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The generation and transmission of millimeter-wave signals for 5G applications require the use of broadband and high output power photodetectors to bridge from the optical and electronic domains. Therefore, the deep knowledge on the equivalent circuit characteristics of these devices is vital. This study reviews and analyzes de-embedding techniques contributing to the characterization of the physical aspects within the active region of uni-traveling carrier photodiodes. De-embedding methods analytically remove the parasitic effects of the electrical transmission lines connected to their active area allowing the extraction of their series resistance and junction capacitance toward the synthesis of an equivalent circuit with lumped elements. The open-short technique is examined and a systematic error introduced by this process underlines the vulnerability of the method on removing parasitics with higher complexity. This error is quantified leading to the implementation of a corrected equation converging with the characteristic features of an $S$-parameter-based de-embedding. These characteristics are also analyzed through simulation approaches showing minimal equivalent inaccuracies on eliminating more complex symmetrical parasitics. A thorough comparison between these three methods is conducted through the calculation of lumped components corresponding to the active region of diodes with different sizes.

Fifth-generation mobile networks (5G) are the solution for the demanding mobile traffic requirements, providing technologies that fulfill the requisites of different type of services. The utilization of the millimeter-wave (mm-wave) band is the straightforward technique to achieve high bit rates. Moreover, analog radio-over-fiber (ARoF) brings outstanding benefits such as low cost, low power consumption, and high spectral efficiency, among others. Thereby, mm-wave ARoF is a strong candidate to pave the way for common public radio interface (CPRI) in the fronthaul for the future 5G architecture. As orthogonal frequency-division multiplexing (OFDM) is the adopted waveform in the 5G standard, it should be also utilized in mm-wave ARoF systems for 5G. However, phase noise is one of the most degrading factors in mm-wave OFDM ARoF systems. Therefore, in this work, an analysis of the phase noise is carried out through an experimental setup up. The configuration of this setup enables to gradually modify the final phase noise level of the system. Furthermore, an original and novel algorithm to compensate the phase noise in OFDM receivers is proposed. The performance of this algorithm is experimentally evaluated through the setup for different phase noise levels and different subcarrier spacings. The obtained results show the effectiveness of the proposed algorithm under those conditions, highlighting the viability of mm-wave OFDM ARoF for 5G and beyond.

This article presents an experimental demonstration of a high-capacity millimeter-wave 5G NR signal transmission with analog radio-over-fiber (ARoF) fronthaul over multi-core fiber and full real-time processing. The demonstration validates the core of the blueSPACE fronthaul architecture which combines ARoF fronthaul with space division multiplexing in the optical distribution network to alleviate the fronthaul capacity bottleneck and maintain a centralized radio access network with fully centralized signal processing. The introduction of optical beamforming in the blueSPACE architecture brings true multi-beam transmission and enables full spatial control over the RF signal. The proposed ARoF architecture features a transmitter that generates the ARoF signal and an optical signal carrying a reference local oscillator employed for downconversion at the remote unit from a single RF reference at the central office. A space division multiplexing based radio access network with multi-core fibre allows parallel transport of the uplink ARoF signal and reference local oscillator at the same wavelength over separate cores. A complete description of the real-time signal processing and experimental setup is provided and system performance is evaluated. Transmission of an 800 MHz wide extended 5G NR fronthaul signal over a 7-core fibre is shown with full real-time signal processing, achieving 1.4 Gbit/s with a bit error rate $$ < 3.8 × 10 - 3 and thus below the limit for hard-decision forward error correction with 7% overhead.

Three convergent processes are likely to shape the future of the internet beyond-5G: The convergence of optical and millimeter wave radio networks to boost mobile internet capacity, the convergence of machine learning solutions and communication technologies, and the convergence of virtualized and programmable network management mechanisms towards fully integrated autonomic network resource management. The integration of network virtualization technologies creates the incentive to customize and dynamically manage the resources of a network, making network functions, and storage capabilities at the edge key resources similar to the available bandwidth in network communication channels. Aiming to understand the relationship between resource management, virtualization, and the dense 5G access and fronthaul with an emphasis on converged radio and optical communications, this article presents a review of how resource management solutions have dealt with optimizing millimeter wave radio and optical resources from an autonomic network management perspective. A research agenda is also proposed by identifying current state-of-the-art solutions and the need to shift all the convergent issues towards building an advanced resource management mechanism for beyond-5G.

