Search Results (280)

An enhanced genetic algorithm (EGA) is proposed to optimize our previously reported seven-tube single-ring anti-resonant hollow-core fiber (SR-ARF) with a record-low loss of 4.30 dB/km at 1080 nm. Taking advantage of an improved roulette wheel selection and a threshold elimination mechanism, the EGA effectively prevents premature convergence and enhances optimization efficiency. By adopting the proposed EGA to optimize fiber structural parameters, the confinement loss of the seven-tube SR-ARF is further reduced to 2.79 dB/km, and the higher-order mode extinction ratio reaches 204 at 1080 nm, confirming robust single-mode operation. The single-mode operation bandwidth reaches up to 240 nm, covering 920 to 1160 nm. According to the optimized structural parameters, we experimentally fabricated a seven-tube SR-ARF, of which the transmission loss is reduced to 3.29 dB/km at 1052 nm and 3.90 dB/km at 1080 nm, while maintaining near-diffraction-limited single-mode guidance with an M² of 1.07/1.05. The proposed EGA model is of great significance for the structural parameter optimization of hollow-core fibers. Full article

Hollow-core fiber (HCF) is often presented as an incrementally better transmission medium that can be slotted into networks designed around solid-core silica. We argue instead that recent progress—most visibly reported as attenuations below 0.1 dB/km and now approaching 0.05 dB/km, together with a broad low-loss window, reduced propagation delay and very low optical nonlinearity—makes it worth asking which long-standing design conventions are intrinsic to optical communication and which are artifacts of silica. Reviewing physical-layer, transceiver and network architecture implications, we suggest that the most durable gains may come not from treating HCF as a drop-in replacement, but from cross-layer co-design, and we outline the studies and demonstrations needed to test where that advantage is real. Full article

As the available spectrum in the conventional C band becomes increasingly limited, ultra-wideband transmission across the O–U wavelength range (1260–1675 nm) provides a promising approach to increasing optical fiber link capacity. To support performance evaluation and preliminary fiber-link selection, this study compares standard single-mode fiber (SMF), pure-silica-core fiber (PSCF), and hollow-core fiber (HCF) links across the O–U bands. A transmission-performance analysis framework was established based on the Gaussian noise (GN) model. Band-specific amplifier parameters and fiber-specific span configurations were incorporated to evaluate transmission reach, optimum launch power, and theoretical capacity. Auxiliary simulations were conducted using VPIphotonics Design Suite 11.1 (VPIphotonics GmbH, Berlin, Germany) for representative C-band cases to examine the consistency of the overall trends predicted by the theoretical analysis. The GN-model analysis and auxiliary simulations show consistent overall trends, indicating that the GN model can serve as a computationally efficient tool for comparative link assessment and preliminary fiber-link selection. Under the unified analytical framework and consistently defined engineering constraints, PSCF offers a clear transmission-reach advantage over conventional SMF, whereas HCF shows greater theoretical power tolerance and capacity potential under the adopted representative parameter assumptions. Under the adopted non-saturated reference operating conditions, the per-channel capacity of HCF is approximately 34–54% higher than that of SMF in the S, C, L, and U bands and also clearly exceeds that of PSCF. These HCF results should be interpreted as model-based theoretical estimates, since practical performance may be affected by loss, dispersion uncertainty, splice/connector loss, bending sensitivity, and mode coupling. Full article

Background: Viral vectors are indispensable tools in gene therapy and neural circuit mapping, offering promising therapeutic strategies for diverse genetic diseases and advancing neuroscience research. To achieve high transduction efficiency while mitigating impurity-induced immunogenicity, the development of viral vectors with improved purity and quality is essential. However, this critical requirement is often unmet by conventional purification methods such as ultracentrifugation, which are time-consuming and frequently result in limited product purity. The pseudorabies virus (PRV) is extensively employed as a viral tool for mapping neural circuits, where improved purity contributes to enhanced accuracy of neural tracing. PRV531 is a retrograde trans-synaptic tracer modified from the PRV Bartha strain, specifically designed to facilitate the precise visualization of hierarchical neural networks. Methods: In this study, we developed a method for the concentration and purification of PRV531 by integrating hollow fiber ultrafiltration (HF) with Capto^TM Core 700 (CC700) chromatography. Initially, to concentrate the viral supernatant, a 500 kDa HF membrane was employed, maintaining a feed flow rate of 80 mL/min, a shear rate ranging from 2000 to 6000 s⁻¹, and a transmembrane pressure (TMP) between 0.5 and 1 bar. Following concentration, the virus underwent purification through CC700 chromatography, operating at linear flow rates ranging from 100 to 300 cm/h. Results: Sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) revealed distinct bands consistent with the expected sizes of major PRV structural proteins, each with molecular weights ranging from 25 kDa to 150 kDa, concurrently demonstrating a substantial reduction in host cell proteins (HCPs) contamination. The purified PRV531 achieved a high final infectious titer of 3.55 × 10⁹ PFU/mL, with an overall functional virus recovery of 8.88% from the crude supernatant to the final product. Conclusion: These data demonstrate that TFF combined with CC700 resin can efficiently purify retrograde trans-synaptic PRV tracer. Furthermore, this approach provides a promising strategy for purifying other viral-based tracers that traditionally rely on conventional centrifugation methods. Full article

