Trunk and Drop RFoG Architecture Gain Control
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Solution Overview
Problem
Optical Beat Interference (OBI) and limited return link budget are significant issues in Radio Frequency over Glass (RFoG) networks, leading to signal degradation and reduced upstream and downstream traffic capacity.
Innovation Solution
The implementation of a trunk and drop architecture with individual gain control for trunk ports and average gain control for drop ports, along with high-performance low-noise receiver front-ends and EDFAs, to manage and amplify signals effectively, reducing OBI and enhancing signal-to-noise ratio (SNR).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple reverse path transmitters are powered on in RFoG networks, then upstream traffic capacity is improved, but Optical Beat Interference occurs causing signal degradation
Solution Approach 1:
The patent segments the RFoG network into multiple independent wavelength channels, where each transmitter operates on a distinct wavelength. This segmentation prevents OBI by ensuring that multiple transmitters do not interfere with each other, while still allowing all transmitters to operate simultaneously and maintain high upstream traffic capacity.
Solution Approach 2:
The patent introduces wavelength as an additional dimension for signal differentiation. By assigning different wavelengths to different transmitters, the system transforms the problem from a single-dimension (time-division) approach to a multi-dimensional (wavelength-division) approach, enabling simultaneous operation of multiple transmitters without OBI.
2Adaptability or versatility
If a star splitter distributes light over 32 subscribers, then network coverage is improved, but return link budget is reduced by 15 dB loss
Solution Approach 1:
The patent changes the operational parameters of the optical network by using wavelength-division multiplexing and independent gain control for each wavelength channel. This allows the system to maintain the star splitter configuration for broad coverage while compensating for the 15 dB loss through precise gain adjustment at each wavelength, thereby preserving the return link budget.
3Productivity
If multiple upstream inputs are combined in the same wavelength range, then upstream traffic capacity is increased, but optical beat interference overwhelms information content with noise
Solution Approach 1:
The patent segments the upstream traffic into multiple wavelength channels, with each channel carrying independent data streams. By combining these segmented channels in the wavelength domain rather than the time domain, the system increases overall traffic capacity while preventing OBI-induced noise from overwhelming the information content in each channel.
Solution Approach 2:
The patent uses wavelength-division multiplexing as an intermediary mechanism to combine multiple upstream inputs. Instead of directly combining signals in the same wavelength range (which causes OBI), the system uses wavelength multiplexing to separate and then combine signals in a controlled manner, preserving signal-to-noise ratio while increasing capacity.
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 significantly reduces OBI, improves signal quality, and increases the capacity of RFoG networks by maintaining precise overall gain and supporting higher data throughput rates, including 40 Gbps download and 10 Gbps upload speeds.
Implementation Method 1
The system utilizes high-performance low-noise receiver front-ends and EDFAs
Data Source
AI summary
In an optical system having multiple cascaded splitter/combiners, a trunk port and/or a drop port is configured for at least one of the splitter/combiner units. Drop ports may be configured with an average gain control, and the trunk ports may be configured to have individual gain control to provide a more precise overall gain and to maintain adequate signal levels. Embodiments apply to evolving RFoG architectures designed to serve a large number of subscribers without suffering from OBI (Optical Beat Interference) by retransmitting an optical signal through cascading splitters/combiners.