Fiber Optic Data Transmission Research Articles

Optical injection locking and optical-fiber data transmission by directly modulated wavelength tunable laser transmitters

Enhancement of the small- and large-signal modulation performance of wavelength tunable laser diode (TLD) transmitters under strong optical injection locking (OIL) is investigated numerically in back-to-back and optical-fiber transmission schemes. Our model is based on the spatiotemporal description of laser dynamics as due to the composite cavity design of TLDs, the usual rate equation formalism is not directly applicable. We demonstrate that TLD transmission strongly depends on wavelength tuning, which was investigated over a 21-nm range between 1529 and 1550 nm emission wavelengths. The best performance for both free-running (FR) and OIL TLDs is achieved at shorter wavelengths, 1529 nm for our device. Although in both cases this is due to larger differential material gain at shorter wavelengths, the underlying physics of the effect is completely different. For an FR TLD, it is the resonance oscillation frequency (ROF) that defines the best modulation speed, while for an OIL TLD, the achievable modulation speed depends on the cavity mode shift due to optical injection. Both the ROF and the cavity mode shift increase when the differential gain increases. However, the ROF is the device’s fixed parameter, while the cavity mode shift is defined by the OIL conditions, and thus, it can be optimized. The superior performance of the optical fiber digital data transmission with the OIL TLD is demonstrated at around 20-Gb/s modulation speed for standard fibers. This result is attributed to an enhanced modulation response and suppressed frequency chirping of the OIL TLD, and it is important for practical utilization of TLD transmitters.

Построение распределенных микропроцессорных систем управления движением поездов

High material requirements of new relay systems make it impossible to modernize devices within existing areas and require the construction of new interlocking system buildings, which significantly affects the volume of capital investments. Transitioning to microelectronic and microprocessor electronic platforms allows for the design of more compact systems with expanded functional capabilities. In global practice, there is a trend towards widespread use of microprocessor-based interlocking system. However, there is a slow pace of device updates, mainly due to the high cost of microprocessor-based interlocking system, which exceeds by several times the cost of similar relay-based interlocking system. The high performance of computing resources and fiber-optic data transmission channels allows for the design of efficient structures for microprocessor-based interlocking system. The article presents a comparative analysis of the structures of microprocessor-based interlocking system. The implemented decentralized structures solve the issues of reducing investments for the design and construction of the station’s cable network. The advantages of using these systems from the point of view of controlling the transportation process are described, conclusions are drawn on the effective use of the capabilities of modern control systems with integrated subsystems in relation to field-based train traffic control technologies.

Development of Unified Hybrid WDM-PON With Spectrally Hidden Data Channel System and FBG Optical Sensor Network

Abstract As the demand for fiber optical data transmission systems and other type of applications, which require optical media, like optical sensing increases, the unauthorized parties are becoming increasingly interested in such systems. Also, with such demand, more complex optical systems are required; thus, the network infrastructure is becoming more crowded. It is vital to economize on the available resources and infrastructure to ensure the needs of all interested business, governmental or end-user sides. Therefore, the present research focuses on the development of a unified hybrid optical system. The developed hybrid optical transmission system adds additional protection to the channels, allows for the unification of standard optical data transmission channels, optical sensors and spectrally hidden data transmission channel systems, and increases the efficiency of the optical components used.

Method for Ensuring Information Security of Object Fiber-Optical Data Transmission System

Currently, ensuring information security of object fiber-optic data transmission systems is an important and urgent task. Therefore, the purpose of this article is to develop an easy-to-implement method for protecting object fiber-optic data transmission systems from unauthorized access to information. This work proposes an easyto-implement method for protecting object fiber-optic data transmission systems from unauthorized access to an information signal, based on weakening the power of this signal. It is shown that the use of the proposed method will not lead to a significant decrease in the data transmission rate in the object fiber-optic data transmission systems, but will increase its information security. The theoretical limit of signal decoding for data transmission technologies over optical fiber Ethernet has been determined. It was found that the lowest value of the theoretical limit of signal decoding corresponds to Fast Ethernet technology (100Base-FX). It was found that when the value of the attenuation coefficient of optical radiation D > 20 dB, the data transmission using Fast Ethernet technology (100Base-FX) is terminated. The results of this article can find application in the means of technical protection of information transmitted over object fiber-optic data transmission systems.

