Optical Telecommunication Systems Research Articles

High-performance InP/InGaAs heterojunction bipolar phototransistors for optoelectronic applications

<span>Phototransistors are attractive devices for applications in optical fiber telecommunication systems. They are used for the detection of optical signals and the amplification of these signals. This paper presents an investigation of how the technological parameters of indium phosphide (InP)/indium gallium arsenide (InGaAs) heterojunction bipolar phototransistor can impact its responsivity at two wavelengths, 1310 nm and 1550 nm. Based on the results of this investigation, we proposed optimized structures for the studied phototransistor. In this work, we used the software technology computer aided-design (TCAD)-Silvaco to simulate the physical and the electrical behavior of the different structures. The proposed optimized phototransistors can be used for various optoelectronic applications.</span>

Providing a method to stabilize the laser output light intensity for optical telecommunication systems

Providing a method to stabilize the laser output light intensity for optical telecommunication systems

Research and analysis of the efficiency fiber-optic communication lines using DWDM technologies

The performance indicators fiber-optic communication lines using spectral technology with separation communication channels are analyzed. The effectiveness of the use network resources optical telecommunication systems using spectral technologies based on the architectural concept of the next NGN (NGN, Next Generation Network) and future FN (FN, Future Network) networks has been studied. This work is devoted to the construction methods for calculating the indicators optical networks and the study methods and tools for improving the efficiency using network and channel resources fiber-optic communication lines using dense spectral multiplexing optical signals with separation communication channels. The problem ensuring effective management channel and network resources in optical communication networks are considered. As a result of the study technology spectral multiplexing, a new approach to the construction of a calculation method is proposed that describes the efficiency managing network and channel resources in fiber-optic communication lines, taking into account the numerous requirements their parameters and transfer characteristics. On the basis of the calculation method, analytical expressions are obtained that allow estimating the resources of the system, indicators informational and spectral efficiency of the functioning fiber-optic communication lines. The results of the research can be applied by cellular operators when designing an optical telecommunications network, in particular, to determine the optimal value of the capacity optical systems based on wavelength multiplexing technology and modulation spectral efficiencies.

Cladding pumped bismuth-doped fiber amplifiers operating in O-, E-, and S-telecom bands.

Bismuth-doped fibers (BDFs) are considered nowadays as an essential part of the development of novel optical amplifiers, which can provide a significant upgrade to existing fiber optic telecommunication systems, securing multiband data transmission. In this paper, a series of BDF amplifiers (BDFAs) for O-, E-, and S-telecom bands based on a cladding pumping scheme using low-cost multimode semiconductor laser diodes at a wavelength of 0.7-0.8 µm were demonstrated for, it is understood, the first time. The developed BDFAs are characterized by a high peak gain of >25-30 dB in the corresponding telecom bands and a relatively low noise figure of 5-6 dB. Comparative analysis shows that most of the parameters of cladding pumped BDFAs are close to those of the best core pumped ones. This research opens up new opportunities for utilizing Bi-doped fibers as a key element of cost-effective and ready-to-work BDFAs for various practical applications.

Nonlinear wavelength conversion cross phase modulation in fiber systems based on directly modulated laser measured

Abstract This study has clarified the simulation of the nonlinear cross phase modulation (CPM) performance signature in optical fiber telecommunication systems. We have been clarified the max Q factor in relation to Cross phase shift modulation for the previous models and proposed model. The optimum optical power varied with spectral time and wavelength variation that is simulated for 90° cross phase shift modulation. Optimum total optical and electrical signal power is demonstrated for 90° Cross phase shift modulation. The max signal quality factor and min BER are assured for various degrees based on cross phase shift modulation. In addition to the optimum signal quality factor is emphasized for 90° Cross phase shift modulation.

Bright Soliton Solution of the Nonlinear Schrödinger Equation: Fourier Spectrum and Fundamental Characteristics

We derive exact analytical expressions for the spatial Fourier spectrum of the fundamental bright soliton solution for the 1+1-dimensional nonlinear Schrödinger equation. Similar to a Gaussian profile, the Fourier transform for the hyperbolic secant shape is also shape-preserving. Interestingly, this associated hyperbolic secant Fourier spectrum can be represented by a convergent infinite series, which can be achieved using Mittag–Leffler’s expansion theorem. Conversely, given the expression of the series of the spectrum, we recover its closed form by employing Cauchy’s residue theorem for summation. We further confirm that the fundamental soliton indeed satisfies essential characteristics such as Parseval’s relation and the stretch-bandwidth reciprocity relationship. The fundamental bright soliton finds rich applications in nonlinear fiber optics and optical telecommunication systems.

