Active Receiver Structure for RFoG Networks
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Solution Overview
Problem
Radio Frequency over Glass (RFoG) networks face challenges with Optical Beat Interference (OBI) and limited return link budget, leading to high noise levels and reduced signal-to-noise ratio (SNR), which impede efficient upstream traffic and overall network performance.
Innovation Solution
An active receiver structure is designed with multiple detectors and an optical multiplexer structure around an active splitter, allowing for the combination of RFoG signals without bandwidth penalty and improving SNR, while eliminating OBI by individually terminating reverse signals at separate detectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple reverse path transmitters are powered on in traditional RFoG networks, then network capacity and bandwidth are improved, but Optical Beat Interference (OBI) occurs causing high noise levels and reduced signal-to-noise ratio
Solution Approach 1:
The patent segments the optical reception function into multiple independent photodetectors, each receiving and converting optical signals from different transmitters independently. This segmentation prevents optical beats between transmitters while allowing multiple transmitters to operate simultaneously, thus maintaining network capacity without OBI interference
Solution Approach 2:
The patent introduces an intermediary optical combining structure that directs optical signals from multiple transmitters to separate photodetectors. This intermediary structure mediates between the multiple transmitters and the reception system, enabling simultaneous operation without direct optical interaction that causes beats
2Productivity
If optical signals are combined using traditional optical combiners, then signal aggregation is achieved, but noise levels increase and signal-to-noise ratio deteriorates
Solution Approach 1:
The patent replaces the traditional optical combining mechanism with a direct optical-to-electrical conversion approach using multiple photodetectors. Instead of combining optical signals optically (which generates noise), the system converts optical signals to electrical signals independently at each detector, eliminating the noise-generating optical combination process
3Productivity
If a single large-area photodetector is used to collect optical signals from multiple transmitters, then signal collection efficiency is improved, but detector capacitance increases limiting achievable bandwidth
Solution Approach 1:
The patent segments the detection function across multiple smaller photodetectors instead of using one large detector. Each small detector has low capacitance and high bandwidth capability, while collectively they provide sufficient signal collection from multiple transmitters through parallel operation
Solution Approach 2:
The patent transitions from a single-dimension approach (one large detector) to a multi-dimensional parallel architecture where multiple detectors operate simultaneously. This dimensional change from serial to parallel detection enables both high signal collection and high bandwidth by distributing the detection load across multiple independent elements
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 solution enhances the SNR and reduces noise interference, enabling higher capacity and longer reach in RFoG networks, supporting up to 40G downstream and 10G upstream speeds with reduced costs and power consumption.
Implementation Method 1
an array of photodetectors, each configured to receive a respective one of the plurality of optical inputs and convert the received optical signal to an electrical signal
Implementation Method 2
a transmission line structure that aggregates a large number of the photodetectors into a single electrical receiver
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
An active receiver structure that combines a large number of detectors without bandwidth penalty may provide a better signal-to-noise ratio (SNR) than conventional Radio Frequency over Glass (RFoG) networks. A transmission line receiver is used to combine a large number of optical detectors into a single radio frequency (RF) signal without a bandwidth penalty and a modest penalty in noise performance that results in an SNR that is much better than traditional optical combining techniques that are followed by a single detector. An optical multiplexer structure may be designed around the active splitter such that passive optical network (PON) operation is not impeded.