Characterization Of Optical Fibers Research Articles

Beam loss detection based on generation of Cherenkov light in optical fibers in the CERN Linear Electron Accelerator for Research

Cherenkov optical beam loss monitors (oBLMs) based on optical fibers are a revolutionary achievement among the monitoring systems in particle accelerators. Due to the nature of the Cherenkov phenomenon and the intrinsic characteristics of optical fibers, the photon production and fiber light transmission need to be studied to deduce the total amount of Cherenkov photons detected by the photosensors attached at the end of the system. Simulations of the Cherenkov oBLM detector system have been implemented using the software with postprocessing considering the light attenuation and capture factors in the optical fiber. In addition, the study includes the longitudinal beam loss localization of the controlled beam losses produced along the CERN Linear Electron Accelerator for Research (CLEAR) test facility line. In this paper, the Cherenkov photon detection by an oBLM installed in the CLEAR facility is simulated, analyzed, and compared with experimental data. Published by the American Physical Society 2024

Double-Clad Antiresonant Hollow-Core Fiber and Its Comparison with Other Fibers for Multiphoton Micro-Endoscopy.

Label-free and multiphoton micro-endoscopy can transform clinical histopathology by providing an in situ tool for diagnostic imaging and surgical treatment in diseases such as cancer. Key to a multiphoton imaging-based micro-endoscopic device is the optical fiber, for distortion-free and efficient delivery of ultra-short laser pulses to the sample and effective signal collection. In this work, we study a new hollow-core (air-filled) double-clad anti-resonant fiber (DC-ARF) as a high-performance candidate for multiphoton micro-endoscopy. We compare the fiber characteristics of the DC-ARF with a single-clad anti-resonant fiber (SC-ARF) and a solid core fiber (SCF). In this work, while the DC-ARF and the SC-ARF enable low-loss (<0.2 dBm-1), close to dispersion-free excitation pulse delivery (<10% pulse width increase at 900 nm per 1 m fiber) without any induced non-linearities, the SCF resulted in spectral broadening and pulse-stretching (>2000% of pulse width increase at 900 nm per 1 m fiber). An ideal optical fiber endoscope needs to be several meters long and should enable both excitation and collection through the fiber. Therefore, we performed multiphoton imaging on endoscopy-compatible 1 m and 3 m lengths of fiber in the back-scattered geometry, wherein the signals were collected either directly (non-descanned detection) or through the fiber (descanned detection). Second harmonic images were collected from barium titanate crystals as well as from biological samples (mouse tail tendon). In non-descanned detection conditions, the ARFs outperformed the SCF by up to 10 times in terms of signal-to-noise ratio of images. Significantly, only the DC-ARF, due to its high numerical aperture (NA) of 0.45 and wide-collection bandwidth (>1 µm), could provide images in the de-scanned detection configuration desirable for endoscopy. Thus, our systematic characterization and comparison of different optical fibers under different image collection configurations, confirms and establishes the utility of DC-ARFs for high-performing label-free multiphoton imaging-based micro-endoscopy.

Surface plasmon resonance in gold-silver bilayer coated D-shaped multimode optical fiber: An approach to refractive index sensing

This paper presents the surface plasmon resonance (SPR) characteristics of D-shaped silica multimode optical fiber coated with bilayer silver-gold film. The effect of various coating thicknesses on the SPR characteristics was investigated through simulation using COMSOL Multiphysics. The inner layer Ag thickness varied from 20 nm to 60 nm, and the outer layer Au thickness ranged from 5 nm to 25 nm. Prior simulation results indicated that a single-layer silver (Ag) coating produces a narrower plasmonic curve than a single-layer gold (Au) coating. The confinement loss and the resonance wavelengths were simulated for the sensing medium with a refractive index (RI) range of 1.40–1.45. The simulation results show that the Ag/Aubilayers coated sensorshavebetter full-width-half-maximum (FWHM) and figure-of-merit (FOM) than the single-layer coated sensors. The Ag/Au with a 40 nm/5 nm thickness exhibits the highest confinement loss, with a wavelength sensitivity of 10 000 nm/RIU and a figure-of-merit (FOM) of 500 RIU−1. The proposed sensor using a D-shaped optical fiber coated with Ag/Au layers has a high potential for remote sensing applications involving chemical liquids, offering robust and accurate measurements within the tested refractive index range.

Characterization of optical fibers doped with nanoparticles for distributed displacement sensing.

