Fiber Optic Telecommunication Research Articles

Combined Large-NSeismic Arrays and DAS Fiber Optic Cables across the Hengill Geothermal Field, Iceland

AbstractFrom June to August 2021, we deployed a dense seismic nodal network across the Hengill geothermal area in southwest Iceland to image and characterize faults and high-temperature zones at high resolution. The nodal network comprised 498 geophone nodes spread across the northern Nesjavellir and southern Hverahlíð geothermal fields and was complemented by an existing permanent and temporary backbone seismic network of a total of 44 short-period and broadband stations. In addition, we recorded distributed acoustic sensing data along two fiber optic telecommunication cables near the Nesjavellir geothermal power plant with commercial interrogators. During the time of deployment, a vibroseis survey took place around the Nesjavellir power plant. Here, we describe the network and the recorded datasets. Furthermore, we show some initial results that indicate a high data quality and highlight the potential of the seismic records for various follow up studies, such as high-resolution event location to delineate faults and body- and surface-wave tomographies to image the subsurface velocity structure in great detail.

Efficient 1400-1600 nm Circularly Polarized Luminescence from a Tuned Chiral Erbium Complex.

Novel chiral Er complexes based on both enantiomers of extended iPrPyBox (2,6‐Bis[4‐isopropyl‐4,5‐dihydrooxazol‐2‐yl)]pyridine) show strong near‐infrared circularly polarized luminescence (CPL) within the 1400 to 1600 nm spectral region under 450 nm irradiation. CPL activity in this region, despite being particularly rare, would open the way to potential applications in the domain, e.g., of fiber‐optic telecommunications and free‐space long‐distance optical communications employing circularly polarized light. Moreover, the long wavelength excitation is advantageous for applications in the field of (circularly polarized) microscopy and bioimaging.

Evaluation of the effectiveness of the effect of photosensitization on the spectral characteristics of the fiber Bragg grating

Currently, fiber Bragg gratings obtained on the basis of photoinduced optical fibers doped with a high concentration of germanium oxide are used as highly sensitive sensors. However, it is worth noting a significant drawback – the manufacturing technology of optical fibers doped with germanium is expensive. When recording Bragg gratings in a standard telecommunication fiber, where the molar concentration of germanium in the fiber core is from 3 % to 5 %, interference occurs due to very low and insufficient light sensitivity. Thus, an important role is played by solving the problem of low photosensitivity of standard telecommunication fibers for recording Bragg gratings. This paper presents the results of studies of the spectral characteristics of fiber Bragg gratings based on standard telecommunication fibers pre-saturated with hydrogen to increase photosensitivity. According to the results obtained, it was found that under the action of UV radiation in the presence of hydrogen, the photosensitivity of the fiber increases and the Bragg wavelength shift is associated with the saturation of the fiber with hydrogen, the effective modulation amplitude of the induced refractive index is equal to 1.2 with a refractive index of 1.438. This work proves that the VBR recorded in the S pre-saturated in hydrogen for 12 days is characterized by increased photosensitivity. The experimental results obtained make it possible to use a Bragg fiber array based on a standard telecommunications optical fiber saturated with hydrogen in the field of telecommunications, seismology, engineering geology as fiber-optic sensors of pressure, deformation, temperature, rotation and rotation, including in extreme environmental conditions

A study of 2H and 1T phases of Janus monolayers and their van der Waals heterostructure with black phosphorene for optoelectronic and thermoelectric applications