Compact silicon-based polarization-independent 1.55/2 μm wavelength diplexer based on a multimode interference coupler with multiple shallow grooves

Faced with the rapid growth of internet traffic demand, which has posed a huge challenge to the current fiber-based communications systems, expanding the telecommunications bands from traditional near-infrared (NIR) region to mid-infrared (MIR) region is emerging as an attractive solution. And on-chip wavelength division multiplexing (WDM) application for NIR/MIR wavelengths is an essential element in future optical telecommunication systems. Here, we propose a compact silicon-based polarization-independent wavelength diplexer for the NIR/MIR wavelengths of 1.55/2 μm, where multiple rectangular grooves are shallowly etched on the silicon MMI waveguide for introducing the refractive-index perturbations on the MMI waveguide eigenmodes. And this refractive-index perturbation scheme provides a simple and scalable method to manipulate the four beat lengths of the two wavelengths at TE- or TM-polarization in a single waveguide via self-imaging effect, leading to a compact footprint. By optimizing the structural parameters, both NIR/MIR wavelength demultiplexing and polarization independence, for the first time, are obtained simultaneously in the present single device. From the results, the proposed diplexer is only 21.6 μm in length, and shows a wide bandwidth of ∼ 100/120 nm around the wavelength of 1.55/2 μm for insertion loss (IL) < 1 dB and extinction ratio (ER) > 15 dB. Moreover, we also realize a compact and polarization-independent wavelength diplexer for 1.31/2 μm by flexibly changing the dimensions, showing the flexibility and extensibility of our refractive-index perturbation scheme. Besides, fabrication tolerances are analyzed and mode propagation profiles are also demonstrated.

Optimized design of an all-optical XOR gate with high contrast ratio and ultra-compact dimensions

In this work, an optimized structure for an all-optical XOR gate with high contrast ratio and extremely compact dimension is proposed based on a photonic crystal platform. The above structure employs silicon rods in a hexagonal lattice configuration. The design works purely on linear interference effect between the incoming light signals without utilizing any non-linear materials. To study the propagation of light within the structure and to generate the bandgap diagram, the Finite Difference Time Domain technique and Plane Wave Expansion methods are utilized. After optimization of the various design parameters, a contrast ratio of 31.76 dB is attained by the proposed structure along with a response time of 0.46 ps and a footprint of 42.24 μm2. The device can be operated in the C Band with optimum performance at 1550 nm, which is the telecommunication wavelength. The operating bit rate for the proposed structure is 2.17 Tbps. The all-optical XOR gate plays a crucial role as the building blocks of various sequential and combinational logic designs suitable for application in optical computing and telecommunication systems.

Enhanced prompt trigger optical switching using nonlinear photonic crystal ring resonator for application on all-optical AND/NAND and OR/NOR logic function

Abstract Nowadays, the development of optical telecommunication systems requires more efficient all-optical elements appreciation to their high data transmission speeds and reduced electromagnetic interferences. In this work, our objective is to attest by simulation a design of an optical switch using 2D photonic crystals from polystyrene, an organic polymeric material with high Kerr non-linearity. This excellent ultra-fast switching leads us to the exploited in the construction of two new structures of all-optical AND/NAND and OR/NOR logic gates. These structures based on non-linear ring resonator NRR of different radius in order to operate a telecom wavelength of 1550.3 µm using RSoft (Full-Wave) software. The average contrast intensity is between 15.52 and 23.42 dB and low delay time varied from 20 fs to 5.0 ps. Hence, resulting a very high output signal for ON-switching (82–130% of P in) and a weak signal for OFF-switching (0.2–7% of P in) through a minimum threshold power around of 1.2 mW/μm2.

Continuous-Variable Quantum Secure Direct Communication Based on Gaussian Mapping

Quantum secure direct communication (QSDC) realizes the transmission of secret messages directly in a quantum channel. A continuous-variable- (CV) based quantum-communication system allows high-speed, large-capacity information transmission in optical telecommunication systems. In this work, we propose a QSDC protocol based on Gaussian mapping. As for Gaussian modulation, the designed Gaussian-mapping scheme effectively solves the problem, which results from the nonuniformity of the secret-message bitstream, and is applicable to different modulation variances. The system performance analysis shows that the proposed scheme can realize inerrant Gaussian modulation of secret messages, and secure transmission of messages under information theory. Moreover, our work hopes to stimulate discussion on experimental realization and practical advance of CV-QSDC protocol.

A Review on Importance of DWDM Technology in Optical Networking

Optical communication uses light signals for transmitting information from source to destination. Optical fiber communication has been more popular for long-distance data transfer in recent years due to various benefits such as low loss, low cost, simple amplification, minimal interference, and lightweight. A simple optical telecommunication system consists of a transmitter, a medium, and a receiver. Wavelength Division Multiplexing (WDM) is a significant improvement in optical communication. WDM is basically used for improving spectral efficiency and to handle more data from several clients. Normal WDM, CWDM, and DWDM are three types of WDM technology. DWDM uses the most denser optical channels in optical networking. Complete detail about all types of WDM is given. The optical spectrum used in the transmission of light signals is also discussed.

