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This article presents the experimental demonstration of a fully photonics-based heterodyne subterahertz (sub-THz) system for wireless communications. A p-i-n photodiode is used as a broadband transmitter to upconvert the signal to the sub-THz domain and a photoconductive antenna downconverts the received wave to an intermediate frequency around 3.7 GHz. The optical signals used for photomixing are extracted from two independent optical frequency combs with different repetition rates. The optical phase locking reduces the phase noise of the sub-THz signal, greatly improving the performance of the system when phase modulation formats are transmitted. The sub-THz carrier is tuned between 80 and 320 GHz in 40-GHz steps, showing a power variation of 21.8 dB. The phase noise at both ends of the communication link is analyzed and compared with the phase noise of the received signal with different wireless carriers. As a proof-of-concept, a 100-Mbit/s binary-phase-shift-keying signal is successfully transmitted over 80-, 120-, and 160-GHz carriers, achieving a bit error rate below 10 −5 in the first two cases. These results show the great potential of THz communications driven by photonics to cover an extensive portion of the THz range without relying on electronic components that limit the operating range of the system to a concrete frequency band.

[EN] The sixth generation (6G) mobile systems will create new markets, services, and industries making possible a plethora of new opportunities and solutions. Commercially successful rollouts will involve scaling enabling technologies, such as cloud radio access networks, virtualization, and artificial intelligence. This paper addresses the principal technologies in the transition towards next generation mobile networks. The convergence of 6G key-performance indicators along with evaluation methodologies and use cases are also addressed. Free-space optics, Terahertz systems, photonic integrated circuits, softwarization, massive multiple-input multiple-output signaling, and multi-core fibers, are among the technologies identified and discussed. Finally, some of these technologies are showcased in an experimental demonstration of a mobile fronthaul system based on millimeter 5G NR OFDM signaling compliant with 3GPP Rel. 15. The signals are generated by a bespoke 5G baseband unit and transmitted through both a 10 km prototype multi-core fiber and 4 m wireless V-band link using a pair of directional 60 GHz antennas with 10 degrees beamwidth. Results shown that the 5G and beyond fronthaul system can successfully transmit signals with both wide bandwidth (up to 800 MHz) and fully centralized signal processing. As a result, this system can support large capacity and accommodate several simultaneous users as a key candidate for next generation mobile networks. Thus, these technologies will be needed for fully integrated, heterogeneous solutions to benefit from hardware commoditization and softwarization. They will ensure the ultimate user experience, while also anticipating the quality-of-service demands that future applications and services will put on 6G networks., This work was partially funded by the blueSPACE and 5G-PHOS 5G-PPP phase 2 projects, which have received funding from the European Union's Horizon 2020 programme under Grant Agreements Number 762055 and 761989. D. PerezGalacho acknowledges the funding of the Spanish Science Ministry through the Juan de la Cierva programme.

In this work we have demonstrated a waveguide integrated uni-traveling carrier photodiode on an InP-membrane-on-silicon platform with 3 dB bandwidth beyond 110 GHz. With design optimization and an improved process, devices as small as $ \text{3}\times \text{2}\;\mu \text{m}^2$ are successfully realized. An electrical equivalent circuit model based on measured S-parameters revealed ultra-small series resistance and junction capacitance as low as 6.5 $\Omega$ and 4.4 fF, respectively, in the diodes. The model also provided insight in the photocurrent dependent characteristics in the bandwidth and resonsivity of the devices. Finally, data transmission measurements are demonstrated, showcasing the high speed telecommunication abilities of the UTC-PD.

This article presents the experimental demonstration of synchronization of two integrated semiconductor distributed Bragg reflector lasers, fabricated with a generic multiproject wafer platform, by means of injection locking. Substantial linewidth reduction and frequency stabilization of the lasers were shown during locking of the lasers to an optical frequency comb. Phase noise was measured for different injected powers and different laser cavities. For a generation of millimeter-wave signals up to 80 GHz, two lasers were simultaneously locked to the comb. Fine-tuning was performed by tuning the repetition rate of the comb and coarse-tuning was carried out by switching to another comb line. A suppression ratio of 37 dB was achieved for unwanted comb lines. The achieved signal purity, phase noise, and suppression of unwanted components demonstrate the viability of injection locking for the generation of high-quality signals at sub-THz and THz frequencies and with substantial tunability.

