Mode Optical Fiber Research Articles

Dynamic control of the mode-locked fiber laser using a GO/PS modulator.

This Letter proposes a novel, to the best of our knowledge, transistor-like optical fiber modulator composed of graphene oxide (GO) and polystyrene (PS) microspheres. Unlike previously proposed schemes based on waveguides or cavity enhancement, the proposed method can directly enhance the photoelectric interaction with the PS microspheres to form a light local field. The designed modulator exhibits a distinct optical transmission change (62.8%), with a power consumption of <10 nW. Such low power consumption enables electrically controllable fiber lasers to be switched in various operational regimes, including continuous wave (CW), Q switched mode-locked (QML), and mode-locked (ML). With this all-fiber modulator, the pulse width of the mode-locked signal can be compressed to 12.9 ps, and the corresponding repetition rate is 21.4 MHz.

Ultra-short bilayer graphene optical fiber intensity modulator based on silver-semicircular hybrid plasmonic waveguide

The intensity modulator is a key component in optical fiber communication. In this paper, an ultra-short graphene light intensity modulator based on hybrid plasmonic waveguide (HPW) array is proposed. Al2O3 embedded with double-layer graphene at a certain interval is placed on the side polishing surface of the microfiber Mach–Zehnder modulator (MZM), and the silver-semicircular array is placed on the surface of the transition material as hybrid plasmonic waveguide for the first time in all-fiber modulator. Analyzing by building a 3D model in finite difference time domain software, the hybrid surface plasmon polariton (HSPP) between silver-semicircles significantly enhances the subwavelength confinement and the light–graphene interaction. The modulation range of the real part of effective refractive index (Neff) can reach to 0.01984 by adjusting the Fermi level of graphene. Therefore, π phase change can be achieved only in a modulation length of 45 μm, and the insert loss can be controlled below 0.0159 dB/μm through the analysis of the imaginary part of the Neff, which also leads to a low total loss of 0.7155 dB. Owing to the excellent phase modulation efficiency, high extinction ratios of 39.39 dB and 47.77 dB can be reached for port 1 and port 2, respectively. Double-layer graphene forms the flat capacitor, which brings high modulation efficiency while achieving a high modulation bandwidth of 59.945 GHz. The application of HPW in graphene optical fiber modulator greatly improves the working efficiency, reduces the difficulty of integration, overcomes high insert loss, improves the extinction ratio, this modulator can be widely used in the future optical fiber communication system.

Highly stable Fabry-Pérot fiber-optic modulation device based on the photothermal effect of V2C MXene

The photothermal effect of MXene has attracted considerable attention because of its vast application potential. In this study, a Fabry-Perot interferometer (FPI)-based fiber-optic modulation device utilizing the good photothermal effect and high thermal conductivity of MXene V2C was realized. The modulation device was fabricated by forming a reflective FPI structure with two layers composed of a polymer layer and a MXene V2C layer on top of a fiber ferrule facet. An excellent pump-to-phase conversion efficiency of 0.332 π/mW was achieved using the device, which is larger than the values of other types of two-dimensional material-based photothermal modulation devices. The extinction ratio (ER) was ∼16.44 dB. The rise and fall time constants were ∼10 ms and ∼9 ms, respectively. The stability of the fabricated device was also investigated; the standard deviations of the extinction ratio and resonance wavelength fluctuation were 0.103 % and 0.002 nm, respectively.

Terabit Optical Wireless-Fiber Communication With Kramer-Kronig Receiver—Part II

A high speed optical wireless-fiber solution was proposed in part I of this research with applications such as network backhaul and data center links. The proposed system is based on the utilization of state-of-the-art modulation and multiplexing techniques in optical fiber and optical wireless communications, including multicore fibers (MCFs) and coherent detection based on Kramer-Kronig (KK) receivers. In this letter, we analyze the performance of the proposed system and compare it with an intensity modulation and direct detection (IM/DD) system. Superior performance of the KK receiver is shown for various modulation formats and optical amplification schemes. We also consider the eye-safety constraint for the optical power as a practical design factor. It is demonstrated that the position of optical amplifiers affects the multiplexing gain and achievable data rate when eye-safety constraint is imposed. Further important challenges for the practical deployment of the system are discussed.