Pristine Janus monolayers (MXY; M ​= ​Mo, W and X/Y = S, Se, Te) in 2H and 1T phases and their corresponding vdW heterostructures with black phosphorene are studied under density functional theory calculations. Phonon spectrum confirms dynamic stability of all monolayers in both patterns except MoSSe, WSSe, WSeTe and WSTe in 1T layout. Direct energy gap is observed for MoSSe, MoSeTe, WSSe, and WSeTe in 2H arrangement. In 1T phase, MoSSe, WSSe and their respective heterostructures exhibit metallic attributes and are suitable for high speed supercapacitors. Remnant heterostructures are indirect band gap semiconductors in both phases. PDOS affirms type-I band alignment of BlackP-MoSSe and BlackP-MoSeTe in 2H and BlackP-WSTe in 1T phase that can be well employed for future IR detectors. Moreover, globally desirable type-II band association is investigated for remaining heterostructures rendering exclusive laser, optoelectronic, photovoltaic and sensing applications. Each system manifests incredible effective masses of charge carriers. Heterostructures present a significant potential drop and work function (Φ). Also, every single heterostructure demonstrates noteworthy charge transfer which is accountable for electrostatic as well as vdW interaction at interface. Furthermore, sophisticated optical properties of all heterostructures are achieved by estimating absorption spectra. Optical responses suggest their eminent optoelectronic device applications like: telecommunication laser, optical fiber, photo diodes and solar cells. In addition, a comprehensive insight into thermoelectric properties of all the systems illustrates their ability for thermoelectric generator. Likewise, these materials are suitable alternative for non-toxic and inexpensive thermoelectric devices for waste heat recovery at ambient temperature.

Reconfigurable liquid crystal diffraction grating based on flexoelectric effect

Reconfigurable optical diffraction grating is of great importance for monochromator, spectrometer, optical fiber telecommunication, laser protection, antenna and more. We report a liquid crystal diffraction grating based on flexoelectric effect. When no voltage is applied, the liquid crystal is unidirectionally aligned and does not diffract light. When a DC voltage is applied, the liquid crystal is switched to a 1-dimensional periodic structure due to flexoelectric interaction and becomes diffracting. The periodicity and refractive index undulation of the periodic structure are determined by the elastic energy, due to the spatial variation of the liquid crystal director, and flexoelectric interaction energy. The diffraction angle and efficiency can be controlled by the applied voltage. The liquid crystal diffraction grating has the advantages of low driving voltage, high diffraction efficiency and independency of the polarization of incident light.

Optical Investigation of p-GaAs/i-GaN0.38yAs1-1.38ySby/n-GaAs Quantum Wells Emitters

We have studied the 1.55 μm optical properties of p-GaAs/i-GaN0.38yAs1-1.38ySby/n-GaAs quantum wells using a self-consistent calculation combined with the anticrossing model. We have found that the increase of injected carriers’ density induces the increase of optical gain and radiative current density. The rise of doping density causes a blue shift of the fundamental transition energy accompanied with significant increase of optical gain. The quantum-confined Stark effect on radiative current density is also studied. The variation of radiative current as function of well width and Sb composition is also examined. In order to operate the emission wavelength at the optical fiber telecommunication domain, we have adjusted the well parameters of p-GaAs/i-GaN0.38yAs1-1.38ySby/n-GaAs.

Generalizing Mathematical Model for Evaluating the Efficiency of Choosing a Radial-ring Standard Structure for a Fiber-optic Telecommunications Network

The article presents a generalizing mathematical model for substantiating the choice of radial-ring typical structure of a fiber-optic telecommunications network. The presented model is based on assessment of the harmonic mean values of radial and ring topological structures relative efficiency coefficients.

Brillouin backscattering analysis in recent generation of telecom optical fibers

This paper reports on examination of the latest generation of telecom optical fibers for the Brillouin backscattering strain sensor application. Over 30 fibers from 5 different manufactures have been tested in terms of their ability to create a stable and accurate strain sensor. It has been proved that fibers that belong to the same standard, according to ITU-T (International Telecommunication Union), and even if provided by one manufacturer, demonstrate fundamentally different Brillouin backscattering response. It has been shown that unimodal Brillouin spectrum cannot be treated as the main parameter for fiber selection. In order to achieve accurate and reproducible results of strain measurement, it is necessary to perform initial examination of the fibers over the range of laser pulse width.

