Fiber Optic System Research Articles

Carbon Black Absorption Enhanced Fiber-Optic Photoacoustic Gas Sensing System with Ultrahigh Sensitivity.

A highly sensitive trace gas sensing system based on carbon black absorption enhanced photoacoustic (PA) spectroscopy (PAS) is reported. A carbon black sheet and a fiber-optic cantilever microphone (FOCM) are integrated to form a fiber-optic cantilever spectrophone (FOCS). The gas concentration is obtained by measuring the acoustic wave amplitude generated by the carbon black sheet, which absorbs the laser passing through the interest gas. Due to the higher laser absorption rate of carbon black than that of flake graphite, the excited solid-state PA pressure wave is enhanced. The ability of the FOCS to detect weak sound waves is related to the laser power and the absorption length. Therefore, an Erbium-doped optical fiber amplifier and a multipass cell are also used to increase laser absorption by the tested gas, which combines with the FOCM to achieve multimechanism enhancement of the system performance. Different from traditional PAS gas detection systems, this system is a noncontact measurement solution, which not only effectively avoids gas flow noise but also makes the sensing element immune to the damage of corrosive gases. The experimental results show that the sensitivity of the system is about four times higher than that of the system using flake graphite as the light-absorbing element. When the average time is 100 s, the minimum detection limit of acetylene is 0.31 ppb. The normalized noise equivalent absorption coefficient of the designed PA system is achieved to be 7.1 × 10-10 cm-1·W·Hz-1/2.

Higher order dispersion-managed solitons for the capacity enhancement of fiber optic communication systems

Higher order dispersion-managed solitons for the capacity enhancement of fiber optic communication systems

A simple and integrated fiber-optic real-time qPCR platform for remote and distributed detection of epidemic virus infection.

Quantitative polymerase chain reaction (qPCR) is a well-recognized technique for amplifying and quantifying nuclear acid, and its real-time monitoring capability, ultrahigh sensitivity, and accuracy make it a "golden-standard" tool in both molecular biology research and clinical diagnostics. However, current qPCR tests rely on bulky instrumentation and skilled laboratorians in centralized laboratories, which spatially and temporally separate the sample collection and test, leading to longer sample turnaround times (TATs) and limited working conditions. Herein, we propose an integrated optical fiber real-time polymerase chain reaction (iF-PCR) system that successfully allows convenient sample collection, rapid thermocycling, closed-loop thermal annealing, and real-time fluorescence detection in a tiny capillary reactor. By leveraging the easy-handling capillary-fiber structure and rapid photothermal actuation of the graphene-decorated fiber head, the whole TAT can be shortened, including sampling and 40 thermocycle amplifications, within 23min, in which an ultrasmall sample volume of ∼15μL is needed. Furthermore, the thermal amplification and fluorescence detection capability of the optical fiber system was cross-checked by a commercial qPCR instrument. The fiber-optic qPCR strategy can correctly distinguish between positive and negative samples of clinical respiratory syncytial virus (RSV) without the need for laboratory professional skills. Taking advantage of the distance signal transmission nature of optical fibers, the proposed strategy enables remote testing, which can eliminate the necessity of instrument deployment in crowded biosafety laboratories and facilitate potential distributed pathogen testing for coping with a new round of pandemics.

Laboratory Tests Using Distributed Fiber Optical Sensors for Strain Monitoring.

Using fiber optics as a tool for different kinds of geotechnical monitoring can be highly attractive and cost-effective when compared to conventional instruments, such as piezometers and inclinometers, among others. A single fiber optic cable may cover a larger monitoring area compared to conventional instrumentation and allows for monitoring more than one physical quantity with the same fiber optic cable. The literature provides several different examples of distributed fiber optic systems usage. For using any sensor, a calibration curve and parameters are required. In the case of strain sensors, calibration is required to derive strain values from the frequency measurement quantity. However, fiber optic sensor cable manufacturers do not often provide cable calibration parameters, and researchers should consult the specialized literature. This article thus presents a bench adjusted for tests with single-mode fiber optic cables, as well as results of tensile tests for defining the function of strain variations in two different optical fiber cables manufactured by different companies using two different distributed interrogators. This paper also proposes a methodology for calibrating fiber optic cable deformation. A few manufacturers of fiber optic cables aim at civil engineering applications. Therefore, we propose a calibration methodology to show the possibility of obtaining calibration parameters of any fiber optic cable, even those manufactured for telecommunications purposes and not only for cables manufactured for civil engineering use. Thus, researchers will not be restricted to the acquisition of special cables for their applications. The results allowed us to conclude that the application of calibrated fiber optic sensors to experimental pile foundations permits the evaluation of the load-displacement behavior of these elements under different loading conditions.