High-scattering optical fibers have emerged as a key component in distributed sensing systems, primarily due to their capacity to enhance signal-to-noise ratio. This paper presents an experimental characterization of optical fibers doped with oxide nanoparticles for displacement sensing. They were manufactured using the phase-separation technique and different doping compounds, including calcium, strontium, lanthanum and magnesium. The Rayleigh backscattering (RBS) signatures in time and frequency domains were acquired using an Optical Backscatter Reflectometer (OBR). The maximum representative length, backscattering gain and strain sensitivity were evaluated. The results indicate that the fiber co-doped with magnesium and erbium chlorides offered the best compromise between strain sensitivity (0.96 pm/μ ϵ) and maximum length (17 m). For conditions of single and multiple perturbations, strain saturation was reached at ≥7000 μm and <1500 μm, respectively. In addition, the results reveal that, under a condition of variable temperature (30-60 °C), the sensor response becomes significantly nonlinear over length, requiring a technique for temperature cross-sensitivity mitigation that accounts for nonlinearities in sensitivity and hysteresis.

Polarization sensitive optical side leakage radiometry for distributed characterization of anti-resonant hollow-core fibers.

A novel technique referred to as optical side leakage radiometry is proposed and experimentally demonstrated for non-destructive and distributed characterization of anti-resonant hollow-core optical fibers with high spatial resolution. Through in-depth analysis of the leakage light collection, we discover a unique polarization dependence, which is validated by our experiment. By leveraging this effect and employing Fourier filtering, this method enables accurate quantification of propagation attenuations for fundamental and higher order modes (with the uncertainty of <1 dB/km), identification of localized defects (with the resolution of ∼5 cm), and measurement of ultra-low spectral phase birefringence (at the level of 10-7) in two in-house-fabricated nested antiresonant nodeless hollow-core fibers. Such a fiber characterization approach, boasting unprecedently high accuracy and a potentially wide dynamic range, holds the potential to become an indispensable diagnosis tool for monitoring and assisting the manufacture of high-quality anti-resonant hollow-core fiber.

The application of optical fiber in network communication

In recent years, optical fiber communication has gained widespread use in daily life due to its robust communication and transmission capabilities, strong confidentiality, anti-interference properties, and the availability of convenient and accessible materials. This technology has made remarkable strides in network communication and integrated device design, among other areas. This article will commence by discussing the fundamental structure of optical fibers and illustrating the propagation of optical signals within them. It will then analyze the benefits, such as higher transmission rates, wider frequency bands, and the low loss characteristics of optical fibers. Subsequently, the article will enumerate two of the most commonly utilized Optical Fiber Communication (OFC) technologies: Wavelength Division Multiplexing (WDM) technology and optical amplifier technology. It will summarize their principles and strengths. Finally, the article will showcase the practical applications of optical fiber communication, particularly focusing on its role in 5G mobile communication, military operations, and radio and television communication.

High Energy Physics Applications on Fiber Optic Sensors in Relative Humidity

Our multidisciplinary research group has been conducting studies in recent years on the use of fiber grating-based sensors for relative humidity measurement in the Compact Muon Solenoid (CMS) instrument at CERN in Geneva. In order to monitor low relative humidity (RH) values even in cold temperatures, our multidisciplinary research group has been working to develop near-field fibre optic sensors based on tin dioxide particle layers, in light of the extensive research conducted in the past few years to evaluate the radiation hardness capability of fibre optic technology in high-energy physics settings. Compared to other sensor types, optical fiber sensors provide several advantages. These benefits mostly stem from the characteristics of optical fibers, which include their tiny size, inexpensive, electromagnetic passivity, resistance to high pressure, and resistance to high temperatures. Sensing is the process of measuring variables like temperatures, stress, or angular velocity by examining the characteristics of light. To evaluate the sensors' performance under the circumstances needed for CERN experiments, untried tests in the [0-65] %RH range at various temperatures were conducted. There were other campaigns of progressive irradiation using γ-ionizing radiations. The results obtained show that the suggested technologies have great potential for usage in High Energy Physics (HEP) activities as a reliable and acceptable replacement for commercial hygrometers in the future.