Ultra-high speed fiber-optic data transmission with a single chip source

Ultra-high speed fiber-optic data transmission with a single chip source

Energy Loss during Splitting of Two Optical Fibers, One of Which is Elliptically Deformed at the Joint

Two fragments of a fiber-optic data transmission line are considered round and elliptical (at the junction) in their cross section. For a single-mode operation, analytical expressions are obtained for the energy losses when connecting two such fragments. It is shown that energy losses increase with increasing eccentricity and simultaneously decrease with increasing waveguide number.

VIDEO SURVEILLANCE SYSTEMS FOR RAILWAY TRANSPORT

The article is devoted to analysis of ways to increase train traffic safety. One of ways to reduce accident rate on railways is timely detection of dangerous objects and notification of all traffic participants, primarily, the driver. Such a notification can be performed with the help of intelligent video surveillance system (IVS). The objective of the article is to study the possibility of using IVS to increase train traffic safety. Method (way to achieve the objective) consists of several stages: development of criteria of compliance of functional possibilities of IVS with tasks to increase train traffic safety, assessment, and calculation of permissible values of fitting criteria. The work suggests a scheme of organization of IVS based on fiber-optic data transmission system (FOTS) and data transmission network, highlights advantages and disadvantages of IVS, formulates requirements for IVS. Advantage of video surveillance is availability of video information about an object to a train driver, which allows to timely prevent an accident. Disadvantage of IVS is high probability of false detection, which can lead to false triggering of a system. To reduce the number of false triggering there are two ways: improvement of algorithms of video analytics in recognition device (RD) and increase of quality of video signals at the input of RD. The work is devoted to reduction of probability of false triggering due to improvement of communication quality. It is noted that an efficient method is the use of a new element base of electronics based on nanostructured materials. These materials allow to improve optoelectronic characteristics of main elements of IVS which are photosensors and photoreceivers.

Research on FBG-Based Sensor Networks and Their Coexistence with Fiber Optical Transmission Systems

Market forecasts and trends for the usage of fiber optical sensors confirm that demand for them will continue to increase in the near future. This article focuses on the research of fiber Bragg grating (FBG) sensor network, their applications in IoT and structural health monitoring (SHM), and especially their coexistence with existing fiber optical communication system infrastructure. Firstly, the spectrum of available commercial optical FBG temperature sensor was experimentally measured and amplitude-frequency response data was acquired to further develop the simulation model in the environment of RSoft OptSim software. The simulation model included optical sensor network, which is combined with 8-channel intensity-modulated wavelength division multiplexed (WDM) fiber optical data transmission system, where one shared 20 km long ITU-TG.652 single-mode optical fiber was used for transmission of both sensor and data signals. Secondly, research on a minimal allowable channel spacing between sensors’ channels was investigated by using MathWorks MATLAB software, and a new effective and more precise determination algorithm of the exact center of the sensor signal’s peak was proposed. Finally, we experimentally show successfully operating coexistence concept of the spectrum-sliced fiber optical transmission system with embedded scalable FBG sensor network over one shared optical fiber, where the whole system is feed by only one broadband light source.

Методы создания магистральных оптоволоконных линий передачи данных на основе бинарных проводников и волоконно-оптических информационно-энергетических каналов

Методы создания магистральных оптоволоконных линий передачи данных на основе бинарных проводников и волоконно-оптических информационно-энергетических каналов

Development of a high-voltage waveguide photodetector comprised of Schottky diodes and based on the Ge–Si structure with Ge quantum dots for portable thermophotovoltaic converters

This paper demontstrates the possibility of developing a high-voltage waveguide photodetector comprised of Schottky diodes and based on a Au/Ge — Si structure with Ge quantum dots pseudomorphic to a silicon matrix, which ensures an increase in the external quantum yield and open-circuit voltage. It is shown on this photodetector that there is a great increase and broadening in sensitivity up to λ = 2.1 μm, which coincides with the main radiation range of a black (gray) body at the emitter temperatures from 1200 to 1700 °C, practically used in thermophotovoltaic converters. This state of the ensemble of Ge quantum dots by means of molecular beam epitaxy can be obtained only under the condition of low growth temperature (250–300 °C). It is established that, below the Si absorption edge, photoresponse on the photodetectors under consideration is determined by two main mechanisms: absorption on the ensemble of Ge quantum dots and Fowler emission. It is shown by the analysis of the Raman scattering spectra on the optical photons of Ge–Si structures that the quantum efficiency of photodetectors based on them in the first case is due to the degree of nonuniform stress relaxation in the array of Ge quantum dots. The photoresponse directly associated with the Ge quantum dots is manifested on Schottky diodes with a superthin intermediate oxide layer SiO2, which eliminates the second mechanism. In further development, the proposed photodetector architecture with pseudomorphic Ge quantum dots can be used both for portable thermophotovoltaic converters and fiber-optic data transmission systems at wavelengths corresponding to basic telecommunication standards (λ = 0.85, 1.3 and 1.55, 1.3, and 1.55 μm) on the basis of silicon technologies.

