Fiber-to-coaxial tap device for HFC network point-to-point conversion

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Solution Overview

Problem

Hybrid fiber-coaxial (HFC) networks face inefficiencies due to their multipoint-to-point architecture, where passive taps require scheduling of transmissions to prevent collisions, limiting concurrent data transmission and bandwidth, and introducing signal losses through splitters and amplifiers.

Innovation Solution

The implementation of a fiber-to-coaxial tap device (FTD) that converts RF signals from subscriber cable modems to digital packets with source addresses, allowing concurrent transmission and eliminating the need for scheduling, and processes packets from a fiber node back to RF signals for specific modems, effectively transforming the network into a point-to-point architecture.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If passive taps are used to combine signals from multiple cable modems, then device complexity is reduced, but transmission efficiency deteriorates due to scheduling requirements and concurrent transmission limitations

Engineering Contradiction:

Improvedevice complexityVSAvoidtransmission efficiency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

An optical network unit (ONU) is introduced as an intermediary device between the coaxial network and the fiber optic network. The ONU performs optical-electrical-optical conversion and packet processing, enabling active management of upstream transmissions from multiple cable modems while maintaining the existing coaxial infrastructure. This mediator resolves the contradiction by providing intelligent scheduling and conversion capabilities without requiring complete system replacement.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If scheduling is implemented to prevent collisions in multipoint-to-point networks, then signal quality is maintained, but bandwidth is reduced due to limited concurrent transmissions

Engineering Contradiction:

Improvesignal qualityVSAvoidbandwidth

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The system transitions from a purely coaxial multipoint-to-point architecture to a hybrid architecture that adds a fiber optic dimension. Multiple cable modems can transmit simultaneously over coaxial cables to the ONU, which then transmits aggregated data over fiber optic cables. This dimensional change enables concurrent transmissions while maintaining signal quality through active management at the ONU.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Productivity

If fiber optic cables are installed directly to each subscriber, then transmission efficiency is maximized, but installation cost increases significantly

Engineering Contradiction:

Improvetransmission efficiencyVSAvoidinstallation cost

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The network is segmented into two distinct segments: an existing coaxial cable segment connecting cable modems to the ONU, and a new fiber optic segment connecting the ONU to the fiber node. This segmentation allows the system to achieve high transmission efficiency over the fiber segment while preserving the existing coaxial infrastructure, thereby reducing installation costs compared to complete fiber deployment.

Inventive Principle:

Principle #1Segmentation

4Device complexity

If passive taps with splitters and amplifiers are used, then device complexity is minimized, but signal losses increase

Engineering Contradiction:

Improvedevice complexityVSAvoidsignal losses

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The passive mechanical signal combining approach of traditional taps is replaced with an active electronic/optical system at the ONU. The ONU uses electronic signal processing and optical conversion to receive, process, and retransmit signals, eliminating the signal losses inherent in passive splitters and amplifiers while maintaining relatively simple device architecture.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 enables concurrent data transmission without collisions, increases bandwidth, and eliminates signal losses associated with traditional HFC networks, while reducing the need for costly fiber installations by utilizing existing coaxial drop cables.

Implementation Method 1

transmit the first digital packets to the fiber node via first optical signals

Methodology Applied

Scientific EffectOptical signal transmission: Optical Fibre

Data Source

PatentUS20250023640A1Transforming a multipoint-to-point HFC cable network to a point-to-point HFC network

Publication Date: 2025.01.16 CHARTER COMM OPERATING LLC

AI summary

A system that includes a fiber-to-coaxial tap device (FTD) that includes a plurality of coaxial connectors, the coaxial connectors operable to be communicatively coupled to corresponding ones of a plurality of subscriber cable modems via corresponding drop coaxial cables. The FTD further includes a fiber connector operable to be coupled to a fiber node via a fiber cable, and processing circuitry operable to receive, via each coaxial connector of the plurality of coaxial connectors, radio frequency (RF) signals originating from a corresponding originating subscriber cable modem, convert the RF signals to digital packets, wherein each digital packet includes a source address that corresponds to the corresponding originating subscriber cable modem, and transmit the digital packets to the fiber node via optical signals.