WDM Laser Sources for PON Interference Avoidance
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Solution Overview
Problem
Current WDM-PON systems face high costs due to expensive optical amplifiers required for high subscriber capacity and lack effective protection mechanisms for centralized WDM sources.
Innovation Solution
Implementing a PON system with intermittent emission of upstream data channels by the OLT, using two sets of laser sources operating at the same wavelength but emitting alternately to avoid interference and ensure protection, and optimizing optical amplifiers to reduce power requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single wavelength channel is shared with multiple subscribers using TDM-PON, then per-subscriber cost is reduced, but per-subscriber bandwidth is sacrificed and the number of subscribers is limited to approximately 32
Solution Approach 1:
The invention segments the single wavelength channel into multiple time slots, with each time slot dedicated to a specific ONU. This time-division multiplexing approach allows multiple subscribers to share the same wavelength channel while maintaining dedicated bandwidth during their allocated time slots, thereby increasing the number of supported subscribers beyond the traditional limit of 32 while keeping per-subscriber cost low.
Solution Approach 2:
The system implements periodic time slots for each ONU, where each subscriber is allocated specific recurring time intervals for data transmission. This periodic structure enables efficient sharing of the wavelength channel among multiple subscribers, allowing the system to support more than 32 subscribers by cycling through them in organized time frames, thus increasing subscriber capacity without requiring additional wavelength channels.
2Quantity of substance
If WDM channels are added to increase subscriber capacity in WDM-PON, then per-subscriber bandwidth is maintained and more subscribers are supported, but system cost increases due to expensive WDM components
Solution Approach 1:
The invention makes the ONU universal by equipping it with both TDM and WDM interface capabilities. The ONU can operate in TDM mode for cost-sensitive applications or in WDM mode for higher performance requirements, allowing the same hardware platform to serve multiple functions and different service levels. This multi-functionality enables the system to support more subscribers through TDM time slot allocation while maintaining the option to upgrade to WDM for specific high-bandwidth users, thereby increasing subscriber capacity without proportionally increasing system cost.
3Ease of operation
If centralized WDM sources are used in RCM-PON to simplify wavelength management, then wavelength allocation control is improved and wavelength mismatch is avoided, but protection mechanisms for the WDM sources are lacking
Solution Approach 1:
The invention implements beforehand cushioning by pre-configuring backup protection mechanisms for the centralized WDM sources. When a wavelength failure is detected, pre-established backup paths or alternative wavelength assignments are activated to maintain service continuity. This prior preparation ensures that the centralized WDM sources have built-in protection against failures, maintaining both the simplified wavelength management advantage and the reliability required for production deployment.
Solution Approach 2:
The system implements feedback mechanisms that continuously monitor the status of centralized WDM sources and automatically trigger protective actions when anomalies or failures are detected. The feedback loop enables real-time detection of wavelength channel issues and initiates appropriate protection responses, such as switching to backup wavelengths or notifying the control system for reconfiguration. This feedback-based protection maintains the ease of wavelength management while ensuring source reliability through automated monitoring and response.
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
This approach reduces the cost of optical amplifiers and enhances protection for the WDM source, achieving a more cost-effective and reliable WDM-RCM-PON system with improved power budget and capacity.
Implementation Method 1
an optical modulator. Latter is used to modulate respectively a received remote optical signal according to a data stream to be uploaded
Implementation Method 2
an optical splitter connected to the first light source transmitter via a first principal optical transmission fiber to distribute each of the first remote optical signals of a specific wavelength via first secondary optical fibers to a plurality of optical network units
Implementation Method 3
the optical combiner forwards the modulated optical signals to a receiver of the OLT through a second principal optical transmission fiber
Data Source
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AI summary
A PON system comprises an OLT connected to an optical splitter via a first principal optical transmission fiber to distribute remote optical signals of a specific wavelength via first secondary optical fibers to a plurality of ONU. The ONUs modulate respectively the received remote optical signal according to data stream to be uploaded via the modulated optical signal as an upstream data channel from that ONU to an optical combiner via second secondary optical fibers being forwarded to a receiver of the OLT through a second principal optical transmission fiber. According to the invention, the light source transmitter at the OLT generates the remote optical signals for the upstream data channel non-permanently. And the optical paths for optical signals of same wavelength defined from the optical splitter to the optical coupler via the respective ONU and corresponding to the first and/or second secondary optical fibers is chosen such to introduce some specific delay on the optical signal of same wavelength modulated at the respective ONU to avoid interference when combined at the combiner.