Optimal Design and Noise Analysis of High-Performance DBR-Integrated Lateral Germanium (Ge) Photodetectors for SWIR Applications

This work presents the high-performance Si/SiO2 distributed Bragg reflector (DBR)-integrated lateral germanium (Ge) p-i-n photodetectors (PDs) for atmospheric gas sensing and fiber-optic telecommunication networks in the short-wave infrared (SWIR) regime. In addition, this study also proposes an optoelectronic compact small-signal noise equivalent circuit model (SSNECM) of the designed device to compute the noise performance at the detectors’ output. Various figure-of merits including current under dark and illumination, responsivity, detectivity, bandwidth, and the noise of the proposed device are estimated at the room temperature (RT) for an incident optical power of 0.5 μW. Furthermore, the impact of width and height scaling on dark current, responsivity, and bandwidth are investigated to optimize the proposed device. The validation of the proposed model is done by comparing various parameters including dark current, responsivity, and detectivity of the designed device with other Ge PDs. The estimated results show the reduced trade-off between responsivity and bandwidth of the designed device. At λ=1550 nm, the proposed device achieves a high detectivity and SNR of >2×1011Jones and 120 dB (at 3 THz), respectively, with the bias voltage of -2V. These encouraging results pave the path for the future development of low-noise and high-speed detectors.

CHROMATIC DISPERSION COMPENSATION IN EXISTING FIBER OPTIC TELECOMMUNICATION LINES WITH THE GROWING BIT RATES NEEDS OF DWDM SYSTEM

The article presents an analysis of the methods of chromatic dispersion compensation in the existing, already built fiber optic telecommunications lines, based on ITU G.652 A and B fibers with the constantly growing demand for bit rates in DWDM systems. Due to the enormous investment costs, it is impossible to replace the cables used with NZDSF, hence the chapter analyzes methods of improving the bandwidth without replacing all cables. Typical models of the optimization of chromatic dispersion in the existing lines are presented.

Design of optical Fabry–Perot filters for spectral combination of laser beams

Types of spectral combinations of beams of industrial lasers are considered. The optical Fabry–Perot filters are demonstrated to be an acceptable alternative to surface and volume diffraction gratings and edge dichroic filters. Known methods for designing Fabry–Perot filters for spectral multiplexing of channels in fiber-optic telecommunications are updated considering peculiarities of industrial lasers such as different emission power, transmission and suppression bandwidths of filters, and maintenance of minimum power loss. The applicability of the proposed approach is demonstrated using filters for combination of beams of ytterbium fiber lasers as an example.

Toward establishing a multiparameter approach for monitoring pipeline geohazards via accompanying telecommunications dark fiber

Effective monitoring and assessment of geohazard risks to long-haul oil and gas pipelines is essential to reduce pipeline accidents and mitigate the resulting human casualties and economic losses. Oil and gas pipelines are often “accompanied” by telecommunications fiber-optic infrastructure deployed along them for communications purpose; the possibility of repurposing unused (so-called dark) fiber as distributed sensor arrays offers exciting opportunities for the development of pipeline risk monitoring systems. Here, we present a multiparameter approach to monitor pipeline geohazards using distributed fiber-optic sensing—including distributed strain, temperature, and acoustic sensing—deployed on telecommunications dark fiber network. Through a series of field experiments on a pipeline telecommunications cable crossing hilly terrain, we demonstrated the feasibility of using multiple cores of a single telecom cable to obtain multiparametric information on the strain, temperature, and vibration. The recorded strain signatures, temperature variations, and vibration signals can be indicative of various disastrous events during geohazards development, such as ground movement, soil erosion, oil and gas leakage, and rockfall. Additionally, we established a preliminary model that allows the synergistic use of the acquired multiparametric data. Overall, our results suggest that preexisting networks of fiber-optic telecommunications infrastructure accompanying pipelines could be leveraged as sensing resources to monitor geohazard risks to pipelines. Deeper fusion of multidimensional data and multiparametric information will enable intelligent monitoring, identification, and assessment of a wide range of pipeline threats.