Component characterization is fundamental for understanding the limits of optical devices, sub-systems, and transmission systems. With the introduction of space division multiplexing in optical fiber transmission systems, new impairments, such as mode dependent loss and differential mode dispersion arise. Spatially-diverse optical vector network analyzers are capable of measuring these characteristics in a fast single sweep over a very large bandwidth. As a result of this large bandwidth, these analyzers are sensitive to differential chromatic dispersion within the interferometric measurement setup. This study discusses the influence and compensation of differential chromatic dispersion in such systems. Partial chromatic dispersion compensation is demonstrated to improve the representation and accuracy of impulse response measurements obtained from optical vector network analyzers for fibers and components with large differential chromatic dispersion. Analysis of a 39-core few-mode multi-core fiber is discussed, reporting variances of -2.9-0.1 ps/nm, and 0.6-6.9 ps/nm for the two mode groups, respectively, between the few-mode cores. A correlation with the total impulse response is observed. Furthermore, a maximum propagation skew of 20 ns between cores is observed after 13.6 km.

Technological innovation with millimeter waves (mm waves), signals having carrier frequencies between 30 and 300 GHz, has become an increasingly important research field. While it is challenging to generate and distribute these high frequency signals using all-electronic means, photonic techniques that transfer the signals to the optical domain for processing can alleviate several of the issues that plague electronic components. By realizing optical signal processing in a photonic integrated circuit (PIC), one can considerably improve the performance, footprint, cost, weight, and energy efficiency of photonics-based mm-wave technologies. In this article, we detail the applications that rely on mm-wave generation and review the requirements for photonics-based technologies to achieve this functionality. We give an overview of the different PIC platforms, with a particular focus on hybrid silicon photonics, and detail how the performance of two key components in the generation of mm waves, photodetectors and modulators, can be optimized in these platforms. Finally, we discuss the potential of hybrid silicon photonics for extending mm-wave generation towards the THz domain and provide an outlook on whether these mm-wave applications will be a new milestone in the evolution of hybrid silicon photonics.

New CW THz detectors based on graphene nanoelectrodes photomixer are completely investigated. The graphene nanoelectrodes are placed on low-temperature-grown (LTG) GaAs as photoconductive material. Due to the high transparency and high conductivity of graphene, increasing carrier densities were obtained which leads to the high performance detection of THz induced photocurrent being one order of magnitude higher than for conventional metallic interdigitated photomixer. The THz measurement was performed in the range of 50 GHz to 1.1 THz.

Non-Orthogonal Multiple Access (NOMA) technique and Carrierless Amplitude Phase (CAP) modulation have been used to demonstrate pay-as-you-grow coherent Passive Optical Networks (PON) and providing a 10 Gbps aggregate data rate.

This paper reports an experimental comparison and analysis of latency for different modulation techniques at different data rates in W-band Radio-over-Fiber (RoF) transmission links. In addition, a software defined radio called GNU-Radio is employed with Universal Software Radio Peripherals (USRP) to generate and retrieve the transmitted signals. Likewise, it is used to test the end to end latency in the W-band RoF link. Our main contribution is achieving a W-Band low-latency wireless fiber link which fits to the key performance indicators of 5G networks. RESUMEN En este artículo se presenta un análisis y comparación experimental de la latencia para diferentes esquemas de modulación con diferentes tasas de transmisión en un enlace radio sobre fibra en banda W. Adicionalmente se usa radio definido por software en conjunto con unas tarjetas denominadas USRP para generar y recibir la señal. De igual forma, este software se usa para evaluar la latencia en el enlace previamente mencionado. La principal contribución de este artículo es que se demuestra un enlace en banda W, radio sobre fibra, el cuál encaja en los indicadores de desempeño de las redes 5G.

A multi-core fiber (MCF) patch panel was designed, allowing easy coupling of individual signals to and from a 7-core MCF. The device was characterized, measuring insertion loss and cross talk, finding highest insertion loss and lowest crosstalk at 1300 nm with values of 9.7 dB and -36.5 dB respectively, while at 1600 nm insertion loss drops to 4.8 dB and crosstalk increases to -24.1 dB. Two MCF splices between the fan-in module, the MCF, and the fan-out module are included in the characterization, and splicing parameters are discussed.

