# Research on an Adaptive Coupling Technique for Spatially Scattered Light

## TL;DR

This paper introduces an adaptive system to efficiently couple scattered light from underwater LiDAR into a fiber, improving efficiency significantly.

## Contribution

A novel adaptive coupling system using a three-lens setup and an improved SPGD algorithm for efficient scattered light coupling.

## Key findings

- The system achieves 88.18% of theoretical coupling efficiency after program adjustment.
- The algorithm avoids local optima and improves coupling efficiency by approximately 88% compared to manual methods.
- The system provides a feasible solution for underwater LiDAR and similar applications.

## Abstract

Focusing on the problems of difficult alignment and low efficiency when coupling the spatially scattered light from 532 nm underwater LiDAR to a single-mode fiber, this paper presents an analysis and simulation of the coupling principle of spatially scattered light and its influencing factors based on the extended light source imaging model, and designs and develops a spatially scattered light adaptive coupling system. The system adopts a three-lens set to receive spatially scattered light, combines a fast steering mirror and displacement stage to adjust the beam position dynamically, and realizes the automatic and efficient coupling of spatially scattered light through a joint control strategy combining rough alignment and precise alignment (using the improved simulated annealing SPGD algorithm). The experimental results show that the best coupling efficiency reaches 88.18% of the theoretical value after program adjustment. This represents an approximate 88% improvement over the best coupling efficiency obtained after manual adjustment, whilst the algorithm effectively circumvents the issue of local optima. This study provides a feasible adaptive solution for underwater LiDAR and similar applications involving scattered light coupling.