Aggregate Data Rate Research Articles

Experimental investigation of high-speed WDM-visible light communication using blue, green, and red InGaN µLEDs.

Micro-light-emitting diodes (µLEDs) hold significant promise for applications in displays and visible light communication (VLC). This study substantiates the viability of a wavelength division multiplexing (WDM)-VLC system using InGaN blue, green, and red µLED devices. The devices exhibited notable color stability and high modulation bandwidth due to the weakly polarized electric field in the blue and green semipolar devices and the stress-optimized structure in the red device. The aggregated data rate reached 11.14 Gbps. Moreover, the blue, green, and red InGaN µLEDs exhibited a wide color gamut, encompassing 119.4% of the NTSC and 89.2% of the Rec. 2020 standards, affirming the potential of blue, green, and red InGaN µLEDs for applications in full-color display and WDM-VLC systems.

Turbidity-tolerant underwater wireless optical communications using dense blue–green wavelength division multiplexing

Underwater wireless optical communication (UWOC) has demonstrated high-speed and low-latency properties in clear and coastal ocean water because of the relatively low attenuation ‘window’ for blue–green wavelengths from 450 nm to 550 nm. However, there are different attenuation coefficients for transmission in ocean water at different wavelengths, and the light transmission more seriously deteriorates with fluctuations in the water turbidity. Therefore, traditional UWOC using a single wavelength or coarse blue–green wavelengths has difficulty tolerating variations in water turbidity. Dense wavelength division multiplexing (WDM) technology provides sufficient communication channels with a narrow wavelength spacing and minimal channel crosstalk. Here, we improve the UWOC in clear and coastal ocean water using dense blue–green WDM. A cost-effective WDM emitter is proposed with directly modulated blue–green laser diodes. Dense wavelength beam combination and collimation are demonstrated in a 20-metre underwater channel from 490 nm to 520 nm. Demultiplexing with a minimum channel spacing of 2 nm is realized by an optical grating. Remarkably, our WDM results demonstrate an aggregate data rate exceeding 10 Gbit/s under diverse water turbidity conditions, with negligible crosstalk observed for each channel. This is the densest WDM implementation with a record channel spacing of 2 nm and the highest channel count for underwater blue–green light communications, providing turbidity-tolerant signal transmission in clear and coastal ocean water.

300-GHz-Band Diplexer for Frequency-Division Multiplexed Wireless Communication

We propose a novel silicon diplexer integrated with filters for frequency-division multiplexing in the 300-GHz band. The diplexer consists of a directional coupler formed of unclad silicon wires, a photonic bandgap-based low-pass filter, and a high-pass filter based on frequency-dependent bending loss. These integrated filters are capable of suppressing crosstalk and providing >15 dB isolation over 40 GHz, which is highly beneficial for terahertz-range wireless communications applications. We have used this diplexer in a simultaneous error-free wireless transmission of 300-GHz and 335-GHz channels at the aggregate data rate of 36 Gbit/s.

A 16-Gb/s/Wire 4-Wire Short-Haul Transceiver With Balanced Single-Ended Signaling (BASES) in 28-nm CMOS

This paper presents a 4-wire, 3-level, and 16-Gb/s/wire transceiver array for short-reach interconnects. The proposed transceiver adopts the balanced single-ended signaling (BASES) to reduce the simultaneous switching noise (SSN) and the electro-magnetic interference (EMI). The four transmit encoders and voltage-mode drivers produce three-level, common-mode-balanced, and multi-lane signals. The receive terminations and equalizers utilize the CM-balancing property of the BASES coding to recover the transmitted signals with a high noise rejection capability. The 4-wire transceiver was fabricated in a 28-nm CMOS technology and achieved a 64-Gb/s aggregate data rate with 3.15-pJ/bit energy efficiency.

