Hollow-core Anti-resonant Fiber Research Articles

High Fidelity Distribution of Telecom Polarization Entangled Photons through a 7.7 Km Antiresonant Hollow-Core Fiber

High Fidelity Distribution of Telecom Polarization Entangled Photons through a 7.7 Km Antiresonant Hollow-Core Fiber

Semi-Empirical Model for Calculating Birefringence and Confinement Loss in Bi-Thickness Fourfold Anti-Resonant Hollow-Core Fiber

Semi-Empirical Model for Calculating Birefringence and Confinement Loss in Bi-Thickness Fourfold Anti-Resonant Hollow-Core Fiber

Suppression of Optical Fringes in Gas Spectroscopy Inside Anti-Resonant Hollow-Core Fibers by Fiber Bending

Suppression of Optical Fringes in Gas Spectroscopy Inside Anti-Resonant Hollow-Core Fibers by Fiber Bending

Enhanced Inhibited Mode-Coupling: Multi-Mode Hollow-Core Anti-Resonant Fiber Designs

Enhanced Inhibited Mode-Coupling: Multi-Mode Hollow-Core Anti-Resonant Fiber Designs

Accurate Loss Prediction of Realistic Hollow-Core Anti-Resonant Fibers Using Machine Learning

Accurate Loss Prediction of Realistic Hollow-Core Anti-Resonant Fibers Using Machine Learning

Spectral Bandwidth Tuning of Photoionization-Induced Blue-Shifted Solitons in gas-Filled Hollow-Core Anti-Resonant Fibers

Spectral Bandwidth Tuning of Photoionization-Induced Blue-Shifted Solitons in gas-Filled Hollow-Core Anti-Resonant Fibers

Highly Amplified Broadband Ultrasound in Antiresonant Hollow Core Fibers

High‐frequency broadband ultrasound in nested antiresonant hollow core fibers (NANFs) is investigated for the first time. NANFs have remarkable features enabling high‐resolution microscale optoacoustic imaging sensors and neurostimulators. Solid optical fibers have been successfully employed to measure and generate ultrasonic signals, however, they face issues concerning attenuation, limited frequency range, bandwidth, and spatial resolution. Herein, highly efficient ultrasonic propagation in NANFs from 10 to 100 MHz is numerically demonstrated. The induced pressures and sensing responsivity are evaluated in detail, and important parameters for the development of ultrasonic devices are reviewed. High pressures (up to 234 MPa) and sensing responsivities (up to −207 dB) are tuned over 90 MHz range by changing the diameters of two distinct NANF geometries. To the best of knowledge, this is the widest bandwidth reported using similar diameter fibers. The results are a significant advance for fiber‐based ultrasonic sensors and transmitters, contributing to improve their efficiency and microscale spatial resolution for the detection, diagnosis, and treatment of diseases in biomedical applications.

Optical absorption spectrum reveals gaseous chlorine in anti-resonant hollow core fibers

We have observed unexpected spectral attenuation of ultraviolet light in freshly drawn hollow core optical fibers. When the fiber ends are left open to atmosphere, this loss feature dissipates over time. The loss matches the absorption spectrum of gaseous (molecular) chlorine and, given enough time, the transmission spectrum of the fiber recovers to that expected from the morphological structure of the fiber. Our measurements indicate an initial chlorine concentration of 0.45 µmol/cm3 in the hollow core, equivalent to 1.1 mol% Cl2 at atmospheric pressure.

Extraction of Attenuation and Backscattering Coefficient along Hollow-Core Fiber Length Using Two-Way Optical Time Domain Backscattering.

Optical time domain reflectometry (OTDR) is a key technique to characterize fabricated and installed optical fibers. It is also widely used in distributed sensing. OTDR of emerging hollow-core fibers (HCFs) has been demonstrated only very recently, being almost 30 dB weaker than that in the glass-core optical fibers. However, it has been challenging to extract useful data from the OTDR traces of HCFs, as the longitudinal variation in the fiber's geometry, notably the core size or the longitudinal variations of the air pressure within the core, results in commensurate changes of the backscattering strength. This is, however, necessary for continuous improvement of HCF fabrication and subsequent improvement in their performance such as minimum achievable loss, potentially enabling the use of HCF in a significantly broader range of applications than used today. Here, we demonstrate, for the first time, that the distributed loss and backscattering coefficient in antiresonant HCFs can be separated, obtaining key data about fiber distributed loss and uniformity. This is enabled by using OTDR traces obtained from both ends of the HCF.

