Millimeter-wave Signal Research Articles

D-band signal generation and transmission without optical filter based on optical carrier suppression and single-sideband modulation.

We experimentally demonstrated a novel and simple scheme to generate D-band millimeter-wave (mm-wave) signal without optical filter based on optical carrier suppression (OCS) and single-sideband (SSB). One intensity modulator (IM) driven by radio frequency (RF) signal at 50 GHz is firstly employed to generate two tones with channel spacing of 2 x RF frequency based on OCS. Another subsequent in-phase/quadrature (I/Q) modulator driven by RF signal at 30 GHz is then applied to generate SSB signal by using independent sideband (ISB). No optical filter is needed so that the whole system can be simplified. After using a D-band photomixer for detection, we finally generated the vector mm-wave at 130 GHz. Based on the proposed system, 4-Gbaud/8-Gbaud quadrature phase shift keying (QPSK) information carried by the generated D-band mm-wave signals were transmitted over 22.5-km single model fiber (SMF) and 1-m wireless distance radio-over-fiber (ROF) link. Bit-error-ratio (BER) performances under hard/soft-decision forward-error-correction (FEC) threshold are shown respectively in cases of two different signals transmission rates.

800-MHz Bandwidth Signal Transmission with Radio over Multi-Mode-Fiber for Cascaded IFoF-Based C-RAN Mobile Fronthaul

Millimeter-wave band signals have the advantage of a high capacity and have been used in fifth-generation (5G) mobile services. An analog radio over multi-mode fiber (A-RoMMF) employing a directly modulated vertical cavity surface emitting laser is a promising technology for relaying millimeter-wave band signals to its dead area because of the advantages of low latency, low cost, and low power consumption. One of the applications of A-RoMMF is a cascaded intermediate-frequency-over-fiber (IFoF)-based centralized radio access network (C-RAN) mobile fronthaul (MFH) system. We conducted two studies on A-RoMMF to extend the transmission distance and bandwidth to adapt it to the system. First, we evaluated the effect of employing a single-mode vertical cavity surface emitting laser (VCSEL) and a multi-mode VCSEL on the transmission characteristics of A-RoMMF. Next, we evaluated the transmission characteristics of A-RoMMF using a cost-efficient bias-tee consisting of an electrical circuit pattern, the frequency response of which has a slope inverse to that of A-RoMMF at the 28-GHz band, to suppress the channel power difference of two component carrier signals for a wide-bandwidth signal transmission. We conducted these evaluations using A-RoMMF itself and herein demonstrate its adaption to a cascaded IFoF-based C-RAN MFH system at the 28-GHz band. When employing it with a 200-m long multi-mode fiber, the system achieves 400-MHz/CC and two component carrier signal transmissions.

A New and Simple Frequency Quadrupling Millimeter-Wave Signal Generation Enabled by a Single Mach-Zehnder Modulator Without Optical Filter

In this work, we have designed and proposed a new optical method to realize the generating of frequency quadrupling millimeter-wave (mm-wave) only employing one Mach-Zehnder modulator (MZM), and no any optical filter is needed. Compared with the previously reported quadruple frequency scheme, this work greatly simplifies the structure of the system, and makes the performance better and the cost lower. In the scheme, the MZM is operated at peak bias point, which is applied to retain the even order optical sidebands and wipe off the odd order optical harmonics. By tuning-up the optical shifter and optical attenuator (OATT) to control the zeroth order optical carrier returns zero, only ±2nd order optical tones are generated. We demonstrated and discussed the presented scheme feasibility based on the detailed mathematical formula derivation and numerical simulation, the simulation results of which show that employing a sinusoidal radio frequency (RF) source with frequency at 10 GHz to drive a push-pull MZM, a 40 GHz millimeter-wave (mm-wave) signal can be obtained. In the work, the performance of the generated quadrupling signal is that the optical sideband suppression ratio (OSSR) is 34.8 dB and the radio frequency sideband suppression ratio (RFSSR) can reach 27.2 dB.

