Optical Fiber Research Articles

Analysis on acoustic modes and Brillouin gain spectra of backward stimulated Brillouin scattering in W-type acoustic waveguide optical fibers

The acoustic Helmholtz equations of W-type acoustic waveguide fibers, including WI- and WII-type acoustic velocity of vl,2 < vl,3 < vl,1 and vl,2 < vl,1 < vl,3, separately are solved by using the method of separation of variables, and their characteristic equations are derived according to the boundary condition and the acoustic Helmholtz equations. The distribution and cut-off of acoustic modes are analyzed by introducing acoustic normalized frequencies. The dependence of the acoustic inner core radius, the acoustic velocities in the acoustic inner and acoustic outer core on acoustic modes, and Brillouin gain spectra (BGS) is investigated. The results indicate that two significant peaks of the BGS are induced by acousto-optic coupling of L01 and L02 acoustic modes with LP01 optical mode. The acousto-optic overlap factor of the L01 acoustic mode decreases first and then increases, and that of the L02 acoustic mode increases first and then decreases with the rise of acoustic inner core radius. Due to the difference of the acoustic mode field distribution, the gain peak induced by L01 mode is sensitive to the acoustic velocity of the acoustic inner core, and that of the L02 mode is sensitive to the acoustic velocity of the acoustic outer core. These conclusions agree well with the reported experimental results, and provide theoretical references for research and application of backward stimulated Brillouin scattering of acoustic waveguide optical fibers.

Design and Assembly of a Miniature Catheter Imaging System for In Vivo Heart Endoscopic Imaging.

In this paper, we present the design and fabrication of a novel chip-on-tip catheter, which uses a microcamera and optical fibres to capture in vivo images in a beating porcine heart thanks to a saline flush to clear the blood field. Here, we demonstrate the medical utility and mechanical robustness of this catheter platform system, which could be used for other optical diagnostic techniques, surgical guidance, and clinical navigation. We also discuss some of the challenges and system requirements associated with developing a miniature prototype for such a study and present assembly instructions. Methods of clearing the blood field are discussed, including an integrated flush channel at the distal end. This permits the capture of images of the endocardial walls. The device was navigated under fluoroscopic guiding, through a guiding catheter to various locations of the heart, where images were successfully acquired. Images were captured at the intra-atrial septum, in the left atrium after a trans-septal cross procedure, and in the left ventricle, which are, to the best of our knowledge, the first images captured in an in vivo beating heart using endoscopic techniques.

Gain-controlled taming of recurrent modulation instability

We show how the recurrence phenomenon characteristic of the nonlinear stage of induced modulational instability in a passive fiber is affected by forcing. An additional linear amplification, even if extremely weak, induces separatrix crossing corresponding to critical values of the gain around which the recurrence process considerably slows down, switching between dynamical orbits of different kind. We present evidence for such phenomenon in a fiber optics experiment where the gain is finely tuned by means of Raman amplification. A theoretical explanation is also provided that matches almost perfectly with our experimental results. Published by the American Physical Society 2024

Long wavelength fluoride optical glass fibers performance signature in high speed local area data networks

Abstract This paper has clarified long wavelength fluoride optical glass fibers performance signature in high speed local area data networks. The signal attenuation and the total fiber pulse broadening are studied versus network length for various fluoride optical glass fibers and AS2 Se3 glass fiber at various spectral wavelengths. The total signal delay time is demonstrated with fiber numerical aperture with 15 km network length for various fluoride optical glass fibers and AS2 Se3 glass fiber at 2.5 μm optimum spectral wavelength. Total fiber signal bandwidth, total Shannon channel bit rate, and NRZ/RZ channel data rate transmission are clarified with 15 km network length for various fluoride optical glass fibers and AS2 Se3 glass fiber at 2.5 μm optimum spectral wavelength.

Damage detection of Kevlar woven fabric using optical fiber multimode interferometer

Kevlar woven fabric is crucial for the lightweight design of aerospace structures due to its unique advantages. However, it is susceptible to damage during operation, making effective damage detection essential for ensuring structural reliability. Nevertheless, conventional sensors used for damage detection have limitations such as complex manufacturing processes and weight. To address this issue, this paper proposed a simple singlemode-multimode-singlemode (SMS) optical fiber sensor to collect vibration signals and construct a damage recognition model based on natural frequency in order to identify the size of damages in Kevlar woven fabrics. To achieve a highly linear and accurate sensor, a length determination criterion for multimode optical fiber segments based on quasi-image, notch, and transmission spectrum loss was proposed. An optical sensor was fabricated based on this criterion. The feasibility and sensitivity of the sensor for vibration signal measurement were verified by constructing a vibration signal measurement device. An experimental study was conducted to detect damage in Kevlar tapes, where the natural frequency changes measured by the SMS sensor were integrated with an optimized multi-variable gray model for damage size detection. The experimental results indicate that the estimated error in damage size is 0.71%. The damage identification system proposed in this paper offers a simple and cost-effective solution for measuring damage in flexible structures using fiber optic sensors.