Low-latency 100 Gb/s PAM-4 PON with a 42.5 dB power budget over the 20 km anti-resonant hollow-core fiber.

The surging growth in data traffic has necessitated the development of higher-speed, lower-latency intensity modulation and direct detection (IM/DD) passive optical networks (PONs) with higher power budgets. To address the inherent limitations of traditional silica-based solid-core fibers, anti-resonant hollow-core fibers have garnered significant attention from both academia and industry. In this Letter, we present an experimental demonstration of 100 Gb/s PAM-4 IM/DD PON transmission over a 20 km anti-resonant hollow-core fiber in the C band, utilizing low-complexity digital signal processing (DSP). The result achieves a record high power budget of 42.5 dB, facilitated by a 3-tap weighted lookup table (LUT) at the optical line terminal (OLT) side and a semiconductor optical amplifier used as a preamplifier at the optical network unit (ONU) side. This represents the highest power budget reported for IM/DD PON to date, to the best of our knowledge,and offers a promising alternative for the future evolution of PON systems.

Glass capillary systems for micro-volume fluorometry

Capillary-based fluorometry can be considered a promising alternative to cuvette-based methods, enabling low-volume measurements while reducing analyte consumption and waste generation. In this work, we compared the performance of three types of glass container systems, i.e., anti-resonant hollow core fibers, capillaries, and standard cuvettes, using green fluorescent protein (GFP) as a reference analyte. Among these, when the volume of the analyte and the fluorescence intensity are assessed, a capillary accommodating 2.9 μL was found as an optimal choice. The capillary-based interrogation setup was further optimized to enhance sensitivity by adjusting the florescence-exciting laser beam position and optimizing the capillary’s shape. The obtained capillary-based setup achieved a noteworthy 85 % reduction in sample volume compared to previous studies utilizing capillary-based fluorometry, highlighting its significant contribution to material conservation. The system achieved a limit of detection as low as 26 μg/mL (1.01 nM) GFP concentration and a resolution of 3.5 μg/mL. With its low cost and potential for reusability, capillary-based fluorometry presents a compelling alternative to traditional cuvette-based fluorometry, offering a promising solution for micro-volume analysis.

Narrowband stimulated Raman scattering and molecular modulation in anti-resonant hollow-core fibres

Raman scattering is the inelastic process where photons bounce off molecules, losing energy and becoming red-shifted. This weak effect is unique to each molecular species, making it an essential tool in, e.g., spectroscopy and label-free microscopy. The invention of the laser enabled a regime of stimulated Raman scattering (SRS), where the efficiency is greatly increased by inducing coherent molecular oscillations. However, this phenomenon required high intensities due to the limited interaction volumes, and this limitation was overcome by the emergence of anti-resonant fibres (ARFs) guiding light in a small hollow channel over long distances. Based on their unique properties, this Perspective reviews the transformative impact of ARFs on modern SRS-based applications ranging from development of light sources and convertors for spectroscopy and materials science, to quantum technologies for the future quantum networks, providing insights into future trends and the expanding horizons of the field.

Optimization of low-loss, high birefringence parameters of a hollow-core anti-resonant fiber with back-propagation neural network assisted hyperplane segmentation algorithm

In engineering, optimizing parameters often involves computationally expensive tasks, especially when dealing with multi-dimensional variables and multiple performance metrics. This falls under the category of multi-objective black-box optimization. To address this, we propose two optimization algorithms for low and medium-dimensional spaces, incorporating relaxation conditions for hyperplane segmentation. For the specific parameter optimization of HC-ARF, we employed a two-stage approach. It combines a BP neural network as a surrogate model with a hyperplane separation optimization algorithm. This method efficiently optimizes both confinement loss (CL) and birefringence, using a weighted sum approach to identify their Pareto sets. We validate the effectiveness and stability of the surrogate model by comparing it with traditional optimization algorithms. Exhaustive experiments confirm the superiority of this algorithm and the results show that our optimized structure achieves impressive performance metrics, including a loss of 0.8 dB/m, a birefringence of 2.2×10−4, and a critical bending radius of 0.5 cm under optimal parameters.

