Dynamic Wavelength Research Articles

LSTM-Based DWBA Prediction for Tactile Applications in Optical Access Network

Historically, the optical access network (OAN) plays a crucial role of supporting emerging new services such as 4 k, 8 k multimedia streaming, telesurgery, augmented reality (AR), and virtual reality (VR) applications in the context of Tactile Internet (TI). In order to prevent losing connectivity to the current mobile network and Tactile Internet, the OAN must expand capacity and improve the quality of Services (QoS) mainly for the low latency of 1 ms. The optical network has adopted artificial intelligence (AI) technology, such as deep learning (DL), in order to classify and predict complex data. This trend mainly focuses on bandwidth prediction. The software-defined network (SDN) and cloud technologies provide all the essential capabilities for deploying deep learning to enhance the performance of next-generation ethernet passive optical networks (NG-EPONs). Therefore, in this paper, we propose a deep learning long-short-term-memory model-based predictive dynamic wavelength bandwidth allocation (DWBA) mechanism, termed LSTM-DWBA in NG-EPON. Future bandwidth for the end-user is predicted based on NG-EPON MPCP control messages exchanged between the OLT and ONUs and cycle times. This proposed LSTM-DWBA addresses the uplink control message overhead and QoS bottleneck of such networks. Finally, the extensive simulation results show the packet delay, jitter, packet drop, and utilization.

Protection Schemes in HPON Networks Based on the PWFBA Algorithm.

In this paper, possibilities for network traffic protection in future hybrid passive optical networks are presented, and reasons for realizing and utilizing advanced network traffic protection schemes for various network traffic classes in these networks are analyzed. Next, principles of the Prediction-based Fair Wavelength and Bandwidth Allocation (PFWBA) algorithm are introduced in detail, focusing on the Prediction-based Fair Excessive Bandwidth Reallocation (PFEBR) algorithm with the Early Dynamic Bandwidth Allocation (E-DBA) mechanism and subsequent Dynamic Wavelength Allocation (DWA) scheme. For analyzing various wavelength allocation possibilities in Hybrid Passive Optical Networks (HPON) networks, a simulation program with the enhancement of the PFWBA algorithm is realized. Finally, a comparison of different methods of the wavelength allocation in conjunction with specific network traffic classes is executed for future HPON networks with considered protection schemes. Subsequently, three methods are presented from the viewpoint of HPON network traffic protection possibilities, including a new approach for the wavelength allocation based on network traffic protection assumptions.

Dynamic wavelength calibration based on synchrosqueezed wavelet transform.

With the developments of the tunable laser source (TLS), there are increasing demands for high-resolution dynamic wavelength calibration in recent years. Considering mutual constraints between wide measurement range and high calibration resolution, we propose a dynamic wavelength calibration method based on an auxiliary Mach-Zehnder interferometer (MZI) and the synchrosqueezed wavelet transform (SSWT). Our proposed method can achieve a calibration resolution of 5 fm and a tuning range of 10 nm. Moreover, the measurement range and spatial resolution of the optical frequency domain reflectometer (OFDR) system are improved to ∼80 m and ∼mm, respectively. Our proposed approach can substantially reduce the subtle spectrum distortion (tens of fm) in coherent optical spectrum analyzer (COSA) systems.

Time-to-frequency conversion method for tunable diode laser absorption spectrum

The dynamic wavelength tuning characteristics of the laser is one of the most important factors affecting the measurement accuracy of Tunable Diode Laser Absorption Spectroscopy (TDLAS) technology. We propose a time-frequency conversion method to obtain accurate measurement spectrum, which uses experimentally measured direct absorption signal (time domain) of standard methane gases to compare with simulated spectrum (frequency domain) from the HITRAN database. Then, a polynomial model is used to establish the relationship between time domain (sample points) and frequency domain (wavenumber). To verify the feasibility and accuracy of the method, the methane absorption signals of three standard concentrations (5%, 10% and 15%) were time-to-frequency converted by our method and etalon, and the methane concentrations were calculated and compared. Comparing methane concentration results, the maximum relative error between our method and etalon is less than 0.5%. The results showed that it is viable to use this method to achieve dynamic wavelength measurement in fast scanning of distributed feedback lasers (DFB), and the restricted polynomial model can properly describe the dynamic wavelength tuning characteristics of lasers. Furthermore, the method has the advantages of high accuracy and low cost, which is important for improving the accuracy of TDLAS technology applications.

