Iet Optoelectronics最新文献

The design of optical elements often requires precise optimisation where metaheuristic algorithms have emerged as a powerful approach. This study aims to optimise a guided-mode resonance reflectance filter chosen due to its extreme parameter sensitivity, which makes it an exemplary platform for evaluating metaheuristic algorithms in photonics. We rigorously compare six established metaheuristic techniques (particle swarm optimisation (PSO), genetic algorithm (GA), shuffled frog leaping algorithm (SFLA), artificial bee colony (ABC), imperialist competitive algorithm (ICA), and differential evolution (DE)) using critical performance metrics. This systematic analysis not only benchmarks algorithm effectiveness for guided-mode resonance filters but also establishes guidelines for optimising parameter-sensitive photonic devices.

In this paper, we put forward an accurate multiple scattering channel model for ultraviolet (UV) signals propagating through the atmosphere. The model incorporates both the altitude-dependent variation of the refractive index structure parameter and the relative height between the UV transmitter and receiver, factors which have often been overlooked in previous studies. To validate the proposed model, we compare it with the established turbulence model through simulations and experiments at transmission distances ranging from 600 to 1000 m. The results demonstrate that the proposed model achieves higher accuracy. Furthermore, we investigate the effects of wind speed, the nominal value of the refractive-index structure parameter at ground level, and the number of photon scattering events on the channel path loss. This work establishes a solid theoretical foundation for the development of UV communication technology.

This paper proposes a hybrid optical modulation scheme that integrates spectrally efficient quadrature amplitude modulation (QAM) and power-efficient multipulse pulse position modulation (MPPM) for underwater wireless optical communication (UWOC) to achieve high spectral and energy efficiencies and combines it with LDPC codes to mitigate the adverse effects imposed by the underwater turbulence channel. Considering the effect of both direct-current (DC) bias level and modulation index on signal-to-noise ratio (SNR), for the first time, an approximate closed-form bit error rate (BER) expression for the hybrid L-QAM-MPPM UWOC system over turbulence channels is derived and verified using Monte Carlo (MC) simulations. Subsequently, comparisons among the hybrid L-QAM-MPPM, conventional MPPM and QAM systems with comparable spectral efficiency for exponentiated Weibull (EW)-modelled turbulence channel indicate that hybrid modulation offers resilience to turbulence, although the BER in the additive white Gaussian noise (AWGN)-only channel is higher. Finally, the effectiveness of LDPC codes in improving the performance of hybrid modulations is discussed, with coded 128-QAM-(12, 2) MPPM offering ∼6.5 and 5.8 dB code gains at a BER of $��{10}^{�-�4�}�$ in strong and moderate turbulence, respectively. These results demonstrate the promise of hybrid modulation with LDPC as a robust and efficient modulation scheme for UWOC systems.

Yongwoon Hwang, Chung Ghiu Lee, and Soeun Kim. “Deep Learning Based Design of Binary Signalling for Optical Wireless Communication Systems With 2D Receiver.” IET Optoelectronics, 2025; 19:e70015. https://doi.org/10.1049/ote2.70015.

Figures 7, 9 and 10 in the originally published version were incorrect. The correct figures are given below:

In addition, the first sentence of Section 6.3, ‘Figure 10 presents the third LED signal pattern set’. was incorrect in the published version. This should have read: ‘Figure 8 presents the third LED signal pattern set’.

We apologise for this error.

This study presents a comprehensive feasibility analysis of low Earth orbit (LEO) satellite-to-ground downlink communication for quantum key distribution (QKD), focusing on 1550 nm wavelength. This wavelength is selected for its compatibility with terrestrial fibre-optic networks, allowing the distribution of quantum keys over extended distances. The analysis models a discrete variable decoy state BB84 protocol, emphasising the system's design requirements for the optical ground station (OGS) receiver, including critical parameters that affect single-mode fibre (SMF) coupling efficiency. Through extended simulations, we assess atmospheric conditions, turbulence effects and adaptive optics (AO) correction to evaluate their impact on light coupling efficiency and achievable key rates. Results highlight the advantage of AO in sustaining secure key rates, particularly under high-elevation satellite passes, and quantify the key volumes attainable across varying levels of turbulence and additional fibre transmission losses. Our findings demonstrate that LEO satellite-based QKD downlinks can be feasibly integrated with terrestrial fibre systems, supporting secure key distribution over potentially large geographic areas without requiring OGSs to be trusted nodes. The results of this work provide practical insights into the technical requirements and configurations needed to realise robust satellite-to-ground QKD links, laying a foundation for future advancements in global quantum-secure communication infrastructure.