Numerical analysis of UFMC and FBMC in wavelength conversion for radio over fiber systems using semiconductor optical amplifier

The 5G networks promise to use advanced access techniques and modulation formats to achieve new requirements of the huge number of users such as higher data, high speed, and low latency. Millimeter-wave (MMW) signal and new modulation schemes such as universal filtered multicarrier (UFMC) and filtered bank multicarrier (FBMC) are playing a fundamental role to accomplish these requirements. UFMC and FBMC are classified under multicarrier modulation formats which are considered as a suitable modulation scheme in 5G and replacing a well-known modulation format of filtered orthogonal frequency division multiplexing (OFDM) which was used in 4G. This interest in using UFMC and FBMC in 5G wireless systems is the reduction of out-of-band (OOB) spectrum in UFMC and reduction of sidelobe suppression in FBMC. The contribution of this paper is to propose a model of wavelength conversion using a semiconductor optical amplifier (SOA) for both schemes UFMC and FBMC- off-set quadrature amplitude (OQAM). In addition, we analyze and compare their performance in terms of bit error rate (BER) and error vector magnitude (EVM) for a wavelength conversion application. Finally, we investigate the main disadvantage of OFDM which is the high Peak to Average Power Ratio (PAPR) for both schemes, and compare between them. Photonic switching of a 4 Gbps 16-QAM UFMC and FBMC-OQAM signal centered at 50 GHz is performed. The optical single-sideband (OSSB) signal is generated with 18.85 dB of sideband suppression ratio (SSR). The results show that the best values of BER and EVM can be obtained when the injection current (IC) is 0.7–0.9A. For converted signal using FBMC-OQAM, it has power penalty ∼ 2.5 dB at BER threshold 1 × 10-3and has also ∼ 2 dB power penalty compared to the UFMC scheme at EVM threshold 5.6%. In addition, the wavelength switching system with FBMC and UFMC modulation schemes achieves the same PAPR.

Secure transmission of W-band millimeter-wave based on CNN and dynamic resource allocation.

A secure transmission scheme of a W-band millimeter-wave radio-over-fiber (RoF) system based on cellular neural network (CNN) and dynamic resource allocation is proposed, in which 7-D CNN chaotic system is composed to heighten the anti-deciphering ability of a secure system, and the spectrum resources are optimized by dynamic allocation. The analyses show that the key space of our scheme can reach approximately 10112. The encrypted W-band millimeter-wave signal is successfully transmitted in the filter-OFDM RoF system of 50-km SSMF and 5 m wireless channel, and the experimental results illustrate that our proposed scheme can enhance the bit error ratio performance by approximately 0.3 dB compared with the traditional one.

Optical Injection Locking for Generation of Tunable Low-Noise Millimeter Wave and THz Signals

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.

Large Tunable 16-Tupled Millimeter Wave Generation Utilizing Optical Carrier Suppression With a Tunable Sideband Suppression Ratio

Coping up with the rising bandwidth demands for 5G ultra-high speed applications, utilizing millimeter (MM) wave spectrum for data transmission over the radio over a fiber-based system is the ideal approach. In this study, a highly conversant and spectrally pure photonic generation of a 16-tupled MM wave signal using a series-connected DD-MZM with a lower modulation index, a splitting ratio, and a wider tunable range is presented. A 160-GHz MM wave is generated through a double sideband optical carrier suppression technique having an optical sideband suppression ratio (OSSR) of 69 dB and a radio frequency sideband suppression ratio (RSSR) of 40 dB. However, the OSSR and the RSSR are tunable with values greater than 15 dB when the modulation index (M.I.) varies from 2.778 to 2.873, ±8° phase drift, and a 15-dB enhancement in the OSSR with a wider nonideal parameter variation range giving acceptable performance can be seen in the model as compared with previous research works.

Self-Start Multi-Wavelength Laser Source with Tunable Delay-Line Interferometer and Optical Fiber Reflector for Wireless Communication System

The radio-over-fiber (RoF) technique has gained a lot of interest recently, as the millimeter-wave signals can be generated and delivered in the optical domain with the advantages of low attenuation, high capacity, and being free from electromagnetic noise interference (EMI). In this paper, we propose and experimentally prove a self-start multi-wavelength laser source based on a distributed feedback laser diode (DFB-LD) for the RoF transport system. The self-start multi-wavelength laser source generates stable laser power with less than 0.18 dB power fluctuation and exhibits good stability. In order to estimate the transmission performance, data is externally modulated onto the multi-wavelength by a reflective semiconductor optical amplifier (RSOA) and transmitted through single-mode fiber (SMF). The experimental result proves that the proposed RoF transport system achieves error-free transmission and clear eye diagrams.

Investigation on Beam Alignment of a Microstrip-Line Butler Matrix and an SIW Butler Matrix for 5G Beamforming Antennas through RF-to-RF Wireless Sensing and 64-QAM Tests.

