Dynamic Wavelength Research Articles

A learning algorithm for TWDM-PON’ DWBA with 5G fronthaul networks

Abstract Time and wavelength-division multiplexed passive optical network (TWDM-PON) is expected to be the fronthaul networks of 5G, which requires low latency and large bandwidth. In this paper, we propose a Q-learning based dynamic wavelength and bandwidth allocation (DWBA) algorithm for TWDM-PON. Simulation results show that the proposed DWBA algorithm can reduce the number of active channels by 40% and provide larger bandwidth with same wavelength number in comparation with the existing algorithms while satisfying the latency requirement of 5G fronthaul networks.

High-Speed Interrogation Approach for FBG Sensors Using a VCSEL Array Swept Source

This paper presents a fiber Bragg grating (FBG) interrogator based on vertical surface cavity emitting lasers (VCSEL). A Fabry–Perot filter technique is developed to directly calibrate the dynamic wavelength behavior of VCSELs at both low and high sweep rates. A broad bandwidth light source is constructed by multiplexing five VCSELs together to increase the number of FBGs that can be tracked. Scanning of the VCSEL-array is accomplished by a high-speed electronic switch circuit. The developed interrogator achieves a sweep bandwidth of 10 nm at a scanning rate of 4 kHz. Low-velocity impact testing of a composite plate with a surface mounted FBG sensor shows that the wavelength detection error was 2.7% when compared with the FBG strain obtained by a high-speed swept laser.

Dynamic bandwidth allocation algorithms for improved throughput and latency performance in CDMA-based next-generation ethernet passive optical networks

In this paper, we propose new scheduling algorithms to improve the performance of the code division multiple access (CDMA) enabled next generation ethernet passive optical networks (NG-EPON). The original dynamic bandwidth allocation (DBA) scheme based on a round robin scheduling algorithm was originally proposed for the first generation CDMA based EPON where the network throughput and delay requirements per optical network unit (ONU) are relatively moderate. On the other hand, in the NG-EPON standard, the network capacity is increased up to 100 Gb/s and stringent requirements are applied to the packet delay. For this reason, in this work, we propose new scheduling algorithms for NG-EPON to assign a grant size on each upstream CDMA code in order to guarantee the newly required network throughput and delay performance. The first DBA algorithm is the first in first out (FIFO) algorithm in which the ONU requests are ordered in terms of their request arrival time. The second scheme is the reservation pattern (RP) algorithm in which each ONU starts transmitting its queue content in its reserved pattern of subcycles following a pre-defined pattern. The performances of the newly proposed algorithms are evaluated and compared. Results show that both newly proposed scheduling schemes can significantly improve the network performance in terms of the packet delay, jitter, and throughput. In addition, the results are compared to many dynamic wavelength and bandwidth allocation (DWBA) algorithms. The results show that the performances are comparable and that CDMA can be a good alternative for WDM for multi-channels based NG-EPON.

Research of Algorithms used for Routing and Assigning Wavelength in WDM Networks

The telecommunications department is the most difficult in today's communication offering the highest amount of bandwidth. With the finest prototypes and test rigs to form optical WDM technology, many companies have appeared for a particular link request, a wavelength and a path must be allocated in the WDM network. Routing and Wavelength Assignment (RWA) problem is called the assignment of a wavelength and a path to the link request, with accessible resources. The aim of this article is to analyze the algorithms for any WDM networks for efficient wavelength assignment routing protocols. As a researcher, we plan to suggest a comprehensive literature study for the development of a new algorithm for efficient allocation and appropriate wavelength usage and the routing of data packets from source to destination to overcome all failures. Before allocation, we use simulations and analyze optic fiber communication methods, various losses depending on dynamic wavelength allocation with minimum and maximum.

High-dynamic wavelength tracking and millimeter-level ranging inter-satellite laser communication link with feedback-homodyne detection.

