • It is expected that upstream overhead will be constant, therefore, other transitions are not needed

  8. Thank you !

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