In this paper, an intuitive approach to assessing advantages of beamforming in 5G wireless communication is proposed as a novel try and practical demonstration of importance of alignment between the transmitter’s and receiver’s beams working in millimeter-wave frequency bands. Since the diffraction loss of millimeter-wave signals matters seriously in propagation, the effects of the misalignment and alignment between beams need to be checked for, which was conducted with a horn antenna and the 4 × 4 Butler matrix which mimic the relationship of the base station and handset antennas. Designing and using the microstrip-line and the substrate integrated waveguide (SIW) Butler matrices, RF-to-RF wireless connectivity between the horn and the microstrip line beamformer as case 1 and the horn and the SIW beamformer as case 2, concerning the changing angle of the beam from either of the two Butler matrices, was tested, showing over 12 dB enhancement in received power. This direct electromagnetic link test was accompanied by examining 64-QAM constellations for beam-angle changing from −30° to +30° for the two cases, where the error vector magnitude in the QAM-diagram becomes less than 10% by beam-alignment for the changing angle.

ANALYSIS OF INDICATORS OF ELECTROMAGNETIC COMPATIBILITY OF COMMUNICATION NETWORKS 5 G

Context. The next generation 5G / IMT-2020 technology, like any new technology, brings its own specific features to all aspects of the practice of its application. One of these particularly important aspects is electromagnetic compatibility. At the stage of preparation for the introduction of 5G radio networks, it is necessary to take early measures to effectively assess the EMC conditions for these networks based on a thorough analysis of the features of 5G technology, and by correctly and accurately assessing these conditions, successfully ensure the electromagnetic compatibility of radio equipment of new networks. Objective. The purpose of this work is to analyze the electromagnetic compatibility of the 5G communication network. Method. An analysis of the main features of the 5G radio interface provides an indication of the expected features of the EMC assessment procedures for these networks. These features mainly relate to taking into account the total interference from the network with its special architecture and dynamics of changes, the choice of new loss models (channel models) for spatially distributed radiation of multidimensional MIMO antennas and a heterogeneous signal propagation medium, as well as taking into account the spectral properties of new signal shapes and character radiation with new non-orthogonal radio access methods.For EMC analysis, a model of signal attenuation in millimeter-wave radio channels was used, taking into account attenuation of radio waves in free space; loss of energy of radio waves when propagating through rains; attenuation of a millimeter wave signal when propagating through the leaves of trees; attenuation of signals when passing through dense obstacles (buildings, structures, etc.). Results. The analysis of attenuation of the millimeter-wave signal in free space from the intensity of precipitation is carried out at various values of optical visibility. The analysis of the attenuation of the millimeter-wave signal from the distance when the signal propagates through obstacles in the form of walls at various values of the wall thickness is carried out. The analysis of the attenuation of the millimeter-wave signal from the depth of the leaf layer is carried out; it covers the signal propagation at different values of the carrier frequency. The analysis of the value of the power of the millimeter-wave signal at the input of the receiver on the intensity of precipitation is carried out at various values of optical visibility. The analysis of the value of the power of the millimeter-wave signal at the input of the receiver versus the distance when the signal propagates through obstacles in the form of walls at various values of the wall thickness is carried out. The analysis of the power value of the millimeter-wave signal at the receiver input from the depth of the leaf layer is carried out, overlaps the signal propagation at various values of the carrier frequency. Conclusions. The conducted studies of EMC indicators allow us to give recommendations on the application of 5G technology in specific practical situations.

84 GHz millimeter-wave PAM4 signal generation based on one PDM-MZM modulator and one polarizer without DAC and filters

In this paper, a novel scheme to employ one external polarization division multiplexing Mach–Zehnder Modulator (PDM-MZM) and one polarizer to generate millimeter-wave four-level pulse amplitude modulation (PAM4) signal is proposed without the usage of expensive and power hungry digital-to-analog converter (DAC). Firstly, we theoretically derive the generation conditions for the mm-wave PAM4 signal scheme. Based on this cost-effective scheme, 6 Gbaud PAM4 signal carried by 84 GHz millimeter-wave transmission over 15 km single-mode fiber (SMF-28) with only 0.5 dB power penalty without any CD compensation is experimentally demonstrated. Furthermore, VPI simulation software is employed to numerically simulate the mm-wave PAM4 signal generation and explore the influences of polarization rotation of the polarizer and direct current (DC)-Bias on the performance of generated W-band signals. In a word, it would be a promising scheme for future 5G short-reach intensity modulation and direct detection (IM/DD) system.