Multi-Directional Strain Measurement in Fiber-Reinforced Plastic Based on Birefringence of Embedded Fiber Bragg Grating.

Embedded fiber Bragg gratings are increasingly applied for in-situ strain measurement in fiber-reinforced plastics, integral to high-end aerospace equipment. Existing research primarily focuses on in-plane strain measurement, limited by the fact that fiber Bragg gratings are mainly sensitive to axial strain. However, out-of-plane strain measurement is equally important for comprehending structural deformation. The birefringence of fiber Bragg gratings shows promise for addressing this problem; yet, the strain transfer relationship between composites and optical fibers, along with the decoupling method for multi-directional strains, remains inadequately explored. This study introduces an innovative method for multi-directional strain measurement in fiber-reinforced plastics using the birefringence of a single-fiber Bragg grating. The strain transfer relationship between composites and embedded optical fibers was derived based on Kollar's analytical model, leading to the development of a multi-directional strain decoupling methodology. This method was experimentally validated on carbon fiber/polyetherimide laminates under thermo-mechanical loading. Its reliability was confirmed by comparing experimental results and finite element simulations. These findings significantly broaden the application scenarios of fiber Bragg gratings, advancing the in-situ measurement technology crucial for the next generation of high-end aerospace equipment.

A Fiber optics based surface enhanced Raman spectroscopy sensor for chemical and biological sensing

This paper investigates an innovative surface-enhanced Raman scattering (SERS) sensor developed on a side-polished multimode optical fiber core. The optical fiber was integrated into specifically designed 3-dimensional printed mold, where manual polishing of the fiber took place. Microsphere Photolithography (MPL) techniques was employed to pattern periodic nanoantenna arrays on the polished surface, incorporating multiple disk diameters at a fixed periodicity. Subsequent gold deposition/lift-off were carried out to transfer the pattern from the photoresist to the fiber core, resulting in highly periodic hexagonal closed pack (HCP) arrays of nanodisks. These arrays can significantly enhance the SERS signal intensity compared to that of the fiber tip. The sensor's performance was demonstrated using various concentrations of Rhodamine 6G (R6G) dye ranging from 10−5 to 10−9 M as a function of disk diameter and sensing surface area. The resulting spectra revealed characteristic peak positions that aligned well with the fingerprint Raman spectra of R6G. The results demonstrates that the sensitivity is 10−9 M for the sensor with an 800 nm disk diameter.

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.

A Study on Sensitivity Improvement of the Fiber Optic Acoustic Sensing System Based on Sagnac Interference.

A new pickup structure was introduced and modified to improve the resolution of the linear Sagnac optical fiber acoustic sensing system. The maximum strains corresponding to the material, diameter, wall thickness, and height of the pickups were analyzed by simulation. An aluminum cylinder with a diameter of 110 mm, a wall thickness of 3 mm, and a height of 120 mm was chosen as the basic pickup. A four-groove pickup with a vertical width of 80 mm and a horizontal width of 20 mm was introduced to improve the sensitivity of the system. The experiments showed that the average peak-to-peak sensitivity of the four-groove pickup increased by 215.54% to 106.806 mV/Pa. The improved pickup can be applied in areas to monitor the situation of invasion of the Sagnac optical fiber acoustic sensing system.

Temperature monitoring and cracking risk analysis of corridor top arch of Baihetan arch dam during construction period

During the construction period, the phenomenon of stress concentration at the top arch of the corridor is obvious, which is easy to produce surface cracks. As a consequence, it is of great importance to research the temperature and stress changes of the corridor during the construction period, analyze the cracking risk of the top arch of the corridor, and put forward the corresponding temperature control measures. This study, the temperature gradient test of the top arch of the corridor is conducted, utilizing the distributed optical fiber buried in the construction place of Baihetan Arch Dam. Considering the influence of creep, the finite element method is used to simulate the thermal stress of the top arch concrete of the corridor, and the cracking risk of the top arch concrete is evaluated. According to varying temperature drops, it is suggested that different temperature control measures to maintain the heat of the top arch of the corridor. The recommended measures are as follows: when the temperature drops by 6 °C, 12 °C and 18 °C, the roof vault of the corridor shall be covered with 20 mm, 40 mm and 50 mm polyethylene insulation covers respectively, and the interior of the corridor shall not be sprayed with 20 mm and 40 mm polyurethane respectively. Temporary storm doors shall be set at the entrances and exits of the corridor. The control measures of temperature can meet the requirements of temperature control and crack prevention of the concrete of the dam body of Baihetan Arch Dam.

