Nyquist Subcarrier DSP for Chromatic Dispersion Compensation
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Solution Overview
Problem
High power consumption and hardware resource requirements in digital signal processing for compensating chromatic dispersion (CD) in optical communication systems, particularly at high data rates, pose challenges in maintaining efficient and cost-effective signal transmission.
Innovation Solution
The implementation of a Nyquist m-subcarrier modulation system, which reduces computational complexity and hardware resources by employing multiple spectrally-shaped subcarrier signals at a lower symbol rate, allowing for efficient CD compensation using smaller sized frequency domain equalizers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If very large scale ASIC DSPs with tens or hundreds of millions of gates are used to perform advanced digital signal processing for CD compensation at high data throughput, then signal distortion compensation performance is improved, but power consumption increases significantly
Solution Approach 1:
The patent divides the single high-rate data stream into multiple lower-rate subcarrier streams. By segmenting the data transmission into parallel subcarriers, each processing channel operates at a lower symbol rate, reducing the computational complexity and power consumption of individual DSP units while maintaining overall high data throughput through aggregation of multiple subcarriers.
Solution Approach 2:
The patent changes the operating parameters by reducing the symbol rate of each subcarrier compared to a single carrier system. This parameter change allows the use of smaller, lower-power DSP circuits that operate at reduced speeds, thereby decreasing power consumption while achieving the same effective data rate through multiple parallel subcarriers.
2Measurement precision
If very large scale ASIC DSPs with tens or hundreds of millions of gates are used for CD compensation, then compensation accuracy is improved, but hardware resource requirements and device complexity increase
Solution Approach 1:
The patent segments the complex high-rate signal processing task into multiple simpler parallel subcarrier processing tasks. Each subcarrier requires a smaller equalizer with fewer taps, reducing the hardware resources needed per channel. The overall compensation accuracy is maintained through the combined effect of multiple subcarriers, each processed with dedicated but smaller DSP units.
Solution Approach 2:
The patent uses multiple copies of simpler subcarrier processing chains instead of a single complex processing chain. Each subcarrier has its own dedicated equalizer and processing path, allowing the system to achieve high compensation accuracy through parallel processing while using less complex individual processing units that can be implemented with fewer hardware resources.
3Productivity
If single carrier modulation is used to achieve high data rates, then data transmission efficiency is maintained, but computational complexity and equalizer size requirements increase
Solution Approach 1:
The patent segments the high-rate data stream into multiple lower-rate subcarrier streams, each requiring smaller equalizers with reduced computational complexity. The overall data transmission efficiency is maintained by aggregating the throughput of multiple subcarriers, while each individual processing channel operates with reduced complexity suitable for practical implementation.
Solution Approach 2:
The patent transitions from a single-dimensional high-rate carrier to a multi-dimensional approach using multiple subcarriers. By adding the dimension of parallel subcarrier processing, the system achieves the same effective data rate with lower per-channel complexity, transforming the problem from handling one high-rate stream to managing multiple lower-rate streams in parallel.
Data Source
AI summary
An optical receiver comprising a frontend configured to receive an optical signal and convert the optical signal into a plurality of digital electrical signals comprising a plurality of spectrally shaped subcarrier signals carrying symbol mapped data information, and a digital signal processor (DSP) unit coupled to the frontend and configured to receive the digital signals from the frontend, demulitplex the digital signals into the subcarrier signals, and compensate chromatic dispersion (CD) for each of the subcarrier signals by applying an equalizer, wherein each of the subcarrier signals is associated with a unique tone frequency and a unique spectral shape. Also disclosed is an optical transmitter comprising a digital signal processor (DSP) unit configured to map data symbols onto a plurality of electrical subcarrier signals that are non-overlapping and spectrally shaped in a frequency domain.