Performance optimization of RSOA based mm-wave radio-over-fibre access network

In this paper, a Reflective Semiconductor Optical Amplifier based, Radio-over-Fibre access network configuration has been proposed to feed future millimeter-wave radio systems. The system architecture combines several approaches to overcome the challenges of millimeter-wave signal transmission. Reflective semiconductor optical amplifier modulator realizes a colorless and relatively cost-effective Remote Antenna Unit. The same optical carrier is used for both downlink and uplink. Optical single-sideband modulation is used at the downlink, which is robust against chromatic dispersion, but the complex realization of this modulation format is not possible at the Remote Antenna Unit. Optical intermediate frequency transmission is applied at the uplink direction, and the required local oscillator signal originates from the central station. The critical element is the reflective optical amplifier, as it compensates for the optical loss and works as an external intensity modulator. The operation of the reflective optical amplifier is modeled by multisection rate and wave equation-based description. The amplification and modulation behaviors of an available reflective optical amplifier are also measured. The experimental work validated the colorless operation and the quality of the modulation versus bias current and input optical power. Finally, system simulation was realized. The uplink and downlink power budgets were balanced, and optimal values for the optical coupling rate and RSOA bias current have been selected.

An Investigation about All-optical Millimeter Wave Generation Technology for High-speed Communication

With the advent of the network information age, users have higher and higher requirements for the bandwidth and capacity of communication systems. Traditional cellular mobile communications can no longer meet the needs of modern communication systems. It is necessary to find a communication system with larger capacity, higher bandwidth and higher transmission rate. Millimeter wave (MMW) communication has high bandwidth, large capacity and high signal transmission rate. Nowadays, all-optical MMW technology generates high-frequency MMW signals in optical domain, which has become a research hotspot of MMW signal generation technology at home and abroad. In this paper, three typical all-optical MMW generation methods are discussed, including direct modulation method, optical heterodyne method and external modulation method. The advantages and disadvantages of each method are analyzed, and the development prospects of the all-optical MMW generation technology are prospected. It is helpful to research new optical MMW technology in the future.

Self-referenced distribution of millimeter waves over 10 km optical fiber with high frequency stability.

In this Letter, an actively stabilized photonic system for millimeter-wave (mmW) signal distribution is proposed and experimentally demonstrated. By interlocking two baseband RF signals obtained from a dual-heterodyne detection through a single carrier compensation module, the phase fluctuations induced by the fiber transmission link is suppressed without the need of a local frequency reference. In the proof-of-concept experiment, a 108 GHz mmW is transmitted over a 10 km fiber link with a performance matching that of the back-to-back case. The feedback system reduces the phase noise of the delivered mmW signal by 37 dB and 28 dB at 0.1 Hz and 1 Hz frequency offset, respectively, and the long-term stability is improved by nearly two orders of magnitude.

Quantum dash multi-wavelength lasers for Tbit/s coherent communications and 5G wireless networks

We report on the design, growth, fabrication, and performance of InAs/InP quantum dash (QD) multi-wavelength lasers (MWLs) developed by the National Research Council (NRC) Canada. The key technical specifications investigated include optical and RF beating spectra, relative intensity noise (RIN), and optical phase noise of each individual wavelength channel. Data bandwidth transmission capacity of 5.376 Tbit/s and 10.8 Tbit/s respectively in the PAM-4 and 16-QAM modulation formats are demonstrated using only a single C-band QD 34.2-GHz MWL chip. We have also developed a monolithic InAs/InP QD dual-wavelength (DW) DFB laser as a compact optical beat source to generate millimeter-wave (MMW) signals. Due to the common cavity, highly coherent and correlated optical modes with optical linewidth as low as 15.83 kHz, spectrally pure MMW signals around 46.8 GHz with a linewidth down to 26.1 kHz were experimentally demonstrated. By using this QD DW-DFB laser, a one GBaud (2 Gbps) MMW over-fiber transmission link is demonstrated with PAM-4 signals. The results show that the demonstrated device is suitable for high speed high capacity MMW fiber-wireless integrated fronthaul of 5G networks.

Extended L-Band InAs/InP Quantum-Dash Laser in Millimeter-Wave Applications

We report on the generation and transmission of a millimeter-wave (MMW) signal with a frequency of 28 GHz by employing an InAs/InP quantum-dash dual-wavelength laser diode (QD-DWL) emitting in the ~1610 nm extended L-band window. The self-injection locking (SIL) technique has been engaged to improve the linewidth and reduce the noise of the optical tone. Besides, the transmission of a 2 Gbits/s quadrature phase-shift keying (QPSK)-modulated 28-GHz MMW beat tone over a hybrid 20-km radio-over-fiber combined with 5-m radio-over-free-space-optics and up to 6-m radio frequency wireless link has been demonstrated. Moreover, comparing the proposed QD-DWL with a commercial laser showcased similar performance characteristics, making the QD-DWL a candidate source for MMW applications.

