Active Optical Combiner for CATV OBI Elimination
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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, necessitating a more efficient solution to enhance capacity and reduce interference.
Innovation Solution
An active optical combiner system that separates forward and reverse path signals, using an active 1×32 splitter with individual detectors for each upstream signal, eliminating optical beat interference by not combining reverse signals optically and reducing the need for high-power EDFAs, thus allowing longer fiber lengths and higher split counts while maintaining signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional optical combiners are used to combine reverse path signals, then signal combining is achieved, but Optical Beat Interference (OBI) occurs that limits upstream and downstream traffic
Solution Approach 1:
The patent segments the reverse path signal handling by providing individual detectors for each upstream input port rather than combining signals optically first. This segmentation prevents OBI by keeping the optical paths separate through the combiner while enabling independent detection of each signal stream.
Solution Approach 2:
The patent introduces individual photodetectors as intermediary devices between the optical combiner output and the signal processing stage. These detectors convert optical signals to electrical signals before further processing, eliminating the need for optical signal combination that causes OBI while maintaining signal integrity.
2Reliability
If high-power EDFAs are used to compensate for signal loss, then signal quality is maintained, but system cost increases
Solution Approach 1:
The patent extracts the signal detection function from the optical domain to the electrical domain by using individual photodetectors for each input port. This eliminates the need for high-power EDFAs by performing detection before any potential signal degradation, thereby reducing system cost while maintaining signal quality.
3Length of stationary object
If fiber length is increased to extend network reach, then coverage area expands, but signal loss increases requiring higher power amplifiers
Solution Approach 1:
The patent performs preliminary signal detection at the optical combiner output using individual photodetectors before signals propagate through long fiber distances. This preliminary detection allows for early signal conversion to electrical domain, preventing cumulative optical signal loss that would otherwise require high-power amplifiers for compensation.
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 active optical combiner system significantly increases upstream and downstream capacity, supports longer fiber lengths, and reduces system costs by eliminating OBI, enabling higher data throughput rates and more efficient RFoG deployments.
Implementation Method 1
a photodetector coupled to the upstream input ports and configured to convert the combined optical signal to an electrical signal
Data Source
AI summary
Systems and methods for optical modulation index calibration in a CATV network.