© 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works In this paper, a combined non-orthogonal multiple access (NOMA) and multiband carrierless amplitude phase modulation (multiCAP) scheme is proposed for capacity enhancement of and flexible resource provisioning in 5G mobile networks. The proposed scheme is experimentally evaluated over a W-band millimeter wave radio-over fiber system. The evaluated NOMACAP system consists of six 1.25GHz multiCAP bands and two NOMA levels with quadrature phase shift keying and can provide an aggregated transmission rate of 30 Gbit/s. The proposed system can dynamically adapt to different user densities and data rate requirements. Bit error rate performance is evaluated in two scenarios: a low user density scenario where the system capacity is evenly split between two users and a high user density scenario where NOMA and multiCAP are combined to serve up to twelve users with an assigned data rate of 2.5 Gbit/s each. The proposed system demonstrates how NOMA-CAP allows flexible resource provisioning and can adapt data rates depending on user density and requirements.

The authors report a novel concept for photonics-assisted and broadband optical-wireless indoor networks based on optically-controlled reconfigurable antenna arrays (OCRAAs) and photonic down conversion (PDC) techniques, operating in the 28 and 38 GHz frequency bands. The antenna bandwidth is optically reconfigured by using photoconductive switches. In this way, the optical backhaul can either be used for high data rate transmission and remotely controlling the antenna operation. Experimental results on 40 Mbaud with complex modulation formats up to 64-QAM wireless transmission supported by PDC are successfully reported under 78 dB link budget requirement. Two OCRAAs have been simultaneously tested in an indoor environment at 1.25 Gb/s wireless data signal transmission. The proposed antenna design significantly increases the degrees of freedom, opening new possibilities in the development of antennas for access networks in the mm-wave frequency range.

Future generation mobile communications running on mm-wave frequencies will require great robustness against frequency selective channels. In this paper, we evaluate the transmission performance of 4.9 Gb/s wavelet-coded orthogonal frequency division multiplexing (OFDM) signals on a 10 km fiber plus 58 m wireless radio-over-fiber link using a mm-wave radio frequency carrier. The results show that a 2 × 128 wavelet-coded OFDM system achieves a bit-error rate of 1e-4 with nearly 2.5 dB less signal-to-noise ratio than a convolutional coded OFDM system with equivalent spectral efficiency for 8 GHz-wide signals with 512 subcarriers on a carrier frequency of 86 GHz. Our findings confirm the Tzannes’ theory that wavelet coding enables high diversity gains with a low complexity receiver and, most notably, without compromising the system's spectral efficiency.

We report an operational photonics-enabled 100 Gbit/s D-band antenna polarization multiplexing system (2 x 2 MIMO) with a carrier frequency of 141 GHz, and experimentally explores antenna misalignment effects on the signal performance in terms of bit error rate. Misalignments from 210 to 10 degrees were evaluated for both the E-and H-plane, highlighting the strict requirements needed to maintain a signal performance below forward-error correction codes thresholds. Our findings indicate tolerable misalignments are below 1 degree, hinting beam steering as a must for future D-band communication links. (C) 2017 Wiley Periodicals, Inc., We report an operational photonics‐enabled 100 Gbit/s D‐band antenna polarization multiplexing system (2 × 2 MIMO) with a carrier frequency of 141 GHz, and experimentally explores antenna misalignment effects on the signal performance in terms of bit error rate. Misalignments from −10 to 10 degrees were evaluated for both the E‐ and H‐plane, highlighting the strict requirements needed to maintain a signal performance below forward‐error correction codes thresholds. Our findings indicate tolerable misalignments are below 1 degree, hinting beam steering as a must for future D‐band communication links.

Ubiquitous broadband Internet access is one of the major goals of the next generation of wireless communications. However, there are still some locations where this is difficult to achieve. This is the case on moving vehicles and, particularly, on trains. Among the possible solutions to this problem, RoF (Radio-over-Fiber) architectures have been proposed as low-latency, cost-effective candidates. Two elements are introduced to extend the RoF approach. First, the carrier frequency is raised into the W-band (75–110 GHz) to increase the available capacity. Second, a mechanical beam-steering solution based on a Stewart platform is adopted for the transmitter antenna to allow it to follow a moving receiver along a known path, thereby enhancing the coverage area. The performance of a system transmitting a 2.5 Gbit/s non-return-to-zero signal generated by photonic up-conversion over a wireless link is evaluated in terms of real-time BER (Bit Error Rate) measurements. The receiver is situated in different positions, and the orientation of the transmitter is changed accordingly. Values below the forward error correction limit for 7% overhead are obtained over a range of 60 cm around a center point situated 2 m away from the transmitter.