POWER, METALLURGICAL AND CHEMICAL MECHANICAL ENGINEERING PHYSICAL DATA CODING USING POLARISING SPIN DEVICES

Objectives. Spin nanoelectronics facilitate fundamentally new ways of encoding and encrypting information implemented using photon spins in fibre-optic data transmission lines. The article discusses the possibility of creating a spin LED emitting circularly polarised light. Methods. In a spin LED, spin-polarised carriers are injected from a ferromagnetic contact combined with a quantum well. Results. Quantum selection rules for describing recombination establish a connection between the circular polarisation of light, emitted along the normal to the surface, and the spin polarisation of the electrons. Conclusion. Physical methods for coding and transmitting information by means of polarised spin devices using the spin degree of freedom are formulated. The configuration principles of a polarised radiation generator (spin LED) are proposed. The approach is based on a heterostructure containing the quantum well InGaAs / GaAs (luminescent layer) and the ferromagnetic layer GaMnAs. It is established that the quantum well emission line is split into two circularly polarised components, which opens up new possibilities for coding and transmission of information in fibre-optic data transmission lines by the methods of polarisation modulation. The circular polarisation of the photoluminescence from the InGaAs / GaAs quantum well is caused by the magnetisation of a nearby ferromagnetic GaMnAs layer. Acknowledgments The author is grateful to the employees of NIFTI UNN named after N.I. Lobachevsky Yu.A. Danilov and M.V. Dorokhin for samples, the employee of ISSP RAS S.V. Zaitsev for optical measurements, the employee of the Moscow State University of Railway Engineering (MIIT) V.P. Solov'ev for useful discussions. The work is partially supported by the grant of the Russian Foundation for Basic Research No. 16-07-00863a and the RF President's grant MK-5754.2016.3.

Результаты экспериментальных исследований маломодовых режимов волоконных брэгговских решеток на многомодовых световодах

Nowadays fiber Bragg gratings (FBGs) are widely used in various devices and applications of fiber optics. They become a basic component for fiber optic sensor networks. The most of those both commercial and prototype fiber optic sensor systems are based on well-researched either singlemode or multimode regime of signal transmission over optical fibers. However some works are concerned with researches of FBGs written on silica multimode optical fibers (MMF) for various photonics and fiber optics applications. Thus, FBGs written on graded-index MMFs are used in optical filters of fiber optic data transmission systems 10G designed for local area networks and radio-over-fiber systems covering micro- and pico-cells. Some works are focused on FBGs written on step-index MMFs. Slanted or tilted multimode FBGs are also widely used in vibration, temperature, deformation etc. fiber optic sensors. Another group of publications is devoted to conventional FBGs on silica telecommunication graded-index MMFs 50/125 as well as 62.5/125 and experimental approbation of various fiber optic sensors based on them. However, the most part of mentioned papers are focused on just analysis of FBG spectral response during laser-excited optical signal propagation that corresponds to a few-mode regime. Few-mode regime adds a new another one dimension to parameter space that is associated with guided modes of particular order which limited number (from two to a few dozens) transfer the most part of optical signal power over tested optical fiber. Optical fiber operating in a few-mode regime of data transmission is interferometer that in combination with FBG can be considered as an alternative basis for design of elements with new unique properties. This work is concerned with experimental researches of few-mode regimes of FBG operating during transferring of laser based optical signals. We tested FBGs written on silica graded-index multimode fibers 50/125 Cat. OM2+/OM3 with Bragg wavelength 1550 nm by using them in a set of developed experimental schemes based on excitation of multimode fibers by corresponding laser sources. The researches were also focused on analysis of both spectral and pulse responses under changing of selected mode mixing and power diffusion processes due to tension and/or stress local and distributed action to FBG or sensor fiber. Results of spectral and pulse response measurements at the output of schemes with installed described FBGs are represented.

