Iet Optoelectronics最新文献

This paper presents a cost-effective and energy-efficient optical digital-to-analog converter (ODAC) transmitter scheme for visible light communication (VLC) systems. The proposed ODAC transmitter enables data transmission while providing lighting, as desired in VLC systems, unlike existing ODAC structures in the literature, by switching power LEDs at high speeds with a MOSFET-based switching circuit design. This paper also discusses the ODAC design stages and presents the points to be considered in detail. In addition, by implementing the hardware design of an ODAC transmitter with a 3-bit resolution, that is, capable of generating 8-PAM signals, based on the proposed ODAC architecture, experimental studies are conducted for energy efficiency and communication performance results via the established VLC system using the designed ODAC. Experimental results demonstrate that the proposed ODAC transmitter achieves a data transmission rate of 18.75 Mbps with a bit error rate (BER) below the forward error correction (FEC) limit at a communication distance of 4 m, while also exhibiting a high power efficiency of 94%.

Recently, deep learning (DL) techniques have been increasingly applied to communication system design, owing to their powerful capabilities in handling complex channel characteristics. We apply a DL technique to binary signalling design for optical wireless communication system, which incorporates a $��2�\times �2�$ light-emitting diode (LED) transmitter array. The $��2�\times �2�$ LED transmitter array is adopted for two-dimensional (2D) arrayed photodiode receiver. The system encodes binary bit streams into $��2�\times �2�$ LED lighting patterns and the 2D received lighting patterns are interpreted as 2D images, which are decoded for retrieving the binary bit stream. For conventional on-off keying (OOK) signal for optical wireless communication system, it is necessary to choose appropriate 2D lighting patterns to represent binary logic symbols effectively. In this paper, we propose a design algorithm for binary signalling to generate appropriate 2D binary symbols. The DL-based signalling design algorithm is implemented as an autoencoder (AE) structure. It is trained with the set of transmitted and received signal patterns over the physical channel model with additive noise. To validate the proposed signalling design scheme, we adopt a two-step approach. Firstly, the signalling design algorithm generates binary LED signal sets after appropriate training processes. Secondly, from the generated signal sets, the LED patterns of interest are investigated considering their symbol error rate (SER) performance. It is confirmed that the proposed design algorithm provides binary signalling sets that meet the required SER performance. Through this study, it is demonstrated that DL-based signalling design is feasible, and the results are expected to contribute to further research aimed at extending the approach to more practical and complex system scenarios.

This paper presents the design and analysis of a tunable metamaterial absorber based on the combination pattern of two-dimensional molybdenum disulfide (MoS₂) and vanadium dioxide (VO₂) resonator. The design of the absorber structure is simple and includes an array of silicon on which the pattern of MoS₂ and vanadium is placed. By using the ability to adjust the MoS₂ carrier concentration and VO₂ phase transition properties, the absorber has dual control over its optical properties through temperature and voltage settings. This design provides the possibility of dynamic control of the resonance frequencies of the absorber. The absorber structure shows 99.3% absorption at 1375.8 nm and 94.3% at 1550.9 nm. By adjusting the parameters of the absorber structure, the absorption peak at wavelengths 1545.6 and 1743 nm reached 99.4% and 95.4%, respectively. The tunability of MoS₂ and vanadium allows precise tuning of absorption peak locations and makes the structure suitable for applications such as sensors, detectors, optical filters and telecommunication devices that require precise wavelength placement.

Wideband reconfigurable multifunctional analogue photonic chip using planar waveguides is proposed and analysed. A variety of planar Bragg gratings (PBGs) are designed and optimised to achieve three functions of fractional Hilbert transform (FHT), optical integration (OI) and optical differentiation (OD) based on the reflection spectrum. We firstly designed the unit chip implementation to verify the fractional-order tunable HT and then integrated the multifunctional units with cascaded MZIs into a single chip. The switching reconfiguration of multiple functions was achieved by optical phase modulation. Finally, we performed the analysis of femtosecond optical pulses to verify the processing effect of ultrafast photonic simulation and computation. The proposed chip achieves the operating bandwidth beyond 160 GHz comprehensively. The root mean squared errors (RMSEs) of the multifunctional temporal optical pulse processing are below 3%. This provides a potential path for ultrafast all-optical signal processing in microwave photonics.