Novel low-cost high-speed optic–electric laser diode pigtail module packaging technology

• At present, the research and development of high-speed laser modules for communication are designed with ceramic components globally. • In module packaging without the ceramic part, the misalignment caused by the deformation results in coupling efficiency loss. • A new type of high-speed laser diode pigtail module is designed to change the structure of a laser module and remove ceramic and process parts. • A laser diode pigtail module package achieves the best coupling efficiency. A high-speed laser diode pigtail for wide-band fiber-optic communications is a key component in optical fiber user loop systems, optical fiber data communication systems, and cable television systems. With the advent of a new type of optic–electric high-speed laser, wide-band communication has emerged. These three systems constitute future mainstreams of optical fiber communications. However, high-speed laser diode pigtails used in module components and process assembly account for extremely high production costs. The proposed pigtail module eliminates ceramic parts and facilitates mass production of the components. An optic fiber (including a jacket) was placed into a ferrule sleeve. The optic fiber did not undergo laser damage, and its stability in the reliability test was ensured by the plastic jacket. The optic fiber terminal surfaces grind the 7° angle to enhance the surface quality of the connector, thereby avoiding reflection and incurring a power loss of 4%. Moreover, achieving alignment in a conventional laser module package without a ceramic part and fiber ferrule is a considerable challenge, and apparently, there are still some issues that need to be resolved. In conventional optical fiber module package, laser welding technique provides a superior joint strength. However, in module packaging without the ceramic part, the misalignment caused by the deformation results in coupling efficiency loss. Therefore, a novel design of laser diode pigtail module packaging is necessary. A transmitter optical subassembly device, receiver optical subassembly device, and transceiver pigtail module can be manufactured in a unified process package. By applying the low-cost packaging technique, the cost and fabrication time of the module packaging were reduced, and the fabrication yield was increased.

W-shaped profile and breather-like soliton of the fractional nonlinear Schrödinger equation describing the polarization mode in optical fibers

We use the fractional nonlinear Schrödinger equation (FNLSE) to describe the polarization mode in optical fiber with Self-Steepening, Self-Frequency Shift, and Cubic-quintic terms to analyze the effects of the fractional time parameter (FTP) on bright and dark solitons as well as breather-like solitons. We use the transformation hypothesis and auxiliary equations method to obtain three families of solutions such as combined bright soliton, dark solitons, and rational solitons. We have shown the effects of the fractional parameter (FP) on the W-shaped profile, bright and dark optical soliton solutions as well as the corresponding chirp component. It is observed that for small values of the FP, optical soliton shape is affected and the soliton is unstable. Moreover, one observes the effects of fraction time on Modulation Instability (MI) gain spectra and MI bands. For certain values of the FP, it is formed sides lobes and for specific small values of the FP, both stability zone increases and amplitude of the MI gain increase while the stability zones increase. To confirm the robustness of the analytical results, we have used a numerical investigation. One exhibits the formation of breathers-like soliton with stable amplitude for small values of the FTP. It results from this study that the FP is efficient and can be used as an energy source where soliton or breathers-like soliton are involved for communication in optical fibers.

Collection efficiency of optical photons generated from microwave excitations of a Bose-Einstein condensate

Stimulated Raman scattering of atoms with $\Lambda$-configuration of levels is a promising tool for transducing microwave photons to optical photons. We consider an atomic Bose-Einstein condensate whose large phase-space density highly amplifies the coupling to the microwave field. Due momentum transfer to the condensate, stimulated photon scattering can occur outside of the phase-matched direction, which can be used to separate the converted photons from the strong Raman readout pulse. Conversely, in the phase-matched direction, superradiant scattering due to bosonic enhancement leads to increased efficiency of the microwave to optical conversion. We determine the optimal conditions for the emitted optical photons to be collected into the guided modes of optical fibers.

Distributed measurement of mode group effective refractive index difference in a few mode optical fibers.

The possibility to perform distributed measurements of the effective refractive index difference between distinct modes in few mode optical fibers is demonstrated using phase sensitive optical time domain reflectometry. Effective refractive index differences between LP02, LP21a and LP21b modes are measured with for a spatial resolution of 24m.

Integration and commissioning of the ATLAS Muon-to-Central-Trigger-Processor Interface for Run-3

The Muon-to-Central Trigger Processor Interface was completely redesigned as part of the ATLAS Level-1 trigger upgrade for Run 3 of the Large Hadron Collider. The new system is implemented as a single AdvancedTCA module, using three large state-of-the-art FPGAs and high-density fiber-optic modules. Trigger information from the muon trigger detectors are received through 208 high speed links, while 60 links are used to send processed trigger information to the L1 Topological Trigger Processor and the Central Trigger Processor. Extensive integration tests with all input and output systems have shown that the data transfer is stable and reliable. We present results from integration tests with connected sub-systems as well as commissioning of the Muon-to-Central Trigger Processor Interface in the ATLAS experiment.

An Optical Fiber Sensor for Axial Strain, Curvature, and Temperature Measurement Based on Single-Core Six-Hole Optical Fiber.