The Integrated Laser Communication/Ranging System, which uses a coded signal as the ranging information carrier, is of great importance to the next large-capacity inter-satellite information network. In this paper, a system design with a high-sensitivity feedback-homodyne detection scheme and an asynchronous ranging algorithm is demonstrated with real-time field-programmable gate array-implementation (FPGA). The parallel fast Fourier transformation (FFT) estimation is applied to improve the speed and the range of the wavelength drift tracking, which can handle a dynamic wavelength drift up to 2.4pm/s (300MHz/s). Meanwhile, for clock sources with subtle dynamic frequency offset and sufficient stability, the proposed fractional symbol ranging method is proven to achieve millimeter-level measurement accuracy. The designed system is shown to perform well in terms of both laser linewidth tolerance and noise resistance.

Efficient T-CONT-Agnostic Bandwidth and Wavelength Allocation for NG-PON2

Dynamic bandwidth and wavelength allocation are used to demonstrate high quality of service (QoS) in time wavelength-division multiplexed–passive optical networks (TWDM-PONs). Both bandwidth and wavelength assignment are performed on the basis of transmission containers (T-CONTs) and therefore by means of upstream service priority traffic flows. Our medium access control (MAC) protocol therefore ensures consistency in processing alike classes of service across all optical network units (ONUs) in agreement with their QoS figures. For evaluation of the MAC protocol performance, a simulator has been implemented in OPNET featuring a 40 km, 40 Gbps TWDM-PON with four stacked wavelengths at 10 Gbps each and 256 ONUs. Simulation results have confirmed the efficiency of allocating bandwidth to each wavelength and the significant increase of network traffic flow due to adaptive polling from 9.04 to 9.74 Gbps. The benefit of T-CONT-centric allocation has also been measured with respect to packet delay and queue occupancy, achieving low packet delay across all T-CONTs. Therefore, improved NG-PON2 performance and greater efficiency are obtained in this first demonstration of T-CONTs allocated to both wavelength and time.

Machine learning based dynamic load balancing DWBA scheme for TWDM PON

Abstract The time and wavelength division passive optical network (TWDM PON) provides broadband services to residential, commercial and industrial users at four different wavelengths. Typically, the industrial users are active in day time and inactive in evening while the residential customers are expected to have quite opposite behavior. This disparity will create an imbalance of traffic load on the wavelengths of TWDM PON. Like IEEE PONs, a load proportional wavelength activation approach cannot work for ITU compliant PONs as ITU standard requires all the wavelengths to be active simultaneously. Moreover, the ONUs cannot be assigned bandwidth on two different wavelengths simultaneously and the migration of an ONU from one wavelength to another causes a tuning delay due to a handshaking mechanism between the OLT and the ONU. Therefore, this work proposes an efficient load balancing dynamic wavelength and bandwidth assignment (LB-DWBA) scheme for TWDM PON to maintain a balanced load between the heavily loaded and least loaded ONUs using a regression based machine learning approach. Simulation results show that LB-DWBA scheme not only reduces the traffic load of heavily loaded wavelengths but also minimizes the bandwidth waste from the excess assigned bandwidth assigned to ONUs using type-5 (T5) traffic class. Overall, the LB-DWBA scheme reduces the average upstream delays of type-2 (T2), type-3 (T3) and type-4 (T4) by 18.9%, 24% and 43% respectively.

Crystal-Orientation-Related Dynamic Tuning of the Lasing Spectra of CdS Nanobelts by Piezoelectric Polarization.

Realizing dynamic wavelength tunability could bring about tremendous impacts in laser technology, pressure nanosensing, and lab-on-a-chip devices. Here, we demonstrate an original strategy to operate the lasing mode shift through reversible length changes of a CdS nanobelt, which is determined by the direction of piezoelectric polarization. The relationships between the direction of applied strain, the lasing mode shift, and the tunable effective refractive index are elaborated in detail. The correlation between the piezoelectric polarization-induced lasing mode red shift and the blue shift in the wavelength of the lasing mode output caused by the Poisson effect is discussed in depth, as well. Our study comprehensively considers the influence of both the cavity size variations and refractive index changes on the control of the lasing mode and provides a deeper understanding of the strain-induced lasing mode shift.