We demonstrate 84-Gb/s four-level pulse amplitude modulation (PAM-4) over up to 1.6-km standard single mode fiber using a 20-GHz single mode short cavity vertical cavity surface emitting laser diode at a transmission wavelength of 1525 nm. Different equalizer approaches including a common feedforward equalizer, a nonlinear Volterra equalizer (NLVE), a maximum likelihood sequence estimator (MLSE) and their combinations are evaluated working either as an equalizer for a standard PAM-4 or a partial response PAM-4 signal with seven levels. It is demonstrated that a standard FFE is not enough for a transmission distance of >0.6 km, while the use of an NLVE or FFE + MLSE is able to improve the transmission distance towards 1 km. The use of partial-response PAM-4 FFE in combination with a short memory MLSE is able to efficiently equalize the bandwidth limitations, showing more than 10-times BER improvement compared to standard NLVE or FFE + MLSE at a transmission distance of 1.6 km. Using a partial-response NLVE instead of an PR-FFE further performance improvement is achieved, resulting in BERs below the KP4 FEC-threshold with a BER-limit of 2E-4 after 1.6-km transmission distance, allowing error free operation.

This article presents a study of antenna alignment impact on bit error rate for a wireless link between two directive W‐band horn antennas where one of them is mechanically steered by a Stewart platform. Such a technique is applied to find the optimal alignment between transmitter and receiver with an accuracy of 1° both in azimuth and elevation angles. The maximum degree of misalignment which can be tolerated is also reported for different values of optical power in the generation of W‐band signals by photonic up‐conversion.

This paper reviews and examines several techniques for expanding the carrying capacity of multimode fiber (MMF) using vertical cavity surface emitting lasers (VCSELs). The first approach utilizes short wavelength division multiplexing in combination with MMF optimized for operation between 850 and 950 nm. Both nonreturn to zero (NRZ) and four-level pulse amplitude modulation (PAM4) signaling are measured and demonstrate up to 170-Gb/s postforward error correction transmission over 300 m. For single wavelength transmission, the use of selective modal launch to increase the optical bandwidth of a standard OM3 MMF to more than 2.1 GHz·km for standard MMF is presented. A statistical model is used to predict the bandwidth enhancement of installed MMF and indicates that significant link extension can be achieved using selective modal launch techniques. These results demonstrate the continued effectiveness of VCSEL-based MMF links in current and future data center environments.

Leveraging client optics based on intensity modulation and direct detection for point-to-point inter-data center interconnect applications is a cost and power efficient solution, but challenging in terms of optical signal-to-noise ratio requirements and chromatic dispersion tolerance. In this paper, real-time 8 × 28.125 GBd dense wavelength division multiplexing four-level pulse amplitude modulation (PAM-4) transmission over up to 80 km standard single mode fiber in the C-Band is demonstrated. Using a combination of optical dispersion compensation and electronic equalization, results below a bit error rate of 1e−6 are achieved and indicate sufficient margin to transmit over even longer distances, if an forward error correction (FEC) threshold of 3.8e-3 is assumed. Moreover, single channel 28.125 GBd PAM-4 is evaluated against optical effects such as optical bandwidth limitations, chromatic dispersion tolerance, and optical amplified spontaneous emission noise.

Precise characterization of space division multiplexing fibers is a key requirement for their further development and deployment in the field. Optical vector network analysis allows to measure all linear parameters of such fibers in a single, fast acquisition over a large bandwidth. As the reference arm of the optical vector network analyzer must approximately match the length of the measured fiber, additional fiber must be introduced when measuring longer fibers. This results in the polarization of the reference arm varying with wavelength over the sweep range employed in the measurement. The resulting fading of the recorded interference signal produces severe distortions of the measurement and hence must be compensated for. This work introduces a simple equalization technique to compensate for this fading, based on introducing a polarizer in the reference path and recording a fraction of the polarized reference as a correction signal. Applying the inverse of the correction signal to the recorded signal, the impact of the polarization fading is almost entirely removed, as are the corresponding measurement distortions. The proposed technique is validated in the measurement of a 39-core few-mode multi-core fiber, significantly improving measurement of wavelength dependent insertion loss.