Soft glass optical fiber characterization with X-ray computed microtomography

The high loss due to the presence of strong phonon resonances makes silica fibers unfit for applications in the mid-infrared spectral range. This has led to the development of specialty optical fibers, based on novel materials and manufacturing techniques. In some cases, the characterization of these new fibers by means of standard techniques may be challenging. Fiber manufacturers would strongly benefit from a tool, which is capable of checking the geometrical and optical properties of fibers (either after fiber drawing, or even in real-time, during the drawing process). Here, we propose and demonstrate that absorption contrast X-ray computed microtomography is a non-destructive technique, capable of characterizing both geometrical and optical properties of specialty optical fibers. We experimentally verified that the tomographic intensity profile in the fiber core has the same shape as the refractive index profile, which we determined via energy-dispersed X-ray spectroscopy. We tested step- and graded-index soft glass fibers, both purchased and made in-house. Owing to the presence of high atomic number elements, which provide higher X-ray cross-section, soft glasses were more suitable than silica for their characterization via X-ray computed microtomography.

Assessment of the Influence of Protective Polymer Coating on Panda Fiber Performance Based on the Results of Multivariant Numerical Simulation.

This article considers the deformation behavior of Panda optical fiber using different models of material behavior for the tasks of predicting residual stresses after drawing when cooling from 2000 °C to room temperature (23 °C) and indenting the fiber into an aluminum half-space at different parameters. These studies were conducted for single- and double-layer protective coatings (PCs), at different values of external load and thickness of single-layer PC. This paper determined the fields of residual stresses in the fiber formed during the drawing process. They are taken into account in modeling the fiber performance in the further process of this research. This article investigated two variants of PC behavior. The influence of behavior models and the number of covering layers on the deformation of the "fiber-half-space" system was analyzed. This paper establishes qualitative and quantitative regularities of the influence of the external load magnitude and relaxation properties of PCs on the deformation and optical characteristics of Panda optical fiber.

Research on Similarity Simulation Experiment of Mine Pressure Appearance in Surface Gully Working Face Based on BOTDA.

In order to study the mountain deflection characteristics and the pressure law of the working face after the mining of a shallow coal seam under the valley terrain, a geometric size of 5.0 × 0.2 × 1.33 m is used in the physical similarity model. Brillouin optical time domain analysis (BOTDA) technology is applied to a similar physical model experiment to monitor the internal strain of the overlying rock. In this paper, the strain law of the horizontal optical fiber at different stages of the instability of the mountain structure is analyzed. Combined with the measurement of the strain field on the surface of the model via digital image correlation (DIC) technology, the optical fiber strain characteristics of the precursor of mountain instability are given. The optical fiber characterization method of working face pressure is proposed, and the working face pressures at different mining stages in gully terrain are characterized. Finally, the relationship between the deflection instability of the mountain and the strong ground pressure on the working face is discussed. The sudden increase in the strain peak point of the horizontally distributed optical fiber strain curve can be used to distinguish the strong ground pressure. At the same time, this conclusion is verified by comparing the measured underground ground pressure values. The research results can promote the application of optical fiber sensing technology in the field of mine engineering.

Characterization of optical fiber using the EMONA TIMS platform: Experience in Telecommunications Engineering, UNED, Costa Rica

Characterization of optical fiber using the EMONA TIMS platform: Experience in Telecommunications Engineering, UNED, Costa Rica

An automation of the detection processes of the strain characteristics of optical fibers, classification of their varieties and identification the influence factor according to Brillouin reflectograms

Research results into the automating the processing of measurement data obtained from the Brillouin optical reflectometer, light guides containing various types of optical fibers are presented in this paper. By analyzing the parameters of the Mandelstam–Brillouin scatter obtained from Brillouin reflectograms, we can classify optical fibers in the studied telecommunication optical cables. This makes it possible to evaluate the change of the Brillouin frequency shift and determine the longitudinal fiber tension. The initial values of the Brillouin frequency shift and the profile of the Mandelstam–Brillouin scatter spectrum are different for each fiber type. The programs for automated processing of Brillouin reflectogram data are discussed. Estimation of the level of the back-reflected signal allows you to identify the factor, that had a predominant effect on the parameters of the Mandelstam–Brillouin scatter signal in the studied sections of optical fibers, and to compensate for the influence of temperature changes in the longitudinal strain distribution graphs. After that, we can plot a graph of the distribution of longitudinal strain along the fiber, caused precisely by mechanical influences on optical fibers. Conclusions about the accuracy of the estimates obtained by various algorithms, based on the accumulated experience in working with the presented programs are drawn.

