OFDMA-PON Upstream Link Using Segmented Wavelength Channels
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Solution Overview
Problem
The commercialization of orthogonal frequency division multiple access-passive optical network (OFDMA-PON) is hindered by the lack of high-speed digital signal processors and data converters capable of real-time operation for high-speed sampling, which is essential for efficient upstream data transmission.
Innovation Solution
The implementation of a simplified upstream optical link structure using a digital signal processor, digital-to-analog converter, and electrical IQ-modulator to generate and transmit orthogonal frequency division multiplexing subcarriers, along with an optical line terminal that includes an optical receiver, IQ-demodulator, and analog-to-digital converter to manage frequency division multiplexing, ensuring cost-effectiveness and efficient resource utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high-speed digital signal processors and data converters are used to support real-time high-speed sampling, then transmission speed and capacity are improved, but system cost and complexity increase significantly
Solution Approach 1:
The patent segments the optical network units into different groups, with each group assigned to a specific wavelength channel. This segmentation allows independent processing of signals on different wavelengths, reducing the need for high-speed processing at each individual node while maintaining overall system capacity through parallel wavelength-division multiplexing.
Solution Approach 2:
The patent introduces wavelength as an intermediary dimension for signal separation and processing. By mapping different ONU groups to different wavelengths, the system achieves high-capacity transmission without requiring each ONU to process all signals at high speed, thus reducing device complexity while maintaining transmission capacity.
2Speed
If high-speed data converters are implemented to support real-time operation, then sampling speed is improved, but cost-effectiveness deteriorates
Solution Approach 1:
The patent divides the optical network into multiple wavelength channels, each serving a specific group of ONUs. This segmentation allows each data converter to operate at lower speeds appropriate for its assigned wavelength group, rather than requiring all converters to support the full system bandwidth, thereby reducing cost while maintaining overall sampling capacity.
Solution Approach 2:
The patent changes the operating parameters of data converters by assigning different sampling rate requirements to different wavelength channels based on their traffic loads and distance requirements. This parameter differentiation allows the use of lower-cost, lower-speed converters for less demanding applications while maintaining high-speed capability where necessary.
3Productivity
If full-size inverse fast Fourier transform is used for OFDM modulation, then spectral efficiency is improved, but processing complexity increases
Solution Approach 1:
The patent segments the large-scale OFDM processing into smaller, wavelength-specific processing tasks. Each wavelength channel performs FFT/IFFT operations only on the subcarriers assigned to its group of ONUs, rather than processing the entire system's worth of subcarriers. This segmentation reduces per-node processing complexity while maintaining overall spectral efficiency through parallel wavelength-division multiplexing.
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 configuration enables cost-effective, high-capacity, and long-reach transmission by allocating subcarriers efficiently, reducing the need for high-speed data converters and allowing for transparent OFDM signal transmission, thereby enhancing network resource management and reducing processing complexity.
Implementation Method 1
The electrical IQ-modulator may be configured to perform a frequency up-shift on the orthogonal frequency division multiplexed signal, which is converted into the analog form, for frequency division multiplexing that is allocated to each optical network unit
Implementation Method 2
The optical signal processor may modulate the electrical orthogonal frequency division multiplexed signal into an optical signal having a single wavelength that is allocated to be the same for each optical network unit, and may transmit the intensity modulated optical signal toward upstream direction
Implementation Method 3
The optical receiver may be configured to detect upstream optical signals that are transmitted by respective optical network units, and to convert the detected upstream optical signals into electrical signals
Implementation Method 4
The electrical IQ-demodulator may be configured to perform a frequency down-shift on the orthogonal frequency division multiplexed signals converted by the optical receiver, on a specific frequency basis for frequency division multiplexing that are allocated in advance
Data Source
AI summary
An orthogonal frequency division multiple access-passive optical network including a plurality of optical network units each configured to generate orthogonal frequency division multiplexed signals, which are allocated thereto, based on a central frequency for frequency division multiplexing that is allocated in advance, and to use the generated signals in upstream transmission.