This article reports on a W-Band (75–110 GHz) Schottky diode based balanced envelope detector in microstrip technology, featuring a transition from WR-10 to microstrip. The manufactured detector provides 20 GHz of input RF bandwidth within the W-band. A video bandwidth between 4 GHz and 6 GHz is achieved for input RF frequencies between 75 GHz and 88 GHz, allowing error free transmission of signals up to 12 Gbit/s.

The most radical evolution in recent mobile communication technology is imminent in the coming years. The fronthaul network architecture is part of this evolution and is expected to support dense deployment of infrastructure to provide increased bandwidth and ultra-low latency for 5th generation (5G) networks in a cost-effective manner. The new fronthaul architecture called cloud radio access network (C-RAN) has been introduced over the last years to increase scalability, manageability, and flexibility of mobile systems. In this context, this paper addresses the principal technology enablers of the C-RAN 5G fronthaul architecture, namely radio-over-fiber, ribbon optical fibers, wavelength-division multiplexing, and millimeter wave (mmWave) frequencies. The convergence of optical fiber networks and mmWave radio pave the way towards a truly efficient fronthaul infrastructure for 5G mobile communications with seamless connectivity for millions of devices and quality-of-service guarantees in terms of latency for the first time ever. We perceive a network scenario with seamless starting and ending interfaces by exploiting space diversity in both radio frequency and optical domains with efficient integrated photonics technology. Furthermore, we introduce the ongoing developments of the Eindhoven-based 5G Brainport testbed towards an open environment for validation and test of end-to-end emerging applications benefitting from the 5G key-performance indicators.

This work presents a dielectric rod antenna array designed for a photonic-enabled beamforming system at subterahertz frequencies. The photonic chip generates an optical group delay, providing the beam-steering capability. The antenna array is fabricated from high-resistivity silicon by micromachining. Simulation results demonstrate a directivity of 14.7 dBi and a beam steering range of 56 degrees at 85 GHz. The system is intended as a sub-THz transmitter for broadband wireless communications. QC 20191202

This paper presents the system integration and packaging of a photodetector at $W$ -band (75–110 GHz) for terahertz (THz) communications. The ErAs:In(Al)GaAs photoconductor and its feeding network based on semi-insulating indium phosphide (InP) substrate are introduced. The design of the bias tee at $W$ -band is described, and the effect of parasitic modes is discussed. Besides, the transition using the $E$ -plane probe between a $W$ -band rectangular waveguide (WR-10) and a coplanar waveguide (CPW) is illustrated. The bias tee and the $E$ -plane probe transition are based on high-resistivity silicon (Si) substrate where wire bonding bridges are added on the top following the CPWs in order to restrict parasitic modes. The integration approach and the packaging structure are addressed. The proposed bias tee and the $E$ -plane probe transition, including the WR-10 rectangular waveguide, are fabricated, integrated, and measured. The measurement is carried out on-wafer in a back-to-back configuration, and the results are presented. The assembly of the fully packaged photodetector is demonstrated, and a THz heterodyne communication system is implemented, which validates the proposed system integration and packaging approach of the photodetector at $W$ -band.

The widespread acceptance and deployment of quantum key distribution (QKD) for data encryption requires a better understanding of the technology concerning device-to-system interfacing and network performance from current vendors. Despite the existence of a few QKD testbeds worldwide, they are neither open-access nor capable of validating components from different system and component vendors business cases. User trials in testbeds have yet to yield a robust, open business case. This paper introduces the open-access QKD testbed currently being developed in the Eindhoven region which will focus on the creation of an open environment for end-to-end validation of distinct business cases, QKD security proofs, and technology certification and standardization. At this site, a quantum-to-the-home network scenario for providing quantum encryption as a service on demand, for end-to-end security to end-users, is also proposed. It is expected that this testbed will lead to a better understanding of what further developments are required for current networks to be augmented with QKD.

