Large Bandwidth Research Articles

Photonic-frequency-interleaving-enabled broadband receiver with high reconfigurability and scalability

The photonic frequency-interleaving (PFI) technique has shown great potential for broadband signal acquisition, effectively overcoming the challenges of clock jitter and channel mismatch in the conventional time-interleaving paradigm. However, current comb-based PFI schemes have complex system architectures and face challenges in achieving large bandwidth, dense channelization, and flexible reconfigurability simultaneously, which impedes practical applications. In this work, we propose and demonstrate a broadband PFI scheme with high reconfigurability and scalability by exploiting multiple free-running lasers for dense spectral slicing with high crosstalk suppression. A dedicated system model is developed through a comprehensive analysis of the system non-idealities, and a cross-channel signal reconstruction algorithm is developed for distortion-free signal reconstruction, based on precise calibrations of intra- and inter-channel impairments. The system performance is validated through the reception of multi-format broadband signals, both digital and analog, with a detailed evaluation of signal reconstruction quality, achieving inter-channel phase differences of less than 2°. The reconfigurability and scalability of the scheme are demonstrated through a dual-band radar imaging experiment and a three-channel interleaving implementation with a maximum acquisition bandwidth of 4 GHz. To the best of our knowledge, this is the first demonstration of a practical radio-frequency (RF) application enabled by PFI. Our work provides an innovative solution for next-generation software-defined broadband RF receivers.

Broadband MIMO all-optical unitary converter based on compact multimode interference on LNOI

We propose and demonstrate a reconfigurable 4 × 4 multi-input multi-output (MIMO) all-optical unitary converter (OUC) based on non-uniform multimode interference (nMMI-OUC) on a lithium-niobate-on-insulator (LNOI) platform, which has the advantages of broadband operation, compactness, low loss, and fabrication-friendliness. To enhance the bandwidth, compact non-uniform multimode interference is utilized to replace uniform multimode interference, achieving the same cross talk and larger bandwidth. Compared with OUC based on uniform multimode interference (uMMI-OUC), the couplers using nMMI-OUC are only half length. The experimental results show that the reconfigurable four mode demultiplexing have been realized with wavelength-dependent loss of less than 3 dB and cross talk of less than −17.3 dB over 100 nm (from 1520 nm to 1620 nm) wavelength range and ∼0.21 dB/coupler at 1550 nm wavelength for nMMI-OUC.

Multi‐Layered Structure as an Efficient Design for Improving Electromagnetic Wave Absorbing Properties of Polypropylene/EVA/Carbon Nanotube Composites

ABSTRACTFlexible and lightweight conducting polymer composites for application as electromagnetic wave absorbing (EMWA) materials were prepared by a one‐step melt‐blending procedure using a polypropylene/EVA (50:50 wt%) blend filled with carbon nanotube. The co‐continuous structure and the preferential localization of CNT in the EVA phase and at the interface are responsible for the low percolation threshold (0.02 vol%) and a conductivity of 10−3 S m−1 with 1.5 wt% of CNT. Metal‐backed configuration was used for measuring the electromagnetic attenuation in both X‐ (8–12 GHz) and Ku‐band (12–18 GHz). Samples 3 mm thick were compared with three‐layered structures constituted by three layers of 1 mm each. The best EMWA response in terms of minimum reflection loss (RL) (−35.5 dB) and large effective absorption bandwidth (EAB) (6.6 GHz) was observed for the three‐layered system with the appropriate arrangement. The low cost of polymer components and processing conditions, lightweight, and processability, due to the low amount of CNT, make this system a promising candidate for applications in both civilian and military areas as telecommunication and stealth technology.

Acquiring pulse a priori information for chirp transform spectrometer systems through phase error measurements

Abstract With the rapid advancement in deep-space exploration, back-end systems such as Chirp Transform Spectrometers (CTS) must be equipped with larger bandwidths, higher frequency resolutions, and enhanced sensitivities. Phase errors in chirp signals distort pulse compression waveforms, significantly affecting CTS system performance. To correct the distorted pulses, we acquire a priori information about the pulse waveform by measuring the phase errors in the CTS system. This paper measures and analyzes phase errors in the expander and compressor signals of a 1GHz bandwidth CTS system. We discuss the impact of these phase errors on pulse waveforms, system frequency resolution, sensitivity, and other critical performance parameters. Additionally, we plot the in-band phase error curves for the system. By utilizing these phase error curves, we can determine the phase error for any input frequency, thereby providing valuable prior information for pulse compression waveform correction. This approach is crucial for guiding subsequent error optimization and compensation in the CTS system.