QoS-Based DWBA Algorithm for NG-EPON

The next-generation Ethernet passive optical network (NG-EPON) is basically classified into two architectures on the basis of the wavelength sharing by the optical network units (ONUs). The single scheduling domain (SSD) and multi-scheduling domain (MSD) EPON are the two different design architectures for NG-EPON. A vital task in NG-EPON is to design dynamic wavelength bandwidth allocation (DWBA) algorithms that can meet the future demands of the network subscribers. A number of DWBA algorithms have been designed for time and wavelength division multiplex (TWDM) EPON. The existing DWBA algorithms for TWDM-EPON could be used in MSD-EPON by making necessary parametric changes. The design and implementation of new DWBA algorithms for MSD-EPON are still required specifically. In this paper, we have proposed a quality of service (QoS)-based DWBA algorithm for NG-EPON. We have comparatively analyzed our proposed DWBA with the existing algorithms like earlier finished time (EFT), weighted bipartite matching (WBM), and earlier finished time with void filling (EFT-VF). The results show that our proposed DWBA algorithm performs better as compared to EFT, WBM, and EFT-VF on the basis of average packet delay and average completion time for NG-EPON.

Wave propagation on splat induced by liquid drop impingement

This study investigates the interaction between an impacting liquid drop and a static, axisymmetric splat generated on a solid prior to impact, focusing mainly on the wave production and propagation on the splat with low impact velocity. Using high-speed video, the wave generation is observed and analyzed, including a first wave caused by drop kinetic energy, and secondary and tertiary capillary waves subjected to surface tension. Also, the wave propagation magnitude is discussed concerning the effects of Weber number and fluid viscosity, the purpose of which is to provide a suitable method for predicting the wave diameter. Results show that increasing Weber number decreases the wave propagation slightly, but this effect becomes less significant at higher Weber number. In particular to the fluid of butanol with high viscosity, the wave propagation is very insensitive to Weber number. The formula based on the kinematic discontinuity theory can be modified to predict the wave propagation magnitude with a fairly good agreement, for both the kinematic wave and the capillary wave. In addition, the dynamic wavelength situated between the first and secondary waves, and the propagation speed of the wave during the drop–splat interaction are also analyzed. This study advances the fundamental understanding of the spray evaporative cooling with low volumetric flux.

High-priority first dynamic wavelength and bandwidth allocation algorithm in TWDM-PON

Abstract Time and wavelength division multiplexing passive optical network (TWDM-PON) is the mainstream scheme of the next generation access network, and it possesses a number of unique characteristics such as high-bandwidth, long-distance data transmission, and connecting lots of users. As the difference among user traffic demands increases, in order to effectively decrease the network delay and improve resource utilization, a high-priority first dynamic wavelength and bandwidth allocation (HF-DWBA) algorithm in TWDM-PON system is proposed in this study. According to the service-level agreement (SLA), in order to determine the priority of an optical network unit (ONU), the proposed algorithm ensures the high-level ONU traffic distribution in terms of wavelength assignment and bandwidth allocation, and it can execute five types of transmission containers (T-CONTs) as well as four kinds of bandwidth allocation strategies. The results of simulation show that in comparison with traditional algorithms, the proposed HF-DWBA algorithm can effectively reduce end-to-end time delay and improve bandwidth utilization ratio, while making fairness among different types of bandwidth allocation strategies.

Wavelength Assignment Vs. Wavelength Converter Placement in Wavelength-Routed Optical WDM Networks

In this paper, we deal with the wavelength assignment and the converter placement problem in wavelength-routed optical WDM Mesh networks. Our objective is to try to assign wavelengths in an efficient manner with/without wavelength conversion to get a very low blocking probability and optimize the performance of the overall network. Thus, we implement and compare the performance of two proposed algorithms namely DWA “Dynamic Wavelength Assignment” and SWA “Static Wavelength Assignment” with well-known algorithms. We first present a literature review about previously proposed approaches, and then we introduce and evaluate our implemented approaches. We also discuss the wavelength converter placement problem in mesh networks. We finally corroborate our theoretical findings through extensive simulations.