Dual-band fiber optical parametric amplification in a structure of highly nonlinear photonic crystal fiber

We investigate fiber optical parametric amplification (FOPA) in a structure of an As2S3 core and TeO2 cladding photonic crystal fiber (PCF). Various amplification features such as wavelength area, parametric gain value, and bandwidth are investigated. In order to design the FOPA system with optimal features, effects of different structural parameters variation on optical features of the PCF and parametric gain subsequently are also investigated numerically based on the finite-difference time domain numerical method. Using 15 cm of this fiber and a continuous wave pump laser of 1.1 W, we attain a gain spectrum of 350 nm with a maximum value of 37 dB around 1550 and 1310 nm, which are favored wavelengths in optical telecommunication systems. In fact, our structure ends in a wideband amplifier in an absolutely compact size, which is optimized exactly for optical telecommunication applications.

Broadband frequency control of light using synthetic frequency lattices formed by four-wave-mixing Bragg scatterings

Recent exploration in synthetic frequency lattices has re-formed the methods of manipulating the light spectrum by analogizing the diffraction management in real space, which can be created by employing electro-optic modulation (EOM) in dielectric waveguides or ring resonators. In the presence of effective gauge potential, that is, the accumulated phase of mode transfer between adjacent lattice sites, the frequency spectrum of incident light can be flexibly tailored. However, the finite bandwidth and modulation depth of EOM vastly restrain the frequency shift and efficiency of mode transfer. Here we experimentally demonstrate that the synthetic frequency lattice can be created with the nonlinear process of four-wave-mixing Bragg scattering. The bandwidth of frequency manipulation is expanded up to terahertz and the frequency shift can be larger than 200 GHz. Furthermore, we can realize effects such as negative refraction and perfect imaging in frequency dimension by changing the effective gauge potentials. The study provides a powerful and promising approach to precisely control light frequency in broadband and may benefit all-optical modulation in optical telecommunication systems.

An Investigation of Optical Gain of Nanomaterial AlGaAsIn/InP under CTLSs in Optical Communications

The fundamental aim of this research paper has been to provide a critical role in the study of an investigation on optical gain enhancement of quaternary nanomaterial AlGaAsIn/InP under the CTLSs (Compressive Type Longitudinal Strains) in optical type telecommunication systems.

Dynamic modeling of the birefringence effects induced in semiconductor optical amplifier for all-optical telecommunication systems

The semiconductor optical amplifiers (SOA) are all-optical multifunctional devices. The improvement of their performance will, therefore, be of great importance for modern optical telecommunication systems. We propose in this article to develop a dynamic model that enables us to simulate the dynamic behavior of SOA's birefringence effects. The determination of a numerical model is a multidisciplinary activity that needs engineering skills, optimization and physics. This numerical model enables to describe the propagation of a picosecond optical pulse passing through the SOA and takes into account its polarization and the phenomenon of energy coupling between the eigenmodes of SOA (TE mode and TM mode). In this paper, we will, first of all describe the numerical algorithm of our model, and then we will propose to make a dynamic characterization of the effect of the nonlinear polarization rotation in the SOA, which will allow us to study the all-optical logic gates as well as all the other digital components based on the nonlinear effect of birefringence in SOA.

A Si-based InP/InGaAs nanowire array photodetector operating at telecommunication wavelength

A Si-based vertical nanowire heterostructure array photodetector is designed and studied by a coupled three-dimensional optoelectronic simulation. Each nanowire is composed of an InP/In0.53Ga0.47As/InP axial p-i-n junction, which is designed to operate at telecommunication wavelengths. The results show that the absorption of the nanowire array strongly depends on the D/P ratio and nanowire diameter. By tuning the D/P ratio and diameter simultaneously, the peak absorption wavelength could be fixed at 1550 nm. Due to the light-trapping and light-concentrating properties, the nanowire array photodetector exhibits a remarkable responsivity beyond 0.8 A/W, several times higher than its thin film counterpart with the equivalent thickness. This work suggests that the III–V nanowire array is promising for high-performance Si-based photodetectors applied in optical telecommunication systems.

