Delta-Sigma Digitization for High-Order 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 analog linear distortions, particularly with high-order modulation formats, and are unable to keep up with increasing data demands, while replacing these networks is impractical and expensive.
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 without requiring significant hardware modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional HFC networks use high-order modulation formats to increase data rates, then bandwidth capacity is improved, but link loss and analog linear distortions worsen signal quality
Solution Approach 1:
The patent replaces the conventional analog signal processing system with a digital signal processing system. Specifically, it introduces a digital signal processor that performs digital filtering, modulation, and signal regeneration, substituting the analog electronic system to overcome the limitations of analog linear distortions and enable reliable high-order modulation formats
Solution Approach 2:
The patent changes the fundamental parameter of signal representation from analog continuous waveforms to digital discrete samples. By converting analog signals to digital form using ADC (analog-to-digital conversion) and processing them through digital signal processing algorithms, the system achieves immunity to analog linear distortions and enables higher modulation orders
2Productivity
If HFC networks are replaced with new infrastructure to meet increasing data demands, then network capacity is improved, but deployment cost and complexity increase
Solution Approach 1:
The patent makes the existing HFC network infrastructure universal by enabling it to support both traditional analog services and new digital high-capacity services through the same physical medium. The digital signal processing unit can handle multiple modulation formats and service types, allowing the existing fiber-coaxial infrastructure to be upgraded to meet increasing data demands without complete replacement
Solution Approach 2:
The patent introduces a digital signal processing unit as an intermediary component between the existing analog HFC infrastructure and the required digital high-capacity services. This intermediary performs analog-to-digital conversion and digital signal processing, enabling the legacy infrastructure to deliver modern digital services without requiring complete infrastructure replacement
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 approach enhances the tolerance to nonlinear noise, supports higher modulation formats, and enables longer transmission distances, reducing latency and improving reliability, thus extending the life of existing fiber infrastructures and increasing network scalability.
Implementation Method 1
analog-to-digital (A/D) conversion techniques, which utilize delta-sigma modulation
Implementation Method 2
a noise shaping unit configured to shape the spread quantization noise out of the low-frequency end of the corresponding frequency spectrum
Implementation Method 3
An optical fiber 110 carries optical analog signals and connects the link between master headend 102, hub 104, and fiber node 106
Implementation Method 4
fiber node 106 converts the optical analog signals from optical fiber 110 into the RF modulated electrical signals
Implementation Method 5
A plurality of coaxial cables 112 carry radio frequency (RF) modulated analog electrical signals and connect fiber node 106 to respective end users 108
Implementation Method 6
HFC network 100 may further utilize electrical amplifiers 114 respectively disposed along coaxial cables 112 to amplify the RF analog signals to respective end users 108
Data Source
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.