Load adaptive merging algorithm for multi-tenant PON environments

Wavelength division multiplexing\ ime division multiplexing passive optical network (WDM/TDM-PON) is the attractive candidate for PON bandwidth sharing among multiple service providers, featuring massive bandwidth and longer reach. This infrastructure reduces the overall cost of the Fiber-to-the-premises (FTTP) services and offers relatively lower tariffs for the end customers. The dynamic bandwidth and wavelength allocation (DBWA) process in such PON networks ensure the fair sharing of the available bandwidth resources among the virtual network operators (vNOs). The earlier reported DBWA schemes with multiple vNOs have not efficiently utilized the unused and residual upstream bandwidth. This study presents a novel load adaptive merging algorithm (LAMA) for converting various individual virtual bandwidth maps(vBWmaps) into a single physical bandwidth map (phyBWMap). The LAMA scheme modifies the existing strict priority scheme called the Priority-Based Merging Algorithm (PBMA) scheme and improves the performance of the merging engine by allocating the phyBWMap in a load adaptive manner to the vNOs in the multi-tenant PON architecture. The proposed algorithm is compared with PBMA in terms of throughput efficiency, upstream delay, and capacity utilization under self-similar and Poison traffic scenarios. The results show that the proposed scheme offers higher bandwidth utilization resulting in increased throughput with lower upstream delays in the multi-tenant PON environment.

Self-Adaptive Resource-Allocation Scheme Combining Traffic Prediction With User Satisfaction in Multi-Wavelength VPON

In this paper, a self-adaptive resource-allocation scheme combining traffic prediction with user satisfaction is firstly established in multi-wavelength VPON. Among VPONs, by proposing a (wavelength utility)-based dynamic wavelength allocation algorithm, the optimal allocation of wavelengths can be achieved. In a VPON: under condition that the total requested bandwidth is larger than the total bandwidth, by introducing a bandwidth constraint factor <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ϵ</i> , the maximum amount of bandwidth granted for high-priority service can be limited, and the “starvation” problem of low-priority service can be prevented. By solving the user satisfaction model, not only the optimal allocation of low-priority service can be obtained, but also the comprehensive user satisfaction is maximized. Under condition that the total requested bandwidth is smaller than the total bandwidth, by combining an ANN prediction model with a user satisfaction model, a bandwidth allocation model based on traffic prediction and user satisfaction is created. By this model, not only the resource utilization is improved but also the transmission delay is reduced. At the same time, user satisfaction is maximized. By adjudicating on the set judgment condition, the self-adaptive function of control system for the above two conditions is implemented. By simulation, the effectiveness of the proposed scheme is demonstrated.

Investigation of the dynamic features of a moveable ultrahigh-Q nanocavity

Although the approach of forming an ultrahigh-Q nanocavity via local refractive index tuning in a PC waveguide was proposed a decade ago, it has not yet been employed to realize a moveable ultrahigh-Q nanocavity, thereby the dynamic physics related to a moving resonator remain unknown. Here we demonstrate that a dynamically-formed cavity is essentially moveable, so that we can use this nanocavity to trap, store, and transfer signal photons, enabling free photon control. For a high cavity moving speed, we find the trapped signal energy will radiate out of the moving cavity. We think this interesting phenomenon originates from Doppler-effect-induced resonant frequency split in a moving resonator and the accompanied change of energy capacity. In addition, we present an analytical model to reveal why and how the trapping and storing processes are accompanied by significant spectral bandwidth compression and dynamic wavelength conversion, which are critical for achieving dynamic ultrahigh-Q nanocavity. This approach may find application in photon memories, quantum computing, and controllable light-matter interactions.