Generation of stabilized electrically-induced micro-plasma at the tip of multimaterial optical fibers

The aim of this work is to optimize the operation of a multimaterial optical fiber device to generate a stabilized electrically-induced micro-plasma. The fiber is composed of a polymer cladding with a central hole surrounded by two cylindrical metal electrodes. When a DC voltage of 1.2 kV is applied between electrodes, an air micro-plasma is generated at the tip of the fiber. In order to stabilize the discharge, studies are focused on the modification of the electrical properties of the fiber tip by covering the electrodes with resistive layers. A comparison between two different layers (semi-conductive and semi-insulating) is shown. Characterizations were also performed for the fiber (head and length), and the plasma (imaging, spatial and temporal stability). The results show the effectiveness of the method to cover at least one of the electrodes by the semi-insulating layer to generate a permanent and stable discharge. In fact, this method allowed to increase considerably the lifetime of our technology and avoid the electric arcs leading to high instabilities. According to the Optical Emission Spectroscopy (OES), the species generated by the fiber-plasma device were identified.The combination of the characteristics of optical fibers with the properties of plasma allows diverse potential applications, such as gas detection in remote, confined, or harsh environments, high-level disinfection and sterilization of medical equipment or high-quality surface treatment (micrometric scale).

How the Material Characteristics of Optical Fibers and Soil Influence the Measurement Results of Distributed Acoustic Sensing.

Fiber optic distributed acoustic sensing (DAS) technology is widely used in security surveillance and geophysical survey applications. The response of the DAS system to external vibrations varies with different types of fiber optic cable connections. The mechanism of mutual influence between the cable's characteristics and DAS measurement results remains unclear. This study proposed a dynamic model of the interaction between the optical cable and the soil, analyzed the impact of the dynamic parameters of the optical cable and soil on the sensitivity of the DAS system, and validated the theoretical analysis through experiments. The findings suggest that augmenting the cable's bending stiffness 5.5-fold and increasing its unit mass 4.2-fold result in a discernible reduction of the system's response to roughly 0.15 times of its initial magnitude. Cables with lower unit mass and bending stiffness are more sensitive to vibration signals. This research provides a foundation for optimizing vibration-enhanced fiber optic cables and broadening the potential usage scenarios for DAS systems.

Unveiling Structural Insights into Nanocrystal-Doped Optical Fibers via Confocal Raman Microscopy.

An in-depth characterization of nanoparticle-doped optical fibers is crucial to understand the potential new functionalities of the engineered glass and thus their applicability fields. The high temperatures of the manufacturing process strongly affect the nanoparticle features, and therefore, their analysis is necessary after fiber drawing. However, the difficulties associated with the use of atomic resolution microscopies to analyze the nanoparticle features in the fiber core, mainly related to sample preparation and expensive costs, usually prevent their study. In this work, we overcome some of those limitations and demonstrate, for the first time, the suitability of structurally and microstructurally studying in detail nanocrystals contained in a fiber core of ∼10 μm by combining confocal Raman microscopy, Rayleigh light-scattering microscopy, and scanning electron microscopy (SEM). A thorough study of cubic-shaped and rod-shaped YPO4 nanocrystals contained in optical fibers reveals their crystallization in tetragonal (t) and monoclinic (m) structures, respectively. The symmetric (ν1) and asymmetric stretching (ν3) Raman modes display a different and remarkable red shift as particle size decreases in both types of nanocrystals, which in the case of the cubic-shaped nanocrystals is fitted to an exponential function along with a Raman peak broadening. Moreover, their Raman dependence vs temperature is evaluated up to 600 °C, observing a phonon softening that follows a linear behavior, which is discussed in detail. These findings add new insights to pure m-YPO4, which was unknown to date, and the REPO4 family and open up new avenues that can be extrapolated to other nanostructures incorporated into optical fiber cores, which will advance progress in the field of nanoparticle-doped optical fibers.

Design and Analysis of a Large Mode Field Area and Low Bending Loss Multi-Cladding Fiber with Comb-Index Core and Gradient-Refractive Index Ring.

The large mode field area fiber can raise the tolerance of power, and high requirements for the bending characteristics of optical fibers are needed. In this paper, a fiber composed of a comb-index core, gradient-refractive index ring, and multi-cladding is proposed. The performance of the proposed fiber is investigated by using a finite element method at a 1550 nm wavelength. When the bending radius is 20 cm, the mode field area of the fundamental mode can achieve 2010 μm2, and the bending loss is reduced to 8.452 × 10-4 dB/m. Additionally, when the bending radius is smaller than 30 cm, there are two variations with low BL and leakage; one is a bending radius of 17 cm to 21 cm, and the other is from 24 cm to 28 cm (except for 27 cm). When the bending radius is between 17 cm and 38 cm, the highest bending loss is 1.131 × 10-1 dB/m and the lowest mode field area is 1925 μm2. It has a very important application prospect in the field of high-power fiber lasers and telecom applications.