640 Gbit/s FSO turbulence-resilient field trial utilizing the cylindrical vector beam.

Free-space optical (FSO) communication has the advantages of large bandwidth and high security and being license-free, making it the preferred solution for addressing the "last kilometer" of information transmission. However, it is susceptible to fluctuations in the received optical power (ROP) due to atmospheric turbulence and pointing errors, resulting in the inevitable free-space optical communication transmission performance degradation. In this work, we experimentally verified the turbulence resistance of the cylindrical vector beam (CVB) over a 3 km long free-space field trial link. A transmission capacity of 640 Gbit/s was conducted by utilizing a 20 GBaud 16-quadrature amplitude modulation (16QAM) through eight-wavelength multiplexing. The experimental results show that the CVB exhibits stronger turbulence resilience compared to the scalar circularly polarized Gaussian beam. Under moderately strong turbulence conditions, the communication stability probability of the first-order CVB improves by about 1/3 compared to the Gaussian beam, while for that of the second-order, the CVB is improved by about 1/5.

High-power high-performance radio-over-fiber link for minimalist wireless base station.

Broadband minimalist wireless base stations without energy-consuming electrical power amplifiers are the rosy scenario of the next-generation wireless communication systems. High-power radio-over-fiber (RoF) links, which are featured by large operation bandwidths, are regarded as the supporting technology for realizing such a vision. Nevertheless, the severe signal-to-noise ratio (SNR) deterioration induced by the second Brillouin scattering in high-power and long-distance RoF links must be first solved. Here, an approach to suppressing the secondary Brillouin scattering-induced SNR deterioration in high-power long-distance RoF links is proposed and demonstrated based on phase modulation driven by a sinusoidal signal. In the proof-of-concept experiment, the Brillouin threshold in a high-power RoF link involving a spool of single-mode fiber (SMF) with a length of 10 km is increased by more than 5 dB with the assistance of phase modulation. The SNR is improved by 31 dB when the optical power injected into the SMF is 22 dBm. In addition, the error vector magnitude (EVM) is optimized from 31.71% to 0.62% for transmitting a 256-QAM wireless communication signal with a center frequency of 5 GHz and a bandwidth of 6.75 MHz in this RoF link under the injected optical power of 22 dBm. Based on this high-power RoF link, a minimalist wireless base station utilizing a photodetector-direct-drive antenna is realized. This scheme is feasible for transmitting broadband wireless communication signals, where a 64-QAM orthogonal frequency division multiplexing (OFDM) wireless communication signal with a center frequency of 10 GHz and a bandwidth of 400 MHz has achieved high-quality transmission in this high-power RoF link under an injected optical power of 22 dBm.

Desain Jaringan Fiber to The Home di Desa Butuh Kidul

This study aims to design a Fiber to the Home (FTTH) network in Butuh Kidul Village, Tengaran District, Semarang Regency. In today's digital era, access to fast and stable internet is a fundamental need for communities. However, many rural areas in Indonesia, including Butuh Kidul Village, still lack adequate internet access. FTTH networks provide a solution by utilizing fiber optic cables that can transmit data at high speeds and with large bandwidth capacity. This research employs the Passive Optical Network (PON) method as the network architecture to enhance efficiency and scalability. The expected outcome is that the local community will benefit from improved internet access, supporting digital village programs and enhancing the quality of life and economic potential. This research is anticipated to serve as a reference for similar network developments in other rural areas.

All-Fiber Micro-Ring Resonator Based p-Si/n-ITO Heterojunction Electro-Optic Modulator.

With the rapid advancement of information technology, the data demands in transmission rates, processing speed, and storage capacity have been increasing significantly. However, silicon electro-optic modulators, characterized by their weak electro-optic effect, struggle to balance modulation efficiency and bandwidth. To overcome this limitation, we propose an electro-optic modulator based on an all-fiber micro-ring resonator and a p-Si/n-ITO heterojunction, achieving high modulation efficiency and large bandwidth. ITO is introduced in this design, which exhibits an ε-near-zero (ENZ) effect in the communication band. The real and imaginary parts of the refractive index of ITO undergo significant changes in response to variations in carrier concentration induced by the reverse bias voltage, thereby enabling efficient electro-optic modulation. Additionally, the design of the all-fiber micro-ring eliminates coupling losses associated with spatial optical-waveguide coupling, thereby resolving the high insertion loss of silicon waveguide modulators and the challenges of integrating MZI modulation structures. The results demonstrate that this modulator can achieve significant phase shifts at low voltages, with a modulation efficiency of up to 3.08 nm/V and a bandwidth reaching 82.04 GHz, indicating its potential for high-speed optical chip applications.