Finely tunable dynamical coloration using bicontinuous micrometer-domains

Nanostructures similar to those found in the vividly blue wings of Morpho butterflies and colorful photonic crystals enable structural color through constructive interference of light waves. Different from commonly studied structure-colored materials using periodic structures to manipulate optical properties, we report a previously unrecognized approach to precisely control the structural color and light transmission via a novel photonic colloidal gel without long-range order. Nanoparticles in this gel form micrometer-sized bicontinuous domains driven by the microphase separation of binary solvents. This approach enables dynamic coloration with a precise wavelength selectivity over a broad range of wavelengths extended well beyond the visible light that is not achievable with traditional methods. The dynamic wavelength selectivity is thermally tunable, reversible, and the material fabrication is easily scalable.

A Software-Defined Programmable Testbed for Beyond 5G Optical-Wireless Experimentation at City-Scale

Wireless traffic will significantly increase in next-generation networks. Therefore, there is a need for novel optical network front-/mid-/backhaul (x-haul) architectures that can deliver ultra-high bandwidth and ultra-low-latency services to wireless and edge cloud systems, as well as support various cloud radio access network (C-RAN) architectures. Designing and evaluating such architectures requires large-scale experimental platforms. In this article, we present the design and implementation of a unique, remotely accessible, disaggregated, and programmable optical network as the key component of the city-scale PAWR COSMOS advanced wireless testbed. We discuss the design and implementation of a dedicated multi-functional Ryu software-defined networking (SDN) controller for the testbed's optical network wavelength channel assignment and topology reconfiguration. We present an example use of the SDN controller for monitoring and automated measurement of the wavelength-dependent amplifier gain in deployed reconfigurable optical add/drop mul-tiplexer (ROADM) units. We also demonstrate a pilot experiment focusing on a wireless handover scheme for C-RAN architectures in the COSMOS testbed, where high traffic volume can be supported by dynamic wavelength allocation via optical switching in the fronthaul. The field-deployed testbed and SDN controller can be used by the research community to push the envelope in the area of optical networks for beyond 5G and 6G.

FPGA-Based Dynamic Wavelength Interrogation System for Thousands of Identical FBG Sensors

Under realistic scenarios, more fiber Bragg gratings (FBGs) are always expected to be multiplexed in one sensor array to share the expensive optical components and electrical devices. However, either the sensing number or the interrogation frequency is limited in previous works due to the huge amount of data generated from large-scale sensing arrays. This paper presents a field-programmable gate array (FPGA)-based dynamic wavelength interrogation system for thousands of identical FBGs. With the advantages of parallel controlling and pipeline processing, FPGA can accelerate the data-processing rate of the wavelength interrogation, realizing a continuous-running and real-time sensing system. The signal-processing system precisely synchronizes the generation of interrogation pulses, the acquisition of reflected signals, and the processing of the wavelength-related data, making the interrogation frequency fundamentally limited by the round-trip time of light pulses traveling in the fiber. Multiple sensing arrays can be independently carried out simultaneously, affecting hardly the interrogation frequency. Experimental results show that over 4000 FBGs with a 3-m spatial resolution in four channels are interrogated with a 150-Hz sensing frequency, 3-nm dynamic range, and ±5.9-pm sensing precision, greatly improving the interrogation frequency while ensuring the multiplexing number.

Dynamic wavelength control of laser pulse profiles at picosecond to nanosecond timescales.

We report on a novel combined laser pulse shaping and dynamic wavelength encoding capability based on a simple architecture implementing direct space to time mapping. There are several potential applications that can be enabled by the ability to control the instantaneous intensity or wavelength of an optical waveform on a picosecond-to-nanosecond timescale. To our knowledge, no known methods can access this temporal regime with a practical architecture. Here, we demonstrate an extension of the Space-Time Induced Linearly Encoded Transcription for Temporal Optimization (STILETTO) technique that can generate optical waveforms with a programmable instantaneous wavelength vs. time. We experimentally demonstrate the technique by generating self-gated spectrograms and show that it can encode dynamic wavelength vs time profiles at timescales not achievable by any other known method.

