Optical Code Research Articles

Bio-sourced flexible supramolecular glasses for dynamic and full-color phosphorescence

Glass, a diverse family of amorphous materials, has significantly advanced human society across various fields. The demand for flexible ultrathin glass, driven by modern optical displays and portable optoelectronics, presents challenges in energy consumption, fabrication complexity, and recycling. Here, we demonstrate flexibility and full-color luminescence in large-scale ultrathin glasses derived from readily available natural resources, specifically egg albumen (EA) and gelatin (GEL), via an evaporation-driven self-assembly process. The dynamic crosslinked networks formed through hydrogen bonding between EA and GEL impart both high hardness and flexibility to the glasses, with hardness and flexural strength values comparable to state-of-the-art inorganic and organic glasses. Additionally, the EA–GEL-based glasses exhibit excitation-dependent and time-gated chiral ultralong phosphorescence with color from blue and red, and a lifetime of up to 180.4 ms. With their easy processability and full-color emission, these biogenic glasses can be fabricated into anti-counterfeiting patterns and optical information codes.

On the performance of optical codes for FSO systems using SAC-OCDMA technique to improve system performance

On the performance of optical codes for FSO systems using SAC-OCDMA technique to improve system performance

MDM‐Incorporated Quad Donut Modes OCDMA‐FSO Scheme for Secure High‐Altitude Platforms‐To‐Satellite Scenarios

ABSTRACTThe next generation of communication networks is envisioned to be driven by high‐altitude platform (HAP)‐to‐satellite systems. License‐free narrow beam free space optics (FSO) can provide uninterrupted connectivity in satellite‐enabled Internet of Things scenarios. This work proposes a HAP‐to‐satellite hybrid mode division multiplexing–optical code division multiple access (MDM‐OCDMA) scheme employing zero cross‐correlation (ZCC) and multidiagonal (MD) codes. In high‐speed satellite communications, a 12 × 10‐Gbps hybrid MDM‐OCDMA scheme carrying four donut modes (0, 1, 2, and 3) enables high channel capacity, sufficient spectral efficiency, and data security under severe link conditions. Based on simulations, the hybrid MDM‐OCDMA scheme using the ZCC code achieves a greater FSO link distance of 420 m compared with when using the MD code at a 10e‐9 error correction limit under clear air and weak turbulent scenario. The reliable transmission distance of 250 m is achievable with the 120‐Gbps proposed system, assuming pointing errors of 2 mrad, 1‐dB receiver, and 2.5‐dB transmitter losses. The results also show that the system can sustain an additional loss of 1.5–2 dB over 250 m for all donut modes. Additionally, the system using ZCC code contributes to low power consumption over MD and variable weight ZCC code and thus requires a minimum received power of −4.02 dBm. It also offers high optical signal to noise of 42–52 dB, −11.58 to −22.20 dB of gain, 11.58–22.20 dB of noise figure, and −48.11 to −58.73 dBm of signal power at output over 200–700 m range up to 2 dB of additional loss. Comparative analysis indicates that the proposed system is more efficient, less complex, adequately distance‐friendly (=420 m), and capable of higher data rates (=120 Gbps) compared with other works. This makes it a promising solution for future high‐speed satellite communications considering the impact of link losses and atmospheric conditions.

Enhanced underwater optical wireless communication using optical code division multiple access with sigma shift matrix code

A high-speed 40 Gbps Underwater Optical Wireless Communication (UOWC) system exploiting code division multiple access is proposed in this paper. Optical Code Division Multiple Access (OCDMA) systems play a crucial role in enhancing transmission capacity by allowing multiple channels to transmit data simultaneously. In this proposed work, four channels each assigned a distinct Sigma Shift Matrix (SSM) code and modulated with a data at 10 Gbps. Laser Diode (LD) sources operating in the green spectrum are used in UOWC systems due to their low attenuation. To ensure the feasibility of implementing the proposed system in real-world environments, the actual scattering and absorption coefficients from five different types of water are considered: Pure Sea (PS), Clear Ocean (CL), Coastal Sea (CS), Harbor I (HI), and Harbor II (HII). The system's performance is evaluated via the Quality Factor (Q-factor), Bit Error Rate (BER), and eye diagrams opening. The simulation results indicate that in PS water, which exhibits the lowest attenuation, the four channels achieve the longest underwater transmission distance of 48 m, with a Q-factor ≥ 4.1, log(BER) ≤ −4.7, and wide eye openings. Since CL and CS have higher attenuation than PS, they enable shorter transmission distances of 27.5 m and 16 m, respectively, while maintaining nearly the same Q-factor, log(BER), and eye diagrams. Conversely, the highest attenuation observed in HI and HII waterbodies results in the shortest underwater spans of 8.2 m and 5.05 m, respectively.

