Advanced Optical Networks Research Articles

Deep learning techniques for quality of transmission estimation in optical networks

A large body of research has recently examined the estimation of the quality of transmission (QoT) in optical networks with deep learning. This paper discusses a lightpath’s quality of transmission to design fiber-optic communication and networks using deep learning algorithms. We need different major estimation parameters for advanced optical fiber communication and networks, i.e., modulation formats, baud rate, and code rate. Currently, the quality of transmission for unspecified optical paths depends on different estimation techniques i.e., (1) analytical models estimating physical layer impairments (PLIs) and (2) margined formulas. This paper focuses on deep-learning techniques that can be applied to optimization and complex systems. The deep learning algorithms contain different classifiers that can simulate results and estimate the bit-error rate, and signal-to-noise ratio of unspecified optical paths with threshold values, traffic volume, and modulation format. We must train and test the datasets for various classifiers, and classification features using Korean network topology. The classifier accuracy and Area Under the ROC Curve (AUC) simulation results are carried out using MATLAB.

High-speed optical channels of advanced optical transport networks OTN/DWDM. Part 2: Communication range, spectral efficiency and symbol rate.

The series of articles presents analytical materials on the throughput and evolution of modulation formats of OTN/DWDM optical channels (part 1), on the communication range, spectral efficiency and symbol rate of OTN/DWDM optical channels (part 2).

High-speed optical channels of advanced optical transport networks OTN/DWDM

The series of articles presents analytical materials on the throughput and evolution of modulation formats for OTN/DWDM FOTS optical channels; in terms of communication range, spectral efficiency and symbol rate of OTN/DWDM FOTS optical channels.

Programmable Optoelectronic Synaptic Transistors Based on MoS2/Ta2NiS5 Heterojunction for Energy-Efficient Neuromorphic Optical Operation.

The optoelectronic synaptic transistors with various functions, broad spectral perception, and low power consumption are an urgent need for the development of advanced optical neural network systems. However, it remains a great challenge to realize the functional diversification of the systems on a single device. 2D van der Waals (vdW) materials can combine unique properties by stacking with each other to form heterojunctions, which may provide a strategy for solving this problem. Herein, an all-2D vdW heterojunction-based programmable optoelectronic synaptic transistor based on MoS2/Ta2NiS5 heterojunctions is demonstrated. The device implements reconfigurable, multilevel non-volatile memory (NVM) states through sequential modulation of multiple optical and electrical stimuli to achieve broadband (532-808nm), energy-efficient (17.2 fJ), hetero-synaptic functionality in a bionic manner. The intrinsic working mechanisms of the photogating effect caused by band alignment and the interfacial trapping defect modulation induced by gate voltage are revealed by Kelvin-probe force microscopy (KPFM) measurements and carrier transport analysis. Overall, the (opto)electronic synaptic weight controllability for combined in-sensor and in-memory logic processors is realized by the heterojunction properties. The proposed findings facilitate the technical realization of generic all 2D hetero-synapses for future artificial vision systems, opto-logical systems, and Internet of Things (IoT) entities.

A burst-mode receiver with quick response and high consecutive identical digit tolerance for advanced intra-vehicle optical networks

Recently, self-driving cars have been eagerly studied and developed. In such applications, to transmit large-capacity data acquired by sensor devices such as radars, LiDARs, and high-definition cameras, optical fiber networks are promising as intra-vehicle systems. One type of intra-vehicle optical network has a unidirectional optical ring topology, in which the optical receiver operates in the burst mode. In this paper, we demonstrate an adaptive time-constant-control circuit that enables a quick response to the burst signal and high tolerance to large consecutive identical digit (CID) signals received during single-ended to differential conversion according to the input data patterns. We present operating principles underlying our proposed time-constant control method. The proposed circuit is designed in a 65-nm CMOS process. The experimental results show that the designed circuit operates quickly with 5-ns settling time and has a high tolerance to a large CID length of 66 bits at 10 Gb/s.