In this paper, we propose a model for the effect of misalignment of antennas due to mechanical vibrations and experimentally validate its accuracy in a Ka-band (26-40 GHz) transmission link. Our approach provides a valuable tool that is analytically tractable and physically simple to implement. To highlight the applicability of the model, a setup based on a centralized radio access network (C-RAN) transmitting and receiving wireless signals in the Ka-band is implemented. With this tool, the robustness of 5G networks to antenna misalignments can be evaluated in terms of bit-error rate. We show how the presence of misalignment in this type of systems induces an error floor observable in the bit-error-rate performance. A simple static decision threshold is implemented taking into account the amount of displacement and, directly related to that factor, on the expected number of fades per unit time. The closed-form expressions derived through this paper are in perfect agreement with the experimental measurements taken from the implemented system.

We demonstrate a heterodyne wireless system using only ErAs:In(Al)GaAs photoconductors driven by two independent telecom laser signals. The maximum Intermediate Frequency (IF) was 2.3 GHz, only limited by the bandwidth of the post-detection electronics. The maximum signal-to-carrier ratio achieved was 42.6 dB.

The fifth generation (5G) mobile systems can be considered the way to ubiquitous Internet, pervasive computing paradigm, and a revolution in industries like automotive, media and entertainment, and eHealth. New 5G fronthaul systems based on centralized radio access networks will eventually use technology enablers such as reconfigurable optical add-drop multiplexers, space-division multiplexing, ribbon fibers, software-defined networking, multiple-input multiple-output signaling, analog radio-over-fiber signals, and beamforming. In this context, this paper addresses the principal technology enablers of the 5G PPP phase 2 projects blueSPACE and 5G-PHOS and their potential interoperability. The convergence of 5G key-performance indicators (KPIs) along with methodologies and usage scenarios is also addressed. Furthermore, the 2020 European championship is perceived here as a unique opportunity to leverage a 5G pan-European trial platform. The technologies developed in both projects are seen as potential candidates for next generation mobile networks, where ultra-low latency, energy efficiency, and millions of connected devices are major network KPIs requirements.

This letter proposes a W-band hybrid photonic wireless link based on a commercial small form-factor pluggable (SFP+) module and experimentally demonstrates its performance. Using a free running laser as local oscillator and heterodyne photonic upconversion, good frequency stability is achieved. Outdoor wireless transmission over 225 m with a bit error rate below 10 -6 is demonstrated, and the maximum reach of the system with typical RF components is calculated, finding wireless distances above 2 km to be feasible. Being based on a commercial SFP+, the proposed hybrid photonic wireless link offers seamless integration with existing distribution networks and passive optical networks, and thus paves the way for future mobile frontand backhaul architectures.

We present a successful experimental evaluation of 4 level Pulse Amplitude Modulation (4-PAM) and Duobinary modulation. An experimental performance evaluation is presented for Duobinary 4 PAM and other modulation formats. All modulation formants used, may be considered to be implemented in future Passive Optical Network (PON) class access networks with limited electrical bandwidth. We compared NRZ, Duobinary, 4-PAM and Duobinary 4-PAM operating at 9 Gbaud over 20 km single mode fiber. The results provides an insight and guidelines on the utilization of these advanced modulation formats.

We report on the first experimental demonstration of carrierless amplitude/phase modulation in a flexible multiband approach for ultrawideband high-data-rate wireless communications. An effective bitrate of 2 GB/s is achieved while complying with the restrictions on the effective radiated power established by the Russian State Commission for Radio Frequencies. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1603–1607, 2016

We report a novel coherent optical OFDM transponder approach capable of recovering microsecond-scale data-burst while adapting to tight filtering constraints present in optical slot switched intradatacenter networks. Filtering effects in such large node-count environments are reviewed. The CO-OFDM performance is experimentally investigated while crossing a long cascade containing up to 100 nodes. The results are compared to the typical Nyquist pulse-shaped approach. CO-OFDM signaling shows 40% extended reach, 50 Gb/s higher gross average rate, and >4 GHz extra detuning tolerance than Nyquist pulse-shaped signals.