This study presents a proof-of-concept system for the joint wireless transfer of data and power to in-body electronic devices (IEDs) using near-infrared (NIR) light technology. The proposed system addresses two critical challenges in IEDs: the need for enhanced safety, privacy and security on wireless communication to IEDs and the limitations of battery-based power sources. The testbed, built primarily from commercial off-the-shelf (COTS) components, comprises an 810 nm NIR LED, a photovoltaic cell (PV) as an energy harvester, a power management integrated circuit (PMIC), a photodetector amplifier and a supercapacitor. Ex vivo experiments using porcine tissue samples demonstrated three key capabilities: (1) data transmission using Gaussian minimum shift keying (GMSK) modulation, (2) optical power transfer and (3) joint data and power transfer. In terms of data transfer, a data rate of approximately 95 kb/s has been established. Meanwhile, in the context of power transfer, the proposed system successfully charges a supercapacitor across a 3 cm-thick ex vivo porcine tissue within almost one day under 525 mW/cm² light exposure (in a continuous wave operation), harvesting approximately 4.2 J of energy at a rate of 45.64 μJ/s. Furthermore, we have demonstrated wireless charging during data transmission, and it is viable. These results validate the feasibility of using optical links for secure, private, and noninvasive communication to IEDs (i.e., forward biotelemetry), which practically prevents remote hacking activities, as the optical beam coverage is very narrow. Furthermore, with the additional feature of wireless charging capabilities, it potentially reduces the need for surgical battery replacements and is expected to lead to improvements in patient care.

The performance of a unique tunable low-loss photonic crystal fibre (PCF)-based refractive index (RI) sensor comprising Gold (Au) and Zirconium Nitride (ZrN) as the plasmonic layer is explored in this article. A comparative analysis of three sensor configurations—Au alone, ZrN alone, and a combination of Au and ZrN—is presented. The sensor achieves the highest spectral sensitivity (WS) of 18,010 nm/RIU at an RI of 1.40 using Au alone and 6150 nm/RIU at an RI of 1.39 using ZrN alone. When both materials are combined, an utmost WS of 38,915 nm/RIU is achieved at an RI of 1.39 for both polarisations, outperforming the other configurations with a confinement loss of only 0.551 dB/cm at an RI of 1.40. This low loss facilitates easy fabrication, allowing for a maximum sensor length of 159 cm, a resolution of 2.57 × 10⁻⁶ RIU, and a limit of detection (LOD) of 6.603 × 10⁻¹¹ RIU²/nm. The bimetallic layer setup enables the opportunity for enhanced optical coupling between the two different types of plasmonic material used, elevating the detection capability of the sensor. The sensing performance displayed can outperform the currently available sensors that use ZrN solely and are very well-compatible with those using Gold alone. However, using gold layer alone gave out better amplitude sensitivity (AS) results which makes it suitable for application when the cost of equipment is in question and the use of ZrN layer alone can also be a smarter choice considering the cost of material, durability and availability of Zirconium in nature when compared to Gold. The tunable sensor can be employed in biomedical applications such as monitoring the glucose level in the bloodstream of patients and detecting blood components such as RBC, WBC, haemoglobin, plasma, and water from blood samples with high precision and accuracy, being able to differentiate between potential interfering molecules.

