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A contention-free scheduling scheme PROPH is proposed for AWGR-based optical DCN to elastically allocate adaptable bandwidth. Assessments validate that the network deploying PROPH decreases 73.6% packet loss and 11.9% server-to-server latency, improves 11.6% network throughput.

In recent years, Kramers-Kronig (KK) receiver has been widely studied because of its simple structure and the ability of digital signal processing (DSP) to recover complex value signals. One practical structure is detecting the optical signal with an AC-coupled photodetector. However, the direct current (DC) component of the photocurrent will be lost, in which case the KK algorithm ceases to be effective. To restore the lost DC component, we propose a simple data-aided method to estimate the DC component by the information of signal mean power stored in the designed data-aided sequences. We introduce a correction coefficient to evaluate the accuracy of our DC estimation by comparing it to the conventional DC sweeping method. Furthermore, the coefficient can be used to combat the DC estimation deviation. We carry out both simulations and experiments to study the performance of the proposed method. The results show that the DC component can be effectively recovered and the system performance is close to the results of the DC sweeping method. At the same time, in the case of low optical signal-to-noise ratio, optimization of correction coefficient can effectively improve the system performance.

The wireless imaging radar need more orbital angular momentum (OAM) modes to irradiate targets alternately to obtain higher azimuth resolution. For that, this present paper investigates the fast-switching technique of radio frequency orbital angular momentum (RF-OAM) beam with the use of an optical-controlled system. Compared with the method using pure electrical device, the optical-controlled method offers conveniences in processing same-frequency radio signal, which will contribute to make the system compact. Moreover, the fast-responding speed of the optical device provide a fast speed of switching. The fast-switching system of RF-OAM beams with different mode and radiation direction is proposed and constructed, and proof-of-concept experiments are performed. The proposed system is realized by employing a program-controlled optical switch and the wavelength multiplexing technique integrated into an optical-controlled circular antenna array (CAA). In the demonstration experiments, the switching between +1-mode and -1-mode RF-OAM beams without steering control is detected within 20ms, then the system achieves the switching between a +1-mode OAM beam with radiation direction -3o and a -1-mode OAM beam with radiation direction 3o at the same rate.

An arrayed waveguide grating router based nanoseconds optical switching data center network is experimentally demonstrated and investigated. Experimental assessments validate the system achieves error-free communication with 465 ns server-to-server latency even at load of 0.9.

The optical single sideband (OSSB) modulation with tunable optical carrier to sideband ratio (OCSR) is a promising and popular technique in wideband analog signal transmission and microwave signal processing, which can improve modulation efficiency and combat the fiber chromatic dispersion. However, in all reported schemes for achieving OSSB modulation with tunable OCSR, the spurious free dynamic ranges (SFDR) of the systems are all limited by the third-order intermodulation distortion (IMD3). In this paper, our object is to improve the SFDR and suppress the IMD3 in a novel OSSB modulation with tunable OCSR. The proposed system consists of a primary channel and a secondary channel. In primary channel, an OSSB modulation with tunable OCSR is implemented. In secondary channel, the optical carrier and first-order sidebands are perfectly cancelled out, which can suppress the IMD3 without gain penalty at the same received optical power. In this way, a large-SFDR OSSB modulation with tunable OCSR is realized. Experimental results exhibit that the IMD3 gets effective cancellations without gain penalty under unchanged total received power, and the output microwave signal power obtains about 11-dB improvement by optimizing the OCSR. A greatly increased SFDR of over 128 dBHz4/5 is achieved in the proposed system.

To further improve the resource efficiency of the p-polyhedron protection scheme against multi-link failures in optical data center networks (ODCNs), the content connectivity is considered when constructing the p-polyhedron structure. In this paper, the content connectivity-based polyhedron protection (CCPP) scheme is proposed. An ILP model and a heuristic algorithm are developed to realize the CCPP scheme. Numerical results show that the proposed CCPP scheme has a lower network redundancy. Moreover, the network redundancy of the CCPP scheme is positively correlated with the degree of content connectivity.