In this paper, the field distribution and effective refractive index of transmission modes in single-core six-hole optical fiber were researched by modeling and simulation experiments. Based on the simulation results, a new type of sensor for axial strain, curvature, and temperature applications measurement was designed and fabricated. The experimental results showed that the axial strain sensitivities at different dips were −0.97 pm/με and −1.05 pm/με in the range from 0 to 2000 με, and the temperature sensitivities were 35.17 pm/°C and 47.27 pm/°C in the range from 25 to 75 °C. In addition, the proposed sensor also detected the curvature change with sensitivities of 7.36 dB/m−1 and 20.08 dB/m−1 from −2.582 m−1 to −1.826 m−1, respectively. Finally, through theoretical analysis, it can be deduced that this has potential application in the field of simultaneous measurement of strain and temperature.

Numerical model for enhancing stimulated Brillouin scattering in optical microfibers.

Stimulated Brillouin scattering (SBS) is useful, among others for generating slow light, sensing and amplification. SBS was previously viewed as a poor method due to the limitation on optical power in high-powered photonic applications. However, considering the many possible applications using SBS, it is now of interest to enhance SBS in areas of Brillouin frequency shift together with Brillouin Gain. A numerical model, using a fully vectorial approach, by employing the finite element method, was developed to investigate methods for enhancing SBS in optical fiber. This paper describes the method related to the numerical model and discusses the analysis between the interactions of longitudinal, shear and hybrid acoustic modes; and optical modes in optical fiber. Two case studies were used to demonstrate this. Based on this numerical model, we report the influence of core radius, clad radius and effective refractive index on the Brillouin frequency shift and gain. We observe the difference of Brillouin shift frequency between a normal silica optical fiber and that of a microfiber - a uniformed silica fiber of a much smaller core and cladding dimensions where nonlinearities are higher. Also observed, the different core radii used and their respective Brillouin shift. For future work, the COMSOL model can also be used for the following areas of research, including simulating "surface Brillouin shift" and also to provide in-sights to the Brillouin shift frequency vBof various structures of waveguides, e.g circular, and triangular, and also to examine specialty fibers, e.g. Thulium and Chalcogenide doped fibers, and their effects on Brillouin shift frequency.

General Step-Index Optical Fiber Modal Characteristic and Sensitivity Analysis

An analytical approach about the general type of step-index optical fiber modes and their variations is presented in this paper. The theoretical model is solved through our analytical method. With the boundary conditions, a composite equation set is established and solved. The precise results of all modes are achieved with a high-precision numerical solution. In this paper, the key modal qualities contain electromagnetic fields' distributions, the effective refractive index, and its tendencies. And the modal sensitivity is based on the partial derivative of the effective refractive index (<inline-formula><tex-math notation="LaTeX">$\partial$</tex-math></inline-formula>n_eff&#x002F;<inline-formula><tex-math notation="LaTeX">$\partial$</tex-math></inline-formula>n_i and <inline-formula><tex-math notation="LaTeX">$\partial$</tex-math></inline-formula>n_eff&#x002F;<inline-formula><tex-math notation="LaTeX">$\partial$</tex-math></inline-formula>r_i). The derivative rule of special function allows analyzing the sensitivity of modes. Furthermore, four qualitative deductions are derived during the process, including the qualitative analysis of modes and their variation, several of which are supported with previous experiments. Our work is beneficial for exploiting new fiber and researching relative fiber sensors.

Influence of Aberrations on Modal Decomposition for LMA Fiber Laser Systems

Understanding the mode components is of great importance to manipulate the optical modes and to improve the optical system performance. However, various forms of aberrations, stemming from misalignment and imperfect optical components and system design, degrade the performance of the modal decomposition (MD) system. Here we analyze the influence of various Zernike aberrations on MD performance in large-mode-area fiber laser systems. Using computer-generated optical correlation filter together with angular multiplexing technique, we can simultaneously measure multi-modal contents. Among the common aberrations, we find that the MD results are least sensitive to vertical astigmatism aberration. However, the vertical coma aberration and horizontal coma aberration have a large impact on MD results under the same aberration strength, which show a rather large change in modal weight and intermodal phase. Our analysis is useful to construct a precise MD system applicable for high-power optical fiber modal analysis and mode control.

Selective excitation of different combinations of LP01 and LP11 polarization modes in a birefringent optical fiber using a Wollaston prism.

We present an effective method for free-space selective excitation of different combinations of LP01 and LP11 polarization modes in a birefringent optical fiber using a Wollaston prism, rotatable polarizer, and achromatic half-wave plate. The method is minimally wavelength-dependent and can be used for high-power sources. The relative coupling efficiencies of different modes can be continuously tuned and the suppression rate of the unwanted modes with respect to the targeted mode exceeds 20 dB. We present input system configurations that allow for the excitation of different individual modes and groups of modes and estimate the maximum coupling efficiencies based on numerical simulations. As example applications, we show the generation of Raman sidebands in different modes, gain tunability of intermodal four-wave mixing, and broadband conversion of a supercontinuum light beam from the fundamental to the LP11 mode.

