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Quantum key distribution (QKD) is one quantum technology that can provide secure encryption keys for data transmission. The secret key rate (SKR) is a core performance indicator in QKD, which directly determines the transmission rate of enciphered data. Here, for the first time, we demonstrate a high-key-rate Gaussian-modulated continuous-variable QKD (CV-QKD) using telecom optical components. The framework of CV-QKD over these components is constructed. Specifically, the high-rate low-noise Gaussian modulation of coherent states is realized by a classical optical IQ modulator. High-baud low-intensity quantum signals are received by an integrated coherent receiver under the shot-noise limit. A series of digital signal processing algorithms are proposed to achieve accurate signal recovery and key distillation. The system can yield a high asymptotic SKR of 10.37 Mbps within 20 km standard telecom fiber, and the secure distance can exceed 100 km. This result confirms the feasibility of CV-QKD with state-of-the-art performance using telecom optical components. Besides, due to the ease of integrating these discrete components, it provides a high-performance and miniaturized QKD solution for the metropolitan quantum network. [ABSTRACT FROM AUTHOR]

There is no question about the value that digital signal processing brings to the area of biomedical research. DSP processors are used to sample and process the analog inputs that are received from a human organ. These inputs come from the organ itself. DSP processors, because of their multidimensional data processing nature, are the electrical components that take up the greatest space and use the most power. In this age of digital technology and electronic gizmos, portable biomedical devices represent an essential step forward in technological advancement. Electrocardiogram (ECG) units are among the most common types of biomedical equipment, and their functions are absolutely necessary to the process of saving human life. In the latter part of the 1990s, portable electrocardiogram (ECG) devices began to appear on the market, and research into their signal processing and electronics design capabilities continues today. System-on-chip (SoC) design refers to the process through which the separate computing components of a DSP unit are combined onto a single chip in order to achieve greater power and space efficiency. In the design of biomedical DSP devices, this body of research presents a number of different solutions for reducing power consumption and space requirements. Using serial or parallel data buses, which are often the region that consumes the most power, it is possible to send data between the system-on-chip (SoC) and other components. To cut down on the number of needless switching operations that take place during data transmission, a hybrid solution that makes use of the shift invert bus encoding scheme has been developed. Using a phase-encoded shift invert bus encoding approach, which embeds the two-bit indication lines into a single-bit encoded line, is one way to solve the issue of having two distinct indicator bits. This method reduces the problem. The PESHINV approach is compared to the SHINV method that already exists, and the comparison reveals that the suggested PESHINV method reduces the total power consumption of the encoding circuit by around 30 percent. The computing unit of the DSP processor is the target of further optimization efforts. Virtually, all signal processing methods need memory and multiplier circuits to function properly. [ABSTRACT FROM AUTHOR]

An autonomous surface vehicle known as a wave glider, instrumented with a low-power towed hydrophone array and embedded digital signal processor, is demonstrated as a viable low-noise system for the passive acoustic monitoring of marine mammals. Other key design elements include high spatial resolution beamforming on a 32-channel towed hydrophone array, deep array deployment depth, vertical motion isolation, and bandwidth-efficient real-time acoustic data transmission. Using at-sea data collected during a simultaneous deployment of three wave glider-based acoustic detection systems near Stellwagen Bank National Marine Sanctuary in September 2019, the capability of a low-frequency towed hydrophone array to spatially reject noise and to resolve baleen whale vocalizations from anthropogenic acoustic clutter is demonstrated. In particular, mean measured array gain of 15.3 dB at the aperture design frequency results in a post-beamformer signal-to-noise ratio that significantly exceeds that of a single hydrophone. Further, it is shown that with overlapping detections on multiple collaborating systems, precise localization of vocalizing individuals is achievable at long ranges. Last, model predictions showing a 4× detection range, or 16× area coverage, advantage of a 32-channel towed array over a single hydrophone against the North Atlantic right whale upcall are presented for the continental shelf environment south of Martha's Vineyard. [ABSTRACT FROM AUTHOR]