Design of an efficient thulium-doped fiber amplifier for dual-hop earth to satellite optical wireless links

Optical wireless communication (OWC) links enable high-speed data transmission between earth stations and satellites. The propagation of optical signals through the atmosphere suffer from atmospheric attenuation and turbulence due to rain, fog, snow, clouds, and wind. The impact of these impairments on propagation of optical signals becomes more pronounced in the case of deep space links. Therefore, optical amplifiers of high output power and gain are extremely useful in deep space links to achieve error free transmission by improving the link budget. In this paper, we propose the design of an efficient Thulium-doped fiber amplifier (TDFA) as booster as well as an in-line based on dual-stage pumping scheme for employment in a dual-hop earth to satellite OWC Link. The pumping scheme, length of Thulium-doped fiber (TDF), and Tm 3+ concentration in the proposed design of TDFA are optimized in such a way so that high output power and gain are achieved for booster and in-line stages, respectively. Output power and gain of 4.6 W and 18.8 dB, respectively are achieved for signal power of 0 dBm at 1807.143 nm when TDFA is used as booster amplifier. Similarly, gain and output power of 66.6 dB and 1.5 W, respectively are achieved for signal power of −35 dBm at 1807.143 nm when TDFA is used as in-line amplifier. A noise figure (NF) of 4.4 dB is achieved for signal wavelength of 1807.143 nm and power of 0 dBm. Finally, the system level performance of the designed TDFA is investigated using bit error rate (BER) metric for a dual-hop earth to satellite OWC wavelength division multiplexed (WDM) transmission system of four quadrature phase shift keying (QPSK) modulated optical signals with an aggregate data rate of 104 Gbps. The BER results showed different possible ranges of error-free transmission at the forward error correction (FEC) limit of 10 - 4 for different values of atmospheric attenuation.

Hybrid-Mux Signal Structure and Resource Allocation for In-Band Distribution Link and ITND Transmission in SFN Environment

This paper investigates the multiplexing and resource allocation to improve the spectrum efficiency and reduce demultiplexing complexity and latency in the wireless in-band distribution link (IDL) and inter-tower networks and datacasting (ITND) for terrestrial broadcasting systems. A novel Hybrid-Mux technology is proposed, which combines orthogonal multiplexing (TDM/FDM), non-orthogonal multiplexing (NOM, or LDM), and hierarchical modulation (HM) with the non-uniform constellation (NUC). Hybrid-Mux technology can achieve high spectrum efficiency, low complexity, and low latency to provide versatile services of mobile/fixed broadcast services, inter-tower communication networks and datacasting, as well as the in-band distribution link to support SFN operation. Two Hybrid-Mux signal structures with 2-layer and 3-layer power-based non-orthogonal multiplexing of different broadcast and network data services are introduced. The throughput optimization of each Hybrid-Mux structure is formulated and resolved under the constraint of ITND and IDL data capacity, SNR requirement, and optimized NUC HM. Simulation results show that, by properly implementing resource allocation and constellation design, the proposed 3-layer Hybrid-Mux structures can achieve higher capacity than the simple 2-layer Hybrid-Mux structure, while the demodulation and demultiplexing complexity is not much increased. A 2-tier ITND service is proposed. It consists of a robust control and datacasting (ITCD) tier and a high data rate intertower networking (ITCN) link. This design can increase the total aggregated system data rate substantively. MIMO structures supporting ITND and IDL transmission are also proposed to further improve the spectrum efficiency.

Adaptive Transceiver Design for High-Capacity Multi-Modal Free-Space Optical Communications With Commercial Devices and Atmospheric Turbulence

In this paper, to achieve higher robustness against atmospheric turbulence for high-capacity free-space optical (FSO) communications, an adaptive multi-modal FSO transceiver has been designed and experimentally demonstrated. We show that based on the dynamically estimated channel state information, modulation formats and power for different transmit modes can be adaptively allocated at the transmitter side. Meanwhile, at the receiver side, we show that the most suitable multi-input/multi-output decoder can be selected and employed to meet the requirement of forward error correction at the minimal expense of power consumption. By employing time-division multiplexed transmitter and receiver emulation and a spatial light modulator for turbulence emulation, an aggregate data rate of 590 Gbit/s/wavelength has been achieved when suffering from strong atmospheric turbulence, verifying the feasibility of the proposed adaptive transceiver over a turbulent FSO link. Moreover, to demonstrate practical applicability, all key devices such as transponder, multiplexer, and demultiplexer are commercially available in this work.