Fiber Optic Sensing System for Disturbance Location Detection with Extended Measurement Range based on Dual Sagnac Interferometer

Fiber Optic Sensing System for Disturbance Location Detection with Extended Measurement Range based on Dual Sagnac Interferometer

A Multisource Signal-Conditioned Fiber Optic Sensing System for Microwave Temperature Acquisition and Prediction

A Multisource Signal-Conditioned Fiber Optic Sensing System for Microwave Temperature Acquisition and Prediction

Dynamics and soliton solutions of the perturbed Schrödinger-Hirota equation with cubic-quintic-septic nonlinearity in dispersive media

<p>This study systematically investigates the dynamics of the perturbed Schrödinger-Hirota equation with cubic-quintic-septic nonlinearity under spatiotemporal dispersion, providing insights into soliton propagation in dispersive media. We begin by examining the system's phase portrait and chaotic behavior, followed by the derivation of exact traveling wave solutions, including optical solitons and periodic solutions, using an enhanced algebraic method. The findings are vividly illustrated through three-dimensional and two-dimensional graphical simulations, which analyze the impact of key parameters on the solutions. This study not only presents a variety of optical soliton solutions, but also clarifies the underlying dynamics, offering theoretical guidance for fiber optic communication systems and holding significant applied value for achieving more efficient and reliable optical communications.</p>

Fibre Optic Method for Detecting Oil Fluorescence in Marine Sediments.

The aim of this study is to verify the possibility of detecting oil in the bottom sediment using a fibre optic system. The presence of oil is assessed on excitation-emission spectra obtained from spectral fluorescence signals of the sediment sample. A factory spectrofluorometer coupled with an experimental fibre optic measurement system was used. During the determination of spectra, the fibre optic system is set at a 45° angle to the sediment surface and placed above its surface. The light exciting the fluorescence and the light emitted by the sediment are transmitted in a combined bundle of fibre optic threads. The analysis of excitation-emission spectra of sediments contaminated with oil shows variability of the shapes of fluorescence spectra depending on the type and degree of oil contamination, which indicates the feasibility of the sensor design for detecting oil in the sediment in situ.

Design of a Novel 31.5 THz Bandwidth Hybrid TDFA-HDFA at 2000 nm and Its Applications in Unregenerated DWDM Lightwave Transmission Systems

We report design and applications of a novel multi-Watt (> 1 Watt output power) 2000 nm band hybrid Thulium- and Holmium-doped fiber amplifier with record wideband 380 nm (31.5 THz) continuously operating bandwidth from 1720-2100 nm. We outline the theory, physics, and simulations behind this design, and show by comparison with previously published experimental results that the design presented is accurate to within ± 0.5 dB in saturated output power and ± 1.0 dB in small signal gain. Applications in future ~300-400 nm bandwidth wideband 2000 nm Pb/s DWDM lightwave fiber optical transmission systems spanning 10,000 km using new hollow core fiber designs are discussed. In particular, we demonstrate robust beginning-of-life optical signal to noise ratio (OSNR) and Q-factor margins for designs of 0.161 Pb/s DWDM unregenerated (without optical-to-electrical-to-optical or O-E-O electronic functions) all-optical transmission in the 2000 nm band over 10,000 km for representative terrestrial and submarine lightwave applications. We achieve a total capacity × distance product of 1608 Pb/s. km (1.61 Exabits/s. km) over a single one-core optical fiber for the 10,000 km system designs. Applications to designs of 40,000 km deployable unregenerated all-optical DWDM 0.124 Pb/s subsea lightwave transmission systems with 5.21 Exabit/s. km capacity × distance product are outlined. Received: 9 September 2024 | Revised: 10 December 2024 | Accepted: 26 December 2024 Conflicts of Interest The author declares that he has no conflicts of interest to this work. Data Availability Statement Exail Tm- and Ho-doped gain fiber specifications are openly available at https://cybel-llc.com/wp-content/uploads/2021/06/IXF-HDF-PM-8-125_edA-Ho-SC-doped-PM-fiber.pdf and https://cybel-llc.com/wp-content/uploads/2021/06/IXF-TDF-PM-5-125_edA-Tm-SC-doped-PM-fiber.pdf. Data of the component devices in Table 1 are openly available at https://retandassociatesllc.com/wp-content/uploads/2024/04/GSLEOP2022-Presentation-RET-v.11-08222022.pdf. Other data are available from the corresponding author upon reasonable request. Author Contribution Statement Robert E. Tench: Conceptualization, Methodology, Software, Validation, Formal analysis, Investigation, Resources, Data curation, Writing - original draft, Writing - review & editing, Visualization, Supervision, Project administration, Funding acquisition.