Noise Levels and Signals Observed on Submarine Fibers in the Canary Islands Using DAS

Abstract In this study, we investigate 70 days of distributed acoustic sensing (DAS) recordings in the Canary Islands using an undersea fiber-optic telecommunication cable that links the islands of Tenerife and Gran Canaria. Two DAS interrogators connected to both ends of the cable turned the fiber into an array of 11,968 strain sensors covering a total length of ∼120 km. We present the details of the experiment, noise analysis, and examples of recorded signals. Seismic ambient noise levels assessment indicates poor local coupling of the cable due to the irregular bathymetry that results in high-amplitude acoustic oscillations in some channels. The DAS array recorded several types of nonseismic (vehicles, surface gravity waves, ships) and seismic signals. Local and regional earthquakes were detected with magnitudes mbLg≥2. Surface waves from teleseismic events at a distance of ∼3000 km were also identified in the strain recordings. Here, we report the first observations with DAS of hydroacoustic T waves generated by oceanic earthquakes located at the Central Mid-Atlantic Ridge and the Cape St. Vincent region. Events had magnitudes from Mw 4.2 to 6.9, and the hydroacoustic waves were recorded at epicentral distances from 780 to 3400 km. Our findings show that submarine fiber-optic cables can effectively be used to assess the seismic activity in remote oceanic areas.

Swelling-Based Chemical Sensing With Unmodified Optical Fibers

We use distributed fiber optic strain sensing to examine swelling of the fiber’s polymer coating. The distributed sensing technique that uses unmodified low-cost telecom fibers opens a new dimension of applications that include leak detection, monitoring of water quality, and waste systems. On a short-range length scale, the technology enables “lab-on-a-fiber” applications for food processing, medicine, and biosensing for instance. The chemical sensing is realized with unmodified low-cost telecom optical fibers, namely, by using swelling in the coating material of the fiber to detect specific chemicals. Although generic and able to work in various areas such as environmental monitoring, food analysis, agriculture or security, the proposed chemical sensors can be targeted for water quality monitoring, or medical diagnostics where they present the most groundbreaking nature. Moreover, the technique is without restrictions applicable to longer range installations.

Twisted Silica Microstructured Optical Fiber with Equiangular Spiral Six-Ray Geometry

This work presents fabricated silica microstructured optical fiber with special equiangular spiral six-ray geometry, an outer diameter of 125 µm (that corresponds to conventional commercially available telecommunication optical fibers of ratified ITU-T recommendations), and induced chirality with twisting of 200 revolutions per minute (or e.g., under a drawing speed of 3 m per minute, 66 revolutions per 1 m). We discuss the fabrication of twisted microstructured optical fibers. Some results of tests, performed with pilot samples of designed and manufactured stellar chiral silica microstructured optical fiber, including basic transmission parameters, as well as measurements of near-field laser beam profile and spectral and pulse responses, are represented.

Testing of a Polarimetric Current Sensor in the Frequency Domain.

This paper proposes an original model of a polarimetric current sensor, in which the measuring coil was made of a single mode telecommunication optical fiber ITU-T G.652, G.653, G.655, and G.657. This sensor was subjected to the commercialization process, which was carried out by a company combining the functionality of a technology transfer center with the capabilities of the Startit Fund Sp. z o.o. The published results included the analysis of the implementation readiness, the analysis of the market potential, the valuation of the industrial property rights of the invention and indicated further directions of scientific research on the sensor, which include the frequency analysis of measurement signals. This prompted the conduct of relevant scientific research. In this paper, the idea of measurement of current using polarimetric current sensor with optical fiber coil has been briefly characterized. It shows the definition and basic properties of the Discrete Fourier Transform (DFT). It discusses the technique of determining the value of each harmonic of signal at the input and output of polarimetric current sensor. The value of measurement errors and total harmonic distortion (THD) have been calculated. The general conclusions for disturbances in the processing realized in polarimetric current sensor have been formulated. In addition, the impact of the molar concentration of the dopant GeO2 in the core of the single mode telecommunication optical fibers and the impact of the number of turns of the measuring coil on the distortion accompanying the process of processing have been determined. Therefore, it can be concluded that the key result obtained during the research is the confirmation of the fact that single mode telecommunication optical fibers can be used to build the measuring coil of a polarimetric sensor used for measuring alternating currents. This means that the considered sensor, when measuring this type of currents, does not introduce additional distortions and distortions of their waveforms.