CO₂ gas-line absorption is emerging as a major L-band impairment in low-loss hollow-core fiber (HCF) links. We compare two transponder-side mitigation strategies—spectral pre-emphasis and spectral avoidance—over span lengths of 100–300 km and transmission reach of up to 3000 km. The preferred strategy depends on reach, launch power, span length, and the stability of the live-link absorption comb. Pre-emphasis is favored at short reach and for short spans, whereas spectral avoidance is superior at moderate to long reach, with a peak capacity gain of about 4 Tb/s. Pre-emphasis is also more sensitive to mismatch between the design-time and live-link absorption combs: increasing the live absorption peak from 0.10 to 0.35 dB/km reduces capacity by up to 8.5 Tb/s, while tripling the CO₂ absorption linewidth reduces capacity by up to 10.3 Tb/s. We further review implementation options for both methods: DGFF-based pre-emphasis at the WSS sites, and DSP-based avoidance via digital subcarrier multiplexing (DSCM) or entropy-loaded orthogonal frequency-division multiplexing (OFDM). These results provide a concise framework for selecting mitigation strategy under realistic operating conditions. Full article

The progress made in several fields after 2023 is rather significant. Attenuation achieved by the best HCFs was reduced to 0.05–0.10 dB/km at 1550 nm, while the lowest attenuation achieved in a single-mode fiber with a pure silica core equals 0.14 dB/km. Polarization mode dispersion (PMD) has been reduced to a level typical of SMFs, through fiber spinning. In November 2024, Microsoft announced a 2-year plan to install 15,000 km of HCF cables between and within data centers processing data for Microsoft Azure cloud services. Furthermore, several HCF manufacturers have emerged: UK-based Microsoft Azure Fiber and two Microsoft subcontractors, namely Corning Inc. and Heraeus Covantics, plus two major HCF manufacturers in China, YOFC and Linfiber. Additionally, extensive work was carried out on optical amplifiers to enable new transmission bands in HCFs, both at short wavelengths (≈1300–1500 nm), with bismuth-doped active fibers, and long wavelengths (≈1700–2100 nm), with thulium- and holmium-doped fibers. On the other hand, progress in HCF standardization, splicing and elimination of loss bands introduced by contaminants, has been marginal. Standardization is blocked by multiple fiber designs being tried, with no clear winner emerging yet. Despite this, hollow-core fibers have been successfully debuted in large-scale commercial data centers and are also used in low-latency data links. Full article

Hollow-core anti-resonant fibers (HC-ARFs) have emerged as a promising platform for next-generation optical systems, offering attractive advantages in low-latency, low-nonlinearity, and high-power handling. However, the development of high-performance functional components, such as polarization beam splitters (PBSs), within this platform faces a significant challenge: the simultaneous achievement of ultra-broad bandwidth, compact device length, high polarization selectivity, and strict single-mode operation remains elusive. To address this challenge, we propose and numerically investigate a novel dual hollow-core anti-resonant fiber (DHC-ARF) based on a hybrid nodal–nodeless architecture. The design integrates three functional units: (1) an asymmetric nested semi-elliptical tube pair that defines the dual cores and serves as the primary wavelength-insensitive coupling channel; (2) nodeless nested circular tubes positioned peripherally to effectively suppress higher-order mode propagation while maintaining low fundamental mode loss; and (3) a selective localized thick-wall region that introduces a polarization-dependent perturbation to the x-polarized supermodes, whose observed behavior is physically consistent with a phase-mismatch effect associated with anti-crossing-like modal interaction near the target wavelength. Through synergistic optimization of these elements, we numerically demonstrate a combination of performance metrics. At the central wavelength of 1.55 µm, the coupling length for the y-polarization (Lcy) is reduced to 6.35 cm, while the coupling length ratio (CLR = $L_{\mathrm{cx}}$/$L_{cy}$) equals 2.001, indicating effective polarization selectivity. Consequently, a device length of 12.7 cm is numerically demonstrated, which is comparable to or shorter than existing ultra-broadband DHC-ARF PBS designs. The proposed PBS is numerically shown to exhibit an ultra-broad bandwidth of 460 nm (spanning 1320 to 1780 nm) with a polarization extinction ratio better than 20 dB, peaking at 53 dB. Furthermore, HOMER (λ) remains above 100 throughout the operating band and exceeds 200 over most of the band, indicating robust single-mode operation. This work not only presents a PBS design with competitive overall performance but also provides a versatile structural paradigm for developing functional components in hollow-core fiber-based integrated optical systems for high-speed communications and precision sensing. It should be noted that this work is based on numerical simulations, and experimental fabrication and validation will be pursued in future work. Full article

