Four-fold truncated double-nested anti-resonant hollow-core fibers with ultralow loss and ultrahigh mode purity

TL;DR

This paper introduces a novel four-fold truncated double nested anti-resonant hollow-core fiber design that significantly reduces fundamental mode loss while greatly suppressing higher-order modes, enhancing performance for high-speed optical applications.

Contribution

The study presents a new fiber structure that improves control over mode phase-matching, achieving ultralow fundamental mode loss and ultrahigh higher-order mode suppression.

Findings

Fundamental mode loss as low as 0.1 dB/km.

Higher-order mode loss up to 6500 dB/km.

Higher-order mode extinction ratio of 50,000.

Abstract

Hollow-core fibers are inherently multimode, making it crucial to filter out higher-order modes within the shortest possible fiber length for applications such as high speed coherent communications and fiber optic gyroscopes. However, current HCF designs face the challenges of simultaneously achieving ultralow fundamental mode loss and ultrahigh HOM suppression. In this study, we present a novel four fold truncated double nested anti resonant hollow core fiber structure that addresses this challenge. Our 4T-DNANF enables greater control over phase-matching between core modes and air modes in the cladding, allowing for minimized FM loss and substantially increased HOM loss. Experimentally, we fabricated several HCFs: one with an FM loss of 0.1 dB/km and an HOM loss of 430 dB/km, and another with an FM loss of 0.13 dB/km with a HOM loss of 6500 dB/km, resulting in a higher-order mode extinction ratio of 50,000.