Optical Fiber Sensors Systems in Oil Tanks: Toward Structural Health Monitoring and Liquid-Level Estimation

This paper presents the development, characterization and analysis of optical fiber integrated sensors systems for structural health monitoring (SHM) in oil tanks. The sensors are based on fiber Bragg gratings (FBGs) embedded in nitrile rubber strips through a vulcanization method. Two sensors arrays (with 5 FBGs each) are fabricated and installed at different regions of the oil tank, namely the metallic side wall and polycarbonate display of the tank. The sensors were characterized as a function of the strain in the nitrile rubber strips, where all analyzed sensors presented a high linearity, since a determination coefficient (R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) higher than 0.999 is obtained. Tests with different oil levels inside the tank indicate the feasibility of the sensors in the shape reconstruction and real-time strain monitoring of the structural element, where even the bending in the sidewall of the tank is estimated. Such results indicated a correlation between the wavelength shift of the FBGs and the liquid level inside the tank, which leads to the possibility of measuring liquid level from the tank strain distribution in a non-contact approach using a Random Forest algorithm for data processing. The proposed non-contact and machine learning-enable liquid level assessment resulted in errors of around 1.07%. Thus, the proposed approach indicate the feasibility of a predictive maintenance of oil tank through real-time monitoring of strain and possible structural flaws of the oil tanks in conjunction to non-contact approach of oil processing monitoring that can be useful in data fusion as well as multiparameter approaches for oil monitoring.

Optical curvature sensor based on polarization characteristics of optical fiber.

Curvature measurement plays an important role in various applications. An optical curvature sensor based on polarization characteristics of optical fiber is proposed and verified by experiments. The direct bending of the fiber causes a change in birefringence, which results in a change of Stokes parameters of the transmitted light. The large curvature measurement range of tens to more than 100 m-1 has been realized in the experiment. For micro bending, a cantilever beam structure is used to achieve a sensitivity of up to 12.26/ m-1 and a linearity of 99.49% in the measurement range of 0 to 0.15 m-1, with a resolution of up to 10-6 m-1 order of magnitude, which reaches the level of the latest report. The method with the advantages of simple fabrication, low cost and good real-time performance gives a new development direction to the curvature sensor.

Experimental Study on Overlying Strata Movement Characteristics and Distributed Optical Fiber Characterization of Stope

In order to study the migration characteristics and strata behavior law of mining-induced rocks in fully mechanized caving face of coal mine, taking the actual geological mining of Longwanggou Coal Mine as the background, using computer software (KSPB) to identify the location of key strata. The physical similar material simulation test was used to monitor the movement characteristics of mining-induced rocks by using the internal displacement sensor (IDS) and distributed optical fiber sensor (DOFS). A three-dimensional physical model of 3.6 m × 2.0 m × 2.0 m was built; the internal displacement of rock was measured by IDS. BOTDA distributed optical fiber was used to monitor the dynamic movement and deformation law of coated rock. Finally, the two monitoring results were compared and analyzed. The results show that: (1) the displacement curve of the fractured rock mass in the key strata shows a “stepped” increase; (2) based on the analysis of displacement continuous monitoring results, the strata behavior law of working face is obtained. The first weighting interval of 61601 working face is 90 cm, and the periodic weighting steps are 105 cm, 115 cm, 135 cm, 150 cm, 165 cm, 180 cm, 215 cm, and 240 cm; (3) the average strain of fiber is proposed. The first weighting and periodic weighting laws of the working face are represented by the average strain, which are consistent with the experimental phenomena. The first weighting in the average strain curve shows the first mutation peak, and the periodic weighting shows the periodic mutation peak change of the average strain curve.

Fabrication and characterization of active polymer optical fibers with a ring-doped structure

This paper employs the solution-doping technique for the fabrication of polymer optical fibers (POFs) doped with two perylene derivatives, Lumogen Yellow 083 and Lumogen Red 305, in different combinations. With the solution-doping technique is very easy to control the amount of dopant penetration into the core of non-doped uncladded fibers, allowing the fabrication of active POFs with a novel ring-doped structure. In addition to manufacturing the fibers, these have also been optically characterized. Specifically, the influence of the combination of dopants, pumping power and wavelength, as well as the light propagation distance, have been measured and analyzed. Furthermore, time-resolved emission characteristics have also been measured to determine the fluorescence lifetimes and to extract information about the energy transfer between the dopants. Finally, the aim of this work has been to investigate the performance of the aforementioned POFs for fluorescent lighting applications, with a special focus on tunable light sources, and also for sensing applications.