High Bandwidth Utilization DWBA Algorithm for Upstream Channel in NG-EPON

In this paper, an (ONU-load and RTTs)-based (OLR) dynamic wavelength and bandwidth allocation (DWBA) algorithm for upstream channel in next-generational Ethernet passive optical network (NG-EPON) is proposed. By proposing adaptive threshold grouping algorithm, the waste of bandwidth resources caused by massive guard timeslots and mismatch between assigned transmission window and frame size is reduced. By adjusting the Optical Network Unit (ONU) scheduling order, the idle time caused by Round-Trip Times (RTTs) is reduced. By proposing joint ONU grouping and RTT scheduling mechanism, load balance among wavelengths is achieved. By proposing a fair allocation scheme, the fairness of bandwidth granting for each ONU is ensured. Finally, by the simulation, the effectiveness of proposed algorithm is demonstrated. The simulation indicates that the rate of bandwidth utilization, the average package delay, the scheduling cycle and the network throughput in the system based on proposed algorithm have better performance.

Dynamic Multiple Multicasts Routing and Wavelength Assignment for Realizing Modified Artificial Fish Model in Mesh-Based Onoc

Dynamic Multiple Multicasts Routing and Wavelength Assignment for Realizing Modified Artificial Fish Model in Mesh-Based Onoc

Retracted] Dynamic Wavelength Scheduling by Multiobjectives in OBS Networks

The burst dropping ratio is witnessed in the contemporary literature as a considerable constraint of optical burst switching (OBS) networks that attained many researchers’ efforts in the recent past. Among the multiple practices endeavoring to reduce the burst drop ratio, the optimal burst scheduling is one dimension in this regard. The transmission channel scheduling and appropriate wavelength allocation are critical objectives to achieve optimal burst scheduling in regard to minimal burst drop ratio. Many of the scheduling models depicted in the contemporary literature aimed to achieve the optimum scheduling by electing the channels, which depend on optimum utilization of idle time. Some of the studies tried to select channels by any metrics of quality, and significantly minimal amount of studies focused on wavelength allocation for lowering BDR. Moreover, in regard to this, this study tried to achieve optimum wavelength allocation beneath manifold objective QoS metrics, which is identified as “multiobjective dynamic wavelength scheduling (DyWaS).” The experimental study carried through the simulations evinced that the proposed model DyWaS escalated the optimality of burst scheduling through wavelength allocation compared with other existing methods represented in the contemporary literature.

FPGA-Based High-Speed Optical Fiber Sensor Based on Multitone-Mixing Interferometry

We report a real-time high-speed fiber Bragg grating (FBG) interrogator based on a fiber-optic interferometer. The signal processing is performed by using a low-cost field-programmable gate array (FPGA) system, which is programed to implement a phase-generated carrier (PGC) demodulation algorithm with multitone mixing (MTM) to provide distortion-free signals with high tolerance to modulation depth variations and light intensity fluctuations. The system can stream data at rates up to 1 MS/s and allows multiplexed processing up to two channels. Experimental results show simultaneous measurements of two FBGs, one of which was actuated at frequencies up to 100 kHz. The system features a 3-dB bandwidth of 280 kHz, and a dynamic wavelength resolution of 4.7 fm/Hz <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\mathrm {1/2}}$ </tex-math></inline-formula> . We also demonstrate a strong reduction of distortion using the MTM approach with respect to the standard technique. Finally, we study the origin of the noise, demonstrating a reduction in common noise sources by using one of the FBGs as a reference. The system can measure FBGs centered at any position within the spectral band of the source, is polarization-independent, and is easily scalable to more than two measurement channels from the same interferometer.

Study on dynamic wavelength matching technology of laser radar based on volume grating narrowband optical filtering

Study on dynamic wavelength matching technology of laser radar based on volume grating narrowband optical filtering

Dynamic Bandwidth allocation algorithm for avoiding Frame rearrangement in NG-EPON

Next Generation Ethernet Passive Optical Network (NG-EPON) is considered to be future prospective access technology that could help to achieve 100Gbps data rates. Wavelength bonding is a phenomenon that can help Optical Network Units (ONU) to enhance their transmission capabilities. Using wavelength bonding, an ONU could transmit on multiple wavelength channels in parallel. The ONUs can achieve data transmission rates ranging from 25Gbps to 100Gbps. In upstream direction, ONUs share different available channels in time-sharing manner to effectively utilize the resources in NG-EPON. Dynamic Wavelength & Bandwidth Allocation (DWBA) algorithm is required for efficient allocation of wavelength and bandwidth resources in upstream direction. DWBA plays a vital role to help ONUs for transmission on multiple channels simultaneously. When an ONU transmits on multiple channels, a frame-rearrangement problem would occur at the Optical Line Terminal (OLT). OLT suffers from an extra overhead of frame-rearrangement; as the received frames at OLT are not in proper sequence. DWBA can play a vital role in avoiding frame rearrangement overhead. We proposed a DWBA algorithm to avoid/minimize frame rearrangement problem and efficient bandwidth allocation in NG-EPON. Our proposed DWBA avoids and minimizes frame-rearrangement problem and provides efficient resource allocation. We comparatively analyzed and evaluated our proposed DWBA with the existing DWBA algorithm. The simulation results show that our proposed DWBA minimizes frame-rearrangement problem as compared to existing DWBA algorithms and proves to be more efficient based on average (end-to-end) delay and completion time.