Subwavelength grating-assisted high-performance on-chip TM polarizer with large bandwidth

Subwavelength grating-assisted high-performance on-chip TM polarizer with large bandwidth

Reducing heat load density with asymmetric andinclined double-crystal monochromators: principles and requirements revisited.

xxxx Asymmetric double-crystal monochromators (aDCMs) and inclined DCMs (iDCMs) can significantly expand the X-ray beam footprint and consequently reduce the heat load density and gradient. Based on rigorous dynamical theory calculations, the major principles and properties of aDCMs and iDCMs are presented to guide their design and development, particularly for fourth-generation synchrotrons. In addition to the large beam footprint, aDCMs have very large bandwidths (up to ∼10 eV) and angular acceptance, but the narrow angular acceptance of the second crystal requires precise control of the relative orientations and strains. Based on Fourier coupled-wave diffraction theory calculations, it is rigorously proved that the iDCM has almost the same properties as the conventional symmetric DCM, including the efficiency, angular acceptance, bandwidth, tuning energy range and sensitivity to misalignment. The exception is that, for the extremely inclined geometry that can achieve very large footprint expansion, the iDCM has (beneficially) a larger bandwidth and wider angular acceptance. Inclined diffraction has the `rho-kick effect' that can be cancelled by the second reflection of the iDCM (even with misalignment), except that inhomogeneous strains may cause non-uniform rho-kick angles. At present, fabrication/mounting-induced strains pose low risk since they can be controlled to <0.5 µrad over large areas. The only uncertain challenge is the thermally induced strains, yet it is estimated that these strains are naturally lowered by the large footprint and may be further mitigated by optimized cryogenic cooling to the 1-2 µrad level. Overall, aDCMs and iDCMs have more stringent requirements than normal DCMs, but they are feasible schemes inpractice.

Large Modulation Bandwidth GaN-Based Micro-LED Arrays on Si Substrates With Graded in Composition Barriers

Large Modulation Bandwidth GaN-Based Micro-LED Arrays on Si Substrates With Graded in Composition Barriers

Performance of Ad Hoc Wireless Networks under Coexistence Scenario: A Case Study

Owing to the possibility of interference, signal contention, and performance degradation, coexisting IEEE 802.11 (WiFi) and IEEE 802.15.4 (Zigbee, 6LoWPAN) technologies in the 2.4 GHz ISM band presents considerable issues. More packet loss, delay, and decreased throughput for low-power networks can arise from IEEE 802.11's larger bandwidth, higher transmission power, and higher data rates overpowering IEEE 802.15.4's lower power and narrower bandwidth transmissions. This work explores the main facets of their coexistence, emphasising the effects of interference on performance measures including throughput, latency, and energy efficiency and frequency overlap. Dynamic frequency selection and channel allocation algorithms are only a few of the interference reduction techniques that are examined in the analysis. This research offers valuable insights into the more harmonious coexistence of these two wireless technologies in shared surroundings, enabling dependable operation for low-power IoT networks and high-speed Wi-Fi applications. These insights are gained through simulation and experimental validation.

Impact of Cell Layout on Bandwidth of Multi-Frequency Piezoelectric Micromachined Ultrasonic Transducer Array.

Piezoelectric micromachined ultrasonic transducers (PMUTs) show considerable promise for application in ultrasound imaging, but the limited bandwidth of the traditional PMUTs largely affects the imaging quality. This paper focuses on how to arrange cells with different frequencies to maximize the bandwidth and proposes a multi-frequency PMUT (MF-PMUT) linear array. Seven cells with gradually changing frequencies are arranged in a monotonic trend to form a unit, and 32 units are distributed across four lines, forming one element. To investigate how the arrangement of cells affects the bandwidth, three different arrays were designed according to the extent of unit aggregation from the same frequency. Underwater experiments were conducted to assess the acoustic performance, especially the bandwidth. We found that the densest arrangement of the same cells produced the largest bandwidth, achieving a 92% transmission bandwidth and a 50% burst-echo bandwidth at 6 MHz. The mechanism was investigated from the coupling point of view by finite element analysis and laser Doppler vibrometry, focusing on the cell displacements. The results demonstrated strong ultrasound coupling in the devices, resulting in larger bandwidths. To exploit the advanced bandwidth but reduce the crosstalk, grooves for isolation were fabricated between elements. This work proposes an effective strategy for developing advanced PMUT arrays that would benefit ultrasound imaging applications.

