Delta-Sigma Digitization for Noise-Tolerant HFC Optical Links

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Solution Overview

Problem

Conventional hybrid fiber-coaxial (HFC) networks face limitations in achieving high data rates due to link loss and nonlinear noise, particularly with high-order modulation formats, which are not adequately addressed by existing analog optics technology, making it difficult to support increasing data demands without expensive infrastructure replacements.

Innovation Solution

The implementation of a digital optical network using delta-sigma modulation and demodulation techniques, which convert analog signals into digitized bit streams for transmission over digital optical links, effectively separating noise from the signal and allowing for higher modulation orders and longer distances, while reducing latency and data requirements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional analog optics technology is used in HFC networks, then existing infrastructure can be maintained, but link loss and nonlinear noise limit achievable data rates and transmission distances

Engineering Contradiction:

Improvetolerance to nonlinear noiseVSAvoiddata rate

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent replaces the conventional analog optical transmission system with a digital optical transmission system using delta-sigma modulation. This substitution transforms the transmission medium from analog to digital domain, fundamentally changing how signals are processed and transmitted over the optical fiber, thereby overcoming the limitations of analog optics regarding noise tolerance and data rate.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the fundamental parameter of signal representation from analog continuous waveforms to digital discrete bit streams. By using delta-sigma modulation to convert analog signals to digital form, the system achieves improved noise tolerance and higher data rates while maintaining compatibility with existing fiber infrastructure.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If high-order modulation formats are used to increase data rates, then bandwidth efficiency improves, but the system becomes more sensitive to nonlinear noise and intermodulation distortion

Engineering Contradiction:

Improvebandwidth efficiencyVSAvoidsensitivity to nonlinear noise

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent substitutes analog modulation schemes with digital delta-sigma modulation. This replacement allows the system to achieve high bandwidth efficiency through digital signal processing while being inherently more robust against nonlinear noise and intermodulation distortion that plague analog high-order modulation systems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If fiber infrastructure is replaced to support higher data rates, then network capacity increases, but deployment cost and complexity increase significantly

Engineering Contradiction:

Improvenetwork capacityVSAvoidinfrastructure replacement cost

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent makes the existing optical fiber infrastructure multi-functional by enabling it to carry digital delta-sigma modulated signals that can support higher data rates. Instead of replacing the fiber infrastructure, the system upgrades the signal processing layer, allowing the same physical medium to deliver enhanced network capacity at lower cost.

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Length of stationary object

If analog signals are transmitted over long distances, then network coverage expands, but link loss degrades signal quality

Engineering Contradiction:

Improvetransmission distanceVSAvoidsignal quality

Core Design Contradiction:

Length of stationary objectVSReliability

Solution Approach 1:

The patent replaces analog signal transmission with digital delta-sigma modulated signal transmission over the optical fiber. This substitution enables long-distance transmission while maintaining signal quality because digital signals are inherently more resistant to attenuation and noise accumulation over distance compared to analog signals.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS11323180B2System and methods for efficient digitization in a communication network

Publication Date: 2022.05.03 CABLE TELEVISION LAB INC

AI summary

An analog signal processor includes a sampling unit configured to (i) filter, in the frequency domain, a received time domain analog signal into a low-frequency end of a corresponding frequency spectrum, (ii) sample the filtered analog signal at a frequency substantially higher than the low-frequency end, and (iii) spread quantization noise over an expanded Nyquist zone of the corresponding frequency spectrum. The processor further includes a noise shaping unit configured to shape the spread quantization noise out of the low-frequency end of the corresponding frequency spectrum such that the filtered analog signal and the shaped quantization noise are substantially separated in the frequency domain, and a quantization unit configured to apply delta-sigma modulation to the filtered analog signal using at least one quantization bit, and output a digitized bit stream that substantially follows the amplitude of the received time domain analog signal.