Principles of Automated Data Processing of Mandelstam – Brillouin Backscatter Characteristics for Evaluating the State of Optical Fibers

For early diagnostics of the state of optical fibers (OFs) located in the laid optical cables (OCs), it is necessary to identify potentially unreliable sections of the S in advance, which over time can lead to the destruction of fibers and disrupt the normal operation of fiber-optic communication lines (FOCLs). For diagnosis and forecasting of the state of the OFs that are in the laid OCs, Brillouin optical pulse reflectometers (BOTDR) are used, in which the back-reflected signal of the spontaneous Mandelstam – Brillouin scattering (MBS) is analyzed. In the process of obtaining a trace of the distribution of the Mandelshtam – Brillouin backscatter spectrum (MBBS) along the OF, the Brillouin frequency shift (BFS) is determined. After this, a graphs of the distribution of strain along the light-guide is constructed. A classification of varieties of single-mode optical fibers based on analysis of the MBS characteristics is discussed in this paper. It is shown how by the characteristics of the frequency profiles of the MBBS, one can determine the type of fiber and also evaluate the change in the strain and BFS. The MBBS profile come under influence by the functional dependence of the distribution of acoustic modes in the OF, their longitudinal direction. Both of them depend on the structure of the OF layers, as well as on the types and concentration of various alloying additives of the core OF. For single-mode OFs, when describing the MBS process, it is necessary to take into account the spatial distribution and interaction of the main optical and several acoustic modes. After uploading the data file from the BOTDR, it is necessary to process the information in order to determine the BFS and the strain along the light-guide. This process can be automatized, if a database has been formed. When a new Brillouin reflectogram appears, the MBBS profile from it must be compared with templates from the generated database. To classify the fiber types, it is necessary to evaluate the degree of matching of the explored MBBS profile with all the database templates. To assess the degree of coincidence of the considered MBBS profiles, needs to be defined the overall part of the frequency band for analysis. The programs for the automated processing of the Brillouin reflectograms data are presented. Based on the analysis of Brillouin reflectograms, it is possible to identify a factor that had a predominant influence on the characteristics of the MBS signal in the explored sections of single-mode optical fibers. As a result of the program's work, a template is output that, according to the program's estimates according to the algorithm described above, has the best match with the downloaded image. To increase the accuracy of assessing the similarity of the explored profiles, it is also recommended to carry out calculations according to the above-described algorithm when aligning not only the maximum levels, but also combine the graphs along the frequency axis. It is clear that during the overlay the frequencies of the "peaks" (BFS), there will be a very strong coincidence of the patterns, and the type of the OFs will be determined correctly, while at some temperatures a good degree of similarity with another pattern could be obtained. The obtained estimate of the BFS allows one to determine the degree of the OF strain. The identification of the MBBS profile and other characteristics of the MBS allows you to create a database various types of the OFs and different manufacturers, which can be used to classify the type of the OFs. The results presented in this exploratory development show how based on the analysis of BOTDR reflectograms, it is possible to automatically determine the type of the OF in OC, to identify a factor that has a predominant effect on the frequency response and strain in the explored sections of the OFs in FOCL, which can improve the efficiency of predicting the operational parameters of the physical channels of optical telecommunication systems.

Telecommunication Compatibility Evaluation for Co-existing Quantum Key Distribution in Homogenous Multicore Fiber

Quantum key distribution (QKD) is regarded as an alternative to traditional cryptography methods for securing data communication by quantum mechanics rather than computational complexity. Towards the massive deployment of QKD, embedding it with the telecommunication system is crucially important. Homogenous optical multi-core fibers (MCFs) compatible with spatial division multiplexing (SDM) are essential components for the next-generation optical communication infrastructure, which provides a big potential for co-existence of optical telecommunication systems and QKD. However, the QKD channel is extremely vulnerable due to the fact that the quantum states can be annihilated by noise during signal propagation. Thus, investigation of telecom compatibility for QKD co-existing with high-speed classical communication in SDM transmission media is needed. In this paper, we present analytical models of the noise sources in QKD links over heterogeneous MCFs. Spontaneous Raman scattering and inter-core crosstalk are experimentally characterized over spans of MCFs with different refractive index profiles, emulating shared telecom traffic conditions. Lower bounds for the secret key rates and quantum bit error rate (QBER) due to different core/wavelength allocation are obtained to validate intra- and inter-core co-existence of QKD and classical telecommunication.

Optical neural networks based on optical fiber-communication system

In this work, we propose a novel design for optical neural network system based on reservoir computing. The optical neurons in the system consist of directional couplers, optical fibers, and optical amplifiers. The nonlinear activation function of optical neuron can be obtained by the optical amplifiers. Mach–Zehnder phase modulators and the directional couplers are used to build the readout matrix in the output layer. The performance of the system is studied by a commercial software of optical fiber telecommunication system. The results show that the randomly connected optical neuron networks of the reservoir computing can provide a better performance.

Photodetector device for fiber optical telecommunication systems

Photodetector device for fiber optical telecommunication systems