An Optical 1×4 Power Splitter Based on Silicon-Nitride MMI Using Strip Waveguide Structures.

This paper presents a new design for a 1 × 4 optical power splitter using multimode interference (MMI) coupler in silicon nitride (Si3N4) strip waveguide structures. The main functionality of the proposed design is to use Si3N4 for dealing with the back reflection (BR) effect that usually happens in silicon (Si) MMI devices due to the self-imaging effect and the higher index contrast between Si and silicon dioxide (SiO2). The optimal device parameters were determined through numerical optimizations using the beam propagation method (BPM) and finite difference time domain (FDTD). Results demonstrate that the power splitter with a length of 34.6 μm can reach equal distribution power in each output port up to 24.3% of the total power across the O-band spectrum with 0.13 dB insertion loss and good tolerance MMI coupler parameters with a shift of ±250 nm. Additionally, the back reflection range over the O-band was found to be 40.25-42.44 dB. This demonstrates the effectiveness of the incorporation using Si3N4 MMI and adiabatic input and output tapers in mitigating unwanted BR to ensure that a good signal is received from the laser. This design showcases the significant potential for data-center networks, offering a promising solution for efficient signal distribution and facilitating high-performance and reliable optical signal routing within the O-band range. By leveraging the advantages of Si3N4 and the MMI coupler, this design opens possibilities for advanced optical network architectures and enables efficient transmission of optical signals in the O-band range.

Augmented detection of septal defects using advanced optical coherence tomography network-processed phonocardiogram.

Cardiac auscultation is a traditional method that is most frequently used for identifying congenital heart disease (CHD). Failure to diagnose CHD may occur in patients with faint murmurs or obesity. We aimed to develop an intelligent diagnostic method of detecting heart murmurs in patients with ventricular septal defects (VSDs) and atrial septal defects (ASDs). Digital recordings of heart sounds and phonocardiograms of 184 participants were obtained. All participants underwent echocardiography by pediatric cardiologists to determine the type of CHD. The phonocardiogram data were classified as normal, ASD, or VSD. Then, the phonocardiogram signal was used to extract features to construct diagnostic models for disease classification using an advanced optical coherence tomography network (AOCT-NET). Cardiologists were asked to distinguish normal heart sounds from ASD/VSD murmurs after listening to the electronic sound recordings. Comparisons of the cardiologists' assessment and AOCT-NET performance were performed. Echocardiography results revealed 88 healthy participants, 50 with ASDs, and 46 with VSDs. The AOCT-NET had no advantage in detecting VSD compared with cardiologist assessment. However, AOCT-NET performance was better than that of cardiologists in detecting ASD (sensitivity, 76.4 vs. 27.8%, respectively; specificity, 90 vs. 98.5%, respectively). The proposed method has the potential to improve the ASD detection rate and could be an important screening tool for patients without symptoms.

Performance Analysis of Wavelength Division Multiplexing-Based Passive Optical Network Protection Schemes by Means of the Network Availability Evaluator

This paper is focused on the performance analysis of protection mechanisms utilized in common wavelength division multiplexing-based passive optical networks. The main aim of the proposed research is providing an option of comparing different traffic protection scenarios for advanced optical network designs, evaluating their possible realizations from a viewpoint of the total optical power budget and analyzing their network availabilities with accommodation to concrete optical access infrastructures. First, a short basic classification of passive optical network architectures utilizing advanced wavelength division multiplexing techniques is introduced. Second, considered presumptive protection scenarios deployed to this kind of passive optical networks involved in the performance analysis are presented. For the performance analysis, corresponding reliability diagrams, relations and formulas used for the calculation of the total network availability are prepared for any specific scenario. In addition, the optical power budget is considered and subsequently evaluated for each protection scheme. For evaluating possible migration scenarios related to considered protection schemes and for comparing protection possibilities of various passive optical networks, a realization of the appropriate simulation tool must be executed. The simulation program utilizes specific parameters of particular optical components utilized in a selected protection scheme and presents its resultant network availability. Values of considered specific parameters can be changed according to the well-known data resources or specific network operator’s data. Subsequently, relevant simulation results obtained by the Network Availability Evaluator that can provide insights into relationships between a number of protection schemes are used for the performance analysis. Finally, an evaluation of the total network availability for considered traffic protection scenarios utilized in passive optical networks with advanced wavelength division multiplexing is included.

