The biggest barrier for many scientific and commercial applications in communications, spectroscopy, life sciences, food safety, biomedicine as well as industrial metrology is the lack of appropriate sources and detectors of THz radiation with enough power and sensitivity with small footprints and portability. Currently available photonic based THz systems have already demonstrated great potential in terms of high tunability, standard room temperature operation, and signal quality, however they are still suffering from many drawbacks, such as big size equipment (needs an optical table), mechanical disturbance (additional to noise and alignment), high power consumption (electrical and optical), and low flexibility system (each application needs a new setup). We therefore propose a new THz system platform, aimed to overcome all the above drawbacks, based on photonic integrated circuits (PICs) and nanotechnology.
The fifth-generation (5G) of mobile systems is considered a key enabler technology for autonomous driving vehicles. This is due to its ultra-low latency, high-capacity, and network reliability. In this paper, a full end-to-end 5G automotive platform for benchmarking, certificating, and validating distinct use cases in cooperative intelligent transport systems, is proposed. Such an automotive platform enables fast service creation with open-access and on demand services designed for public use as well as for innovative use cases validation such as highway chauffeur system, truck platooning, and real-time perceptive intersection, to name a few. The distinct set of technologies that compose the end-to-end 5G automotive ecosystem framework is described. The holistic 5G automotive ecosystem can handle system and networking interoperability, handover between mobile cells, mobile edge computing capabilities including network slicing, service orchestration, and security. Moreover, the latency performance of a vehicular network with two vehicles is experimentally addressed by using the holistic platform. Up- and down-stream packet transmissions between the two vehicles in an open environment with real-traffic conditions is considered. The results pave the way towards latency levels within the range of 5G key performance indicators and consequently enabling autonomous driving systems. The 5G platform can be further useful for governmental agencies to define new policies and regulations, being able to address critical points such as data protection, liability, and legal obligation, regardless whether systems are partially or fully automated.
KEYWORDS: Antennas, Modulation, Analog electronics, Single mode fibers, Avalanche photodetectors, Wireless communications, Radio over Fiber, Radio optics, Clocks, Signal to noise ratio
An IFoF/V-band link is experimentally presented in a 100MBd QPSK downlink transmission across 7km fiber by a high-power EML and over-the-air by 60GHz beamforming antenna with 32-radiating elements, comprising the first demonstration of a cost-effective end-to-end directional Fiber-Wireless link for dense 5G millimeter-wave networks.
With the digitalization of industry and society, data centers have grown into an essential key strategic infrastructure, centralizing the processing, storage and distribution of vast amounts of information. Through continuing centralization, their size grows ever larger, while at the same time they need to remain flexible and dynamic to adapt to the temporary nature and diverse requirements of many tasks. Modular data centers can fulfil this requirement, allowing quick deployment and provisioning, while being highly reconfigurable - however, in such data centers interconnectivity is a complex and difficult issue. Wired connections based on optical fibers are the standard in data centers, but come at a significant cost and lack reconfigurability. The introduction of wireless connectivity at millimeter and tera-Hertz frequencies offers similar capacities, while allowing dynamic and re configurable deployment and wireless or hybrid data center architectures have been suggested. In this context, the innovations in high capacity millimeter wave communications and in the convergence of optical and wireless networking developed for 5G mobile networks may offer a potential technology candidate for high-density and high-capacity data center network deployments. Such networks allow the layout and topology of the network to be changed on demand and to adapt to the changing needs of different applications, creating a data center network that matches the multi-purpose nature of the computation and storage hardware. In this paper, the recent trends in wireless technologies for data centers are reviewed and connected to the innovations of optical and wireless convergence seen in 5G networks, perceiving a data center network that is better able to cope with the demanding requirements in terms of network reconfigurability, installation and running cost, as well as power consumption and cooling efficiency.
KEYWORDS: Transmitters, Antennas, Circuit switching, Receivers, Switching, Signal attenuation, Beam steering, Switches, Signal processing, Radio over Fiber
A spatial circuit switching system based on a beam steering application for W-band wireless links is proposed and experimentally demonstrated. The system enables two simultaneous transmissions of a 2.5 Gbit/s data signal over a carrier of 81 GHz, while allowing the receiver to dynamically switch between them. The performance of the system is tested with the real-time measurements of the BER, achieving values below the FEC limit for 7% of overhead and serving to prove the viability of wireless spatial circuit switching in the next generation of wireless access networks.
