Ultra-high Bit Research Articles

Enabling ultra-high bit rate transmission with CFBG as dispersion compensator in an OptiSpan 240 km DWDM network

Abstract In this paper, a dispersion compensation technique for an ultra-long haul optical network utilizing a chirped fiber Bragg grating (CFBG) is presented. A high bit-rate signal of 40 Gbps is inputted into each channel. The CFBG, employed for dispersion compensation, is positioned after demultiplexing, enabling effortless network upgrades. The grating parameters of the implemented CFBG are mathematically analyzed and optimized to counteract net dispersion of over 3153 ps/nm across the channel. The design is verified using the OptiSystem software, resulting in a successful transmission up to 240 km with an average Q-factor of 8.09, utilizing an amplification gain of 49.5 dB. Additionally, the achieved optical signal-to-noise ratio (OSNR) level using the symmetrical amplification technique surpasses the acceptable value, with an average bit error rate of 10−16.

Planning tools for next-generation DSP-based passive optical networks above 50G [Invited Tutorial

Next-generation optical access networks are evolving towards ultra-high bit rates (above 50 Gbps per wavelength) and extended fiber reach architectures. This trend will likely push the optoelectronics to their limits, thus requiring impairment compensation based on digital signal processing (DSP) techniques in the transceivers. In this paper, which is an invited follow-up of a tutorial given at ECOC 2023, we first present an overview of this evolving scenario and then propose a unified analytical model that is able to predict the performance of these new systems for both direct-detection and coherent transceiver types. We believe that this model can be useful for preliminary scalability studies of new access architectures (as it happens in international standardization bodies). Moreover, when they are deployed, it can be useful as a base for network planning tools, particularly if future transceivers will be, as expected, highly reconfigurable at the DSP level.

A Novel Array Programming Scheme for Large Matrix Processing in Flash-Based Computing-in-Memory (CIM) With Ultrahigh Bit Density

Computing-in-memory (CIM) architecture is a promising approach to breaking the bottleneck in von Neumann’ architecture. To shed light on large matrix operations in flash-based CIM with ultrahigh bit density (4–5 bit/cell), this work presents a novel incremental positive–negative step pulse programming (IPNPP) array programming scheme. The proposed scheme utilizes positive pulses for rough tuning and subsequent negative pulses for fine-tuning to cells’ threshold voltages. By adopting the IPNPP scheme in 55-nm NOR flash CIM arrays, it is shown that the latency and power consumption could be lowered effectively. As for image dehazing of ultrahigh-resolution images, ~180.6-TOPS/W high energy efficiency with great accuracy and variation tolerability has been demonstrated successfully. Our results indicate that the IPNPP is effective for CIMs that require high precision and low power consumption.

Generation, based on compression of similariton, of pulses at 100 GHz–2.5 THz and ultra-high bit rates of 40 Gb/s–1.28 Tb/S by OTDM

Generation, based on compression of similariton, of pulses at 100 GHz–2.5 THz and ultra-high bit rates of 40 Gb/s–1.28 Tb/S by OTDM

Phase Shift Optimization Algorithm for Achievable Rate Maximization in Reconfigurable Intelligent Surface-Assisted THz Communications

Terahertz (THz) band communications are considered a crucial technology to support future applications, such as ultra-high bit rate wireless local area networks, in the next generation of wireless communication systems. In this work, we consider an ultra-massive multiple-input multiple-output (UM-MIMO) THz communication system operating in a typical indoor scenario where the direct link between the transmitter and receiver is obstructed due to surrounding obstacles. To help establish communication, we assume the aid of a nearby reconfigurable intelligent surface (RIS) whose phase shifts can be adjusted. To configure the individual phase shifts of the RIS elements, we formulate the problem as a constrained achievable rate maximization. Due to the typical large dimensions of this optimization problem, we apply the accelerated proximal gradient (APG) method, which results in a low complexity algorithm that copes with the non-convex phase shift constraint through simple element-wise normalization. Our numerical results demonstrate the effectiveness of the proposed algorithm even when considering realistic discrete phase shifts’ quantization and imperfect channel knowledge. Furthermore, comparison against existing alternatives reveals improvements between 30% and 120% in terms of range, for a reference rate of 100 Gbps when using the proposed approach with only 81 RIS elements.