TWDM-PON中支持区分服务的节能动态波长带宽分配算法

TWDM-PON中支持区分服务的节能动态波长带宽分配算法

Adaptive dynamic wavelength and bandwidth allocation algorithm based on error-back-propagation neural network prediction

With the emergence of new services such as high-definition video, cloud computing and virtual reality, Wavelength Division Multiplexing/Time Division Multiplexing-Passive Optical Network (WDM/TDM-PON) has become a key technology for future access network. The development of Software Defined Networking (SDN) and machine learning also brings new opportunities to the flexibility of WDM/TDM-PON. In this paper, an Adaptive Dynamic Bandwidth Allocation algorithm based on error-back-propagation Neural Network Prediction (ADBA-NNP) was proposed to reduce the Round-trip-time (RTT) delay in the bandwidth-scheduling period. A Dynamic Wavelength Allocation (DWA) algorithm and a novel architecture of WDM/TDM-PON was proposed to simple the multi-carrier source. The experimental results validated that the proposed algorithm could dynamically allocate wavelengths under multi-carrier at 12.5G intervals. Compared with the traditional algorithms, the proposed algorithm could reduce the transmission delay by 25%.

Quasi-Passive Reconfigurable Node for 5G Mobile Optical Backhaul Networks

A novel multi-dimensional quasi-passive reconfigurable (MD-QPAR) node for 5G mobile backhaul optical WDM mesh networks is proposed in this paper. The proposed MD-QPAR is capable of providing dynamic power and wavelength allocations for signals from any input port(s) to any output port(s). Each input/output port is connected to one possible direction or the local wireless nodes, and hence, the data rate, flexibility, robustness, and reliability requirements in 5G backhaul networks can be satisfied. In addition, the MD-QPAR is “quasi-passive,” where it only consumes power during network reconfigurations and there is no power consumption during steady-state operations, to enable high energy efficiency. Three possible MD-QPAR structures are proposed and studied. Simulations under the optical Flow traffic assumption are carried out and the signal blocking probability and the scalability are investigated. Proof-of-concept experiments are also undertaken and the MD-QPAR with Structure II is demonstrated. Results show that dynamic power and wavelength distributions from any input port(s) to any output port(s) can be realized, and the power penalty due to the MD-QPAR is limited to <0.5 dB.

Resource Management in Cloud and Tactile-Capable Next-Generation Optical Access Networks

This paper introduces OCLDN, an agile, programmable, and scalable optical cloud distribution network, which exploits content distribution networks to deliver killer cloud and tactile services to end users at very high speeds, ultra-low latency, and low cost. With OCLDN, a software-defined-networking-based mini-cloud data center is installed at the central office of a next-generation passive optical network, which includes a cloud-based tactile steering server, and supports all types of cloud applications. These applications have stringent quality-of-service (QoS) requirements and, thus, require a fast, adaptive, and effective bandwidth allocation mechanism. Therefore, in this paper, we introduce a new dynamic wavelength and bandwidth allocation (DWBA) scheme that meets the QoS requirements of tactile services via dedicating it upstream wavelength(s), and also enables inter-channel statistical multiplexing so as to maximize the network throughput without impairing the QoS requirements for all types of services. Extensive simulations demonstrate the ability of the proposed DWBA to outperform existing schemes, and highlight its effectiveness in meeting the QoS demands for tactile and non-tactile services.

On the efficiency and fairness of dynamic wavelength and bandwidth allocation algorithms for scheduling multi-type ONUs in NG-EPON

Abstract In the Next Generation Ethernet Passive Optical Network (NG-EPON), Optical Network Units (ONUs) can work on multiple wavelengths simultaneously to achieve higher peak rates. There are three types of ONUs (25G, 50G and 100G ONUs) sharing all the 100 Gb/s bandwidth. Each type of ONUs has a total bandwidth constraint due to ONUs’ working wavelength capabilities. In this paper, we investigate the fairness and efficiency of dynamic wavelength and bandwidth allocation (DWBA) algorithms for scheduling multi-type ONUs while considering their bandwidth capacity constraints. Proposed DWBA algorithms can achieve high efficiency, excellent fairness as well as good wavelength load balancing.