Performance Analysis of fso Communication system with Different Modulation Schemes

Free-space optical communication (FSO) is a technology which use optical signals to transmit data wirelessly, providing a viable alternative to conventional wired systems. The Free Space Optical (FSO) communication system has emerged as an attractive option due to its large license free bandwidth, high security and low cost It is one of the very promising technologies for wireless communication. However, the sensitivity to weather conditions is one of the major disadvantage of FSO systems. Weather factors, such as rain, fog, snow, and dust, can significantly attenuate the optical signals, which can lead to a reduction in signal strength and it can affect potentially data transmission reliability. Present work focusses on two key performance parameters Average Bit Error Rate (ABER) and Outage Probability (OP) which is of much importance due to the adverse impact of weather factors on FSO communication system. For the present study the OP and ABER performance are analysed over Gamma- Gamma (G-G) fading for FSO links in the presence weak and moderate atmospheric turbulence with four different modulation schemes. The CDF functions for the channel model has been derived and MATLAB codes are used to predict the OP and ABER performance for the FSO communication system.

Finite Element Modeling of a Flat Cell of Highly Porous Piezocomposite with Inclined Edges Taking into Account Nonuniform Polarization

Introduction. Highly porous composites — metal foams — are widely used due to their mechanical properties. The literature presents various methods for their mathematical modeling, including those based on periodic Gibson-Ashby cells. Piezoactive composites have a number of properties, such as high sensor sensitivity and a large bandwidth. This is the reason for the interest in their modeling. However, when constructing such models from piezoceramic materials, a certain difficulty, associated with the selection of the distribution of preliminary polarization, arises. It should be noted that this issue, specifically for highly porous piezoceramics, has not been sufficiently studied in the literature. Therefore, the objective of this work was to establish the effect of the polarization model on the characteristics of the piezoactive composite.Materials and Methods. The design material is PZT-4 piezoceramics, whose polarization depends significantly on the conditions of its guidance (model geometry, electrode arrangement). The study was divided into two steps: in the first, the residual polarization was calculated based on the theory known in the literature, the implementation of which was performed in the ACELAN package; in the second, a number of problems for a composite cell were solved, and the dependence of its properties on the polarization model was found. The finite element method implemented in the ACELAN package was used as a method for solving the corresponding boundary value problems of electroelasticity for piecewise inhomogeneous bodies.Results. The problem of determining nonuniform polarization for two types of flat cell designs of highly porous piezoceramics was solved. Some features of the obtained polarization distribution were noted, in particular, its nonuniformity and the presence of counter polarization in some edges. The problems of determining natural frequencies and vibration modes “intra cell” and their dependence on the polarization model (homogeneous and nonhomogeneous) were solved. It was noted that some frequencies differed by 10%, while the vibration modes qualitatively coincided. The dependence of the stress-strain state and output characteristics on polarization, whose difference in some values reached 15%, was analyzed.Discussion and Conclusion. The process of polarization of highly porous piezoceramics has a number of features that must be taken into account to obtain reliable information about its mechanical and electrical behavior. Auxetic properties, the difference in the mechanical and electrical response of the cell in question are directly related to these features. Thus, the polarization model has a significant impact on the characteristics of the piezoactive composite, which determines the importance of its correct selection. The results obtained should be taken into account when modeling representative volumes of highly porous piezoelectric composites to determine their effective properties, on the basis of which models of piezoelectric devices are constructed, and their output characteristics are calculated.

Large-Bandwidth Lithium Niobate Electro-Optic Modulator for Frequency-Division Multiplexing RFID Systems

In the face of increasingly complex application scenarios, there is an urgent need for (Radio Frequency Identification) RFID systems that are capable of accurately identifying microwave signals of different frequency bands. Based on the acumen detection characteristics of microwave signals by lithium niobate electro-optic modulators, applying large-bandwidth thin-film lithium niobate electro-optic modulation to RFID systems can achieve efficient operation across multiple frequency bands. This study discusses, in detail, the design, simulation, fabrication, and testing process of the electro-optic modulator to obtain a high-performance, large-bandwidth lithium niobate electro-optic modulator. By using multilayer lithography techniques to prepare thick traveling-wave electrodes, the problem of irregular cross-sections during the fabrication of thick electrodes has been successfully reduced, improving the stability and controllability of the device. Test results show that the insertion loss of the electro-optic modulator is about 6 dB, the extinction ratio is 36.5 dB, the optical waveguide mode field is 1 μm, the full-band characteristic impedance is 50 Ω, the test bandwidth is 50 GHz, and the half-wave voltage is 1.8 V. Compared with existing optimization schemes, this design not only achieves a large bandwidth and a small half-wave voltage, but also proposes a new fabrication process scheme, optimizing the process and resulting in samples with stable performance.