Persistent Photoluminescence and Mechanoluminescence of a Highly Sensitive Pressure and Temperature Gauge in Combination with a 3D-Printable Optical Coding Platform.

Distinct types of luminescence that are activated by various stimuli in a single material offer exciting developmental opportunities for functional materials. A versatile sensing platform that exhibits photoluminescence (PL), persistent luminescence (PersL), and mechanoluminescence (ML) is introduced, which enables the sensitive detection of temperature, pressure, and force/stress. The developed Sr2MgSi2O7:Eu2+/Dy3+ material exhibits a linear relationship between ML intensity and force and can be used as an ML stress sensor. Additionally, the bandwidth of the PL emission band and the PL lifetime of this material are remarkably sensitive to temperature, with values of ≈0.05nmK-1 and 1.29%/K, respectively. This study demonstrates PersL pressure sensing for the first time, using long-lasting (seconds) lifetime as a manometric parameter. The developed material functions as an exceptionally sensitive triple-mode visual pressure sensor; specifically, it exhibits: i) a sensitivity of ≈-297.4cmGPa-1 (8.11nmGPa-1) in bandshift mode, ii) a sensitivity of ≈272.7cm-1/GPa (14.8nmGPa-1) in bandwidth mode, and iii) a sensitivity of 42%GPa-1 in PL-lifetime mode, which is the highest value reported to date. Notably, anti-counterfeiting, night-vision safety-sign, 8-bit optical-coding, and QR-code applications that exhibit intense PersL are demonstrated by 3D-printing the studied material in combination with a polymer.

Joint phase control in metasurfaces for optical convolution operations

Combining the propagation and geometric phases in a metasurface facilitates the independent control of multiple parameters of the light field. However, the geometric phase often displays a random distribution, making it difficult to observe directly. We introduce a frequency-dependent phase response: at frequency f1, there is a superposition of the geometric and propagation phases, whereas at frequency f2, the propagation phase remains constant, and only the geometric phase is applied. The superposition can be interpreted as a convolution process in far-field Fraunhofer diffraction, enabling convolution metasurface devices to generate complex orbital angular momentum beams array and patterned array. Notably, the geometric phase aligns with the characteristic distribution of orbital angular momentum beams, allowing direct observation of the loaded geometric phase. These findings open what we believe to be new avenues for manipulating and calculating complex vector optical fields, optical information coding, controlling light-matter interactions, and enhancing optical communication.

A method of multi-bit optical coding by constructing Brewster angles to enhance photonic spin Hall effect

The photonic spin Hall effect, characterized by its polarization-driven spin-related displacement, has played an essential role in coding information processing. In this Letter, using a two-period double-layer dielectric plate, the displacement changes within the angle region are first observed, and a two-bit effective coding is achieved through non-uniform quantization of displacement values and coding. Afterward, by constructing Brewster angles (BAs), effective three-bit coding is achieved at the selected BA by dividing the angle domain. By changing the relative refractive index of the constituent materials (nB), effective coding is achieved at corresponding angles (45°–85°). By connecting two-bit and three-bit coding, a five-bit coding is fulfilled. By setting the last six invalid values, effective correspondence of 26 English letters is obtained. At the same time, the largest displacement peak itself is huge and varies accordingly with different values of nB. This work can provide some reference for designing optical coders.

NIR-I Activated Orthogonal NIR-IIb/c Emissions in a Lanthanide-Doped Nanoparticle for Fluorescence Imaging and Information Encryption.