Cost-effective ROADM design to maximize the Traffic Load Capacity of u-DWDM coherent metro-access networks

The current constant growing in traffic demands caused by the popularization of cloud services, mobile and social networks is requiring architectural changes at the underlying networks so as to provide a more highly dynamic connectivity. Cost-effective and energy efficient solutions are also required in flexible network subsystems in order to make available future sustainable networks. In this context, a novel cost-effective and energy-efficient solution DWDM ROADM (D-ROADM) node design has been recently considered to enable optical Metro-Access networks convergence. In this paper, we assess the D-ROADM capabilities in a dynamic ultra-Dense Wavelength Multiplexing (u-DWDM) coherent Ring Network scenario. In particular, the metric Blocking Bandwidth Probability (BBP) vs. Traffic Load Capacity (TLC) has been considered. Our numerical evaluations show that the performance penalty of cost-effective D-ROADM based networks could be reduced to 35% for 62.5 GHz DWDM channels when compared to WSS-based ROADMs.

Nano-Pressure and Temperature Sensor Based on Hexagonal Photonic Crystal Ring Resonator

In the present work, two-dimensional (2D) hexagonal photonic crystal ring resonator (PCRR) structure is designed for both pressure and temperature sensing based on effective refractive index modulation of silicon. The nanosensor is designed to monitor the pressure from 0.04 to 6 GPa and temperature from 5 to 540 °C. The proposed nanosensing platform is composed of hexagonal PCRR and two inline quasi-waveguides in a 2D hexagonal lattice with circular rods arranged in air host. The hexagonal PCRR is playing a very important role in sensing the different pressure and temperature levels over a wide dynamic range. The plane wave expansion method (PWE) is implemented to calculate photonic band gap (PBG), which is used to identify the operating wavelength range of the sensor. The functional parameters of the sensor are evaluated by finite-difference time-domain method (FDTD). The functional parameters are the dynamic range, resonant wavelength, sensitivity, transmission efficiency, and quality factor. The FDTD results show that the resonant wavelength of the PCRR is red shifted with increasing the pressure and temperature. The designed sensor offers high sensitivity, high transmission efficiency and good quality factor with ultra-compact size; hence, it is extremely suitable for nanotechnology-based sensing applications.

Molecular Recognition at Local Doped Sites of Locally Functionalized Single-Walled Carbon Nanotubes for Selective Wavelength Shift of Near Infrared Photoluminescence

Locally functionalized single-walled carbon nanotubes (lf-SWNTs) have local defects on the sp2 carbon networks of the tube wall through a limited amount of chemical modification, by which they emit red-shifted and quantum yield-enhanced photoluminescence (PL) in comparison to that of pristine SWNTs.[1-6] The newly generated PL (E 11*) of lf-SWNTs shows spectral shifts depending on the chemical structures of the modified molecules and dynamic wavelength shifts have been observed by protonation of amino groups[1] and saccharide recognition[6] at the doped sites. Such external stimuli responsiveness would be applicable to develop advanced sensing and imaging materials and optical devices using the near infrared (NIR) PL functions. Based on findings in the saccharide recognition study[6], we extend molecular designs of our molecular recognition approach for development of stimuli-responsive wavelength-shift systems using lf-SWNTs. Crown ethers, which bind cations such as metal ions with selectivity based on ring sizes and donor atoms, are useful molecular motifs for metal sensing and supramolecular self-assemblies. We newly synthesized azacrown ether-modified lf-SWNTs (crown-SWNTs) and crown-SWNTs showed a new PL peak at 1138 nm (E 11*), which was red-shifted and intensified in comparison to E 11 PL at 989 nm. When a AgNO3 solution was added to the crown-SWNTs solution, the E 11* PL showed a larger peak shift to a longer wavelength region compared to the E 11 PL. According to the cation recognition mechanism of the azacrown ether, it is considered that the observed wavelength shift is induced by electronic character changes from electron donating to withdrawing of the modified groups due to the Ag+ inclusion in the ring. The molecular recognition approach, therefore, is promising to create new types of NIR PL nanomaterials whose PL properties can be modulated by the molecular actions.