Orbital angular momentum (OAM) mode multiplexing is achieving utmost interest for the enhancement of transmission capacity and spectral efficiency. We have reported a (2 × 8 × 112 Gbps) 1792 Gbps bi-directional FSO link based on WDM-OAM multiplexing and dual-polarization quadrature phase-shift keying (DP-QPSK) modulation technique. An optical frequency comb lines (OFCL) generator, capable to generate 44 comb lines with flatness ∼ 0 dB is employed as a broadband laser source. The efficiency of the system is not only checked for clear weather but also for different turbulence situations (weak, moderate, and strong atmospheric turbulence). According to the best of our knowledge, this is the first one where the effect of atmospheric turbulence on DP-QPSK data carrying OAM modes has been checked for a bidirectional link. The combination of coherent detection with digital signal processing is utilized for compensating wave-form distortion and noise cancellation due to atmospheric turbulence. A very low power penalty of 1.65 dB in clear weather and 4.91 dB in strong atmospheric turbulence at a BER ∼ 10 −9 with open eye and clear constellation diagrams depicts the feasibility of the proposed system. • An OFCL generator has been developed and used as BLS in the proposed system. • The proposed OFCL generator can generate 44 comb lines with flatness∼0dB. • A data transmission rate of 1792 Gbps has been achieved using WDM-OAM multiplexing and DP-QPSK modulation techniques. • Power penalty is ∼1.65dB in clear weather and ∼4.91 dB in strong atmospheric turbulence. • Low BER∼10−9 with open eye and clear constellation diagrams has been achieved. • The effect of atmospheric turbulence on DP-QPSK data carrying OAM modes has been checked for first time. [ABSTRACT FROM AUTHOR]

Orthogonal frequency-division multiplexing-based passive optical network (OFDM-PON) with low-cost direct detection is the current research focuses of access networks. It can realize multi-dimensional bandwidth allocation based on subcarriers and time slots. In general, the inverse fast Fourier transform (IFFT) with Hermitian symmetric (HS) mapped symbols is applied to generate the real-valued baseband signal for intensity modulation. However, only half of the subcarriers can be employed to carry user data, while the other half are modulated by the corresponding conjugate data. Therefore, both IFFT and FFT are not fully utilized in HS-OFDM systems. Under the same bandwidth granularity (data subcarriers) and data transmission rate, the non-HS OFDM (NHS-OFDM) can reduce IFFT/FFT size by half. The hardware implementation and power consumption will be significantly reduced compared to the HS-OFDM. In this paper, we design and implement the baseband HS/NHS-OFDM transceivers based on field programmable gate array chips and data converters. On-chip resource usage and power consumption are analyzed and compared. It shows that the NHS-OFDM transmitter (receiver) can save up to 58% (58%) multipliers, 46.8% (41.7%) registers, and 48% (42.9%) look-up tables. About 11.9% (19.6%) of on-chip power consumption is reduced for the transmitter (receiver). In addition, the two real-time baseband transceivers are comparatively investigated in a directly-modulated laser-based direct detection transmission system. The bit error rate (BER) performance after 20 km standard single-mode fiber transmission is measured with both offline and real-time digital signal processing (DSP) algorithms. It exhibits that the NHS-OFDM system's power penalty is negligible at the BER of 3.8e−3, compared to the HS-OFDM. Moreover, the real-time receivers have a similar BER performance to corresponding offline ones. • We designed and implemented low-complexity real-time NHS-OFDM transceivers based FPGA for the low-cost PON. • A modified C2R/R2C conversion method is proposed for the NHS-OFDM transceivers. • A low-complexity timing synchronization method is employed in real-time NHS-OFDM systems. [ABSTRACT FROM AUTHOR]

The current Very Large-Scale Integration (VLSI) technology has reached its peak due to the fundamental physical limits of Complementary Metal-Oxide-Semiconductor (CMOS). Quantum-dot Cellular Automata (QCA) is considered a proper alternative to CMOS technology in digital circuit design. QCA has features like low power, small area, and high speed in nanoscale digital circuit design. A code converter is a circuit that converts a determined code to another one. Code converters such as Binary to Gray, Gray to Binary, and Binary to BCD converters have a crucial role in fast signal processing in digital systems. Also, code converters are used as a base unit for data transmission into the Arithmetic Logic Unit (ALU) to perform processes. A Binary-to-Gray converter converts the input data to a Gray number. In this paper, we propose a 3-bit Binary to Gray and vice versa code converter in QCA. Previous proposed designs could only convert Binary to Gray code or vice versa, but the proposed design convert both B2G and G2B codes into a circuit. We design our circuit in both reversible and non-reversible modes. The simulation of the proposed design is done using the QCADesigner 2.0.3 tools. The simulation results show that the proposed design is superior to the existing designs in terms of evaluation parameters such as cell count, area, latency, and quantum cost. [ABSTRACT FROM AUTHOR]