Applying the orthogonal principle for distinguishable second near-infrared (NIR-II) emissions has brought new dimensions for ratio fluorescence imaging (RFI) detection and information encryption, deepening the tissue detection depth and improving signal-to-noise ratio and information security. However, the orthogonal NIR-II emissions underlying these advanced optical applications have been reported only in heterogeneous structures and mixtures, limiting their practicality and potential impact. Herein, NIR-I-activated orthogonal NIR-IIb/c (1530/1825nm) emissions nanoparticles (ONNPs) are developed by spatially separated doping of Tm3+ and Er3+ emitter upon switching 808 and 980nm excitations. RFI techniques and orthogonal NIR-II emission ONNPs are used to demonstrate vessel depth detection based on wavelength-dependent optical attenuation properties in tissue. The superiority of the optical coding and encoding process in a 4×1 binary matrix is demonstrated for anticounterfeiting and decryption imaging of quick-response (QR) code for information storage. The research progress of this NIR-II orthogonal emissions probe will drive the development of biomedical sensing, imaging safety, and future biophotonics technologies.

Performance analysis of MDM-OCDMA free space optical system using shift ZCC codes

Abstract Free space optical communication is promising wireless technology which saves cost, saves time, has high security and acts as backend, backhaul system. Optical code division multiplexing based on spectral amplitude coding is a potential method to support many users with high data speeds. Optical code division multiplexing reliant spectral amplitude coded zero cross-correlation free space optical communication is proposed in this work incorporating shift zero cross-correlation codes. Mode Division Multiplexing is used to lower the cost of the system and to minimize the interferences. With the realization of the proposed system, the capacity of 100 Gbps is accomplished supporting 10 different users. Different atmospheric turbulences are also analyzed over FSO to investigate their effects on BER.

Design and Investigation of a 10 Gb/s Hybrid Spatial-time Diversity FSO-CDMA Communication System

Abstract This paper presents a novel strategy for free space optical (FSO) communication system that combines hybrid spatial-time diversity and optical code division multiple access (OCDMA). The authors demonstrate a 10 Gb/s hybrid spatial-time diversity FSO-CDMA experimental system for the first time. They investigate the bit error rate (BER) and physical-layer security under weak and strong turbulence conditions. The experimental results demonstrate that the proposed scheme can improve the performance of the FSO-CDMA system. In the hybrid spatial-time diversity FSO-CDMA system, the BER of the eavesdropper (Eve) exceeds the hard-decision forward-error-correction threshold of 3.8E-3. It is also worth noting that Eve can intercept and recover data without a matched decoder in a spatial diversity FSO-CDMA system. As a result, the proposed scheme can simultaneously enhance reliability and physical-layer security compared to time or spatial diversity systems.

Construction of Optimal Two-Dimensional Optical Orthogonal Codes with at Most One Pulse per Wavelength.

Two-dimensional optical orthogonal codes have important applications in optical code division multiple access networks. In this paper, a generic construction of two-dimensional optical orthogonal codes with at most one pulse per wavelength (AM-OPPW 2D OOCs) is proposed. As a result, some optimal AM-OPPW 2D OOCs with new parameters can be yielded. The new AM-OPPW 2D OOC may support more subscribers and heavier asynchronous traffic compared with known constructions.

Switching in microseconds: design of a 5 × 5 non-blocking free space optical switch at 1550nm with a piezo-actuator and beam-steering lens system

Modern data center networks (DCNs) require optical switches with ultra-low loss, ultra-fast reconfiguration speed, high throughput, and high extinction ratio performances. In this work, we propose the design of a 5 × 5 optical switch at 1550 nm based on a piezo-actuator serving as a translating input optical source, and a beam-steering system built of spherical lenses to complete the switching behaviour. An ultra-fast actuator switching speed is estimated as 1.55 μs latency for a single connection with a demo circuit. We further simulate the beam-steering system end-to-end in a commercial optical design software CODE V and demonstrate a theoretical 2.16 dB insertion loss for a single connection in the switch at optimum alignment.

Performance enhancement of optical pulse coding phase-sensitive OTDR system with genetic-optimized code.

Optical pulse coding (OPC) in phase-sensitive optical time-domain reflectometry (φ-OTDR) traditionally relies on standard coding sequences as probe pulse trains, which usually suffer the problem of distorted probe pulse caused by the gain saturation in erbium-doped fiber amplifier (EDFA). To improve the signal-to-noise ratio (SNR) and mitigate distortion caused by the EDFA gain saturation, a genetic-optimized code (Go-code) based OPC φ-OTDR (GOPC φ-OTDR) scheme is proposed in this paper. The unique Go-code sequence generated by the distributed genetic algorithm (DGA) is explored in the field of φ-OTDR for the first time, and the coding sequence was optimized to adapt to the vibration sensing requirements in φ-OTDR. Theoretical analyses focused on EDFA gain saturation effects and coding gain were conducted. The experiment of GOPC φ-OTDR demonstrated significant improvements compared with Golay φ-OTDR, achieving less distortion in decoding response and approximately 7.48 dB phase demodulation SNR enhancement within a 10-km sensing range. This research marks Go-code's pioneering exploration into φ-OTDR, demonstrating substantial advancements in optimization metrics, and opening avenues for exploring advanced OPC technologies.