Uplink and Downlink NOMA Based on a Novel Interference Coefficient Estimation Strategy for Next-Generation Optical Wireless Networks

Non-orthogonal multiple access (NOMA) has been widely recognized as a promising technology to improve the transmission capacity of wireless optical communication systems. NOMA considers the principle of successive interference cancellation (SIC) to separate a user’s signal at the receiver side. To improve the ability of optical signal detection, we developed a quantum dot (QD) fluorescent concentrator incorporated with multiple-input and single-output (MISO) to realize an uplink NOMA-based optical wireless system. However, inaccurate interference assessment of multiple users using the SIC detection algorithm at the receiver side may lead to more prominent error propagation problems and affect the bit error rate (BER) performance of the system. This research aims to propose a novel recurrent neural network-based guided frequency interference coefficient estimation algorithm in a NOMA visible light communication (VLC) system. This algorithm can improve the accuracy of interference estimation compared with the traditional SIC detection algorithm by introducing interference coefficients. It provides a more accurate reconstruction possibility for level-by-level interference cancellation and weakens the influence of error propagation. In addition, we designed uplink and downlink NOMA-VLC communication systems for experimental validation. When the power allocation ratio was in the range of 0.8 to 0.97, the experimental results of the downlink validated that the BER performance of both users satisfied the forward error correction (FEC) limit with the least squares (LS)-SIC and the long short-term memory recurrent neural networks (LSTM)-SIC detection strategy. Moreover, the BER performance of the LSTM-SIC algorithm was better than that of the LS-SIC algorithm for all users when the power allocation ratio was in the range of 0.92 to 0.93. In particular, our proposed system offered a large detection area of 2 cm2 and corresponding aggregate data rate up to 40 Mbps over 1.5 m of free space by using QDs, and we successfully achieved a mean bit error rate (BER) of 2.3 × 10−3 for the two users.

An 8b9b 77.44-Gb/s Noise-Immune Spatial-Delta Coded Transceiver for Short-Reach Memory Interfaces in 28-nm CMOS

A noise-immune spatial-delta coding (SDC) scheme is proposed for single-ended multi-lane links. The SDC technique allows differential sensing of single-ended PAM2 signals for high signal integrity while still achieving the same pin efficiency as the 8b9b data bus (DBI) scheme, providing high compatibility with conventional DDR interfaces. The SDC encoding/decoding functions are implemented with simple XOR gates to minimize power and latency overhead. Continuous-time linear equalizers in the receiver compensate for distortions in incoming pseudodifferential signals with high tolerance on dynamic common-mode switching associated with the SDC operation. An 8b9b SDC transceiver prototype array composed of nine data channels and a differential clock channel has been fabricated in 28-nm CMOS technology for demonstration. The transceiver array achieves a 77.44 Gb/s aggregate data rate with 9 wires at 9.68 Gbaud/s. The bit error rate is measured to be less than 1e-12 while consuming 4.9 pJ/b from a 1.25-V supply.

Hierarchical Bandwidth Modulations for Ultra-Broadband Communications in the Terahertz Band

Terahertz (THz)-band (0.1–10 THz) communication will be key in enabling high speed wireless links due to the wide available bandwidths. At THz frequencies, the path-loss is governed by high spreading loss due to small antenna apertures and by molecular absorption loss due to water vapor. The latter also determines the available transmission bandwidth, which shrinks with distance. Modulations that consider the high propagation loss and the distance-dependent bandwidth are needed to fully exploit the THz channel’s bandwidth. Using a hierarchical constellation to simultaneously service users at symbol rates, Hierarchical Bandwidth Modulation (HBM) leverages molecular absorption to increase aggregate data rates in a broadcast system while offering flexibility to receivers experiencing high path loss. This paper introduces HBM and evaluates its performance. The symbol error rate performance for a 4/M-QAM HBM system is derived and verified using simulations. These results are used to define the design constraints for an HBM system: the HBM functional region and transition region. The functional region is verified using an experimental testbed for ultrabroadband communications. The results show that with proper design HBM successfully achieves its goal to exploit the distance-dependent characteristics of the THz channel, to spatially multiplex users, and to increase the system capacity.