Applications of photonic crystal fibers in optical communication

Abstract Photonic crystal fiber is a category of optical fibers, getting great attention by its promise to offer a range of optical characteristics that are not achievable in conventional optical fibers. Engineered dispersion and nonlinear characteristics of photonic crystal fiber (PCF) make it an attractive candidate for nonlinear optics and advanced optical networking in the all-optical domain. An optical network consists of different optical components such as laser sources, amplifiers, regenerators, and convertors for proper signal transmission over long distances. In recent years, the performance of the components has been improving by employing the appealing properties of PCF. The PCF’s application on such components is discussed, and the simulated results on gain amplification, regeneration, conversion, fiber laser are reviewed. These developments reveal that the enhanced performance provided by PCF makes it suitable for different optics applications.

High-performance silicon PIN diode switches in the 2-µm wave band.

The 2-µm wave band has attracted significant research interest due to its potential applications for next-generation high-capacity optical communication and sensing. As the key component, fast optical switches are essential for an advanced and reconfigurable optical network. Motivated by this prospect, we propose and demonstrate two typical silicon PIN diode switches at 2 µm. One is based on a coupled microring resonator (CMRR), and the other is based on a Mach-Zehnder interferometer (MZI) with a push-pull-like configuration. The measured insertion loss of the CMRR switch is <2.5 dB, and the cross talk is <-10.8 dB. The insertion loss of the MZI switch is <2 dB, and the cross talk is <-15.6 dB. The switch times of these two structures are both lower than 12.5 ns.

Highly versatile near-infrared emitters based on an atomically defined HgS interlayer embedded into a CdSe/CdS quantum dot.

The availability of colloidal quantum dots with highly efficient, fast and 'non-blinking' near-infrared emission would benefit numerous applications, from advanced optical communication and quantum networks to biomedical diagnostics. Here, we report high-quality near-infrared emitters that are based on well known CdSe/CdS heterostructures. By incorporating an HgS interlayer at the quantum dot core/shell interface, we convert normally visible emitters into highly efficient near-infrared fluorophores. Employing thermodynamically controlled sequential deposition of metal and chalcogen ions, we achieve atomic-level precision in defining the thickness of the HgS interlayer (H). This manifests in 'quantized' jumps of the photoluminescence spectrum when H changes in discrete, atomic steps. The synthesized structures show highly efficient photoluminescence, tunable from 700 to 1,370 nm, and fast radiative rates of ~1/60 ns-1. The emission from individual CdSe/HgS/CdS colloidal quantum dots is virtually blinking free and exhibits nearly perfect single-photon purity. In addition, when incorporated into a light-emitting-diode architecture, these quantum dots demonstrate strong electroluminescence with a sub-bandgap turn-on voltage.

A review of optical networking technologies supporting 5G communication infrastructure

The advanced communication networks require heterogeneous emerging technologies to be combined while enabling various future applications. The integration of 5G wireless and optical technology is considered an unavoidable approach to reach this goal. Based on 5G mobile communications and densification of cells, the upcoming idea of smart city becomes feasible and put on a lot of attention from the research community due to its effect on everyday life’s improvement and modernization. The concept of a smart city should support everything from electrical grids to traffic management and requires the transmission of a huge amount of data. Smart city planning with a reliable communication infrastructure that can provide stringent network requirements is unfeasible without the joint of optical and wireless technologies. This paper aims to provide an overview of recent developments of advanced optical networking to provide 5G transport networks and their applications in connecting a huge number of devices in future smart city infrastructures. The implementation of optical technologies in 5G core networking open numerous questions of how wireless and optical can coexist to provide sophisticated future applications, such as the smart city concept. Within this research, we will provide the answers to some of the key related questions.

