50 GBaud PON Modulation for Link-Margin-Based Rate Switching
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Solution Overview
Problem
Existing passive optical networks (PON) systems face limitations in data rate flexibility, with downstream rates fixed and upstream bursts varying, leading to reduced performance when link margins are insufficient for higher data rates.
Innovation Solution
A system that transmits 50 Gbps, 75 Gbps, and 100 Gbps at a single baud-rate using 2-bits per sample, employing NRZ, DSQ-8, and PAM-4 modulations, allowing dynamic switching based on link margin to optimize data rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher data rates (100 Gbps) are transmitted using PAM-4 modulation, then data rate is improved, but signal-to-noise ratio requirement increases making the system more sensitive to optical power loss
Solution Approach 1:
The system dynamically switches between PAM-4 and NRZ modulation schemes based on link conditions. When link margin is sufficient, PAM-4 provides 100 Gbps throughput. When link degradation is detected, the system transitions to NRZ modulation which is more robust to noise and power loss, maintaining reliable communication at 50 Gbps or lower rates.
Solution Approach 2:
The invention changes the modulation parameter (from PAM-4 to NRZ) in response to varying link conditions. This parameter change allows the system to adapt to different optical power loss scenarios, maintaining both high data rates when possible and reliability when link conditions deteriorate.
2Device complexity
If downstream rate is fixed at 50 Gbps for all links, then system complexity is reduced, but links with sufficient margin cannot operate at higher data rates
Solution Approach 1:
The downstream data rate is made dynamic rather than fixed. The OLT monitors link conditions and adjusts the downstream rate adaptively, allowing links with good margins to operate at 100 Gbps using PAM-4 while maintaining 50 Gbps or lower for links with higher power loss, optimizing overall network productivity.
Solution Approach 2:
The system changes the operating data rate parameter based on link quality assessment. This allows the network to exploit available link margin for higher throughput where possible, while automatically reducing rates on degraded links to maintain reliability.
3Ease of operation
If upstream bursts are transmitted at rates that are integer multiples of downstream rate, then synchronization is simplified, but granular control over upstream data rates is limited
Solution Approach 1:
The upstream burst rate is made dynamic and adaptive rather than strictly tied to integer multiples of downstream rate. The system can allocate upstream rates of 50 Gbps, 25 Gbps, 12.5 Gbps, or lower based on individual link conditions and service requirements, providing fine-grained control while maintaining practical synchronization through the PON protocol framework.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables faster data reception with granular control over downstream and upstream traffic, maintaining performance across varying link conditions without significant complexity or latency.
Implementation Method 1
50 Gbps is achieved using 50 GBaud NRZ
Implementation Method 2
100 Gbps is achieved using 50 GBaud PAM-4 (4-level modulation per sample)
Data Source
AI summary
In various embodiments, the present disclosure includes a system for sending 50 gigabits per second (Gbps), 75 Gbps, and 100 Gbps at 50 gigabaud (GBaud) for passive optical networks (PON) downstream and upstream. The system allows for transmission of three data rates at a single baud-rate while only using 2-bits of information per sample. A motivation for sending three data rates at a single baud-rate is to allow for further granularity in the control of the data-rates for downstream and upstream traffic in a flexible PON system based on the link margin. For example, the system can use non-return-to-zero (NRZ) at 50 GBaud for 50 Gbps and can use four-level pulse-amplitude modulation (PAM-4) at 50 GBaud for 100 Gbps. In addition for 75 Gbps, a double square-8 (DSQ-8) constellation can be used at 50 GBaud.