Search Results (63)

Stable generation and propagation of single-polarization single-mode (SPSM) beams in hollow-core fiber (HCF) has become an important research direction. However, their routine use is yet to become a reality, a major obstacle is to maintain the polarization state of light at a sufficiently long transmission distance in a wide spectral range. In the paper, a hollow-core anti-resonant fiber (HC-ARF) that can support SPSM beam transmission with an average loss of 15 dB/km in wavelengths beyond 1000 nm is proposed. SPSM guidance is achieved by setting the cladding tubes in the orthogonal direction to have different structures and material properties. Different cladding tube structures break the degeneracy of polarization modes, and different cladding tube materials make the polarization modes experience enough loss difference. In the range of more than 600 nm, the y-polarization loss ≈ 9.3 dB/km, while the x-polarization is > 500 dB/km, and the birefringence is > 1.7 × 10⁻⁵. In addition, the SPSM optimization process and bending losses in different directions are also discussed in detail. Full article

We propose a new hollow-core fiber design based on a hybrid structure of nested elliptical and semicircular tubes. We numerically investigate the loss and single-mode performance of this design in the communication band and derive the values of each parameter of the fiber cladding structure that theoretically lead to the best performance of the fiber. The resulting structure has a minimum confinement loss as low as 0.00033 dB/km at 1550 nm and an astonishing extinction ratio of 2,439,607 for the higher-order modes, showing excellent loss and single-mode performance. In addition, the design also exhibits excellent bending insensitivity, with the loss gradually dropping well below 0.01 dB/km when the bending radius exceeds 14 cm. The proposed fiber structure has a very promising application in optical communication systems. Full article

A novel nested structure of hollow-core anti-resonant optical fiber is proposed to achieve low loss, large effective mode area, and wide transmission band simultaneously in the near-infrared range of 1200–2200 nm. It is composed of six elliptical cladding tubes nested with six large circular cladding tubes, and six small circular cladding tubes are introduced in the gap of the elliptical tubes. The transmission characteristics of the hollow-core anti-resonant optical fiber are numerically investigated using the full-vector finite element method. The effects of structural parameters such as the cladding tube thickness and the tube diameters on the fiber transmission characteristics are analyzed in detail. The results indicate that within the wavelength range of 1200–2200 nm, the confinement loss remains below 0.017 dB/km, and the minimum confinement loss can be as low as 1.2 × 10⁻⁴ dB/km at 1500 nm. The effective mode area remains as large as ~1142.5 μm². It should be noted that in the wide wavelength range of 1000 nm, the dispersion exhibits excellent characteristics ranging from 0.7 to 1.4 ps/(nm·km). Our fiber can find potential applications in ultra-long-distance and ultra-high-power transmission systems with a wide operating wavelength band. Full article

In this paper, an all-fiber light-induced thermoelastic spectroscopy (LITES) sensor based on hollow-core anti-resonant fiber (HC-ARF) and self-designed low-frequency quartz tuning fork (QTF) is reported for the first time. By utilizing HC-ARF as both the transmission medium and gas chamber, the laser tail fiber was spatially coupled with the HC-ARF, and the end of the HC-ARF was directly guided onto the QTF surface, resulting in an all-fiber structure. This design eliminated the need for lens combinations, thereby enhancing system stability and reducing cost and size. Additionally, a self-designed rectangular-tip QTF with a low resonant frequency of 8.69 kHz was employed to improve the sensor’s detection performance. Acetylene (C₂H₂), with an absorption line at 6534.37 cm⁻¹ (1.53 μm), was chosen as the target gas. Experimental results clearly demonstrated that the detection performance of the rectangular-tip QTF system was 2.9-fold higher than that of a standard commercial QTF system. Moreover, it exhibited an outstanding linear response to varying C₂H₂ concentrations, indicating its high sensitivity and reliability in detecting C₂H₂. The Allan deviation analysis was used to assess the system’s stability, and the results indicated that the system exhibits excellent long-term stability. Full article

This study innovatively presents a hollow-core anti-resonant fiber integrating double-tube nesting and a single-layer anti-resonant wall. Featuring an exclusive two-layer cladding configuration along with an outer cladding circular ring, it differs significantly from traditional fibers. After careful parameter optimization, at 1.55 μm wavelength, the fiber shows excellent performance. Its confinement loss drops to 0.00088 dB/km, 1–2 orders lower than traditional ones. The proportion between the loss of the lowest higher-order mode and that of the fundamental mode reaches 19,900, indicating excellent single-mode performance. In the case of a bending radius of 11–14.2 cm, the x-polarization loss is below 0.001 dB/km, showing good bending resistance. Through structural comparisons, this paper quantitatively reveals the effects of the anti-resonant wall, cladding tube, and outer cladding ring on fiber performance. From the practical fiber-drawing process, it thoroughly analyzes the impact of the outer connecting tube’s offset angle on fiber performance. This research provides crucial theoretical support for new hollow-core fiber design, manufacture, and application, and is expected to drive technological innovation in this field. Full article