Beam Tilt Aberration Detection of the Seven-Unit Phased Fiber Laser Array.

In this paper, we present a method based on the conjugate image principle and micro-nano optics to detect tilt aberrations of a phased fiber laser array system. A co-aperture optics system was adapted to detect the tilt aberrations of a seven-element phased fiber laser array system simultaneously. A Kepler telescope was designed to construct the conjugate relation between the exit pupil of a fiber optic laser array system and a microlens array and also to match the size of the seven beams and the microlens array. The apochromatic theory was used to meet the multispectral (1064 ± 0.3 nm, 1030 ± 0.3 nm, and 633 ± 0.2 nm) detection needs. A far-field detection unit was also designed to evaluate beam quality. When the actual beam was offset by 1 pixel, the beam tilt was about 0.7 µrad. The maximum detection error of the seven-element system was about 7 µrad. It could not only directly detect the beam's tilt angle but also maintained detection accuracy while reducing the algorithm complexity.

Exploring the significance of quantum cryptography in future network security protocols

In an era of unprecedented technological advancement, the rise of quantum computing poses both opportunities and challenges to network security. While quantum computers promise to revolutionize data processing and problem-solving, they also render traditional cryptographic protocols vulnerable, threatening the integrity of current network security systems. Quantum cryptography, particularly quantum key distribution (QKD), emerges as a groundbreaking solution, leveraging the principles of quantum mechanics to ensure unparalleled data security. Unlike classical methods, QKD guarantees secure communication by detecting eavesdropping attempts, as any observation of quantum states disrupts their integrity. This paper explores the pivotal role of quantum cryptography in shaping future network security protocols amidst a landscape of increasing cyber threats. It provides a comprehensive analysis of QKD systems, their integration into existing infrastructure, and their resilience against potential quantum-based attacks. The discussion includes real-world implementations, such as satellite-based QKD networks and fiber-optic quantum communication systems, illustrating their practical viability and scalability. Furthermore, the paper addresses current challenges, including cost, technical complexity, and interoperability with classical networks, offering insights into ongoing research aimed at overcoming these hurdles. As global reliance on digital infrastructure grows, the transition to quantum-resilient security frameworks becomes imperative. Policymakers, industry leaders, and technology developers must collaborate to advance quantum cryptographic technologies and ensure their accessibility. By securing communication channels against both classical and quantum threats, quantum cryptography is positioned to redefine the foundations of network security, paving the way for a more secure and interconnected digital future.

Novel insights into high-order dispersion and soliton dynamics in optical fibers via the perturbed Schrödinger–Hirota equation

This study offers a comprehensive analysis of the Perturbed Schrödinger -Hirota Equation (PSHE), crucial for understanding soliton dynamics in modern optical communication systems. We extended the traditional Nonlinear Schrödinger Equation (NLSE) to include higher-order nonlinearities and spatiotemporal dispersion, capturing the complexities of light pulse propagation. Employing the modified auxiliary equation method and Adomian Decomposition Method (ADM), we derived a spectrum of exact traveling wave solutions, encompassing exponential, rational, trigonometric, and hyperbolic functions. These solutions provide insights into soliton behaviors across diverse parameters, essential for optimizing fiber optic systems. The precision of our analytical solutions was validated through numerical solutions, and we explored modulation instability, revealing conditions for soliton formation and evolution. The findings have significant implications for the design and optimization of next-generation optical communication technologies.