Millimeter-wave radio-over-fiber system using optical phase modulation and photonic downconversion for uplink fronthaul transmission.

This Letter proposes a high-performance radio-over-fiber (RoF) system for high-speed and high-fidelity analog waveform transmission of radio signals in the millimeter-wave band in the uplink direction. At the antenna site, the system utilizes a newly fabricated low half-wave voltage broadband phase modulator to convert a millimeter-wave radio signal into an optical signal. At the receiver, by using photonic downconversion and optical filtering technology, a simple direct detection and downconversion of the signal to the microwave band can be achieved simultaneously. As a demonstration of proof of concept, we successfully transmitted a 1024-quadrature amplitude modulation (QAM) narrowband orthogonal frequency-division multiplexing signal at 38 GHz and a 60 Gb/s 64-QAM single-carrier signal at 26.5 GHz over a 20 km RoF system. The system is promising for facilitating the deployment of ultra-dense small cells in high-frequency bands in 5G and beyond networks.

Radio-over-Fiber Dual-Parallel Mach–Zehnder modulator system for photonic generation of Millimeter-Wave signals through two stages

In this work, we presented a radio-over-fiber (ROF) access network through two modulation stages for the generation of multiple millimeter wave (mm-wave) signals with frequencies of 20, 40, 60 and 80 GHz for the transmission rate of 10 Gbps as a function of the variation of link distance and signal power. The specific purpose of the paper was to design and to investigate a RoF system based on the variation of mm-wave frequencies in order to implement a simple and effective system. In stage 1, there are two modulators in parallel (MZMa and MZMb) called dual-parallel Mach–Zehnder modulator (DP-MZM) and in stage 2 there is only one modulator (MZMd), connected to three pulse generators: Non-Return-to-Zero (NRZ), Return-to-Zero (RZ) and Gaussian, which were selected individually to each simulation in optisystem software. A single-mode fiber (SMF) and optical filter Gaussian (GOF) and an erbium-doped fiber amplifier (EDFA) were also used to send signals to base stations (BSs). The numerical analyzes of the results of the eye diagrams showed excellent bit error rate (BER) and quality factor (Q-factor) values, which proved the good performance of the proposed RoF- DP-MZM system, for the three encoding formats used, which was able to generate 3-tupling mm-wave for multiple wireless accesses.

Modulation Index and Phase Imbalance of Dual-Sideband Optical Carrier Suppression (DSB-OCS) in Optical Millimeter-Wave System

This paper presents a Dual-sideband Optical Carrier Suppression (DSB-OCS) technique which is used to generate an optical millimeter-wave (mm-wave) signal in radio over fiber (RoF) systems. The proposed system employs a Dual-Electrode Mach-Zehnder Modulator (DE-MZM) and a carrier of 40 GHz mm-wave for data transmission through the RoF systems. Characteristics determining the performance of the system, among which are the modulation index, phase imbalance and dispersion parameters, are included. The performance evaluations of the system show that the mm-wave signal output power follows MZM’s transfer function when the modulation index is raised. Moreover, the generated optical mm-wave signal power is affected by phase imbalance and optical splitting ratio. It is observed that the optical fiber dispersion influences the DSB-OCS system by decreasing the amplitude of the mm-wave and the signal-to-noise ratio (SNR).

Performance of Injection-Locked Quantum-Dash MMW Source Under Clear and Dusty Weather Conditions

We report on the generation and transmission of 30 GHz millimeter-wave (MMW) beat-tone signals employing external- (EIL) and self-injection-locked (SIL) InAs/InP quantum-dash based dual-wavelength laser (QD-DWL) sources emitting in mid L-band. Later, successful transmission of 2 Gbps quadrature phase-shift-keying (QPSK) signal over clear weather conditions on 2 m wireless (WL), and hybrid channels consisting of 20 km single-mode fiber (SMF) and 2 m WL, and 20 km single-mode fiber (SMF), 5 m free-space-optics (FSO) and 2 m WL, are demonstrated employing both MMW sources, with a slight ∼1.4 dBm extra received optical power requirement from SIL QD-DWL. Lastly, examining the effect of dusty weather conditions on the MMW transmission over 20 km SMF, 0.9 m FSO and 1 m WL hybrid channel, considering both EIL and SIL sources, showed maximum visibility range (V) of 12 ± 2 m and 16 ± 2 m for successful transmission, respectively. These investigations reinforce the simple, cost-effective, and energy-efficient SIL QD-DWL as a candidate L-band millimeter-wave (MMW) source compared to the EIL counterpart in 5G and next-generation radio-over-fiber wavelength-division multiplexing networks.