A compact wideband coupler design for 5G applications

Abstract This paper presents the design of a compact broadband coupler specifically dedicated to 5G applications. The innovative approach proposed skillfully merges two distinct methods: the use of stepped impedance structures and meanders. The aim is not only to miniaturize the structure and extend the bandwidth, but also to maintain high performance, particularly within the 3.5 GHz core frequency band. The effectiveness of this approach is reflected in a remarkable reduction in size, down by 59% compared with conventional designs. In addition, the achievement of a large fractional bandwidth 40% is a significant result of this study. Equally important, this coupler offers a precise quadrature phase difference between its two output ports. The extensive experimental results confirm the relevance of this innovative approach, making it a promising choice for the design of compact, high-performance couplers for state-of-the-art 5G applications.&amp;#xD;

VOXEL Video Streaming Over Wireless Networks

High-density point clouds expressing attractive 3D images are attracting attention. These gigantic media require large bandwidth allocations, making them problematic to stream to resource-constrained hand-held devices. This paper proposes a method for point cloud compression and streaming of large point clouds using a web server. Storing large point cloud videos on a web server allows users to publish data sets without using additional applications or sending large amounts of data ahead of time. HTTP/2 improves transfer efficiency by compressing headers into binary format and reduces latency by sending many multiplexed requests using a single TCP session. The large size of the point cloud data and the current limitations of wireless channels demand point cloud compression methods. MATLAB is used for the purpose of analysis, at results show an average compression ratio of 30:1. Our proposed system achieves lower average latency between successive frames resulting in an increased frame rate to 72.46 fps when streaming 4M points, and 82.51 fps in the case of streaming 800K points compared to much lower rates in conventional work.

Achromatizing photolithographically patterned metasurfaces with arbitrary, variable unit cell size

In recent years, across many fields, a large emphasis has been placed on the development of optical materials that can realize arbitrary control over the phase, transmission, and polarization of light, particularly across a broad wavelength range. Metasurface optics, or arrays of subwavelength structures with highly tailorable geometry and composition on a thin substrate, have emerged as a promising contender to fulfill these needs. Several methods for the achromatization of metasurfaces have been demonstrated, including the use of amorphous nanopost shapes as well as multiple, simple nanopost shapes. We present what we believe to be a novel technique that can be used separately or in conjunction with these techniques to provide achromatic phase control: arbitrary aperiodicity. By varying the period, or spacing between adjacent nanoposts, metasurfaces can be demonstrated that achieve desirable phase behavior and high transmission over a relatively large bandwidth. We detail the design and fabrication of such a device, in the form of a 1 cm diameter polarization insensitive metasurface with a vortex phase profile that exhibits achromatic behavior over a ∼12% bandwidth centered at 1650 nm. We demonstrate simulated phase residuals below 0.4 rad and transmission above 85% for this bandwidth, as well as measured phase residuals below 0.6 rad and transmission above 88% for this bandwidth. By showing that we can create such a device with deep-UV photolithographic fabrication techniques, we make clear the fidelity of our aperiodic technique in realizing mass-manufactureable, large-area achromatic metasurfaces for the near-infrared.

Ultra‐Large Bandwidth and Ultra‐High Sensitivity Germanium/Silicon Avalanche Photodiode

AbstractGermanium/silicon (Ge/Si) avalanche photodiode (APD) has emerged as a highly desirable component for optical communication, sensing, and computing, attributed to its inherent gain. Conventional schemes typically suffer from limited bandwidth and significant excess noise due to the high gain, restricting the high‐sensitivity detection in burgeoning high‐speed applications. Here, a Ge/Si APD is developed with an ultra‐large bandwidth at an optimal gain. This breakthrough is achieved by implementing an extremely narrow multiplication layer to enhance the space charge effect, overcoming the intrinsic bandwidth limitation in conventional APDs while elaborately harnessing the gain to a moderate value to ensure the optimal sensitivity. The device possesses a bandwidth of 67 GHz at an optimal gain of 6.6 and enables data reception of 240 Gb s−1 four‐level pulse amplitude modulation signal—the largest bandwidth and highest single‐channel bitrate among all reported APDs. The presented APD suggests promising applications for high‐speed and high‐sensitivity data communication owing to its competitive performance, cost‐effectiveness, and high‐yield production.