Shadow Fiber Network for HFC Upstream Congestion
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Solution Overview
Problem
Current hybrid fiber cable (HFC) systems face limitations in upstream data transmission bandwidth, leading to congestion and bottlenecks, especially in CATV systems where only a small frequency range is allocated for upstream data, restricting the ability of households and businesses to send high amounts of data effectively.
Innovation Solution
A 'shadow' optical fiber network is introduced to extend the functionality of HFC systems by running parallel to neighborhood CATV cables, using Coax Fiber Terminals (CFTs) to segregate and transmit upstream data via optical fibers, thereby alleviating congestion and increasing available bandwidth while maintaining backward compatibility with existing equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a small frequency range is allocated for upstream data in CATV systems, then downstream bandwidth is maximized, but upstream data transmission capacity is limited
Solution Approach 1:
The invention segments the upstream data transmission path by introducing shadow optical fibers that run parallel to the existing coaxial cable infrastructure. Coax Fiber Terminals (CFTs) are deployed at strategic points to intercept upstream data signals from coaxial cables and redirect them onto the shadow optical fiber network, effectively dividing the transmission load between the legacy coaxial system and the new optical fiber system.
Solution Approach 2:
Coax Fiber Terminals (CFTs) serve as intermediary devices that bridge the legacy coaxial cable network and the new shadow optical fiber network. The CFTs intercept upstream data signals on the coaxial cable, convert them to optical signals, and transmit them over the shadow optical fiber to the optical node, thereby mediating the data flow between two different transmission media.
2Quantity of substance
If optical fiber is extended to each household, then upstream bandwidth is maximized, but infrastructure cost and complexity increase significantly
Solution Approach 1:
Instead of fully replacing the coaxial cable infrastructure with optical fiber to every household, the invention applies partial action by deploying shadow optical fibers only for upstream data transmission while maintaining the existing coaxial cable system for downstream services. This selective approach provides optical fiber bandwidth benefits without the complete infrastructure overhaul.
Solution Approach 2:
The shadow optical fiber infrastructure is designed to serve multiple functions: it carries upstream data from multiple CFTs simultaneously using wavelength division multiplexing, provides high-bandwidth transmission capability, and integrates with the existing HFC network architecture. The optical node performs multiple tasks including receiving optical signals, converting them to RF signals, and managing multiple coaxial cable connections.
3Productivity
If Coax Fiber Terminals are deployed to intercept upstream data, then upstream congestion is reduced, but device deployment complexity increases
Solution Approach 1:
The Coax Fiber Terminal is designed as a self-contained device that autonomously performs signal interception, wavelength conversion, and optical transmission functions. The CFT automatically detects upstream data signals on the coaxial cable, converts them to appropriate optical wavelengths, and transmits them over the shadow optical fiber without requiring manual configuration or intervention, thereby reducing deployment complexity.
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 significantly increases upstream bandwidth by removing bottlenecks in CATV transmission, allowing for a 10× increase in available upstream data capacity with minimal changes to existing infrastructure, enhancing data transmission efficiency without requiring extensive upgrades to legacy systems.
Implementation Method 1
transmit this upstream data as optical signals to an optical node
Implementation Method 2
transform at least some of the upstream RF signals to upstream optical signals
Data Source
AI summary
System and method to extend the upstream data capacity of an HFC CATV system by extending a “shadow” optical fiber network deeper into the various CATV cable neighborhoods, with coax fiber terminals (CFT) spaced roughly according to the distribution of CATV active devices such as RF amplifiers. The CFT can intercept local upstream data from various neighborhood sub-regions and transform this upstream data into upstream optical data, thus relieving upstream data congestion in the 5-42 MHz CATV frequency region. The system can produce an order of magnitude improvement in upstream capability, while maintaining high compatibility with legacy HFC equipment. The CFT may exist in multiple embodiments ranging from low-cost “dumb” CFT to sophisticated CFT that can additionally provide GigE to the home (GTTH) service. Methods to maintain good compatibility with legacy CMTS devices, and methods to utilize DOCSIS MAP data for more efficient data transmission are also discussed.