We evaluate the impact of Power-over-Fiber (PoF) technology on the fronthaul of a 5G-NR network with an Analog-Radio-over-Fiber at 25.5 GHz on a 10 km long multicore fiber. The study in this Letter analyzes the bit error rate (BER) performance for different levels of energy transmitted by the PoF system. 133 mW of maximum optical power at reception is demonstrated showing negligible BER impact or data transmission BER improvement in a dedicated and shared scenario. Comunidad de Madrid (Y2018/EMT-4892); Ministerio de Ciencia, Innovación y Universidades (RTI2018-094669-B-C32); Horizon 2020 Framework Programme (762055).

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.

The sixth generation (6G) mobile systems will be the ultimate technology to support any networking requirement. 6G along with fog computing mobile nodes can support any application and use case within the supply chain delivery, regardless of the systems of systems complexity. In this paper, a holistic end-to-end framework platform based on the integration and leverage of 6G and fog mobile systems for physically-entangled systems is proposed. The framework platform, which relies on 6G fog enabled-delivery drones, terahertz communication, and artificial intelligence technologies, is described. The framework can be applied for highly cooperative, autonomous, and dynamic applications and systems such as supply chain’s last mile delivery of goods, harbour cranes, and maritime ports to help increasing access to goods in general, reduce traffic congestion and energy comsumption, and ease CO2 emissions from transportation. The proposed framework paves the way towards next generation supply chain management including last mile delivery.

This paper presents and experimentally validates an SDN/NFV architecture for the management of optical beamforming connectivity and network services for beyond 5G fronthaul, controlling OBFN coherent and incoherent systems, ARoF transceivers, BBUs with analog output/input and RRHs. © 2020 IEEE.

This paper presents an experimental demonstration of analog radio-over-fiber (ARoF) fronthaul for high-bandwidth, high-capacity millimeter wave (mm-wave) extended fifth generation mobile network (5G) new radio (NR) signals over an optical distribution network with optical space division multiplexing (SDM). ARoF is shown to alleviate fronthaul capacity bottlenecks, transporting an 800 MHz wide extended 5G NR signal and allowing to maintain full centralization in a centralized radio access network (C-RAN). The proposed ARoF fronthaul architecture features a transmitter that generates the ARoF signal and an optical signal carrying a reference local oscillator (LO) employed for downconversion at the remote unit (RU) from a single radio frequency (RF) reference at the central office (CO). An SDM based RAN with 7-core multi-core fiber (MCF) allows parallel transport of the uplink ARoF signal and reference LO at the same wavelength over separate cores. Transmission of an 800 MHz wide extended 5G NR fronthaul signal over 7-core MCF is shown with full real-time processing, achieving 1.4 Gbit/s with BER

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.

Wavelength division multiplex (WDM) passive optical network (PON) is considered for converged fixed mobile broadband access networking. We propose to utilize low-cost tunable lasers at the remote sites, together with a centralized wavelength locker. Practical implementations require a transparently added downstream signaling channel and upstream per-channel pilot tones for channel tagging and remote wavelength control. We demonstrate, for the first time, 26-Gbps discrete multitone transmission modulated on a low-cost wide tunable vertical surface emitting laser over up to 40 km of standard single-mode fiber. The results confirm that converged fixed mobile WDM-PON systems based on low-cost lasers carrying discrete multitone modulation are a technically viable approach.

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.

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.