Ultra-high speed random bit generation based on Rayleigh feedback assisted ytterbium-doped random fiber laser

In this paper, we propose an ultra-high speed random bit generator without the time-delay signature based on an ytterbium-doped random fiber laser (YRFL) with Rayleigh scattering feedback. The spectrum of the YRFL has a relatively broad bandwidth (0.35 nm) and the lasing temporal intensity shows random fluctuations without cavity induced time-delay signatures (TDS), which are essential for ultra-high speed random bit generation The chaotic signal and its time-delayed signal sampling at 40 Giga samples per second (GS/s) are converted to digital 8-bit signals. By selecting 5 least significant bits from each 8-bit digital signal and using bitwise exclusive-OR operation, we experimentally achieve 200 Gbps physical random bit generation based on ytterbium-doped random fiber laser with the verified randomness. The combination of broadband emission and free of TDS makes random fiber lasers new promising sources for high performance random bit generation in a simple and compact configuration, which has a great potential in cryptography and secure communication applications.

High Figure of Merit Optical Buffering in Coupled-Slot Slab Photonic Crystal Waveguide with Ionic Liquid.

Slow light with adequate low group velocity and wide bandwidth with a flat band of the zero-dispersion area were investigated. High buffering capabilities were obtained in a silicon-polymer coupled-slot slab photonic crystal waveguide (SP-CS-SPCW) with infiltrating slots by ionic liquid. A figure of merit (FoM) around 0.663 with the lowest physical bit length of 4.6748 µm for each stored bit in the optical communication waveband was gained by appropriately modifying the square air slot length. Posteriorly, by filling the slots with ionic liquid, the was enhanced to be 4.2817 μm with the highest FoM of 0.72402 in wider transmission bandwidth and ultra-high bit rate in terabit range, which may become useful for the future 6G mobile communication network. Ionic liquids have had a noticeable effect in altering the optical properties of photonic crystals. A polymer was used for the future incorporation of an electro-optic effect in buffers to realize the dynamic controlling of optical properties. Ionic liquids enhanced the transmission rate through optical materials. Additionally, the delay time in the ns-range was achieved, providing longer delay and ultra-low group velocity, which is important for light-matter interaction in light amplifiers and nonlinear devices.

Quantum dot semiconductor optical amplifier: investigation of ultra-fast cross gain modulation in the presence of a second excited state

In this paper, a theoretical model is proposed to investigate and analyze an ultra-fast cross gain modulation (XGM) in quantum dot semiconductor optical amplifiers (QDSOAs). The proposed model is based on a set of carrier’s rate equations, propagation equations for pump and probe signals and phase equations. To investigate the XGM mechanism, nonreturn-to-zero (NRZ) pulse trains with various bitrates are supposed to propagate as the input pump signals through the QDSOA’s active layer. The probe signal is assumed to be a continuous wave (CW) signal. Furthermore, optical gain of quantum dots (QDs) is calculated using a density matrix approach. For the first time, to the best of our knowledge, a second excited state is considered in the band diagram of QDs, to obtain the ultra-fast XGM in QDSOAs. Therefore, in the presented model, the rate equations are written for the carriers in the ground state, first and second excited states (ES2), continuum state and the wetting layer. In the presence of ES2, gain recovery time and gain saturation is reduced and, therefore, ultra-high bitrate pulse trains can be modulated with negligible pattern effects and wave distortion. The effect of the injection current density increment and carrier’s relaxation lifetime decrement are illustrated to show the improvement in the XGM mechanism in the QDSOA. It is shown theoretically that ultra-high bitrate XGM up to 450 Gbps is possible due to the reduced gain recovery time in the presence of ES2. It is demonstrated that at the same pump power for higher injection current densities and lower carrier relaxation lifetimes, the pattern effect and wave distortion has almost vanished. Although, in this case, the extinction ratio (ER) is decreased. It is shown that to recover the ER, the input pump power should be increased. Furthermore, based on the results in the presence of ES2, the ER is decreased by 0.5 dB.