We report the development of bundled optical-guiding crystal scintillators (OCSs) with ultrafine and uniform scintillator cores (~12 μm) for high-resolution X-ray imaging. Conventional OCS fabrication using iodide scintillators often suffers from iodine volatilization, bubble formation, and core discontinuities, which limit structural uniformity and device reliability. To address these limitations, a hollow-fiber-based fabrication strategy was introduced. Hollow glass fibers were first bundled and drawn without scintillator materials, followed by capillary infiltration of a Tl-doped Cs₃Cu₂I₅ (Tl: CCI) melt. This approach enabled the stable formation of densely packed bundled OCS structures with uniform core diameters of 10–12 μm while suppressing volatilization-induced defects. Radioluminescence measurements confirmed a broad emission peak at ~442 nm, consistent with Tl:CCI scintillation. X-ray imaging experiments demonstrated superior spatial resolution and image contrast compared with a commercial CsI:Tl columnar scintillator. The bundled OCS exhibited an average contrast transfer function (CTF) of 30.7% at ~10 lp/mm, exceeding the reference value. These results demonstrate that the hollow-fiber architecture provides an effective route toward scalable ultrafine-core scintillators and highlight the potential of Tl:CCI-filled OCSs for next-generation high-resolution X-ray imaging. Full article

This paper provides a comprehensive overview of the progress in fiber-optic gyroscope technology, covering 260 key studies of the last ten years. A critical comparative analysis of fiber-optic gyroscope with alternative inertial sensors (Micro-Electro-Mechanical Systems, Hemispherical Resonator Gyroscope, Ring Laser Gyroscope) has been carried out. Confirming the unique advantages of fiber-optic gyroscope for autonomous navigation. Fundamental limitations of accuracy are considered in detail: temperature drifts, polarization noise, and Rayleigh backscattering. Modern hardware methods for suppressing these errors, including the use of photonic crystal and hollow fibers (Air-Core/Hollow-Core), are also considered in this work. The central place in the review is occupied by the analysis of the technological paradigm shift from bulky discrete circuits to hybrid integrated photonics (Indium Phosphide, Silicon Nitride, Lithium Niobate) and hybrid architectures to reduce weight and size characteristics. The role of artificial intelligence (Deep Learning, Long Short-Term Memory) methods in nonlinear drift compensation and calibration is discussed. The usage of the Brillouin effect and optomechanics promising areas are outlined, necessary to create a new generation of navigation systems operating in the absence of Global Navigation Satellite Systems signals. Full article

Urban Air Mobility (UAM) is increasingly recognized as one of the promising methods for future urban transportation, offering higher average speeds than conventional means of transportation. This study investigates the sustainable and efficient production of hollow propeller blades (837 × 85 × 40 mm) using high pressure resin transfer molding (HP-RTM), driven by high demand for UAM, particularly for wingless multicopters. Unlike conventional monolithic or sandwich structures, the propeller blade in this project features a hollow design using a lost core made from water soluble salt. Full article

Fiber interferometers are widely used in precision measurement fields such as seismic observation, gravitational-wave detection, and aerospace guidance. However, phase noise in the Hz–kHz range has become an important factor limiting further improvement in measurement accuracy. In this work, a solid-core photonic crystal fiber (PCF) and a hollow-core photonic bandgap fiber (HC-PBGF) were introduced into the sensing arms of a fiber interferometer to reduce phase noise in this frequency range. Theoretical analysis showed that, compared with a conventional solid-core fiber, the PCF and the 19-cell HC-PBGF used in this study could reduce the phase noise by approximately 3 dB and 7 dB, respectively. The experimental results agreed well with the theoretical predictions, confirming that both fibers can effectively suppress high-frequency phase noise, with HC-PBGF showing superior noise reduction performance. This work provides a feasible approach for improving the performance of fiber interferometers in precision measurement. Full article