An experimental study towards the development of highly sensitive opto-mechanical sensors based on FSBS in telecom optical fibers

An experimental study towards the development of highly sensitive opto-mechanical sensors based on FSBS in telecom optical fibers

Analysis of optical soliton interactions and their parallel transmission characteristics in optical fibers

Analysis of optical soliton interactions and their parallel transmission characteristics in optical fibers

Zona Incerta GABAergic Neurons Facilitate Emergence from Isoflurane Anesthesia in Mice.

The zona incerta (ZI) predominantly consists of gamma-aminobutyric acid (GABAergic) neurons, located adjacent to the lateral hypothalamus. GABA, acting on GABAA receptors, serves as a crucial neuromodulator in the initiation and maintenance of general anesthesia. In this study, we aimed to investigate the involvement of ZI GABAergic neurons in the general anesthesia process. Utilizing in-vivo calcium signal optical fiber recording, we observed a decrease in the activity of ZI GABAergic neurons during isoflurane anesthesia, followed by a significant increase during the recovery phase. Subsequently, we selectively ablated ZI GABAergic neurons to explore their role in general anesthesia, revealing no impact on the induction of isoflurane anesthesia but a prolonged recovery time, accompanied by a reduction in delta-band power in mice under isoflurane anesthesia. Finally, through optogenetic activation/inhibition of ZI GABAergic neurons during isoflurane anesthesia, we discovered that activation of these neurons facilitated emergence without affecting the induction process, while inhibition delayed emergence, leading to fluctuations in delta band activity. In summary, these findings highlight the involvement of ZI GABAergic neurons in modulating the emergence of isoflurane anesthesia.

Nitrogen-vacancy centers as a self-gauged micro-scale heater and its application for multi-modal sensing

The optical excitation of nitrogen-vacancy (NV) color centers in diamonds mostly results in fluorescence emission. During this process, a portion of the incident energy is transferred to phonon vibration, which heats the diamond crystal. For single NV color centers, the heat generated by the optical cycle is negligible, while for an ensemble of NV defects, the generated heat accumulates rapidly and heats the diamond. The temperature rise is rapid due to the high thermal conductivity of the diamond. In addition to the ability to be heated by light, the NV defect's unique properties also allow for the precise measurement of temperature using optically detected magnetic resonance. Here, we experimentally demonstrate that microcrystalline diamond containing NV center ensembles can be used as a self-gauged microheater. We attached a microcrystal diamond to an optical fiber in an endoscope configuration, evaluated its performance as a self-gauged heater under varied biologically relevant environments, and discussed its potential applications. In addition to the aforementioned capabilities, the NV defect enables the precise measurement of local magnetic fields. This provides a unique multimodal sensor to probe temperature-controlled magnetic phenomena at microscopic scales.

Coherent random fiber laser emission from CdSe/ZnS quantum dots.

We experimentally demonstrate the coherent random laser emission by combining CdSe/ZnS colloidal quantum dots (CQDs) with hollow optical fiber. Through the localized surface plasmon resonance (LSPR) induced by Ag nanoparticles (NPs), well-distinguished discrete spikes are observed from the Ag modified hollow fiber loaded with CdSe/ZnS QDs solution. In addition, coherent random laser action with low threshold is also realized in the hollow optical fiber filled with high packing-density CdSe/ZnS QDs even if the Ag NPs is not introduced. The self-assembled clusters of CdSe/ZnS QDs serve as the optical gain media as well as the strong scattering centers. The angle measurement experiments show that the directional emission of random laser can be adjusted by using different pumping manners. This facile, inexpensive, low pump threshold random laser could be widely used in photonic devices and display imaging.&#xD.

Revealing the Impact of Composition on Oil Monitoring Performance of Ni-Ti-Cu Coated Optical Fiber

Shape Memory Alloy-coated optical fiber provides an economical, Smart, and real-time monitoring technological solution for Industry 4.0. In this work, the compositional influence of Ni-Ti-Cu coating on optical signal actuation has been studied. Morphological studies showed improvement in the grain size, surface roughness, and a better shape memory effect. Thermal characteristics revealed an increase in the phase transformation temperature of NiTiCu with higher copper content. Experimental analysis of optical fiber sensors in Mineral Oil resulted in a gradual shift in the actuation temperature range. A sensitivity of ∼52 mV/°C was recorded in the actuation window, showcasing the improved response time for copper-rich composition. A comparison of coated-uncoated optical fiber performance in oil has also been presented, and delamination studies were conducted by continuously exposing the samples to hot oil. The work can be referred for requirement-based composition selection for real-time and smart monitoring capability in the Oil industries.

Cytocidal Effects of Interstitial Photodynamic Therapy Using Talaporfin Sodium and a Semiconductor Laser in a Rat Intracerebral Glioma Model.