Analysis of EDFA Parameters Amenable for Ultra High Bitrate Based DWDM System

Exponential growth in data centric services often leads to overhaul of backbone and access networks. Design of high transmission capacity of up to 640Gbps DWDM system with EDFA was analyzed to meet less distortion in an optical backhaul system. Further the length of EDFA and pump power of EDFA are varied and evaluated for 16, 32 and 64 channels data transmission efficiently, such that it caters to the requirements of access networks. Parameters such as pump power and length of optical Amplifier in DWDM system are studied and its output characteristics are analyzed from co-channel and counter-channel propagations. The dependences parameters such as maximal BER, minimal SNR values among all the channels with signal power detection for each pump power results are obtained and compared to the same. Evaluations of Quality factor and BER for each pump power with all three configurations were done for different lengths of EDFA. The DWDM system with suggested optimum EDFA parameters gives good results in terms of Q-factor, eye opening and BER.

Digital Orthogonal-Filters Enhanced Spatial Modulation for High-Speed Indoor Optical Wireless Communications

Spatial modulation (SM) has been proposed and studied in high-speed indoor optical wireless communication systems to improve the spectral efficiency and system capacity by exploring the spatial domain information of transmitters. However, the correct detection of active transmitter(s) is critical, and it typically requires precise channel state information (CSI) and low correlation between channel gains. To overcome this limit, in this paper an orthogonal-filters enhanced SM scheme is proposed for high-speed indoor optical wireless communication systems, where the use of orthogonal-filters can improve the correct detection of active transmitter(s) significantly. The proposed scheme is experimentally demonstrated, and results show that with 4-pulse amplitude modulation (PAM-4) and two transmitters, 7.5 Gb/s optical wireless data transmission is achieved with 2.5 GS/s symbol rate. The power penalty of proposed scheme on the receiver sensitivity is negligible, and the active transmitter(s) can be correctly detected even under high channel correlations and without CSI. The scalability of proposed orthogonal-filters enhanced SM scheme is also studied, and it is shown that higher dimensions can be realized to achieve higher spectral efficiency, which provides a promising solution in indoor optical wireless communications to achieve ultra-high bit rate.

Rain attenuation and worst month statistics verification and modeling for 5G radio link system at 26 GHz in Malaysia

AbstractThe explosive daily dependence on wireless communication services necessitates the research to establish ultrawideband communication systems with ultrahigh bit rate transmission capabilities. The advent of the fifth‐generation (5G) microwave link transmitting at millimeter‐wave (mm‐wave) frequency band is a promising technology to accommodate the escalating demand for wireless services. In this frequency band, however, the behavior of the transmission channel and its climatic properties are a major concern. This is of particular importance in tropical regions where the climate is mainly rainy with large raindrop size and high rainfall rate that may interact destructively with the propagating signal and cause total attenuation for the signal. International Telecommunication Union (ITU) introduced a global rain attenuation model to characterize the effect of rain on the propagating signal at a wideband of frequencies. The validity of this model in tropical regions is still an open question for research. In this paper, real measurements are conducted at Universiti Teknologi Malaysia (UTM), Johor Bahru, Malaysia, to investigate the impact of rain on the propagation of mm‐waves at 26 GHz over the microwave 5G radio link system. Rainfall rate and rain attenuation data sets are collected for one year at one sample per min sampling rate. Both data sets are used to estimate signal propagation conditions in comparison to the ITU model prediction. From the presented results, it is found that at 0.01% percentage of time and rainfall rate of about 120 mm/hr, the propagated signal would experience 26.2 dB losses per kilometer traveled. In addition, there is a significant deviation between the empirical estimation of the worst month parameters and the ITU worst month parameter prediction. Similarly, rainfall rate and rain attenuation estimated through the ITU model imposes a large deviation as compared with the measurements. Furthermore, more accurate empirical worst month parameters are proposed that yielded more accurate estimation of the worst month rainfall and rain attenuation predictions in comparison to the ITU model predictions.