A novel 3D electrically small antenna with dual-band is presented, optimized, and measured in this article. The proposed antenna is composed of three circular split ring resonators and a vertical line, which has been obtained through rotating angles of three circular split ring resonators from the same direction to 260°, 0°, and 340°. The optimized electrically small antenna is worked in 0.789 GHz and 1.183 GHz and has been verified that the simulated results are similar to the measured results. The design of the antenna structure conforms to the miniaturization in modern wireless communication systems. A novel 3D electrically small antenna with dual-band is presented, optimized, and measured. This dual-band electrically small antenna is realized by rotating angles of the defect. To further applications, our design scheme is applied in a paper-based device with the same high performance. This article provides a new address to design a multi-band antenna.

To accommodate three typical 5G services with satisfied performance requirements, spectrum slicing has been adopted and widely studied in the wireless transmission part. For the wired transmission part, the high-capacity and large-scale optical network is widely used for transferring 5G traffics. To improve the spectrum efficiency and reduce the time delay while accommodating 5G services, optical networks need to adapt to the wireless spectrum slicing. Traditionally, all spectrum resources in optical networks form a resource pool which is equally allocated to applications bit by bit until it is all used up. Although this pattern reduces the resource maintenance complexity, it has a high operation complexity for 5G services. If some important network functions are realized in advance, a 5G service can be easily deployed with simplified operations and satisfied performance requirements. In this letter, a novel framework of core function prepositioning is proposed to efficiently accommodate 5G services in optical networks. It adopts the centralized control model and two network functions of fast connection establishment and disaster-resilient survivability are realized in planned spectrum areas in advance. This framework adapts to the wireless spectrum slicing and has a significant performance boost while accommodating 5G services.

Space division multiplexing elastic optical network (SDM-EON) enables high-capacity transmission, in which the network nodes should provide high switching flexibility while limiting the complexity and costs of nodes. Architecture on demand (AoD) nodes can meet these requirements but the slow configuration time of optical backplane in AoD nodes makes it difficult to serve latency-sensitive requests. In this paper, we propose a hybrid optical backplane based on micro-electromechanical systems (MEMS) and semiconductor optical amplifier (SOA) switches to provide fast configuration time for AoD nodes. Moreover, we propose quantitative measures of node switching flexibility in SDM-EONs and of link configuration speed in AoD nodes. Based on the hybrid backplane architecture and the measurement approaches, we propose a flexibility and fragmentation aware routing, spectrum and core allocation algorithm and an AoD synthesis algorithm. Simulation results show that the hybrid AoD nodes with support of spatial lane change can reduce network blocking probability. The AoD based on this hybrid backplane structure can improve the network performance by 32.8% compared to the AoD based on the traditional MEMS. Compared with traditional reconfigurable optical add/drop multiplexers (ROADMs), the hybrid AoD nodes can control the number of wavelength selective switch (WSS) ports.

As a pathbreaking approach to generate orbital angular momentum (OAM) beam, uniform circular array (UCA) has been extensively researched and applied. However, the impact of the imperfect UCA (IUCA) converted from a UCA with the position of antenna elements on the purity of the generated OAM beam is rarely considered. In order to verify the effect of position deviation on the OAM beam, this letter deduces the analysis model of the IUCA and the OAM mode purity model. The OAM mode purity refers to the weight of the intensity of the “expected OAM mode.” Numerical simulation results show that the OAM beam generated by IUCA is a superposition of OAM beams with a series of different modes, and this results in a certain OAM beam received being contaminated. Compared with the radius deviation, the azimuth deviation of antenna elements has more obvious influence on the OAM mode purity. Moreover, low-mode OAM beams are more suitable for long-distance transmission. Properly increasing the antenna array radius can improve the purity of high-order OAM modes.

A photonics system for baseband-free arbitrary-phase-coded microwave waveform pulse (APCMWP) generation is proposed and demonstrated. The proposed system realizes the generation of APCMWP, and further solves the baseband components problem in the pulsed process. The system uses a polarization-multiplexing dual-drive Mach–Zehnder modulator (PM-DMZM) and an optical band pass filter (OBPF) to obtain a polarization-multiplexed single-sideband modulated (SSBM) optical signal with carrier intensity-phase modulation, then uses a balanced photodetector (BPD) to properly detect the polarization-multiplexed SSBM optical signal, APCMWP with baseband components suppression can be easily generated. A detailed theoretical analysis and a proof-of-concept experiment are provided. The generations of 1.2-GBaud 9.6-GHz and 2-GBaud 12-GHz baseband-free APCMWP are verified.