In Vivo Contactless, Cellular-Resolution Imaging of the Healthy and Pathological Human Limbus With 250-kHz Point-Scanning SD-OCT.

To demonstrate that high-seed, ultra-high-resolution spectral-domain optical coherence tomography (SD-OCT) technology can image in vivo fine morphological features in the healthy and pathological human limbus. A compact, fiberoptic SD-OCT system was developed for imaging the human limbus. It combines ∼1.5-µm isotropic spatial resolution in ocular tissue and an acquisition rate of 250,000 A-scans per second. The imaging probe was outfitted with two microscope objectives to provide flexibility in the choice of wide field of view and extended depth of focus versus high lateral resolution. The clinical potential of the system was evaluated by imaging subjects with limbal stem cell dysfunction (LSCD; n = 4) and healthy controls (n = 6). Limbus images acquired from the healthy controls showed normal cellular structure of the limbal crypts, palisades of Vogt (POVs), and vasculature of the underlying scleral tissue. Images acquired from the LSCD subjects showed distortions or absence of POVs, invasion of highly scattering conjunctival tissue over the limbal and peripheral corneal epithelium, scarring and thinning of the limbal epithelium, and neovascularization. The combination of high OCT spatial resolution and rapid image acquisition rate allows for in vivo, contactless, volumetric visualization of fine morphological details that could be beneficial for the precise diagnosis and grading of LSCD, planning of treatment, and evaluation of the effectiveness of the treatment approaches. The OCT technology described here could improve the clinical diagnostics and grading of LSCD, preoperative planning, and postoperative evaluation of LSCD subjects, in addition to monitoring the effectiveness of various LSCD treatments.

Broadband Thermo-Optic Photonic Switch for TE and TM Modes with Adiabatic Design

Optical power switches are essential components in fiber optic communication systems, requiring minimal losses, a broad operating wavelength range, and high tolerance to fabrication errors for optimal performance. Adiabatic optical power switches inherently meet these criteria and are well suited for manufacturing processes which support large-scale production at low costs. This paper presents the design and simulation of an adiabatic switch with a flat response in the whole 1525–1625 nm wavelength range (C band and L band) for both TE and TM polarizations. The switch is based on the thermo-optic effect induced by local variations in temperature. The impacts of the design parameters, such as the device length and dissipated heat, are analyzed. The simulation results indicate that the switch achieved high efficiency and low insertion losses, highlighting the potential of adiabatic switches for reliable and scalable integration into advanced optical circuits.

A Modified Regular Perturbation Model for the Single-Span Fiber Transmission Using Learnable Methods

In fiber optic communication systems, the dispersion and nonlinear interaction of optical signals are critical to modeling fiber optic communication, and the regular perturbation (RP) model is a simplified modeling method composed of parallel branches, which has obvious advantages in deep learning backpropagation. In this paper, we propose a simplified single-mode fiber signal transmission model based on the RP model, which significantly improves the fitting accuracy of the model for dispersion and nonlinear interactions at the same complexity by adding trainable parameters to the standard RP model. We explain in the paper that this improvement is applicable to dual-polarization systems and still effective under the conditions of large launch power, without dispersion management, and containing amplified spontaneous emission (ASE) noise. The model uses the standard split-step Fourier method (SSFM) to generate labels and updates parameters through gradient descent method. When transmitting a dual-polarization signal with a launch power of 13 dBm, the modified regular perturbation (MRP) model proposed in the paper can reduce the fitting errors by more than 75% compared to the standard RP model after transmitting through a 120 km standard single-mode fiber.

Beyond 200 Gb/s/λ C-band PAM-4 low-latency transmission over 20-km nested antiresonant nodeless fiber.

