Optimal non-circular fiber geometries for image scrambling in high-resolution spectrographs

TL;DR

This paper introduces a novel 'D'-shaped fiber geometry designed to improve scrambling and reduce modal noise in high-resolution spectrographs, demonstrating its advantages over traditional fiber shapes.

Contribution

It presents the design, fabrication, and comparative analysis of a new 'D'-shaped fiber geometry for enhanced optical scrambling in spectrograph applications.

Findings

D-fiber shows superior scrambling performance.

D-fiber reduces modal noise compared to polygonal fibers.

Fabrication process for the novel fiber geometry is detailed.

Abstract

Optical fibers are a key component for high-resolution spectrographs to attain high precision in radial velocity measurements. We present a custom fiber with a novel core geometry - a 'D'-shape. From a theoretical standpoint, such a fiber should provide superior scrambling and modal noise mitigation, since unlike the commonly used circular and polygonal fiber cross sections, it shows chaotic scrambling. We report on the fabrication process of a test fiber and compare the optical properties, scrambling performance, and modal noise behavior of the D-fiber with those of common polygonal fibers.