Low-threshold bistable reflection assisted by oscillating wave interaction with Kerr nonlinear medium* *Projected supported by the Open Fund by State Key Laboratory of Advanced Optical Communication Systems and Networks (Grant No. 2017GZKF18), the National Natural Science Foundation of China (Grant Nos. 12064017, 61765008, 11764020, 11864017, 11804133, and 51567011), the Jiangxi Provincial Natural Science Foundation (Grant No. 20181BAB206034), the Fundamental Research

Owing to the enormously enhanced oscillating wave, a minute variation of the incident light intensity will give rise to a change in the dielectric constant of the Kerr nonlinear medium and lead to a bistable reflection with an ultra-low threshold intensity, which is closely related to the angle of incidence and the thickness of the Kerr nonlinear medium. The criterion for the existence of optical bistability is derived. Our bistability scheme is simple and not limited to the TM-polarization.

Scalable selective high order mode pass filter architecture with asymmetric directional couplers.

We propose a novel design architecture to realize scalable selective mode filter based on the asymmetric directional coupler structure. In this structure, any arbitrary high-order mode can pass, whereas other unwanted modes are blocked. Furthermore, multiple optical modes can be blocked by only adjusting the structural parameters. As a proof of concept, we experimentally demonstrated a three-mode device and the scalability of the proposed structure is demonstrated by another design of four-mode filter. The proposed architecture offers scalability and high-design flexibility, and it has excellent potential to be used in advanced mode division multiplexing optical networks.

Design of High Speed Optical Fiber Cables and Transmission Techniques in Advanced Optical Networks

In the present paper, design of high velocity fiber-optic communication networks with ultra wide-dense wavelength division multiplexing (UW-DWDM), space division multiplexing (SDM) and optical transmission techniques is presented. All connects in the (SDM) are split into subgroups of various chemical and geometrical characteristics .The parameters have been designed at: i) Δn, the relative refractive index difference for both the core and also the clad, ii) x%, the percentage of doping in silicon material by Germanium material. The Δn and x% parameters are also preserved during their technological boundaries of attention. UW-DWDM has 1200 channels that transferred at the fiber-optic wavelengths from 1450 nm up to 1650 nm within 140 connects from UW-SDM wherever every connect is prepared to own the same compressed chromatic dispersion. From this technique, it is noticed that the connect design parameters suffer more nonlinearity with the number of connects. So, two different propagation techniques have been used to investigate the transmitted bit-rate as a criterion to enhance the system performance. The first technique is Soliton propagation, where the control parameters lead to equilibrium between the pulse spreading due to dispersion and the pulse shrinking because of nonlinearity. The second technique is the maximum time division multiplexing (MTDM) technique where the parameters are adjusted to lead to minimum dispersion. Two cases are investigated; no dispersion cancellation and dispersion cancellation. The investigations are conducted over an enormous range of the set of controlling parameters. Thermal effects are considered through three basic quantities, namely: the transmission bit rate, the dispersion characteristics and the spectral losses.

Getting single photons on the right track

Quantum Optics As the field of quantum optics moves from the optical bench to more practical on-chip platforms for the development of quantum-based technologies, methods are required for the controlled propagation of single photons within an integrated optical circuit. Papon et al. demonstrate an effective nano-opto-electromechanical approach that can route single photons generated from an on-chip quantum emitter between two coupled waveguides robustly and quickly when their separation is controlled by application of a voltage bias. Such controlled manipulation presents an essential building block for developing advanced quantum optical circuits and networks. Optica 6 , 524 (2019).