The paper describes the application of IR-UWB technology for organizing the radio part of Radio-over-Fiber system. Four physical layer components are proposed and designed in the paper: three microstrip filters and UWB antenna. Firstly the effective SCRF mask was calculated to ensure electromagnetic compatibility with existing radio services. Then this mask was considered as a cost function for filters design. The simulation was made with Agilent Genesys™ and CST Microwave Studio. All the devices have shown good performance and could be implemented on one circuit board for reducing losses.
We propose, experimentally demonstrate, and evaluate the performance of a multimode (MM) transmission fiber data link which is based on orbital angular momentum (OAM) modes. The proposed scheme uses OAM modes to increase capacity or reach without recurring to mode division multiplexing (MDM) or special fibers: we first excite an OAM mode and couple it to a 50 m, 100 m, 200 m and 400m MM fibers. We compare three OAM modes and a conventional optical multimode under the same launch and received optical power conditions. The proposed OAM based solution is a promising candidate for the data centers interconnects and short range links that employ the existing multimode fiber infrastructure.
This paper presents a solution for upgrading optical access networks by reusing existing electronics or optical equipment: sliceable transponders using signal spectrum slicing and stitching back method after direct detection. This technique allows transmission of wide bandwidth signals from the service provider (OLT - optical line terminal) to the end user (ONU – optical network unit) over an optical distribution network (ODN) via low bandwidth equipment. We show simulation and experimental results for duobinary signaling of 1 Gbit/s and 10 Gbit/s waveforms. The number of slices is adjusted to match the lowest analog bandwidth of used electrical devices and scale from 2 slices to 10 slices. Results of experimental transmission show error free signal recovery by using post forward error correction with 7% overhead.
KEYWORDS: Digital signal processing, Semiconductor lasers, Phase shift keying, Semiconductors, Receivers, Interference (communication), Signal to noise ratio, Frequency modulation, Transmitters, Optical communications
We discuss about digital signal processing approaches that can enable coherent links based on semiconductor lasers. A state-of-the art analysis on different carrier-phase recovery (CPR) techniques is presented. We show that these techniques are based on the assumption of lorentzian linewidth, which does not hold for monolithically integrated semiconductor lasers. We investigate the impact of such lineshape on both 3 and 20 dB linewidth and experimentally conduct a systematic study for 56-GBaud DP-QPSK and 28-GBaud DP-16QAM systems using a decision directed phase look loop algorithm. We show how carrier induced frequency noise has no impact on linewidth but a significant impact on system performance; which rises the question on whether 3-dB linewidth should be used as performance estimator for semiconductor lasers.
KEYWORDS: Signal to noise ratio, Fermium, Frequency modulation, Machine learning, Digital signal processing, Error analysis, Particle filters, Receivers, Laser beam characterization, Detection and tracking algorithms
The use of machine learning techniques to characterize lasers with low output power is reviewed. Optimized phase
tracking algorithms that can produce accurate noise spectra are discussed, and a method for inferring the amplitude noise
spectrum and rate equation model of the laser under test is presented.
Expanding software defined networking (SDN) to transport networks requires new strategies to deal with the large number of flows that future core networks will have to face. New south-bound protocols within SDN have been proposed to benefit from having control plane detached from the data plane offering a cost- and energy-efficient forwarding engine. This paper presents an overview of a new approach named KeyFlow to simultaneously reduce latency, jitter, and power consumption in core network nodes. Results on an emulation platform indicate that round trip time (RTT) can be reduced above 50% compared to the reference protocol OpenFlow, specially when flow tables are densely populated. Jitter reduction has been demonstrated experimentally on a NetFPGA-based platform, and 57.3% power consumption reduction has been achieved.