The introduction of millimeter wave (mm-wave) frequency bands for cellular communications with significantly larger bandwidths compared to their sub-6 GHz counterparts, the resulting densification of network deployments and the introduction of antenna arrays with beamforming result in major increases in fronthaul capacity required for 5G networks. As a result, a radical re-design of the radio access network is required since traditional fronthaul technologies are not scaleable. In this article the use of analog radio-over-fiber (ARoF) is proposed and demonstrated as a viable alternative which, combined with space division multiplexing in the optical distribution network as well as photonic integration of the required transceivers, shows a path to a scaleable fronthaul solution for 5G. The trade-off between digitized and analog fronthaul is discussed and the ARoF architecture proposed by blueSPACE is introduced. Two options for the generation of ARoF two-tone signals for mm-wave generation via optical heterodyning are discussed in detail, including designs for the implementation in photonic integrated circuits as well as measurements of their phase noise performance. The proposed photonic integrated circuit designs include the use of both InP and SiN platforms for ARoF signal generation and optical beamforming respectively, proposing a joint design that allows for true multi-beam transmission from a single antenna array. Phase noise measurements based on laboratory implementations of ARoF generation based on a Mach–Zehnder modulator with suppressed carrier and with an optical phase-locked loop are presented and the suitability of these transmitters is evaluated though phase noise simulations. Finally, the viability of the proposed ARoF fronthaul architecture for the transport of high-bandwidth mm-wave 5G signals is proven with the successful implementation of a real-time transmission link based on an ARoF baseband unit with full real-time processing of extended 5G new radio signals with 800 MHz bandwidth, achieving transmission over 10 km of 7-core single-mode multi-core fiber and 9 m mm-wave wireless at 25.5 GHz with bit error rates below the limit for a 7% overhead hard decision forward error correction.

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.

A bidirectional analogue radio-over-fiber link relying on photonic heterodyning and time-division duplex is experimentally demonstrated, successfully transmitting 5G OFDM signals with data rates of 2.4 Gbit/s and 1.2 Gbit/s in down- and uplink directions over 4 m of wireless distance. An optical frequency comb laser is used together with a demultiplexing module based on injection locking to generate stable K-band (18 – 27 GHz) signals, which eliminates the need for complex high-speed electronics for mm-wave generation.

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.

In this paper we analyze the perspective of digitized radio over fiber (DRoF) fronthaul, showing how to meet the requirements to cope with the future radio access networks (RANs). This entails the introduction of space division multiplexing (SDM) while increasing the flexibility and capacity of the DRoF transceivers.Since the evolution of the DRoF fronthaul is being revised and re-defined, in the blueSPACE project we propose two different DRoF transceiver options. The first option consists on simple transceiver, based on the recent standard specifications and, therefore, expected to be deployed in the short-term. The second options is a more advanced transceiver that features high flexibility, relying on a strong DSP and targeting a long-term deployment. Besides a basic characterization of both solutions, we also analyze additional aspects related to the design and implementation of these two DRoF solutions and their integration into an SDM based RAN. This includes the programmability and interaction with the control plane.

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&centerdot;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.

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.

5G mm-wave communications requires a highly densified network of radio access stations to ensure sufficient coverage. Low-complexity nodes based on C-RAN and ARoF fronthaul combined with advanced antenna concepts offer a suitable and potentially low cost technology for single and multi-beam 5G applications.

This paper presents the novel SDN/NFV 5G fronthaul network scenarios deployed in the blueSPACE project. blueSPACE envisions the upgrade of the fronthaul network to include optical SDM transmission for further increasing the network capacity. One of the novelties is the introduction of ARoF transceivers to reduce the 5G fronthaul bandwidth requirements, in addition to the DRoF solutions that are used for the 4G fronthaul interface and the 3GPP's NGFI. Moreover, ARoF transceivers enable to develop optical beamforming technologies for beam steering and multi-beam transmission. Finally, power of fiber solutions to remotely feed small cells are also considered.

This work presents a comparison between Orthogonal Frequency Division Multiplexing OFDM and Generalized Frequency Division Multiplexing GFDM to evaluate the latency and bit error rate in a Fiber-wireless link in 3.5 GHz band using Software Defined Radio SDR, taking into account its feasibility for the 5G networks in the future.

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.

This article presents a 3.5 GHz Radio-over-Fiber experimental setup by combining WDM-PON and Software Defined Radio (SDR) for 5G networks applications. We performed a measurement of latency in the order of 1 ms with a Bit Error Rate (BER) lower than 10 -9 .

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.

Wireless connectivity and photonic-wireless links in data centers allow fast deployment and dynamic reconfigurability. Technological advances in millimeter and sub-THz communications will soon go beyond 5G and trigger 6G systems. We present how data centers could benefit from such 6G technologies, particularly in assuring flexibility and adaptability, without compromising scalability.