Over 23.43 Gbps visible light communication system based on 9 V integrated RGBP LED modules

In this paper, integrated transmitter modules with 9 V high-voltage light emitting diode (LED) chips and built-in hardware pre-equalization circuits are designed and fabricated for wavelength division multiplexing (WDM) visible light communication (VLC) system. The measured −3 dB electrical modulation bandwidths are 764.6 MHz, 929 MHz, 921.5 MHz and 756.6 MHz for the purple, blue, green and red channels, respectively, resulting in an aggregate bandwidth of about 3.37 GHz. Based on polar coding scheme combined with high-order quadrature amplitude modulation and orthogonal frequency division multiplexing (QAM-OFDM), experimentally, the maximum aggregate data rate for the offline VLC system exceeds 23.43 Gb/s in 1 m indoor free-space link and the bit error rates (BERs) of all wavelength channels are under 7% pre-forward error correction (pre-FEC) limit of 3.8×10−3. In particular, the blue-ray channel always presents zero BER, i.e. an infinity Q-factor, within the experiment condition range.

An Integrated Fiber-FSO-5G NR Sub-THz Link With 86.112 Gbps High Aggregate Data Rates

An integrated fiber-free-space optical (FSO)-fifth-generation (5G) new radio (NR) sub-THz link through a cross-media of 20 km single-mode fiber (SMF), 500 m optical wireless, and 0.5 m RF wireless is proposed and successfully implemented. 5G NR communication operates effectively with four sub-THz frequencies of 150, 175, 200, and 225 GHz. Each sub-THz frequency carries a 21.528-Gbps 32-QAM-OFDM signal. By transmitting four 5G sub-THz signals, an integrated fiber-FSO-wireless link with high aggregate data rates of 86.112 Gbps (21.528 Gbps × 4) is realized. It is an innovative link to extend 5G communications to 86.112 Gbps data rates over long-haul wired/wireless transmission. Satisfactorily low bit error rate (<3.8 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> forward error correction limit) and error vector magnitude (<10%) show that this newly demonstrated fiber-FSO-wireless link is promising for 5G NR communication in sub-THz band. It exhibits an excellent fiber-FSO-5G NR sub-THz link with the vantages of high accumulative data rates, long-haul wired-wireless transmission, and low complexity.

Optical Beam Steerable Visible Light Communication (VLC) System Supporting Multiple Users Using RGB and Orthogonal Frequency Division Multiplexed (OFDM) Non-Orthogonal Multiple Access (NOMA).

In order to achieve high-capacity visible light communication (VLC), five dimensions in physics, including frequency, time, quadrature modulation, space, and polarization can be utilized. Orthogonality should be maintained in order to reduce the crosstalk among different dimensions. In this work, we illustrate a high-capacity 21.01 Gbit/s optical beam steerable VLC system with vibration mitigation based on orthogonal frequency division multiplexed (OFDM) non-orthogonal multiple access (NOMA) signals using red, green, and blue (RGB) laser-diodes (LDs). The OFDM-NOMA can increase the spectral efficiency of VLC signal by allowing high overlapping of different data channel spectra in the power domain to maximize the bandwidth utilization. In the NOMA scheme, different data channels are digitally multiplexed using different levels of power with superposition coding at the transmitter (Tx). Successive interference cancellation (SIC) is then utilized at the receiver (Rx) to retrieve different power multiplexed data channels. The total data rates (i.e., Data 1 and Data 2) achieved by the R/G/B OFDM-NOMA channels are 8.07, 6.62, and 6.32 Gbit/s, respectively, achieving an aggregated data rate of 21.01 Gbit/s. The corresponding average signal-to-noise ratios (SNRs) of Data 1 in the R, G, and B channels are 9.05, 9.18 and 8.94 dB, respectively, while that of Data 2 in the R, G, and B channels are 14.92, 14.29, and 13.80 dB, respectively.