Mode division multiplexing using an orbital angular momentum mode sorter and MIMO-DSP over a graded-index few-mode optical fibre.

Mode division multiplexing (MDM)– using a multimode optical fiber’s N spatial modes as data channels to transmit N independent data streams – has received interest as it can potentially increase optical fiber data transmission capacity N-times with respect to single mode optical fibers. Two challenges of MDM are (1) designing mode (de)multiplexers with high mode selectivity (2) designing mode (de)multiplexers without cascaded beam splitting’s 1/N insertion loss. One spatial mode basis that has received interest is that of orbital angular momentum (OAM) modes. In this paper, using a device referred to as an OAM mode sorter, we show that OAM modes can be (de)multiplexed over a multimode optical fiber with higher than −15 dB mode selectivity and without cascaded beam splitting’s 1/N insertion loss. As a proof of concept, the OAM modes of the LP11 mode group (OAM−1,0 and OAM+1,0), each carrying 20-Gbit/s polarization division multiplexed and quadrature phase shift keyed data streams, are transmitted 5km over a graded-index, few-mode optical fibre. Channel crosstalk is mitigated using 4 × 4 multiple-input-multiple-output digital-signal-processing with <1.5 dB power penalties at a bit-error-rate of 2 × 10−3.

A Standard of the Units of Average Power and Attenuation of Optical Radiation for Fiber-Optical Communications and Data Transmission Systems

The results of an investigation of the metrological characteristics of a standard, which can store, reproduce and transfer the unit of average power from 0.1 mW to 5 mW in the 0.6–1.7 μm spectral range with a relative expanded uncertainty not exceeding 0.002, and an attenuation from 0.05 dB to 60.00 dB, with an expanded uncertainty of less than 0.2 dB, are presented.

Design of Fiber Data Transmission System Based on FPGA

Optical fiber data transmission system has advantages of long-distance transmission, low error rate, high speed data transmission, using FPGA chip NIOSII embedded processor and on chip peripheral constitute the core components, without changing the basic framework of the system, can be upgraded and functional changes to the FPGA internal hardware and software, improved design flexibility, reduced the development cost.

Multigigabit W-Band (75–110 GHz) Bidirectional Hybrid Fiber-Wireless Systems in Access Networks

We experimentally demonstrate multigigabit capacity bidirectional hybrid fiber-wireless systems with RF carrier frequencies at the W-band (75–110 GHz) that enables the seamless convergence between wireless and fiber-optic data transmission systems in access networks. In this study, we evaluate the transmission performances in two scenarios: a fiber-wireless access link that directly provide high-speed connections to wireless end users, and a fiber-wireless-fiber signal relay where a high capacity wireless link can be used to bridge two access fiber spans over physical obstacles. In both scenarios, we compare the transmission performances in terms of achievable wireless distances with and without using a high-frequency electrical power amplifier at the wireless transmitter. A downlink 16-Gbit/s QPSK signal and an uplink 1.25-Gbit/s ASK signal transmission over the two implementations are experimentally evaluated in terms of bit-error-rate (BER) performance. Results show that the use of the power amplifier can extend the wireless distance from ∼1 m to over 15 m in an indoor environment with BER performance within the 7% FEC threshold.

Fiber-Optics Data Transmission for a Gyro Stabilized Platform

An optical fiber based data transmission link for a four-axis gyro stabilized inertial reference system is presented. The operation and configuration of the gyro stabilized platform is introduced to explain the requirement of data transmission. Four passive fiber optic rotary joints (FORJs) instead of traditional electrical sliprings are used to transmit optical signals between these relatively rotating gimbals. The hardware and software design of this optical fiber communication system operated at an updating rate of 1kHz are described to achieve high-speed, real-time, reliable data transmission. The experimental results show that the fiber optic rotary joint-based data transmission link is real-time and reliable. The use of FORJs as fiber optic sliprings will also result in an extremely low friction torque by comparing to electrical slipring assemblies. This allows the system designer to optimize the servo control performance for such high-precision gyro stabilized inertial reference systems.