Design guidelines for collimating or focusing graded-index fiber tips.

Graded-index optical fiber probes suitable for focusing or collimating the output of an optical fiber at a wavelength of 1.3 µm have become an enabling technology in optical coherence tomography imaging applications for in vivo bioimaging. Such fiber tips however remain uncommon in other photonics applications. This paper provides the first numerical study of graded-index fiber tips covering a broad range of wavelengths spanning from the UV to short-infrared. The wavelength dependency and the influence of probe geometry on performance characteristics such as far-field divergence angle, spot size and working distance are analyzed. The paper yields easily accessible design guidelines for the fabrication of collimating or focusing fiber tips. Fiber collimators have considerable potential for use in free-space systems and could benefit a range of devices such as variable attenuators, dynamic wavelength equalisers and large 3D optical cross-connect switches, whereas focusing fiber tips have applications in high-resolution imaging.

An Effective Evaluation of Wavelength Scheduling for Various WDM-PON Network Designs with Traffic Protection Provision

Recently, metropolitan and access communication networks have markedly developed by utilizing a variety of technologies. Their bearer communication infrastructures will be mostly exploiting the optical transmission medium where wavelength division multiplexing techniques will play an important role. This contribution discusses the symmetric sharing of common optical network resources in wavelength and time domains. Wavelength-Division Multiplexed Passive Optical Networks (WDM-PON) attract considerable attention regarding the next generation of optical metropolitan and access networks. The main purpose of this contribution is presented by the analysis of possible scheduling of wavelengths for our novel hybrid network topologies considered for WDM-PON networks. This contribution briefly deploys adequate Dynamic Wavelength Allocation (DWA) algorithms for selected WDM-PON network designs with the provision of traffic protection when only passive optical components in remote nodes are utilized. The main part of this study is focused on the use of wavelength scheduling methods for selected WDM-PON network designs. For evaluation of offline and online wavelength scheduling for novel hybrid network topologies, a simulation model realized in the Matlab programming environment allows to analyze interactions between various metropolitan and access parts in the Optical Distribution Network (ODN) related to advanced WDM-PON network designs. Finally, wavelength scheduling methods are compared from a viewpoint of utilization in advanced WDM-PON networks designs.

Bin-packing based offline dynamic bandwidth and wavelength allocation algorithms for power efficiency in Super-PON

Enduring the rapidly growing demand for high data rates is the main challenge for the current network providers. Super passive optical network (Super-PON), a prominent next generation Ethernet PON (NG-EPON) candidate, can suffice this exponentially increasing data rate requirements. However, to appease such requirements, it employs many transceivers and increases the power-consumption of the network. In this work, we focus on reducing the carbon footprint of Super-PON and propose power-efficient dynamic bandwidth and wavelength allocation (DBWA) algorithms, namely best fit bin-packing sleep mode aware (BF-SMA) and updated BF-SMA (UBF-SMA). The proposed algorithms use SMA for bandwidth scheduling and different bin-packing techniques for wavelength allocation. In bin-packing, the number of available wavelengths and their efficient allocation is based on the network load. For restricting the number of available wavelengths, we can switch off the non-essential transceivers at the OLT, which also helps in maximizing the wavelength utilization and increasing the power efficiency. The simulation results show that in comparison to the state-of-the-art DBWA algorithms, the proposed algorithms improve the power efficiency and reduce the average delay of a Super-PON system. Furthermore, we use Jain’s fairness index to validate the fairness of the proposed DBWA algorithms.