High degree of heterogeneity of future optical networks, such as services with different quality-of-transmission
requirements, modulation formats and switching techniques, will pose a challenge for the control and optimization of
different parameters. Incorporation of cognitive techniques can help to solve this issue by realizing a network that can
observe, act, learn and optimize its performance, taking into account end-to-end goals. In this letter we present the
approach of cognition applied to heterogeneous optical networks developed in the framework of the EU project CHRON:
Cognitive Heterogeneous Reconfigurable Optical Network. We focus on the approaches developed in the project for
optical performance monitoring and power consumption models to implement an energy efficient network.
We present a detailed experimental investigation of a hybrid optical-fiber wireless communication system operating at the 75 to 110 GHz (W-band) for meeting the emerging demands in short-range wireless applications. Measured W-band wireless channel properties such as channel loss, frequency response, phase noise, and capacity are reported. Our proposed system performs a sextuple frequency up-conversion after 20 km of fiber transmission, followed by a W-band wireless link. A 500 Mbit/s amplitude shift keying signal transmission is experimentally demonstrated for performance analysis purposes.
KEYWORDS: Orthogonal frequency division multiplexing, Polarization, Single mode fibers, Optical fibers, Radio over Fiber, Digital signal processing, Receivers, Computing systems, Multiplexing, Modulation
We propose and demonstrate a 2 × 2 multiple-input multiple-output (MIMO) wireless over fiber transmission
system. Seamless translation of two orthogonal frequency division multiplexing (OFDM) signals on dual optical
polarization states into wireless MIMO transmission at 795.5 Mbit/s net data rate is enabled by using digital
training-based channel estimation. A net spectral efficiency of 2.55 bit/s/Hz is achieved.
KEYWORDS: Multimode fibers, Radio optics, Single mode fibers, Modulators, Interference (communication), Signal generators, Phase measurement, Frequency modulation, Modulation, Microwave radiation
Using a novel optical frequency multiplication technique, microwave signal carriers up to 20-GHz are delivered to a significantly simplified remote radio access unit fed by a multimode fibre link having modal bandwidth below 1-GHz, as well as standard single mode fibre. Measurement results show that the remotely generated carriers have very narrow linewidths below 20-Hz, and exhibit much lower phase noise (< -90 dBc/Hz) than even a commercially available high frequency electronic signal generator. Thus by using optical frequency multiplication, existing in-building silica multimode fibre infrastructure, and the emerging polymer optical fibres may be used to not only transport fixed data services such as gigabit Ethernet but also to transparently distribute in-doors (and for short links), signals of present WLANs as well as future broadband WLAN services leading to significant system-wide cost reduction. It also enables the radio signal processing to be consolidated in a single central site, which is beneficial for advanced signal processing such as needed in multiple-input multiple output (MIMO) systems.
Optical label switching based on combined differential phase shift keying (DPSK) modulation and subcarrier multiplexing is experimentally demonstrated at 10 Gbit/s DPSK encoded payload and 100 Mbit/s amplitude modulated subcarrier-multiplexed labeling. This scheme is spectral efficient and robust to fiber dispersion.
We demonstrate all-optical label encoding and updating for an orthogonally labeled signal in combined IM/FSK modulation format utilizing semiconductor lasers, semiconductor optical amplifiers and electro-absorption modulators. Complete functionality of a network node including two-hop transmission and all-optical label swapping is also experimentally demonstrated with overall penalty of less than 2 dB, proving the orthogonal IM/FSK labeling scheme to be a feasible solution for future optically labeled networks.
The influence of in-band crosstalk on the error performance of all optical networks with different topologies is studied. A statistical crosstalk model is used for evaluating the bit- error rate. The model accounts for optical preamplification. We present a network topology having the best performance while using the largest transmission path.
An efficient method for evaluating the error probability of optical ASK/DD systems subject to interferometric noise is presented. The receiver decision variable is statistically described by its moment generating function (mgf). The theoretical results, obtained with the aid of the new derived mgf, are in good agreement with experiment, employing directly modulated light sources, while the common used Gaussian statistics for the photocurrent yields larger power penalties. The analysis takes into consideration polarization statistics, photodetector shot noise, non-ideal extinction ratio, and receiver thermal noise. Error probabilities are calculated using the saddlepoint approximation which is numerically simple and gives accurate results.
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