Adaptive Nonlinear Pre-Distortion for Optical Transmitter Performance
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Solution Overview
Problem
High-speed data optical communication systems face performance degradation due to linear and nonlinear distortion phenomena, particularly with commercial DACs and driver amplifiers, and existing pre-distortion methods require extensive time and effort to measure frequency response characteristics, which change with data transmission rate and modulation methods.
Innovation Solution
Implementing an adaptive nonlinear pre-distortion function at the transmitter with a nonlinear Volterra filter and updating filter coefficients using a least mean square algorithm to maintain optimal channel response, while applying timing recovery and synchronization at the receiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pre-emphasis is used to overcome bandwidth limitation by increasing signals in the high-frequency domain, then system performance is improved, but substantial time and effort are required to measure and identify the exact frequency response characteristics of each device
Solution Approach 1:
The patent changes the fundamental parameter approach from frequency-domain pre-emphasis to time-domain pre-distortion using Volterra filters. This allows the system to compensate for nonlinear distortions without requiring extensive frequency response measurements, thereby maintaining system performance while reducing measurement time and complexity
Solution Approach 2:
The patent replaces the conventional pre-emphasis mechanism with a pre-distortion mechanism using Volterra filters. This substitution enables the system to handle nonlinear distortions more effectively without relying on detailed frequency response characterization, thus reducing the time and effort required for device measurement
2Reliability
If pre-distortion method is used to equalize the channel at the transmitter, then channel equalization is improved, but the filter coefficient value obtained from receiver equalizer cannot be directly applied due to varying system performance
Solution Approach 1:
The patent implements a feedback mechanism where the receiver measures the actual received signal quality and sends correction information back to the transmitter. The transmitter uses this feedback to dynamically adjust its pre-distortion filter coefficients, ensuring optimal channel equalization while adapting to varying system performance conditions
Solution Approach 2:
The patent transforms the static filter coefficient approach into a dynamic system where coefficients are continuously adapted based on real-time channel conditions. The Volterra filter coefficients are updated dynamically to match changing system performance, resolving the issue of coefficient mismatch between transmitter and receiver
3Measurement precision
If adaptive pre-distortion is implemented with dynamic coefficient updates, then channel equalization accuracy is improved, but the complexity of calculating coefficients through received and sending data increases
Solution Approach 1:
The patent replaces the complex iterative calculation process with a more efficient algorithm that directly computes Volterra filter coefficients from measured channel characteristics. This substitution maintains high equalization accuracy while significantly reducing the computational complexity and processing requirements for coefficient calculation
Data Source
AI summary
Proposed is a technology for compensating for the performance of a transmitter using a pre-distortion method in an optical communication system, wherein a signal sending apparatus may include a transceiver, and at least one controller operably connected to the transceiver, wherein the at least one controller is configured to receive a digital signal, to modulate the digital signal into a PAM signal, to provide the PAM signal to a signal receiving apparatus, to obtain a distortion coefficient value from the signal receiving apparatus, to perform a nonlinear pre-distortion on PAM signals on the basis of the distortion coefficient value, and to provide a result signal generated on the basis of the nonlinear pre-distortion to the signal receiving apparatus.