Observation of 550 MHz passively harmonic mode-locked pulses at L-band in an Er-doped fiber laser using carbon nanotubes film**Project supported by the National Natural Science Foundation of China (Grant No. 61605107), Young Eastern Scholar Program at Shanghai Institutions of Higher Learning, China (Grant No. QD2015027), the “Young 1000 Talent Plan” Program of China, the Open Program of the State Key

We demonstrate a passively harmonic mode-locked (PHML) fiber laser operating at the L-band using carbon nanotubes polyvinyl alcohol (CNTs-PVA) film. Under suitable pump power and an appropriate setting of the polarization controller (PC), the 54th harmonic pulses at the L-band are generated with the side mode suppression ratio (SMSR) better than 44 dB and a repetition frequency of 503.37 MHz. Further increasing the pump power leads to a higher frequency of 550 MHz with compromised stability of 38.5 dB SMSR. To the best of our knowledge, this is the first demonstration on the generation of L-band PHML pulses from an Er-doped fiber laser based on CNTs.

Allocation of spectral and spatial modes in multidimensional metro-access optical networks

Introduction of spatial division multiplexing (SDM) has added a new dimension in an effort to increase optical fiber channel capacity. At the same time, it can also be explored as an advanced optical networking tool. In this paper, we have investigated the resource allocation to end-users in multidimensional networking structure with plurality of spectral and spatial modes actively deployed in different networking segments. This presents a more comprehensive method as compared to the common practice where the segments of optical network are analyzed independently since the interaction between network hierarchies is included into consideration. We explored the possible transparency from the metro/core network to the optical access network, analyzed the potential bottlenecks from the network architecture perspective, and identified an optimized network structure. In our considerations, the viability of optical grooming through the entire hierarchical all-optical network is investigated by evaluating the effective utilization and spectral efficiency of the network architecture.

Numerical investigation on broadband mid-infrared supercontinuum generation in chalcogenide suspended-core fibers**Project supported by the National Nature Science Foundation of China (Grant Nos. 61435003, 61377042, 61505024, and 61421002), Open Fund of State Key Laboratory of Advanced Optical Communication Systems and Networks, China (Grant No. 2015GZKF004), Open Found of Key Laboratory of Specialty Fiber Optics and Optical Access Networks, Shanghai University, China

As2S3 and As2Se3 chalcogenide 3-bridges suspended-core fibers (SCFs) are designed with shifted zero-dispersion wavelengths (ZDWs) at around 1.5 μm, 2 μm, and 2.8 μm, respectively. A generalized nonlinear Schrödinger equation is used to numerically compare supercontinuum (SC) generation in these SCFs pumped at an anomalous dispersion region nearby their ZDWs. Evolutions of the long-wavelength edge (LWE), the power proportion in the long-wavelength region (PPL), and spectral flatness (SF) are calculated and analyzed. Meanwhile, the optimal pump parameters and fiber length are given with LWE, PPL, and SF taken into account. For As2S3 SCFs, SC from a 14 mm-long fiber with a ZDW of 2825 nm pumped at 2870 nm can achieve the longest LWE of and PPL up to ∼72%. For As2Se3 SCFs, the LWE of 15.5 μm and the highest PPL of % can be achieved in a 10 mm-long fiber with ZDW of 1982 nm pumped at 2000 nm. Although the As2Se3 SCFs can achieve much longer LWE than the As2S3 SCFs, the core diameter of As2Se3 SCFs will be much smaller to obtain a similar ZDW, leading to lower damage threshold and output power. Finally, the optimal parameters for generating SC spanning over different mid-IR windows are given.

Channel-selective wavelength conversion of quadrature amplitude modulation signal using a graphene-assisted silicon microring resonator

Compact and flexible all-optical signal processing is highly desirable in future optical networks for its high-speed processing without optical-electrical-optical conversion. Recent progress of silicon photonics and graphene has driven the increasing research interest of ultra-compact highly efficient chip-scale all-optical signal processing. In this Letter, by exploiting a graphene-silicon microring resonator (GSMR), we propose and experimentally demonstrate channel-selective wavelength conversion of multi-channel quadrature amplitude modulation (QAM) signals. Efficient selective conversion of four-channel 16-QAM signals are observed. The selective suppression ratio and bit error rate of selective conversion are studied, showing favorable operation performance. The proposed channel-selective wavelength conversion of multi-channel signals using GSMR may find various applications in future advanced optical networks for robust data management.