Calculation of Fundamental Mode Properties for Single-Mode Fibers

In this research, properties for the fundamental mode of single-mode step-index optical fibers with core diameters 9.8–15.6 µm, core refractive index and cladding refractive index are calculated at a wavelength of 1.55 µm by using RP Fiber Calculator and then compared with the results obtained from equations. It is shown that there is a good agreement for all properties. These results can be useful for designing practical fibers

Investigation of Total Energy Density and Power Flow for Propagating Modes of Square-Core Optical Fiber

Investigation of Total Energy Density and Power Flow for Propagating Modes of Square-Core Optical Fiber

A Gas-Liquid Sensor Functionalized With Graphene-Oxide on Chalcogenide Tapered Fiber by Chemical Etching

This work presents a gas-liquid sensor based on chalcogenide etched-tapered fiber (ETF) functionalized with graphene oxide film. Unlike the preparation of conventional tapered fiber sensors, the core diameter of the optical fiber of this gas-liquid sensor was kept constant, and part of its cladding was removed via the chemical corrosion method that the fiber optic modes were the invariant. The energy distribution of transmission mode in the original fiber and tapered fiber is simulated respectively, and obtained the conclusion that the tapered fiber structure has higher sensing sensitivity. The sensors could detect VOCs such as formaldehyde (HCOH) and butane (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> ) in the mid-infrared band. Results showed that the ETF sensor had a high detection sensitivity of both HCOH solution (2.6731 a.u./mg·mL <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> ) and C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> gas (0.2773 a.u./vol.%). A layer of graphene oxide (GO) film was coated on the ETF to further improve the sensitivity of the sensor. The GO coated etched-tapered fiber (GO-ETF) sensor’ sensitivity was substantially improved owing to the strong hydrophilicity and biocompatibility of GO which can absorb bioactive molecules. The high detection sensitivity of both solution and gas were 4.5091 a.u./mg·mL <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> and 0.4812 a.u./vol.%, respectively, which were 1.69 and 1.74 times higher than that of the sensor without a coating of GO film. The results further showed that the sensor had a rapid response speed, low detection limit, good repeatability, and stability.

Influence of attenuation on the generation of optical vortices in multihelicoidal optical fibers

In this paper we have studied influence of attenuation on conversion processes of the fundamental mode (FM) in multihelicoidal optical fibers (MHF) in the vicinity of the point of accidental spectrum degeneracy within the framework of the scalar approximation. To this end, we have obtained expressions for modes of the MHF, which consist of the FM and an optical vortex (OV), and shown that conversion of the FM into the OV takes place. The difference in the attenuation coefficients for the partial fields of MHF’s modes leads to deterioration in the conversion process even with an ideal system’s tuning. At sufficiently large values of attenuation coefficients the conversion of the incoming FM into the vortex vanishes. Also we have shown the presence of exceptional point (EP) in the spectra of modes of the MHF and demonstrated enhanced sensitivity of the fiber in the vicinity of the EP to perturbations.

High sensitivity magnetic field sensor based on a Mach-Zehnder interferometer and magnetic fluid

An intensity modulation optical fiber magnetic field sensor based on MZI and magnetic fluid is proposed and demonstrated. The MZI is composed of a no core fiber-thin core fiber-no core fiber (NTN) structure and the cladding of thin core fiber is etched by hydrofluoric acid. The fiber structure is immersed in magnetic fluid. The sensitivity of the etched device is 5.3 times that of the non-etched device. The maximum sensitivity of magnetic field intensity achieved in our experiment as high as 0.563 dB/Oe. Meanwhile, the fringe visibility achieved 30.78 dB. This device has the advantages of convenient manufacture, small volume and high sensitivity. It has application potential in the field of magnetic field sensing.

ІНТЕЛЕКТУАЛЬНІ ТЕХНОЛОГІЇ МОНІТОРИНГУ ТЕХНІЧНОГО СТАНУ СУЧАСНИХ ВИСОКОВОЛЬТНИХ КАБЕЛЬНИХ ЛІНІЙ ЕЛЕКТРОПЕРЕДАЧІ

The review concerning application of fiber-optic technologies in power industry, in particular, for monitoring of modern power cables with cross-linked polyethylene insulation and integrated fiber-optic module is carried out. The new intelligent tools for control of electrical, thermal and mechanical characteristics and partial discharges in power cable lines are presented. The current operational experience for the system of Smart Cable Guard in an emergency is described. The prospects to develop and use the intellectual technologies for monitoring of technical state of up-to-date high-voltage cable power lines and their operate reliability are grounded by analysis of new diagnostic methods controlling the level of partial discharges, temperature distribution and mechanical damage in polyethylene insulation and other elements of the high- and extra-high-voltage cables with integrated fiber-optic modules. References 51, figures 8.