Ultra-High bit rate all-optical AND/OR logic gates based on photonic crystal with multi-wavelength simultaneous operation

ABSTRACTIn this paper, a novel two-dimensional photonic crystal based all-optical AND/OR logic gates are designed, simulated and optimized. The structure is built on a linear square lattice photonic crystal platform. A multi-wavelength operation, together with a simultaneous operation, is achieved at ultra-high bit rates. The concurrent operation is attained without altering the proposed design continuously, as stated in the literature. It provides simplicity because there is no auxiliary input required along with the absence of externally attached phase shift units. The enhancement process has been done to the rod radius. A magnificent representation tool is developed. The benefit of the mentioned tool lies in the data combination of different operating wavelengths, contrast ratio, and bit rate; which will establish an efficient optimization process. Each gate is enhanced independently, then an overall improvement has been done. As a result, the operation at 1.52 µm will provide a successful multi logic gate operation with ultra-high bit rates of 6.76 and 4.74 Tbit/s for AND and OR logic gates, respectively. The design has an acceptable size of (19.8 × 12.6 µm) and a contrast ratio of 9.74 dB and 17.95 dB for the designed AND and OR gate, respectively. The design is highly sensitive to the waveguide length to verify the gates on demand.

A survey on key roles of optical switching and labeling technologies on big data traffic of Data Centers and HPC environments

The tremendous big data and IP traffic growth rate between interconnected Data Centers (DC) and High Performance Computing (HPC) environments have imposed the need for ultrahigh link capacities and ultrahigh packet switching speeds, at network nodes. In order to overcome these ultrahigh demands, and particularly packet routing and forwarding speeds, long tested and established technologies, such as optical switching and labeling technology, seem to provide adequate solutions, not only by conveying ultrahigh bit rate data streams, but also by achieving multi Tb/s cross connection throughputs, in a cost and energy efficient way. By adoption of optical switching and labeling technology, big data streams are propagating directly in optical layer, thus lessening down bottlenecks, latency issues, and multi stage hierarchy layering. This paper, apart from optical switching and labeling potentials, investigates thoroughly other critical issues, strictly related to the proper choice of employing a switching architecture layout, such as its implementation technology, its elasticity potentials, in terms of flexible bandwidth (BW) provisioning, its adopted control plane lying on top of data infrastructure plane, providing cognition, control and orchestration over its network elements, as well as related to the proper choice of optical labeling techniques adopted, in conjunction with current, advanced, coherent, multi level modulation formats, for ultrahigh link capacities and packet switching speed demands of scalable, big data interconnected DCs and HPC environments.

Ultrahigh-speed violet laser diode based free-space optical communication beyond 25 Gbit/s

Violet laser diode (VLD) based ultrahigh-speed free-space optical (FSO) system is demonstrated for point-to-point data transmission. By directly encoding the VLD with 64-quadrature amplitude modulation discrete multi-tone (64-QAM DMT) data stream for optical wireless communication through 0.5–10 m in free space, the point-to-point VLD-based FSO link allows delivering the 64-QAM DMT data at an ultrahigh bit rate of up to 26.4 Gbps. After receiving with a high-speed p-i-n photodiode, such a VLD-FSO link can provide clear constellation plot with error vector magnitude (EVM) of 8.57%, signal-to-noise ratio (SNR) of 21.34 dB and bit error ratio (BER) of 3.17 × 10−3 under forward-error-correction criterion. The EVM increases from 8.8% to 9.4% and the SNR decreases from 21.1 to 20.6 dB to slightly degrade the reachable data rate from 25.8 to 24 Gbit/s with transmission distance lengthening from 3 to 10 m.

Performance Investigation of Inter-satellite Optical Wireless Communication (IsOWC) System Employing Multiplexing Techniques

With the increasing advent in digital age, it is required to set up an inter-satellite optical wireless communication (IsOWC) that can support ultra-high bit rate. Here the proposed IsOWC system is implemented using dense wavelength division multiplexing and sub carrier multiplexing. The proposed model is designed to work at three different wavelengths i.e. 850, 1064 and 1550 nm. The performance of the proposed models is measured in terms of Q-Factor and Bit error rate at a different transmitted optical power level and transmission bit rate. It is observed that by incorporating multiplexing techniques, higher transmission bit rates can be achieved. It is observed that maximum bit rate achieved by proposed IsOWC system employing multiplexing technique is multiple of the number of channels used in multiplexing i.e. four times the individual PSK modulated optical system. Finally, it is concluded that IsOWC system employing multiplexing techniques provides enhanced performance than single PSK modulated optical wave with existing optical infrastructure.