Design of hollow-core anti-resonant optical fiber based on bragg elements with low-loss and wide bandwidth

A type of anti-resonant hollow-core optical fiber consisting of Bragg elements is proposed. The confinement and bending losses are numerically simulated using the finite element method. It is found that the introduction of concentric rings to form anti-resonant structure can reduce the mode transmission loss by 2 ∼ 4 orders of magnitude compared with the anti-resonant element composed of only one dielectric layer, therefore it can achieve ultra-low loss optical transmission. The influence of the structural parameters on the confinement loss was investigated. Furthermore, it is demonstrated that each dielectric layer independently contributes to the confinement of the core modes. It is also found that the Bragg reflection structure can effectively suppress the coupling between core and cladding modes, and achieve broadband low-loss optical transmission under small bending radius. In particular, it can achieve a low transmission loss of less than 0.1 dB km−1 over a wide wavelength range of 600 nm at the bending radius of 3 cm.

Nested hollow-core anti-resonant fiber with elliptical cladding for 2 µm laser transmission

In this work, a nested hollow-core anti-resonant fiber (HC-ARF) with an elliptical cladding for high-power lasers for 2 µm laser transmission was proposed and theoretically investigated. The dual-layer elliptical tubes nested within the fiber enable the low-loss single-mode transmission. The finite element method (FEM) was employed to analyze and optimize the structure of fiber, with a total loss of less than 5 × 10−4 dB/m across the wavelength range of 1920nm to 2040nm. An extremely low loss of 1.22 × 10−5 dB/m at 1948nm was realized. A high-order mode extinction ratio (HOMER) exceeding 3 × 104 was maintained across a significant bandwidth and a size tolerance ratio under 15%. Furthermore, a low loss of 5 × 10−5 dB/m at 1948nm with a bending radius over 15 cm was obtained, indicating high bending resistance. It was demonstrated that the proposed fiber has exceptional transmission performance for 2 µm laser transmission.

Design and Study of Low Loss, High Birefringence Quasi-Symmetric Hollow-Core Anti-Resonant Fiber

Design and Study of Low Loss, High Birefringence Quasi-Symmetric Hollow-Core Anti-Resonant Fiber

Design and theoretical analysis of broadband bend-resistant low-loss hollow-core anti-resonant fiber

With the development of modern fiber-optic communication technology, bend-resistant low-loss fiber within the S+C+L bands is essential to meeting the requirements of dense wavelength division multiplexing (DWDM) systems, and a small-tube-added multi-nested hollow-core anti-resonant fiber (SM-HC-ARF) is proposed. In conventional double-nested HC-ARF, a pair of circular tubes are tangent to both the inner and outer tubes to form a multi-nested structure. A small tube is put in the gap between the nested structure to enhance the anti-resonance effect further. The influence of fiber structural parameters on transmission characteristics is analyzed by the finite element method combined with the perfect matching layer condition. The numerical results show that, in the range of 1460–1625 nm, the bending loss and the confinement loss are less than 1.17 (at a bending radius of 8 cm) and 0.80 dB/km, respectively. Specifically, at 1550 nm, the bending loss is 0.43 dB/km, and the confinement loss is 0.33 dB/km. The broadband anti-bending low-loss SM-HC-ARF can be expected to apply in the DWDM system and other optical communication technologies.

Theoretical Analysis and Fabrication of a Nested Antiresonant Hollow-Core Fiber With low Tight Bend Loss

Theoretical Analysis and Fabrication of a Nested Antiresonant Hollow-Core Fiber With low Tight Bend Loss

Polarization filter of hollow-core anti-resonant fiber in the 1550 nm band based on SPR effect

Hollow-core anti-resonant fiber (HC-ARF) with unique light propagation through air present a promising avenue for advanced applications of polarization filters based on HC-ARF. This paper proposes a single-mode and single-polarization filters (SMSPF) around 1550 nm based on HC-ARF with tellurite glass as the substrate material. The polarization filtering characteristics of the HC-ARF with varying wall thickness and gold wire filling are simulated and analyzed using the finite element method. A single-mode single-polarization (SMSP) HC-ARF with a continuous bandwidth of 30 nm is obtained, and a polarization filter with low polarization loss and a high filtering bandwidth of 390 nm is achieved through the surface plasmon resonance (SPR) effect.

Design, Simulation, and Characterization of a Partial Negative Curvature Antiresonant Hollow-Core Fiber for Low Loss Terahertz Wave Transmission

Design, Simulation, and Characterization of a Partial Negative Curvature Antiresonant Hollow-Core Fiber for Low Loss Terahertz Wave Transmission