In recent years, hybrid fiber-wireless (Fi-Wi) networks that integrate optical network technology and wireless communication technology have received widespread attention. The technical integration in Fi-Wi networks provides users with the possibility to establish high-quality connections that guarantee flexibility and economy. However, there are heterogeneous structures and resource types between the subnets of the Fi-Wi network. This article considers the segmented application of network slicing technology in the optical backbone and hybrid access parts of Fi-Wi networks. In this way, the seamless connection of wired and wireless networks can be realized, and meanwhile adapt to the multiple network service forms and differentiated service quality requirements introduced in the 5G network era. In this article, we design a dynamic slicing (PDSM) scheme based on traffic prediction. This scheme includes all four procedures of service provisioning, which are network slice creation, traffic prediction, online reconfiguration of network slices and intra-slice routing, and resource allocation based on the prediction results. It is more flexible than the traditional static slicing scheme in the scenario, where the network state changes dynamically. We develop a prediction-based dynamic slicing algorithm (PD-MSRA) with intra-slice multi-path routing and shared resource allocation for the entire workflow of PDSM. We evaluate the performance of PD-MSRA on a variety of network topologies, and also implement several comparison algorithms including static slicing strategies. Simulation results show that the PDSM scheme using PD-MSRA achieves low bandwidth blocking rate and the optimization of resource utilization.

The circular phased array is one of the main methods to generate radio frequency orbital angular momentum (RF-OAM) beams with high purity and capability of OAM-beams steering, but OAM beams generation and steering are only related to angle, not range dimensions. Therefore, the mode of OAM beams can be easily received in a wide range and intercepted by unintended eavesdroppers in the beam axis. As a promising solution, a range-angle dependent OAM beams transmission scheme is highlighted by the frequency diverse array (FDA) for the sake of the OAM secure transmission in this paper. In order to realize the range-angle dependent OAM beams, a special frequency interval between adjacent antenna elements in the FDA is designed and illustrated. The modes of OAM beams generated by the FDA can only be observed in the legal target location. Numerical results show that the scheme can effectively realize the safe transmission of OAM beams, i.e., reducing the possibility of the OAM beams being tapped, improving the OAM-beams transmission performance, and enhancing the energy efficiency with low complexity.

The Multi-access Edge Computing (MEC) system interconnected by metro optical network is gaining much attention recently. The proximity of computing resources in MEC provides the possibility of low-latency access for user equipment (UE). However, since the computing capacity of edge server is limited, the task failure may occur due to the unacceptable computing latency if the corresponding server is overloaded. Note that there is more than one MEC server at the network edge and the computationally intensive tasks on the overloaded server can be sent to nearby light-loaded servers for processing via peer offloading. In this article, we design a latency-aware task peer offloading (LA-TPO) scheme, which is an economic solution for the overload problem of MEC. We formulate the LA-TPO into a mixed integer non-linear programming (MINLP) model and develop a GA-based heuristic algorithm to jointly optimize the offloading decisions and the routing and computing resource allocation. We compare the MINLP and proposed algorithm under various scenarios, and the results show that the GA-based LA-TPO can achieve low latency, high success ratio of tasks as well as the optimization of resource utilization.

A wideband microwave photonic phase shifter (MPPS) based on a dual-polarization dual-parallel Mach–Zehnder modulator (DP-DPMZM) is proposed and experimentally demonstrated. The proposed system has the features of chromatic dispersion (CD) immunity and tunable optical carrier to sideband ratio (OCSR), which can realize long fiber transmission distance with improved power efficiency. It is realized by carrier suppress double sideband (CS-DSB) plus optical carrier (OC) modulation at two orthogonal polarization states. The phases of output RF signals can be tuned continuously and independently by controlling the phases of the OCs. The experiment results show that the continuous 360° phase shifts of output RF signal over 5–25 GHz are both realized in the cases of back-to-back and fiber transmission. No CD-induced power fading and phase severe shaking of the RF signals appear after the dispersion compensating fiber (DCF) of −331 ps/nm at 1545 nm transmission. By optimizing the OCSR of the system, the output RF power efficiency of the proposed scheme realizes significantly improvement when input RF powers and output optical powers are both fixed. The possibility of generating frequency doubling signal is also verified.