In the last decade, substantial progress has been made to improve the performance of optical gyroscopes for inertial navigation applications in terms of critical parameters such as bias stability, scale factor stability, and angular random walk (ARW). Specifically, resonant fiber optic gyroscopes (RFOGs) have emerged as a viable alternative to widely popular interferometric fiber optic gyroscopes (IFOGs). In a conventional RFOG, a single-wavelength laser source is used to generate counter-propagating waves in a ring resonator, for which the phase difference is measured in terms of the resonant frequency shift to obtain the rotation rate. However, the primary limitation of RFOG performance is the bias drift, which can be attributed to nonreciprocal effects such as Rayleigh backscattering, back-reflections, polarization instabilities, Kerr nonlinearity, and environmental fluctuations. In this paper, we review the challenges and opportunities of achieving performance enhancement in RFOGs. Full article

Here, we report a numerical study of supercontinuum generation in an antiresonant optical fiber with a hollow core filled with a mixture of deuterium (D₂) and hydrogen (H₂). For 1 ps pulses at a wavelength of 1.03 μm with different chirp values, we demonstrate a possibility of obtaining a mid-IR coherent supercontinuum with a spectral width of 2300 nm, initiated by cascade processes at resonance frequencies of vibrational and rotational levels of D₂ and H₂. We show that an increase in the chirped pulse duration to 25 ps while maintaining the energy and spectral width allows increasing the quantum conversion efficiency in the mid-IR from 10 to 50% and expanding the range of optimal fiber lengths at which a high degree of supercontinuum coherence is achieved. Full article

This paper employs five different general-purpose optimization methods to perform parameter optimization on single-layer hollow antiresonant fibers. It provides guidance on the establishment of hyperparameters for various optimization methods, with the aim of further defining and standardizing the necessary conditions and convergence criteria for applying optimization algorithms to specialty optical fibers. Through numerical experiments, the study ultimately obtains the converged optimal performance and the range of optimized parameter guidance for single-layer, double-layer, and triple-layer antiresonant fibers with different topological structures. Full article

This paper proposes a novel optimization method for hollow-core, anti-resonant fiber based on a gradient descent algorithm assisted via a radial basis-function surrogate model. This approach significantly reduces the number of optimization iterations, achieving a stable improvement in birefringence performance by an order of magnitude across the operating wavelength band. Furthermore, various optimization algorithms were compared, and the indicators of their Pareto sets were analyzed to demonstrate the effectiveness of the proposed method in multi-objective optimization. Full article

A highly sensitive sensor, which can detect the temperature and strain simultaneously, is proposed using a hollow-core anti-resonant fiber with composite nested tubes. The sensing fiber contains two kinds of nested tubes, and two different sensing mechanisms, the resonance coupling effect and the intermodal interference, are realized in the same section of a hollow-core anti-resonant fiber fully filled with ethanol. Five conjoined nested anti-resonant tubes are introduced to suppress the confinement loss of the higher-order mode LP₀₂. One hybrid conjoined nested tube, which consists of a half-circular anti-resonant tube and a half-circular resonant tube, is introduced to induce a resonant coupling between the LP₀₂ mode in the core and the dielectric mode in the nested resonant tubes. Numerical investigations demonstrate the shifts of the feature wavelengths of the resonance coupling effect, and the intermodal interference shows different velocities with temperature and strain, while a simultaneous measurement of temperature and strain can be realized with high sensitivities (3.36 nm/°C and −0.003 nm/με to temperature and strain, respectively). Since the sensor can be fabricated by full infiltration with liquid into the large-size core and cladding tubes of hollow-core anti-resonant fibers, and special post-processing, such as selective infiltration or coating, is notneeded. The proposed sensors based on hollow-core anti-resonant fibers with functional liquid infiltration provide a more efficient and versatile platform for the temperature and strain sensing. Full article

In this work, we propose a new type of hollow-core anti-resonant fiber (HC-ARF) structure called a coin-slot structure. In this type of structure, two more layers of glass walls are added into the outer cladding capillary, which can effectively prevent light from leaking out of the fiber. In aiming to explore the influence of the outer resonant tube on loss at a wavelength of 2 μm, the fundamental mode loss, high-order mode loss, and higher-order mode extinction ratio (HOMER) under different geometric parameters are studied. Full article