Despite perovskite solar cells (PSCs) having seen significant improvements in efficiency, their path to industrialisation and commercialisation is hindered by considerable challenges. A major concern is the toxicity associated with lead-based perovskites, which also suffer from rapid degradation. To mitigate these issues, researchers are investigating lead-free alternatives. In this study, we developed a device structure for a lead-free PSC utilising Cs₂TiBr₆ and La₂NiMnO₆ as absorbers. By modifying the thickness of these layers with distinct bandgap values, we achieved current matching in the design, which was carried out utilising the solar cell capacitance simulator (SCAPS-1D) with the AM 1.5 G 1 sun light spectrum. The proposed optimised device structure includes layers of FTO, SnO₂, Cs₂TiBr₆, La₂NiMnO₆, GO and Au. SCAPS-1D is also utilised to assess the impact of defect density, different hole transport layers (HTLs) and operating temperature on the performance of the proposed double-absorber solar cell (DASC). Additionally, it is also examined how the back-reflective coating and varying solar spectra affect the proposed structure. At 300 K, the optimised design achieved a power conversion efficiency (PCE) of 33.38%, an open circuit voltage (V_oc) of 0.9158 V, a short-circuit current density (J_sc) of 43.47 mA/cm² and a fill factor (FF) of 83.85%.

This paper proposes a novel design for a wavelength Multiplexer/Demultiplexer circuit based on the complementary-metal-oxide-semiconductor (CMOS) platform. The wavelength-division multiplexing (WDM) specifications for this device include free spectral range of 100 GHz (equivalently $��0.8��\text{nm}�$), channel spacing of 50 GHz, crosstalk less than −23 dB, dispersion less than 30 ps/nm, and preferably shape factor greater than 0.6, alongside minimal insertion loss and device footprint. The new design incorporates four additional ring resonators compared to previous studies, resulting in significant enhancement in crosstalk by 13 and 4 dB for the through port and drop port signals, respectively. Additionally, the transmission shape factor increases by 25% and 50% for the through port and drop port, respectively. The design approach employs a genetic algorithm to achieve optimal coupling coefficients for a multi-objective optimisation problem without a mathematical closed form, significantly reducing the computation time. This proposed algorithm seeks a balanced solution where all performance parameters reach acceptable values rather than optimising each parameter individually. This method proves to be both efficient and expedient, effectively eliminating the trial-and-error approach and the need for visual investigation of the Z-domain of the circuit transmission commonly used in the literature.

Currently, ultraviolet (UV) communication is proposed for use in unmanned aerial vehicle (UAV) communication, while the efficient transmission of images with limited bandwidth has posed a persistent challenge. This paper introduces a light-emitting diode-based UV communication system combined with semantic compression for image transmission. The experimental results show that the proposed semantic UV communication (SUC) system could transform a 7.19 MB image to a file of approximately 304 kB with the aid of deep learning, effectively reducing the bandwidth required for transmission. In addition, by jointly designing the encoding and modulation process and incorporating the interference light signals from the receiver’s detector into the joint coding-modulation (JCM) system for training, the resulting modulation strategy is matched with the actual transmission conditions. The experimental results demonstrated that the system could work well over 100 m while sending images with good quality in the face of error bits interference.

Water presence in raw meat not only degrades its quality by diluting the natural flavours, but also increases the risk of bacterial growth, altering texture, and juiciness which ultimately affects the quality of end products. Therefore, quality assessment of raw meat in markets as well as in eateries is important to ensure the consumer's safety and satisfaction. In this paper, we propose a nondestructive technique to detect water presence in raw meat and steak cooking temperature optimisation using a fibre Bragg grating (FBG) temperature sensor inserted into the piece of raw meat. The contribution of this paper is twofold: First, the water presence in the piece of raw meat is detected by analysing the shift in Bragg wavelength corresponding to time-dependent gradual decrease in temperature of heated probe of FBG sensor due to convective heat transfer from probe to meat. Secondly, the optimum cooking temperature of a particular type of steak is achieved after quality assessment of meat by analysing the shift in Bragg wavelength corresponding to time-dependent gradual increase in probe temperature due to convective heat transfer from meat to probe. The results show that the proposed sensing system can complete the error-free detection of water in 250 g piece of raw meat within 30 s for water contents of 50, 75, and 100 g which account for 20%, 30%, and 40% of the net weight of meat, respectively. Moreover, the simulated and experimental values of temperature sensitivity (TS) of FBG sensor used in this work are around 13 and 10 pm/°C, respectively. The proof of the concept of a smart restaurant based upon the proposed work is also discussed. This study provides a nondestructive, simple, and fast solution for detection of water in raw meat and achieving the optimum cooking temperature for different types of steaks.