Following successful adoption of cloud computing, many service providers (SPs) are now using high-performance Virtual Machines (VMs) located in large datacenters owned by public cloud infrastructure providers to deploy their virtual network functions (VNFs). Since using these VMs has a cost depending on utilization time, a complex problem of VNF placement and scheduling (VPS) must be addressed to achieve satisfactory network performance (e.g., latency) while minimizing the cost paid to lease VMs. In this study, a cost-efficient VPS scheme (CE-VPS) is proposed to address the VPS problem in public cloud networks considering dynamic requests of ordered sequences of VNFs. Our CE-VPS scheme goes beyond existing solutions as it models some important practical aspects such as an additional latency incurred by booting a VM and installing a VNF instance. Also, CE-VPS considers that VNFs can be multi-threaded or single-threaded, and that their throughput as a function of allocated computing resources must be modeled differently. CE-VPS is formulated as a mixed inter linear program (MILP) and also as an efficient heuristic algorithm. CE-VPS achieves lower cost and latency than conventional Best-Availability and Cost-Efficient Proactive VNF Placement schemes, and a better trade-off between resource consumption and latency performance than a conventional Low-Latency scheme.

This article proposes a pulsed arbitrary-phase-coded microwave signals (APCMSs) photonics generation system. The key to this scheme is to achieve the single-sideband modulated (SSBM) optical signal with the conversion capability between intensity modulation and phase modulation by utilizing dual-parallel Mach–Zehnder modulator (DPMZM) and optical bandpass filter (OBPF). Through heterodyne detection of the SSBM optical signal, pulsed APCMSs can be generated. Unlike previous continuous-wave (CW) APCMSs and pulsed binary phase-coded microwave signals (PCMSs) photonics generation schemes, our scheme provides a pulsed APCMSs generation scheme. The scheme realizes the generation of APCMSs without CW background signals, and the scheme is not only suitable for binary phase codes but also suitable for arbitrary phase codes. The useless CW background signals are effectively suppressed without cascading an intensity modulator for gating operation and the coded phases are linear with the input pre-encoding signals amplitudes, leading to great improvement of practical application values. A theory analysis, a system simulation, and a proof-of-concept experiment are provided. Simulation demonstrates the generations of 2-Gbps 14-GHz and 1-Gbps 16-GHz pulsed APCMSs. The generations of 2-Gbps 14-GHz and 1-Gbps 16-GHz pulsed PCMSs with a 13-bit binary Barker-code and a 16-bit quaternary Frank-code are verified in experiment.

As a type of virtual network architecture, network slicing is considered as one of the most innovative aspects of 5G networks, where dedicated slices are created for services to meet their diverse requirements in terms of bandwidth and E2E latency. In this article, the transport network slice provisioning requirements imposed by network operation and emerging services are investigated. Then we review the 5G E2E network slice control and orchestration architecture. As a component of this architecture, comparing with overlay virtualization, an optical underlay virtualization provisioning framework (including topology, bandwidth, and control function virtualization) is presented for the first time. Related optical underlay data plane slicing techniques are discussed, especially for two candidates recently proposed in ITU-T: M-OTN and SPN, with FlexO and FlexE as their key enablers. Finally, several significant challenges that need to be addressed to fully realize the vision of optical underlay network slicing and then E2E slicing are investigated.

In the last five years or so, there has been a great interest in RF OAM to address the contradiction between the lack of wireless spectrum resources and the continually growing demands of the bandw...