Dynamic MBSFN Beam Area Formation in 6G Multibeam Non-Terrestrial Networks

Providing innovative services and ensuring ubiquitous, ultrahigh-density, extreme-data-rate, and very low latency communications are essential for future sixth-generation systems, where the importance of non-terrestrial networks (NTNs) will incredibly rise. However, the management of both the capacity and the radio spectrum remains one of the main challenges, when a huge number of devices require access to dissimilar broadcast services at the same time. To cope with these issues, traditional single-beam satellite systems can be replaced with very high throughput satellite, where multibeam transmissions increase the capacity and improve the spectrum utilization while limiting interbeam interference. In this article, we propose a dynamic multicast/broadcast single-frequency network (MBSFN) beam area formation (D-MBAF) algorithm that dynamically groups beams into dedicated MBSFN beam areas (MBAs) to increase the aggregate data rate (ADR) of the multibeam NTN system and deliver a given video content to all the interested NTN terminals. D-MBAF leverages multicast subgrouping by clustering the NTN terminals into different MBAs that are simultaneously served with different data rates. Furthermore, the D-MBAF algorithm delivers the video content in different flows: the base layer with lower resolution and a set of enhancement layers with higher resolutions. Radio resources are efficiently allocated to avoid interference among the beams belonging to different MBAs. A simulation campaign is carried out under different scenarios to assess the effectiveness of the proposed D-MBAF algorithm in terms of mean throughput, ADR, resource block utilization, and number of sent layers. Obtained results confirm that the D-MBAF algorithm outperforms the single-frequency multibeam transmission and the multilayer video delivery schemes used as benchmarks.

Feasibility Study of Quasi-Optical MIMO Antennas for Radiative Near-Field Links

This article presents a feasibility study of single feed per beam quasi-optical (QO) antennas for enabling incoherent multiple-input multiple-output (MIMO) array front-end architectures at 270 GHz. The objective is to reach ultrafast and radiated energy efficient point-to-point (PtP) wireless links by exploiting the multimode capacity of radiative (Fresnel region) near-field links. In this article, we present a feasibility study of the number of independent links achievable with QO MIMO incoherent arrays. For this purpose, we present theoretical curves of the level of EM co-coupling and interference between the multiple modes versus the link distance. The study focuses at the 252–325 GHz spectral bandwidth defined by the new IEEE 802.15.3d standard. A specific and new MIMO array architecture operating at 270 GHz based on a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2 \times 2$ </tex-math></inline-formula> array of parabolic reflectors is proposed for a link distance of 100 m. The proposed PtP MIMO system is capable of generating 16 dual-polarized modes in a 70 GHz bandwidth with signal-to-interference ratio >17 dB and a power co-coupling coefficient of −3 dB without the need for interference cancelation techniques. Combining this architecture with wideband front ends could potentially lead to an aggregated data rate in the order of terabit per second in a PtP wireless line-of-sight link, not previously achieved experimentally to the best of authors’ knowledge.

High-speed long-distance visible light communication based on multicolor series connection micro-LEDs and wavelength division multiplexing

Multicolor series connection micro-LED arrays with emission wavelengths of violet, blue, green, and yellow were fabricated, and their optoelectronic properties and communication performances were investigated. The designed series connection micro-LED array exhibited the light output power of multiple milliwatts, whereas mostly keeping a slightly reduced modulation bandwidth, thus, enabling a higher signal-to-noise ratio compared to a single pixel and showing superior performance in the field of long-distance visible light communication (VLC). The achievable data rates of 400-, 451-, 509-, and 556-nm micro-LED arrays using bit/power loading orthogonal frequency division multiplexing were 5.71, 4.86, 4.39, and 0.82 Gbps, respectively. The aggregate data rate of 15.78 Gbps was achieved for the proof-of-concept wavelength division multiplexing system under a transmission distance of 13 m, which was the best data rate-distance product performance for the LED-based VLC to the best of our knowledge. In addition, the long-distance VLC based on yellow micro-LED was also demonstrated for the first time in this paper.

On‐Chip Polarization‐ and Frequency‐Division Demultiplexing for Multidimensional Terahertz Communication

AbstractIntegrated terahertz (THz) technology is of great significance for driving high‐speed communication, sensing, and imaging with its advantages of miniaturization, low cost, and high efficiency. Recent research has focused on highly‐efficient transmitters and ultrafast detectors, as well as exploring new devices for coupling, transmission, and polarization control. However, multidimensional on‐chip multiplexing and demultiplexing techniques in the THz region still remains unexplored, due to the lack of multifunctional integrated components and systems. Here, a novel silicon‐based integrated multidimensional THz (de)multiplexer for high‐capacity communication is proposed and demonstrated based on ring resonators and polarization beam splitter‐rotators, which simultaneously enable the manipulation of THz polarization and frequency. Furthermore, a THz communication system operating in the 380 GHz band is experimentally demonstrated. By using on‐chip polarization‐ and frequency‐division multiplexing techniques, an aggregate data rate of 8 Gbit s−1 is successfully achieved with quadrature phase‐shift keying modulation scheme. This work provides a spectrally efficient way for accelerating the development of on‐chip THz technologies and the application in future large‐volume communications.

