Active Optical Combiner for RFoG Upstream OBI Mitigation
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Solution Overview
Problem
Optical Beat Interference (OBI) limits upstream and downstream traffic in RFoG communication channels, and existing mitigation techniques are either ineffective or costly, as wavelength collisions still occur and require significant resource allocation.
Innovation Solution
An active optical combiner system that separates and amplifies upstream signals individually at each port, eliminating optical beat interference by not combining reverse signals optically, and using a transmission line structure to combine electrical signals, which reduces noise and increases bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple reverse path transmitters are powered on in traditional RFoG networks, then upstream traffic capacity increases, but Optical Beat Interference occurs when transmitters are close in wavelength
Solution Approach 1:
The patent segments the upstream signal combination process by separating the optical and electrical domains. Each ONU's optical signal is converted to electrical signal individually at separate OECs, then electrical signals are combined in the electrical domain through an RF combiner, avoiding optical domain interference while maintaining multi-transmitter capability
Solution Approach 2:
The patent introduces electrical signals as an intermediary medium between optical transmitters and the combiner. Optical signals from multiple transmitters are converted to electrical signals individually, allowing them to be combined without direct optical interaction, thus eliminating OBI while preserving upstream capacity
2Object-affected harmful factors
If existing OBI mitigation techniques are implemented at ONUs or CMTS, then interference is reduced, but system complexity and cost increase significantly
Solution Approach 1:
The patent replaces the optical domain combination mechanism with an electrical domain combination mechanism. Instead of using complex optical wavelength management or sophisticated scheduling algorithms, the system uses straightforward electrical signal combining through RF combiners, significantly reducing system complexity
Solution Approach 2:
The patent uses electrical signals as an intermediary to simplify the combination process. By converting optical signals to electrical signals at individual OECs before combining, the system avoids the need for complex optical wavelength control or intelligent scheduling, reducing both complexity and cost
3Productivity
If optical signals from multiple transmitters are combined optically in traditional RFoG, then signal aggregation is achieved, but Optical Beat Interference limits both upstream and downstream traffic
Solution Approach 1:
The patent introduces electrical signals as an intermediary between optical transmitters and the aggregation point. Each optical transmitter is converted to electrical signal individually through separate OECs, then electrical signals are aggregated through RF combiners, eliminating direct optical interaction and thus OBI while maintaining traffic capacity
Solution Approach 2:
The patent segments the signal aggregation process into individual optical-to-electrical conversion stages followed by electrical combination. This segmentation prevents multiple optical transmitters from interacting in the optical domain, eliminating OBI while preserving the ability to aggregate multiple upstream signals
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
The solution enhances upstream and downstream capacity, allows longer fiber lengths, and supports higher split counts, reducing costs and complexity while maintaining high performance and compatibility with existing systems.
Implementation Method 1
an output of the photodetector connected to an input of an amplifier
Implementation Method 2
an output of the photodetector connected to an input of an amplifier, an output of the amplifier connected to an input of a RF switch
Data Source
AI summary
Systems and methods for relaying upstream signals received from a plurality of subscribers to a remote head end. Some preferred embodiments include upstream transmitters in one or more Optical Network Units that may be dynamically and individually controlled to determine whether the upstream transmission is in burst mode or continuous mode.