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).

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.

For a future 5G Ethernet-based fronthaul architecture, 100G trunk lines of a transmission distance up to 10 km standard single mode fiber (SSMF) in combination with cheap grey optics to daisy chain cell site network interfaces are a promising cost- and power-efficient solution. For such a scenario, different intensity modulation and direct detect (IMDD) Formats at a data rate of 112 Gb/s, namely Nyquist four-level pulse amplitude modulation (PAM4), discrete multi-tone Transmission (DMT) and partial-response (PR) PAM4 are experimentally investigated, using a low-cost electro-absorption modulated laser (EML), a 25G driver and current state-of-the-art high Speed 84 GS/s CMOS digital-to-analog converter (DAC) and analog-to-digital converter (ADC) test chips. Each modulation Format is optimized independently for the desired scenario and their digital signal processing (DSP) requirements are investigated. The performance of Nyquist PAM4 and PR PAM4 depend very much on the efficiency of pre- and post-equalization. We show the necessity for at least 11 FFE-taps for pre-emphasis and up to 41 FFE coefficients at the receiver side. In addition, PR PAM4 requires an MLSE with four states to decode the signal back to a PAM4 signal. On the contrary, bit- and power-loading (BL, PL) is crucial for DMT and an FFT length of at least 512 is necessary. With optimized parameters, all Modulation formats result in a very similar performances, demonstrating a transmission distance of up to 10 km over SSMF with bit error rates (BERs) below a FEC threshold of 4.4E-3, allowing error free transmission., The work leading to these results has received funding from the European Union's Seventh Framework Programme under Grant Agreement No. 644526 (ABACUS), the European Union's Horizon 2020 Research and Innovation Programme under Grant Agreement No. 644526 (iCIRRUS), and the German Ministry of Education and Research (BMBF) under contract numbers 16KIS0477K (SENDATE Secure-DCI) and 13N13744 (SPeeD)

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.

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 report on achieving 28 Gbaud 4-PAM transmission with post-equalization over a 240 km SSMF link without re-engineering the transmission link design. The results demonstrate the prospect of re-using conventional links for inter data center connections.

A real-time 10Gbps polarization independent quasicoherent receiver for NG-PON2 access networks is proposed and experimentally validated. The sensitivity of this receiver is-33dBm and making feasible a 35dB power budget (required for E2 class).

We demonstrate a novel optical transceiver scheme with a net flexible bit rate up to 100Gbit/s with 5 Gbit/s granularity, using an eight-dimensional modulation format family, and investigate its performance on capacity, reach, and power tolerance.

Twenty-four dimensional modulation format with 2 bit/symbol spectrum efficiency is proposed and investigated in an up to 100 Gbit/s VCSEL-based IM-DD transmission system with respect to the channel bandwidth and the power budget.

In this paper, we present the latest experimental work on millimetre-wave links operating at fiber-like capacity regimes: from UWB communications supporting up to 35 Gbit/s to D-band communications operating at 352 Gbit/s. We provide insights on these technologies and hints on next steps to achieve 1 Tbit/s in the air.

Transmission of a 46.8 Gbit/s multi-band cap signal is experimentally demonstrated over a 50 m W-band radio-over-fiber link. Bit error rates below 3.8×10−3 are achieved, employing nine cap bands with bit and power loading.

This paper presents the vision of the 5G STEP-FWD project, funded by the European Commission, with the objective to propose a novel optical-wireless networking solution for the provision of high speed connectivity to end users. The features of the new architecture, based on the utilization of Ultra-Dense Wavelength Division Multiplexing Passive Optical Networks as the backhaul network, providing access to hyper dense mmWave networks, are presented in detail. Moreover, the research challenges to meet the 5G requirements in terms of low latency, spectral and energy efficiency are highlighted, followed by the description of way the project 5G STEP-FWD is going to address them.

We experimentally demonstrate pre-emphasis based performance for a 2 km long 7-core multicore fiber link. Simultaneous transmission below the FEC threshold is achievable for all cores by using signal equalization in a FPGA.