Controlled optical photonic crystal AND gate using nematic liquid crystal layers

Two optical AND gates built in 2D photonic crystal (PhC) platform have been proposed and numerically simulated using 2D finite element method (FEM). The suggested logic gates consist of five PhC waveguides and silicon annular ring resonator filled by nematic liquid crystal (NLC) of type E7. The first proposed AND gate can handle two inputs and support two operating wavelengths, λ = 1.5 and 1.55 µm. However, the second proposed AND gate can handle three inputs at λ = 1.5 µm. The reported logic gates offer high and low transmission levels with a threshold of 0.5 and an ultra-high bit rate of not less than 0.3 Tbits/s. Further, the suggested AND gates operation can be switched off by using the NLC layer.

Tunable optical delay line for optical time-division multiplexer

A novel three-stage all-pass filter (APF) is proposed as a tunable optical delay line to construct an optical time division multiplexer (OTDM), with which, we can get ultrahigh bit rates with several low-speed channels. The proposed design mitigates the deleterious effects of group delay dispersion and provides wide bandwidth with small ripples and continuously tunable long delays achieved with small variations in the effective refraction index, making it suitable for high-speed optical networks on chip.

Novel Plasmonic Data Storage Based on Nematic Liquid Crystal Layers

In this paper, compact plasmonic data storage with high-speed sequential writing/reading rate has been proposed and numerically simulated using two-dimensional finite difference time domain method. The proposed storage is composed of a combination of two nematic liquid crystal (NLC) layers and nano-silver sheet perforated with two rectangular nano-holes. The suggested storage has been designed for storing visible light in one of the two nano-holes based on the biasing states of NLC layers. Tuning the dimensions of the proposed storage results in storing three different binary states “01,” “10,” and “11” with 0.4 power absorption efficiency, 13 dB crosstalk and 1 Gbps sequential writing/reading rate. It is expected that such proposed two-bit binary storage can be used as a basic unit for constructing large scale storage device with high storage capacity and ultra-high bit rate.

PERFORMANCE EVALUATION OF 1 TBPS QPSK DWDM SYSTEM OVER ISOWC

Optical wireless communications has been in latest trends of high speed communications. They enable the use of optical wireless channel in applications like inter satellite links and underwater communications etc. In this paper, we communicate an ultra high bit rate i.e. 1 Tbps (10 x 100 Gbps) QPSK WDM System over optical Wireless communication Link. The system is a Line of Sight optical wireless link incorporating Coherent QPSK modulation Scheme for10 channels each at 100 Gbps The performance is evaluated in terms of Q-Factor and Minimum Bit Error Rate which are noticed to be in acceptable standards. The Link is analyzed under various parameters such as Power, Distance etc and maximum achievable distance is noticed to be 50,000 km at power values ranging from 0 dBm to 40 dBm. Key WordsWDM, CO-QPSK, OWC ---------------------------------------------------------------------***---------------------------------------------------------------------

Fabrication of FePt and CoPt Magnetic Nanodot Arrays by Electrodeposition Process

Fabrication of Co-Pt and Fe-Pt ferromagnetic nanodot arrays for the application of ultra-high density bit patterned media (BPM) by electrochemical processes was described. In order to form patterned substrates for nanodot arrays with the density higher than 1 Tbit/inch2, electron beam lithography technique was employed. Nanopatterns with 25 nm and 18 nm pitch, which correspond to 1 and 2 Tbit/inch2 were successfully formed by optimizing the condition of the lithography process, and Co-Pt and Fe-Pt with relatively high coercivity of 4.8 kOe and 10.3 kOe were formed by electrodeposition. By utilizing the nanopatterned substrates, Co-Pt and Fe-Pt nanodot arrays with 25 nm and 35 nm pitch were uniformly formed. These results demonstrate capability of the electrochemical processes for fabricating magnetic nanodot arrays with Tbit-level density.