Nonlinearity Compensation for Coherent Optical Satellite Communications

2026-03-09

AI Summary

This work addresses the severe performance degradation in satellite-to-ground optical uplink communications caused by fiber Kerr nonlinearities induced by high-power optical amplifiers. To mitigate this, the authors develop an uplink model incorporating nonlinear effects and, for the first time, reduce the complex nonlinear phase rotation to a single-parameter representation. By integrating this simplification with a lookup table (LUT)-based approach, they enable low-complexity constellation shaping and joint transmitter–receiver phase compensation. The proposed scheme supports channel-adaptive rate adjustment and achieves up to a 6 dB improvement in maximum tolerable link loss with negligible added computational complexity, thereby significantly enhancing both system robustness and spectral efficiency.

Technology Category

• Search and Optimization: Non-convex Optimization
• Constraint Satisfaction and Optimization: Satisfiability
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems

Application Category

• Semantics and Knowledge: Methods to enhance, augment, integrate or synergize semantic models such as knowledge graphs and LLMs
• Search and Retrieval-Augmented AI: Retrieval-Augmented Generation (RAG) and multi-modal RAG
• Economics, Online Markets and Human Computation: Cost models of using LLMs in production systems

Abstract

Optical satellite uplinks rely on high-power optical amplifiers (HPOAs) to overcome free-space attenuation and enable long-distance transmission. However, at high power levels, fiber Kerr nonlinearity becomes significant and degrades system performance. In this work, we develop a realistic model for optical uplinks that accounts for nonlinear effects and analyze their impact, highlighting key differences from conventional longhaul fiber systems. We then introduce low-complexity digital signal processing techniques for nonlinearity compensation, based on constellation shaping via a look-up table (LUT) and a simple nonlinear phase rotation applied at the transmitter and/or receiver. The LUT also enables adaptive rate tuning according to channel conditions, enhancing robustness against link variations. Simulation results show that the proposed techniques increase the maximum acceptable link loss by up to 6 dB with negligible complexity. Finally, we show that, at the system level, propagation in the HPOA can be modeled as a simple nonlinear phase rotation, equivalent to propagation in a zero-dispersion noiseless fiber link, and fully characterized by a single parameter - the characteristic nonlinear power.

Problem

• nonlinearity
• coherent optical satellite communications
• Kerr effect
• high-power optical amplifiers
• free-space attenuation

Innovation

• nonlinearity compensation
• coherent optical satellite communications
• constellation shaping
• look-up table (LUT)
• characteristic nonlinear power