We demonstrate the first known experiment of a real-time end-to-end 40-Gb/s pulse amplitude modulation (PAM)-4 system for next-generation access applications using 10-Gb/s class transmitters only. Based on the measurement of a real-time 40-Gb/s PAM system, low-cost upstream and downstream link power budgets are estimated. Up to 27 and 25 dB power budgets for 10- and 20-km standard single-mode fiber upstream links using erbium-doped fiber amplifiers (EDFA) preamplifiers are achieved. For downstream links using booster EDFAs and avalanche photodiode receivers, power budgets of 26.5 and 24.5 dB are feasible for 10- and 20-km SMFs, respectively. In addition, we show that colorless 40-Gb/s PAM-4 transmission over 20-km SMF in the C-band is achievable.

In this paper, new analytical formalisms to evaluate the packet throughput of multiservice multirate slotted ALOHA optical code-division multiple-access (OCDMA) networks are proposed. The proposed formalisms can be successfully applied to 1-D and 2-D OCDMA networks with any number of user classes in the system. The bit error rate (BER) and packet correct probability expressions are derived, considering the multiple-access interference as binomially distributed. Packet throughput expressions, on the other hand, are derived considering Poisson, binomial, and Markov chain approaches for the composite packet arrivals distributions, with the latter defined as benchmark. A throughput performance evaluation is carried out for two distinct user code sequences separately, namely, 1-D and 2-D multiweight multilength optical orthogonal code (MWML-OOC). Numerical results show that the Poisson approach underestimates the throughput performance in unacceptable levels and incorrectly predicts the number of successfully received packets for most offered load values even in favorable conditions, such as for the 2-D MWML-OOC OCDMA network with a considerably large number of simultaneous users. On the other hand, the binomial approach proved to be more straightforward, computationally more efficient, and just as accurate as the Markov chain approach.

This manuscript introduces a 5G radio access network architecture concept based on ultra-dense wavelength division multiplexing (UDWDM) and incorporating an optical fronthaul network that uses a novel wireless antenna system for radio frequency transmission and reception. A ring topology is proposed where optical signals travel within the 5G UDWDM passive optical networks and millimeter waves are generated in the optical line terminals by optical heterodyning. The wireless transmission of the millimeter waves is conducted by an innovative phased array fed reflector antenna approach for mobile communications that grants high antenna gain due to highly focused radiation characteristics, as well as multiplexing gain by multiple beam generation. Furthermore, beam steering is provided by a radio frequency analog beamformer network. Finally, implementation options synthesizing the total system are discussed.

This work presents the design of a mathbf{1x4} optical true time delay beamforming network integrated into a Si3N4photonic chip for hybrid millimeter wave/photonic systems. The spectral periodicity of a ring resonator-based tree structure is exploited to provide simultaneously the same delay configuration to different gigabit optical channels, increasing the effective beamforming bandwidth. The free spectral range is fixed to 33.3 GHz to assure the combability with wavelength division multiplexing applications. The simulation results show that the progressive delay between outputs can be continuously tuned from 0 ps to 20 ps. These values assure the operation at 60 GHz band.

A low complexity Ka-band hybrid photonic-wireless link based on a commercial SFP+ module is demonstrated, offering an economical and efficient solution for access provisioning to rural areas. A rain forest environment is emulated and low BER is achieved.

In this work, the impulse response of a 39-core 3-mode fiber is measured and analyzed, finding durations of 0.6 ns-3.0 ns, with total group delay varying by 17 ns between cores and observing largely different modal dispersion and wavelength dependence of propagation delay.

We demonstrate a 100 G 24-dimensional carrierless amplitude and phase modulation for the intra-datacenter interconnections. Its merits of the extended reach and the enhanced tolerance for the power loss and thermal are investigated.

We experimentally demonstrate a hybrid millimeter wave/photonic system with beamforming capabilities at 60 GHz. The true time delay configuration is remotely set in the optical domain and it is maintained by using a 7-core fiber with sub-picosecond accuracy.

The key-performance indicators (KPIs) that will be delivered by 5G networks such as extremely low-latency, high capacity, robustness and highly flexible network are key enablers for applications such as autonomous driving, cooperative robotics, transport and processing of large volumes of video and images, to name but a few. This paper presents the ongoing build up and deployment of the Eindhoven based 5G-Brainport testbed towards an open environment for validation and test of end-to-end applications benefitting from the 5G KPIs.