Coherent Raman scattering (CRS) techniques such as coherent anti-Stokes Raman scattering (CARS) provide chemically specific vibrational contrast with signal levels far exceeding spontaneous Raman scattering (SpRS). Extending these to broadband excitation enables multiplex detection across wide spectral regions, including the fingerprint region, CH-stretch bands and high-frequency vibrational modes. This review provides a structured overview of excitation architecture for broadband CRS, ranging from low-energy oscillator schemes to energy-scalable platforms. The discussion is organized along key design parameters, including spectral bandwidth, excitation intensity, and probe delay, which jointly determine the accessible operating regimes. Rather than representing competing methods, the reviewed architectures are presented as a complementary toolbox for application-driven spectroscopy in chemically reactive environments and complex biological systems. In addition, a representative OPCPA-based implementation is presented as a platform demonstration to illustrate accessible operating regimes, single-shot stability, and multiplex detection capability under realistic experimental conditions. Full article

This study investigates the radiation-induced attenuation (RIA) of an Anti-Resonant Hollow-Core Fiber (AR-HCF) exposed to neutron and gamma radiation in a nuclear reactor environment. The AR-HCF—with a revolver-style structure—was characterized for RIA and compared to a solid, pure-silica-core fiber. Experimental results demonstrate that the AR-HCF exhibits substantially higher radiation tolerance compared to pure-silica, solid-core fibers, by about a factor of six in terms of dB/m. Numerical modeling in COMSOL Multiphysics (Version 6.3) was performed to simulate potential contributors of RIA, including silica compaction due to neutron fluence and changes in light confinement. These simulations ruled out these effects as primary causes of the measured attenuation. We also show that our results are consistent with the radiolytic generation of nitric acid within the hollow core, an interpretation that aligns with findings from a prior study. The results included in this manuscript provide insight into the behavior of AR-HCFs in the radiation field of a nuclear reactor, a topic with very limited prior literature, and underscore their potential for use in high-radiation environments such as fission and fusion reactors, particle accelerators, and space applications. The findings also point to promising future directions, including spectral characterization and dosimetry applications that leverage the unique properties of these fibers. Full article

This paper presents the design and experimental validation of a highly sensitive vector magnetic field sensor based on three mutually orthogonal Fabry–Perot interferometers (FPIs). The orthogonally arranged FPIs are bonded to a giant magneto-strictive material (GMM) block. Under an applied magnetic field, the magneto-strictively induced strain in the GMM block is transferred to the FPIs. Meanwhile, the FPIs, composed of single-mode fiber (SMF)–hollow-core fiber (HCF)–SMF, are further modulated by CO₂ laser, by which the higher sensitivities are obtained. The highest sensitivities of FPIs achieved 245.13, 159.06, and 168.59 pm/mT on the X-Y, X-Z, and Y-Z planes, respectively. By demodulating the distinct wavelength drifts of the three orthogonal FPIs, both the magnitude and direction of the magnetic field can be simultaneously determined. Full article

Mid-infrared (MIR) femtosecond lasers, resonant with the absorption bands of amide-related molecular groups in the range of 6.1 to 6.5 μm, have been demonstrated to be effective for tissue ablation. However, the flexible and stable delivery of such pulses to micrometer-scale tissue regions for controlled ablation remains challenging. Here, we utilize a silica-based anti-resonant hollow-core fiber (AR-HCF) to deliver high-power MIR femtosecond pulses with high temporal and spectral fidelity, featuring pulse durations of approximately 340 fs and peak power densities exceeding 1 GW/cm², for selective tissue ablation. Benefiting from the small numerical aperture of the AR-HCF, a relatively stable and consistent beam spot size can be maintained over a millimeter-scale propagation distance. Precise control of the ablation depth can be achieved by appropriately selecting the scanning parameters, with penetration depths reaching the sub-millimeter scale. Furthermore, for the first time, we systematically compare the tissue ablation performance of MIR femtosecond lasers at resonant wavelengths (6.4 and 6.1 μm) and a non-resonant wavelength (5.5 μm) under identical scanning conditions. An ablation depth ratio of more than 8:1 is observed, demonstrating the high efficiency and selectivity of the resonance-based ablation mechanism. These results establish flexible delivery of high-power MIR femtosecond pulses in tissue-resonant bands via silica-based AR-HCF as a powerful platform for selective, precise, and efficient tissue ablation, providing a promising approach for interventional and minimally invasive surgery. Full article