The rapid growth of modern Internet applications demands ever-increasing transmission capacity and reduced latency in optical interconnect systems utilizing intensity modulation and direct detection (IM/DD). However, the intrinsic limitations of silica-based standard single-mode fiber (SMF) will ultimately be insufficient to meet these escalating demands. The nested antiresonant nodeless fiber (NANF), a newly designed hollow-core fiber, has garnered significant attention as a potential solution to these challenges. In this paper, we simultaneously address the issues of capacity and latency in a self-developed 20 km NANF-based four-level pulse amplitude modulation (PAM-4) IM/DD system. To mitigate the chromatic dispersion-induced power fading encountered in NANF, we implement effective compensation and fast equalization based on Tomlinson-Harashima precoding (THP) and a modified feedforward equalization with parallel multi-output (MFFE). Additionally, we measure the propagation latency in NANF using high-time-resolution entangled photon pairs. Experimental results demonstrate an achievement of beyond 200 Gb/s/λ in a PAM-4 IM/DD system operating in C-band over 20 km NANF transmission. Furthermore, the fast-computational equalizer reduces the processing time by 64.6% compared to conventional FFE. In terms of latency, the NANF demonstrates a 31.72% reduction in time delay compared to SMF, offering a viable pathway for future high-capacity and low-latency fiber-optic systems.

OpticalTrust: A Sensor-to-Blockchain Framework Using Free-Space Optical Communication.

In the dynamic landscape of the tech industry, the escalating requirement for swift and secure data transmission has catalyzed innovation in integrated communication systems. Free-Space Optics (FSOs) has emerged as a promising contender in optical communications. While conventional optical fiber systems can achieve bit rates of up to 40 Gbps with proper design, they are limited primarily by electronics rather than semiconductor laser capabilities. This study presents an integrated framework that combines FSOs, blockchain technology, and sensor networks to address challenges in data transmission, security, and environmental adaptation. This study analyzes FSOs system performance through the Quality (Q) Factor and Bit Error Rate (BER), comparing systems with and without Erbium-Doped Fiber Amplifiers (EDFAs) across various bit rates (8, 12, 16, and 20 Gbps) and transmission distances (5-25 km). To enhance data security and reliability, a blockchain architecture is incorporated with smart contracts and an InterPlanetary File System (IPFS) for storing and validating results generated from FSOs simulation. Additionally, this study explores the design of sensor network models for FSOs technology by investigating how distributed sensor arrays can be theoretically integrated with FSOs systems, with testing focused on FSOs performance and blockchain implementation.

Subsurface multi-physical monitoring of urban development zone using a fiber optic nerve system

Subsurface multi-physical monitoring of urban development zone using a fiber optic nerve system

Adaptive Multichannel Control for Anti-Aliasing in Fiber-Optic Fabry-Perot Vibration Systems

Adaptive Multichannel Control for Anti-Aliasing in Fiber-Optic Fabry-Perot Vibration Systems

Impact of the continuity of spinning rate function on circular SOP conversion performance in spun quarter wave plate

Spun quarter wave plate (SQWP) exhibits superior state of polarization (SOP) conversion performance compared to the conventional quarter wave plate (QWP), with low loss and high accuracy, making it a promising choice for fiber optic systems. The spinning rate function, as a crucial component of SQWP, characterizes the process of spinning rate (ξ) from 0 to maximum (ξmax), playing a vital role in the performance of SQWP. To enhance circular SOP conversion, the traditional way is that we raise the spinning rate, but this increases ellipticity fluctuation (ΔE), impacting SQWP stability. Urgent exploration of alternative solutions is needed. In order to address this issue, in this study, the impact of the continuity of spinning rate function on circular SOP conversion performance in SQWP is thoroughly investigated through theoretical research and numerical simulation. The results show that spinning rate functions with higher order continuity decrease ellipticity fluctuation and enhance the circular SOP conversion performance in SQWP more effectively. We introduce and compare two novel higher order continuous spinning rate functions with the conventional linear and cosine functions regarding their robustness (σ) on circular SOP conversion performance. The average values of σ for the two proposed spinning rate functions are 4.01×10−5 and 2.17×10−6, respectively. They are one and two orders of magnitude smaller than the linear and cosine functions. The results demonstrate that the proposed spinning rate functions outperform conventional linear and cosine functions in both circular SOP conversion performance and robustness. The research findings of this study are expected to offer valuable insights and guidance for the future development and design of SQWP.