In this paper, a rolling shutter optical camera communication system is investigated by analysing the internal working principle of a receiver based on complementary metal oxide semiconductor image sensors. Based on the thorough analysis of system parameters such as the clock signal, integration and read-out times at the sensor level, and the calculation of the bandwidth and the time span of the image frame containing the information signal, it was demonstrated that the communication functionalities can be enhanced. A new model was proposed and validated by developing an experimental testbed and demonstrating matching between the data packet duration and the predicted time span. This enables the optimisation of the samples obtained by the image postprocessing, using different sensor clock signals and evaluating the bit error rate performances. The experimental results demonstrated that the internal design of the camera and its packet structures have impacts on the read-out times. For camera settings of pixel clock frequency and exposure time of 300 MHz and 61 $��\mu �$s, respectively, a data rate of 14.5 kbps at a bit error rate below the forward error correction limit has been achieved.

Continuous monitoring of milk fermentation process during industrial yogurt production using pH metres is often cumbersome and inefficient technique. A simple, cost-effective and accurate alternative sensing technology is required for real-time monitoring. In this paper, we report real-time continuous monitoring of milk fermentation process and determine the fermentation end point during yogurt production using highly-sensitive fibre Bragg grating (FBG) stress sensor. Milk fermentation is monitored in real-time by analysing the shift in the Bragg wavelength of FBG stress sensor inserted into the milk corresponding to time-dependent gradual increase in applied stress on FBG stress sensor because of yogurt coagulation. Required sensitivities for an FBG sensor used for milk having 0% and 2.5% fat are around 3.03 and 3.01 pm/Pa, respectively. A proof of the concept of a smart alarm system (AS) for determination of the fermentation end point of yogurt is discussed in this work. This study presents a cost-effective, simple and non-destructive method for continuous real-time monitoring of milk fermentation process and determination of fermentation end point for small as well as large-scale production of yogurt.

This paper proposes a dual-MIMO (DMIMO) free-space optical (FSO) communication system integrated with hybrid machine learning models (CNN and LSTM) to enhance bit error rate (BER), Q-factor, and data rates for 5G backhaul networks under atmospheric disturbances. Using OptiSystem software, we simulated the system's performance in fog, rain, haze, and snow environments. Results demonstrate data rates up to 120 Gbps and up to 80% BER improvement compared to conventional MIMO systems, especially under dense fog and turbulence. Although the proposed system shows excellent performance in both simulated conditions and also in experimental validation, real-world challenges such as sudden weather changes, pointing errors, and computational complexity were tested in both simulation and experimental environment. Future work will focus on implementing adaptive beam steering to enhance its validation in real-world situations to optimise the system for dynamic environments.

This work demonstrates experimentally the feasibility of using up to 32-PAM in rolling shutter based optical camera communication (OCC). Two different cameras have been used for OCC performance comparison, namely, a low-cost Pi Camera V2.1 and a higher-cost Alvium 1800 U-500m. Based on the limitations evidenced by this analysis, a decoding algorithm has been proposed to recover the transmitted signal from the acquired images. The experimental evaluation has been carried out for distances up to 2 m, using 8-PAM, 16-PAM and 32-PAM, analysing the received samples histograms and the symbol error rate (SER) for both cameras. Based on the collected experimental results, it is concluded that 32-PAM is possible with both cameras, with a maximum SER of 0.16% for the Alvium camera and 5.05% for the Pi Camera. Finally, it is observed that both the signal and noise amplitudes remain constant for the tested distances, resulting in a SER that does not notably depend on the distance between the transmitter and receiver.

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%.