МУЛЬТИЛИНЕЙНЫЕ РЕШЕНИЯ ДЛЯ ДВУМЕРНОГО НЕЛИНЕЙНОГО УРАВНЕНИЯ ХИРОТЫ

At present, the question of studying multidimensional nonlinear integrable equations in the framework of the theory of solitons is very interesting to foreign and Kazakh scientists. Many physical phenomena that occur in nature can be described by nonlinearly integrated equations. Finding specific solutions to such equations plays an important role in studying the dynamics of phenomena occurring in various scientific and engineering fields, such as solid state physics, fluid mechanics, plasma physics and nonlinear optics. There are several methods for obtaining real and soliton, soliton-like solutions of such equations: the inverse scattering method, the Hirota’s bilinear method, Darboux transformation methods, the tanh-coth and the sine-cosine methods. In our work, we studied the two-dimensional Hirota equation, which is a modified nonlinear Schrödinger equation. The nonlinear Hirota equation is one of the integrating equations and the Hirota system is used in the field of study of optical fiber systems, physics, telecommunications and other engineering fields to describe many nonlinear phenomena. To date, the first, second, and n-order Darboux transformations have been developed for the two- dimensional system of Hirota equations, and the soliton, rogue wave solutions have been determined by various methods. In this article, we consider the two-dimensional nonlinear Hirota equations. Using the Lax pair and Darboux transformation we obtained the first and the second multi-line soliton solutions for this equation and provided graphical representation.

Design and Modeling of High-Performance DBR-Based Resonant-Cavity-Enhanced GeSn Photodetector for Fiber-Optic Telecommunication Networks

In this work, we present a novel distributed Bragg reflector (DBR)-based resonant-cavity-enhanced (RCE) GeSn photodetector on Si substrates to achieve high-performance photodetection in terms of responsivity and 3-dB bandwidth (BW) for the short-wave infrared (SWIR) high-speed applications. The proposed structure consists of Si/SiO2 distributed Bragg reflectors (DBRs) to enhance the performance of the device. The top and bottom DBRs create a high-quality ( ${Q}$ ) optical cavity to enable multiple pass reflection schemes to increase the responsivity and also high wavelength selectivity with a sharp response. In addition, with an increase in Sn concentration in the active ( i- GeSn) layer, the photodetection range extends to longer wavelengths due to the shrinkage of bandgap energy. The calculated result shows an enhanced 3-dB BW and responsivity as compared to the existing p-i-n PDs. Therefore, the proposed DBR-based RCE GeSn PD can be a promising device for high-speed SWIR photodetection applications.

Bismuth doped fibre amplifier operating in E- and S- optical bands

Bismuth-doped fibre amplifiers offer an attractive solution for expanding the bandwidth of fibre-optic telecommunication systems beyond the current C-band (1530-1565 nm). We report a bismuth-doped fibre amplifier in the spectral range from 1370 to 1490 nm, with a maximum gain exceeding 31 dB, and a noise figure as low as 4.75 dB. The developed system is studied for forward, backward, and bi-directional pumping schemes and three different signal power levels. The forward pumping scheme demonstrates the best performance in terms of the achieved noise figure. The developed amplifier can be potentially used as an in-line amplifier with >20dB gain in the spectral band from 1405 to 1460 nm.

Ghost Interaction of Breathers

Mutual interaction of localized nonlinear waves, e.g., solitons and modulation instability patterns, is a fascinating and intensively-studied topic of nonlinear science. Here we report the observation of a novel type of breather interaction in telecommunication optical fibers, in which two identical breathers propagate with opposite group velocities. Under controlled conditions, neither amplification nor annihilation occurs at the collision point and most interestingly, the respective envelope amplitude, resulting from the interaction, almost equals another envelope maximum of either oscillating and counterpropagating breather. This ghost-like breather interaction dynamics is fully described by anN-breather solution of the nonlinear Schrödinger equation.