This paper presents an investigation of an optical transmission scheme using a single photodetector (PD) which, as in conventional coherent detection systems, allows the linear transfer of the amplitude and phase information of the optical field into the electrical domain. This is possible by means of optical heterodyne detection and the adjustment of the carrier-to-signal power ratio (CSPR), thus the undesired signal-to-signal beating products (SSBP) due to the PD square-law, can be considered negligible. Through simulation, the CSPR impact on this scheme is determined. Then, its experimental validation is done for a single wavelength and single polarization transmission with a total bitrate of 65 Gb/s over 10 km of standard single-mode fiber (SSMF).

First demonstration of photonically-enabled 1 Gb/s secret wireless data transmission at W-band based on Duffing chaotic systems. The presented results validate a new methodology to increase security by exploiting chaos for gigabit data transmissions.

We demonstrate heterodyne detection of 46 Gbaud polarization-multiplexed QAM signaling using a transmitter based on a conventional dual-polarization I/Q modulator and a receiver consisting of two single-photodiodes without a local oscillator.

This paper regards photonically enabled millimeter wave links for use in 5G. Following a short review of the tradeoff between link directivity, achievable capacity and coverage area, it discusses the use of optical space division multiplexing as suggested in the 2nd phase 5G-PPP project blueSPACE. Finally it relates the latter to the potential use of millimeter waves for broad- and multicast within the framework of 5G.

Next generation wireless communication systems face many challenges to increase the capacity and spectral efficiency of current solutions. The worldwide mobile data traffic increased 4000-fold over the last decade, and is forecast a 7-fold increase between 2016 and 2021. To cope with these stringent demands, prospective solutions are millimeter-wave (mmWave) technology and ultradense small cell networks, given that today most of the mobile traffic is offloaded from mobile networks, i.e., most of mobile users are connected to fixed networks. In addition, enabled by the fast development of electronics, digital signal processing has become essential to enhance the capacity and the performance of current communication systems. In this paper, by using the benefits of multiband modulation schemes and independent sideband (ISB) modulation, high-speed mmWave wireless transmissions in the D-band (110-170 GHz) are reported. D-band radio frequency carrier is generated by means of optical heterodyning, and ISB modulation is applied by means of the Hilbert transform and a double-nested Mach-Zehnder modulator. Total data rates up to 352 Gb/s and spectral efficiencies up to 7.7 bit/s/Hz are experimentally achieved in a single 2 × 2 multiuser multiple-input multiple-output system.

The development of 5G wireless technology is in progress looking to cope with the increasing demands for high capacity, low latency, and ubiquitous mobile access. Cloud/Centralized Radio Access Networks (C-RAN) has been proposed as a promising approach to address the 5G benchmarks. C-RAN is a rising mobile network architecture based on the centralization and pooling of baseband processing elements, with the scope of increasing resource utilization efficiency and air-interface performance gains with fast scaling multi-cell coordination. In this paper we focus on proposing and evaluating a flexible low-latency cross-connect (XC) switch that allows a dynamic scheduling of networking resources between baseband units (BBUs) and remote radio heads (RRHs) in C-RAN deployments. On the one hand, we develop a control plane mechanism for manipulating the XC configuration and state data based on a custom YANG model and Network Configuration (NTCONF) protocol. Using a standard open NETCONF interface, automation of heterogeneous C-RAN resource assignment can be facilitated for 5G architectures. Secondly, we evaluate the performance of our XC in relation to the C-RAN stringent requirements and show that the latency and jitter introduced have negligible influence compared to radio interface limits. The impact of switching delay on the performance of a live system has yet to be tested however, a measured average switching time of 252 ms could still disrupt the ongoing connections.

Analog radio-over-fiber transmission and millimeter-wave and terahertz signal generation through photonic heterodyning are a valuable and versatile solution for many applications. This talk will discuss recent advances, focusing 5G networks, wireless communications and sensing applications.

We propose and experimentally validate an optical true time delay beamforming scheme with straightforward integration into hybrid optical/millimeter (mm)-wave access networks. In the proposed approach, the most complex functions, including the beamforming network, are implemented in a central office, reducing the complexity and cost of remote antenna units. Different cores in a multi-core fiber are used to distribute the modulated signals to high-speed photodetectors acting as heterodyne mixers. The mm-wave carrier frequency is fixed to 50 GHz (VBand), thereby imposing a progressive delay between antenna elements of a few picoseconds. That true time delay is achieved with an accuracy lower than 1 ps and low phase noise.