Single-wavelength transmission at 1.1-Tbit/s net data rate over a multi-modal free-space optical link using commercial devices.

We employ commercial mode-selective photonic lanterns to implement mode multiplexing and demultiplexing for high-capacity free-space optical communications. Moreover, we design a time-division-multiplexed frame structure to efficiently emulate multiple independent transmitters with channelized precoding using only one transmitter. To maximize the throughput of the system, we optimize the modes selected for carrying data, and apply adaptive loading to different channels. By leveraging mode- and polarization-division multiplexing, the free-space optical data link comprising multiple independent channels provides an aggregate net data rate of 1.1 Tbit/s and net spectral efficiency of 28.35 bit/s/Hz. Different from many previous demonstrations based on delayed or partially delayed copies of identical data streams, to the best of our knowledge, ours is a record-high net data rate and net spectral efficiency achieved by a single-wavelength mode-division multiplexed free-space optical communication system with fully independent channels. Moreover, all key devices used in this work, including optical transponder, multiplexer, and demultiplexer are commercially available.

A Tb/s Indoor MIMO Optical Wireless Backhaul System Using VCSEL Arrays

In this paper, the design of a multiple-input multiple-output (MIMO) optical wireless communication (OWC) link based on vertical cavity surface emitting laser (VCSEL) arrays is systematically carried out with the aim to support data rates in excess of 1 Tb/s for the backhaul of sixth generation (6G) indoor wireless networks. The proposed design combines direct current optical orthogonal frequency division multiplexing (DCO-OFDM) and a spatial multiplexing MIMO architecture. For such an ultra-high-speed line-of-sight (LOS) OWC link with low divergence laser beams, maintaining alignment is of high importance. In this paper, two types of misalignment error between the transmitter and receiver are distinguished, namely, radial displacement error and orientation angle error, and they are thoroughly modeled in a unified analytical framework assuming Gaussian laser beams, resulting in a generalized misalignment model (GMM). The derived GMM is then extended to MIMO arrays and the performance of the MIMO-OFDM OWC system is analyzed in terms of the aggregate data rate. Novel insights are provided into the system performance based on computer simulations by studying various influential factors such as beam waist, array configuration and different misalignment errors, which can be used as guidelines for designing short range Tb/s MIMO OWC systems.

Metamaterial-enabled arbitrary on-chip spatial mode manipulation

On-chip spatial mode operation, represented as mode-division multiplexing (MDM), can support high-capacity data communications and promise superior performance in various systems and numerous applications from optical sensing to nonlinear and quantum optics. However, the scalability of state-of-the-art mode manipulation techniques is significantly hindered not only by the particular mode-order-oriented design strategy but also by the inherent limitations of possibly achievable mode orders. Recently, metamaterials capable of providing subwavelength-scale control of optical wavefronts have emerged as an attractive alternative to manipulate guided modes with compact footprints and broadband functionalities. Herein, we propose a universal yet efficient design framework based on the topological metamaterial building block (BB), enabling the excitation of arbitrary high-order spatial modes in silicon waveguides. By simply programming the layout of multiple fully etched dielectric metamaterial perturbations with predefined mathematical formulas, arbitrary high-order mode conversion and mode exchange can be simultaneously realized with uniform and competitive performance. The extraordinary scalability of the metamaterial BB frame is experimentally benchmarked by a record high-order mode operator up to the twentieth. As a proof of conceptual application, an 8-mode MDM data transmission of 28-GBaud 16-QAM optical signals is also verified with an aggregate data rate of 813 Gb/s (7% FEC). This user-friendly metamaterial BB concept marks a quintessential breakthrough for comprehensive manipulation of spatial light on-chip by breaking the long-standing shackles on the scalability, which may open up fascinating opportunities for complex photonic functionalities previously inaccessible.