Misalignment measurement is important in radio frequency orbital angular momentum (RF-OAM)-related communication and radar applications. Misalignment causes distorted vortex wavefront and OAM spectra dispersion, therefore a conventional gradient method cannot be used directly. We propose a misaligned measurement method for RF-vortex beams based on image processing. Theoretical analysis and numerical simulations of the misaligned OAM wavefront demonstrate that the misalignment information can be measured by extracting the features of the OAM mean value distribution and the OAM variance value distribution. It is found in this paper that the extrema of mean OAM distribution and OAM variance distribution correspond to the tilted singularity point and original pivot point, separately. These extrema points can be found by image processing algorithms that recognize round speckles. A proof-of-concept experiment is presented, which employs a 2-D scanning probe to measure a 10°-tilted OAM beam with mode +1. The tilt measurement error is only 0.39°.

White Rabbit protocol enhanced TDM-PON is proposed first time for fast clock and data recovery (CDR) and accurate time synchronization. Experimental results validate 38ns CDR time without cost-high burst-mode receiver and 390ps average time skew.

Multi-access Edge Computing (MEC) performs as a feasible solution when it comes to content delivery, for it can bring contents much closer to users. However, the hand-off (HO) and latency that occur in user movement reduce the users’ quality of service. In this work, we consider the problem of high mobility handoff and content delivery of video streaming in the MEC based EONs. We propose a video pre-caching algorithm considering handoff and content delivery. The algorithm firstly selects the content delivery method and chunks the video accordingly using a preset threshold. Secondly, the algorithm chooses the shortest transmission path and calculates the latency time using Dijkstra method. Simulation results show that our algorithm significantly reduces the latency time and balances the server load compared to the other two baselines.

In this paper, we study the problem of network function deployment while user demands are served by both virtualized network functions (VNFs) and physical network functions (PNFs). A hybrid deployment scheme of VNFs and PNFs (HDVP) is proposed. A heuristic algorithm is developed for the HDVP scheme with the aim of minimizing the total cost of VNFs and PNFs. The results show the HDVP scheme achieves lower cost than the conventional only PNFs serving user demands scheme.

A complex-coefficient microwave photonic filter with continuous tunability is proposed and experimentally demonstrated. The filter taps are based on a 360° tunable microwave photonic phase shifter, which is realized by orthogonally polarized optical single-sideband (OSSB) modulation. The experimental results are shown and regarded as good performance for the proposed filter. The phase shift for the two taps covers a full 360° range from 8 GHz to 26 GHz. Frequency responses with different center frequency are measured within 20–21 GHz with the full free spectral ranges (FSRs) of 185 MHz and 285 MHz, respectively.

Multi-layer satellite network has become a hot spot for its wider coverage and higher bandwidth level. However, due to the frequent link changes and complexity of network, it is hard to find out a mechanism to handle well on long delay and high packet loss level. This paper proposes an optimized OSPF protocol called OOWLP to eliminate unnecessary routing convergence to optimize the packet loss level and delay ultimately. Link plan table, which records link contacting plan, will be used to update the link state database periodically so that we can eliminate the flooding procedure caused by scheduled link changes. On the other hand, Constrained Shortest Path First (CSPF) will be used to get business differentiated routes in multi-layer satellite network to optimized the throughput capacity in congestion scenario. We divide the sending packets into different businesses and get the routes for each business with longer duration limited by remaining bandwidth. Simulation results show that in normal scenario, average packet loss rate and delay performance are improved 17.42%, 51.44ms respectively, average packet loss rate and throughput capacity performance are optimized 79.05%, 9.81Mbps respectively in congestion scenario compared to standard OSPF. As a result, the proposed mechanism is able to shorten the average delay and lower the packet loss level in multi-layer satellite network.

A reconfigurable optical data center network is proposed, in which the optical bandwidth can be automatically reconfigured by reallocating time slots based on the real time traffic. Numerical investigations validate that the network performance of packet loss after reconfiguration decreases by 58.5%, and the end-to-end latency decreases by 63.8% with comparison to the network with rigid link interconnections, and thereby increasing the 9.4% of throughput at load of 0.8.

We propose a new beat interference cancellation receiver (BICR) to recover the polarization division multiplexing (PDM) single-sideband (SSB) signals without signal-to-signal beat interference (SSBI) by using optical filters. Our method has simple principles and structures, and it works well under a very low carrier-signal power ratio (CSPR). Also, our proposed method needs no complicated algorithms for recover the signal and mitigate the SSBI.