This preclinical study was conducted to investigate the efficacy of interstitial PDT (i-PDT) for malignant gliomas arising deep within the brain, which are difficult to remove. C6 glioma cells were implanted into the basal ganglia of rats, and 3 weeks later, the second-generation photosensitizer talaporfin sodium (TPS) was administered intraperitoneally. Ninety minutes after administration, a prototype fine plastic optical fiber was punctured into the tumor tissue, and semiconductor laser light was irradiated into the tumor from a 2-mm cylindrical light-emitting source under various conditions. The brain was removed 24 h after the i-PDT and analyzed pathologically. The optical fiber was able to puncture the tumor center in all cases, enabling i-PDT to be performed. Histological analysis showed that tumor necrosis was induced in areas close to the light source, correlating with the irradiation energy dose, whereas apoptosis was induced at some distance from the light source. Irradiation using high energy levels resulted in tissue swelling from strong tumor necrosis, and irradiation at 75 J/cm2 was most suitable for inducing apoptosis. An experimental system of i-PDT using TPS was established using malignant glioma cells transplanted into the rat brain. Tumor cell death, which correlated with the light propagation, was induced in tumor tissue.

An optical fiber high sensitivity temperature sensor with MZI and FPI parallel connection

Accurate detection of temperature is of great significance in the field of medical research. The focal point of this article centers around an optical fiber sensor that integrates Fabry Perot interferometer (FPI) filled with polydimethylsiloxane (PDMS) and Mach Zehnder interferometer (MZI), leveraging the principle of the vernier effect. By introducing the vernier effect principle, the sensitivity is 31.09 nm/°C in the detection range of 36 ∼ 40°C, and the maximum temperature measurement error is about 0.55 %. In addition, good linear response and longtime stability make it suitable for application in various scenarios where accurate temperature measurement is required.

Discovery of a hyperluminous quasar at z = 1.62 with Eddington ratio >3 in the eFEDS field confirmed by KOOLS-IFU on Seimei Telescope

Abstract We report the discovery of a hyperluminous type 1 quasar (eFEDS J082826.9-013911; eFEDS J0828-0139) at $z_{\rm spec} = 1.622$ with a super-Eddington ratio ($\lambda _{\rm Edd}$). We perform the optical spectroscopic observations with KOOLS-IFU (the Kyoto Okayama Optical Low-dispersion Spectrograph with optical fiber) on the Seimei Telescope. The black hole mass ($M_{\rm BH}$) based on the single-epoch method with Mg ii $\lambda$2798 is estimated to be $M_{\rm BH} = {(6.2 \pm 1.2) }\times 10^8\, M_{\odot }$. To measure the precise infrared luminosity ($L_{\rm IR}$), we obtain submillimeter data taken by SCUBA-2 on the James Clerk Maxwell Telescope and conduct the spectral energy distribution analysis with X-ray to submillimeter data. We find that $L_{\rm IR}$ of eFEDS J0828-0139 is $L_{\rm IR} = {(6.8 \pm 1.8)} \times 10^{13}\, L_{\odot }$, confirming the existence of a hypeluminous infrared galaxy. $\lambda _{\rm Edd}$ is estimated to be $\lambda _{\rm Edd} = {3.6 \pm 0.7}$, making it a quasar with one of the highest BH mass accretion rates at cosmic noon.

Soliton solutions of nonlinear coupled Davey–Stewartson Fokas system using modified auxiliary equation method and extended (G′/G2)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(G'/G^{2})$$\\end{document}-expansion method

The captivating realm of the nonlinear coupled Davey–Stewartson Fokas system is explored in this research paper. As a powerful tool, the proposed system is utilized for the realistic representation of various non-linear dynamical mechanisms in different fields of sciences and engineering including non-linear optical fibers, plasma physics and water waves theory. Two distinct exact methods, namely the modified auxiliary equation method and the extended (G′/G2)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(G'/G^{2})$$\\end{document}-expansion method, are utilized to acquire the exact soliton solutions of the non-linear coupled Davey–Stewartson Fokas system. A plethora of novel soliton solutions containing anti-kink, kink, bright, dark, dark-bright, bright-dark and some other singular soliton solutions, have been obtained using the employed exact methods. The significance of proposed manuscript lies in the novelty of obtained solutions. Kink, dark and bright solitons have wide applications in optical fiber communications, plasma physics and water waves dynamics. The acquired nontrivial exact solutions contain exponential, trigonometric, rational and hyperbolic functions. Some obtained solutions are visually represented through graphical simulations of 3D, 2D-contour and 2D-line plots, providing a comprehensive visualization of the soliton dynamics.The modulation instability of the proposed nonlinear system has been investigated, which ensures the stability of the system.