Optically Allowed Photoluminescence from a Direct-Gap Si-Ge Superstructure on Si0.4Ge0.6

Light emission from Si nanostructures has been of great interest for some time now owing to the need for silicon-based light sources for applications in silicon photonics. Both Si and Ge possess indirect band gaps, which makes them very inefficient light emitters. Band gap engineering has been proposed as one way to overcome this limitation and although light emission with greatly improved efficiency has been obtained at low temperatures the emission at room temperature is still very weak, because of exciton dissociation. Recently, through employing novel band gap engineering computations, entirely new Si/Ge [M. d’Avezac, J.-W. Luo, T. Chanier, and A. Zunger, Phys. Rev. Lett. 108, 027401 (2012)] and Si [H. J. Xiang, B. Huang, E. Kan, S.-H. Wei, and X. G. Gong, Phys. Rev. Lett. 110, 118702 (2013)] supercell structures possessing direct gaps have been proposed. According to d’Avezac et al., a SiGe2Si2Ge2SiGen superstructure should have a direct and dipole-allowed gap of 0.863 eV, which is ideally suited for optical fiber data transmission applications. Here we report on the growth of such a structure and its optical properties. Two similar samples were prepared by different growth methods: molecular beam epitaxy (MBE) and solid phase epitaxy (SPE). In both samples the superstructure (terminated with n = 12 monolayers of Ge) was grown on a 30-nm thick buffer layer of Si0.4Ge0.6 on a 5 µm thick relaxed buffer layer of Si0.4Ge0.6on a 750 µm thick (001) Si substrate. The photoluminescence (PL) spectra were measured using a Bomem DA3 FTIR spectrometer, with the samples excited at low temperatures with either 70 mW of 405 nm or 35 mW of 458 nm laser light.Photoluminescence (PL) spectra obtained at 6 K with excitation at 405 nm are shown in Fig. 1. Similar spectra were obtained with 458 nm excitation. No PL was detected from the two samples in the energy range 1000-1850 meV or at room temperature. The sharp drop at low energy near 700 meV is due to the cut-off in the instrumental response. A strong low-energy PL doublet is seen, with peaks near 780 and 820 meV, together with a much weaker peak at 872 meV. The ratio of intensities of the strong and weak peaks is the same in both samples. The intensities of all three PL peaks decrease with increasing temperature up to 25 K, but the weak peak decreases in intensity faster than that of the strong peaks. The weak peak at 872 meV is most likely the dipole-allowed direct-gap transition expected at 0.863 eV in the superstructure. The small difference in energy between theory and experiment could be the result of a difference in strain within the layer in the sample compared with the ideal (perfect) modeled structure or from assumptions in parameter values in the model. The strong peaks at 820 and 780 meV are assigned to the no-phonon and transverse-optic-phonon emission lines, respectively, of the Si0.4Ge0.6 buffer layer. The ~40 meV separation between the two strong peaks is characteristic of the phonon energies in SiGe alloys. The energies of the peaks, however, are much lower than that expected for a bulk Si0.4Ge0.6 alloy (~0.97 eV). The energies and general appearance of these peaks is reminiscent of what has been obtained from PL studies of SiGe nanostructures imbedded in Si. It is therefore likely that this PL arises predominately at the Si0.4Ge0.6/superstructure interface where there is type-II band alignment. In conclusion, we have obtained experimental evidence of the predicted direct-gap optically-allowed transition in a special supercell comprised of a number of ultrathin layers of Si and Ge.

Simulation and Design of a Low Crosstalk Hexagonal Photonic Crystal Crossover Waveguide

In this paper, an optical waveguide junction is introduced to reduce crosstalk based on a hexagonal structure of photonic crystals for TE modes. The wavelength is 1330 nm which is an important wavelength for optical fiber data transmission. Simulation results show that the proposed design exhibits a reduction of -50 dB in crosstalk. It translates to a considerable isolation improvement between two crossover waveguides. FDTD method is used to obtain the transmission coefficient.

Standard apparatus for measuring polarization mode dispersion in fiber-optic data transmission systems

Methods and instruments for ensuring the uniformity of polarization mode dispersion measurements in fiber-optic data transmission systems are described. The results of the development of a standard measuring instrument and working standards of the unit of dispersion are presented. The results of metrological investigations of a standard measuring instrument are also given.