Low-loss, high-birefringence, bend-resistant hollow-core anti-resonant fibers for infrared wavelengths have important applications in the fields of precision interferometric sensing, laser systems, and optical communications. In this paper, an eight-tube cladding quasi-symmetric hollow-core anti-resonant fiber is proposed, and two other anti-resonant fibers are designed based on this fiber structure. The finite element analysis method is used to numerically analyze the limiting loss, birefringence coefficient, bending resistance, and other properties of the three optical fibers after the optimized design. The results show that the limiting loss of the three optical fibers at λ = 1.55 μm is lower than 10⁻⁴ magnitude, and all of them obtain a birefringence coefficient of 10⁻⁴ magnitude; at the same time, the three optical fibers have their own characteristics and advantages, and the first optical fiber can reach a birefringence coefficient of 9.25 × 10⁻⁴ at λ = 1.52 μm.The limiting loss at λ = 1.55 μm is 3.42 × 10⁻⁵ dB/km. The minimum bending radius of the three types of anti-resonant fibers is less than 40 mm, which represents good bending characteristics, and the eight-tube cladding quasi-symmetric optical fiber has a bending loss of less than 2.10 × 10⁻³ dB/km when the bending radius is 28 mm. The three types of optical fibers have obtained good results in improving the mutual constraints between low limiting loss and high birefringence, with better results than the other two types. The obtained results have high development potential. Full article

A new type of anti-resonant hollow-core fiber for terahertz waveguides is proposed. By introducing central support pillars and an elliptical structure, the fiber achieves high birefringence while maintaining low confinement loss and low material absorption loss. The fiber structure is optimized through simulation using the finite element method. The optimized fiber exhibits a birefringence of up to 1.22 × 10⁻² at a frequency of 1 THz, with a confinement loss of 8.34 × 10⁻⁶ dB/cm and a material absorption loss of 7.17 × 10⁻³ dB/cm. Furthermore, when the bending radius of the fiber is greater than 12 cm, the bending loss of the anti-resonant optical fiber at 1 THz is less than 1.36 × 10⁻⁴ dB/cm, demonstrating good bending resistance and high practical value. It is expected to play a significant role in optical communication systems. Full article

In this paper, we propose a novel type of hollow-core anti-resonance fiber (HC-ARF). The cladding region of this fiber is formed by a combination of nested tubes and U-shaped tubes, and the centrally symmetric arrangement significantly reduces sensitivity to polarization. The influence of parameters on the performance of the designed HC-ARF LMA is analyzed by a finite element algorithm. The simulation results demonstrate that the designed structure achieves a large mode area of 3180 µm², bending loss of 2 × 10⁻² dB/km, and confinement loss of 5 × 10⁻³ dB/km at a wavelength of 1064 nm. Similarly, at a wavelength of 1550 nm, the large mode area, bending loss, and confinement loss are 3180 µm², 1.4 × 10⁻² dB/km, and 4 × 10⁻² dB/km, respectively. These results indicate unprecedentedly large mode areas and ultra-low losses compared to previous studies. Within the bending radius under consideration, the bending loss remains below 1.35 × 10⁻² dB/km. Furthermore, by increasing the fiber radius, the large mode area can reach an extraordinary 6250 µm². The proposed device exhibits excellent mode area and outstanding polarization insensitivity, along with favorable bending performance. We believe that the designed fiber holds promising applications in high-power miniaturized fiber lasers, fiber amplifiers, and various high-power fiber communication systems, and it can be applied in sensors that require polarization insensitivity and better bending performance. Full article

A large core size and bending resistance are very important properties of mid-infrared energy transfer fibers, but large core sizes usually lead to the deterioration of bending properties. A negative-curvature nested node-free anti-resonant hollow-core fiber (AR-HCF) based on quartz is proposed. It was made by adding a nested layer to a previous AR-HCF design to provide an additional anti-resonance region while keeping the gap between adjacent tubes strictly correlated with the core diameter to produce a node-free structure. These features improve the fiber’s bending resistance while achieving a larger core diameter. The simulation results show that the radial air–glass anti-resonant layer is increased by the introduction of the nested anti-resonant tube, and the weak interference overlap between the fiber core and the cladding mode is reduced, so the fiber core’s limiting loss and sensitivity to bending are effectively reduced. When the capillary wall thickness t of the fiber is 0.71 μm, the core diameter D is 70 μm, the ratio of the inner diameter of the cladding capillary to the core diameter d/D is 0.62, the diameter of the nested tube is d₀ = 29 μm, the fiber has a lower limiting loss at the wavelength of 2.79 μm, and the limiting loss is 3.28 × 10⁻⁴ dB/m. At the same time, the optimized structure also has good bending resistance. When the bending radius is 30 mm, the bending loss is only 4.72 × 10⁻² dB/m. An anti-bending low-loss micro-structure hollow fiber with a bending radius of less than 30 mm was successfully achieved in the 2.79 μm band. An anti-bending low-loss anti-resonant hollow-core fiber with this structure constitutes a reliable choice for the light guiding system of a 2.79 μm band Er, Cr: YSGG laser therapy instrument. Full article