Perfect vortex Laguerre-Gauss beams as a carrier in the MMF/FSO communication system

This paper presents a novel, to the best of our knowledge, high-speed transmission system that integrates a new structured light beam, specifically the perfect vortex Laguerre-Gaussian (PVLG) beam, with an optical code division multiple access (OCDMA) system utilizing a premutation vector (PV) code. The PVLG beams are distinguished by their unique shape, which remains nearly invariant during propagation regardless of the azimuthal order of the orbital angular momentum (OAM), facilitating the multiplexing of multiple OAM beams within the same spatial area. Additionally, the system employs hybrid multimode fiber (MMF) and free space optics (FSO) channels, with consideration of foggy weather conditions in the FSO channel. A comparative analysis between the performance of PVLG beams and standard LG beams is conducted. Performance evaluation metrics include the Q-factor, bit error rate (BER), and eye diagrams, providing comprehensive insights into received signal quality. The results demonstrate that the system utilizing PVLG beams outperforms the one using standard LG beams. Specifically, the system achieves a maximum MMF length of 0.35 km with a BER of approximately 10−4 and a Q-factor of around three when the MMF cable channel is used only. For the FSO channel, the achievable ranges are 1.1 km, 0.7 km, and 0.35 km under low fog (LF), medium fog (MF), and high fog (HF) conditions, respectively, maintaining the same BER and Q-factor values. Moreover, the hybrid MMF/FSO channel extends the transmission range to 1.2 km under LF conditions and to 0.45 km under HF conditions, with consistent BER and Q-factor values. Each of the four PVLG beams carries 40 Gbps, resulting in a total transmission capacity of 160 Gbps. Thus, the proposed system is well positioned to meet the high-speed data transmission demands of next-generation 6G networks.

Design and Evaluation of a Hybrid 2D-SWZCC OCMDA System with Multicarrier MM-Wave

This paper presents a hybrid communication system combining optical code division multiple access (OCDMA) and multicarrier millimeter-wave (MM-Wave) architecture operating at 35, 55, 75, and 95 GHz connected to a home network center (HNC) and the end user (EU). Hybrid Link reduces congestion on complex RF networks by combining optical fiber backhaul with radio links. The OptiSystem simulation demonstrates successful data transmission and transmission capacity at 40Gbps over various distances. Furthermore, this new 40G-MM wave OCDMA system that takes advantage of a two-dimensional single-weighted zero cross-correlation (2D-SWZCC) system with a multiplexing scheme of polarization wavelength multiplies the same N channels to M OCDMA code of the MM-Wave system that dramatically increased scalability. The comparative analysis shows that the proposed 2D-SWZCC hybrid algorithm outperforms 1D-SWZCC regarding scalability. This study contributes to developing communication algorithms with high data rates and provides promising solutions for method limitations and scalability in hybrid-MM-Wave-OCDMA architectures.

Optimizing Fi-Wi network performance through advanced multiplexing techniques: a comparative analysis for enhanced quality metrics

Abstract Fi-Wi networks, emblematic of the convergence between optical fibers and wireless access, stand resolutely at the vanguard of the transformative redefinition of communication paradigms. As advanced communication networks persistently redefine the contours of connectivity, characterized by their unparalleled speed, minimal latency, and augmented capacity, the exigency for innovative approaches undergoes heightened intensification. The crux of this study pivots upon the methodical application of multiplexing techniques, notably wavelength division multiplexing (WDM), optical code division multiplexing (OCDMA), and optical time division multiplexing (OTDM), each deployed with precision to elevate the nuanced performance of the Fi-Wi network. The multifaceted optimization of these techniques not only imparts an impetus to data transfer rates, mitigates latency, and augments spectral efficiency but concurrently instigates the realm of wireless connectivity. The research undertakes a technical exploration of the deployed multiplexing strategies, delineating their idiosyncratic advantages. A discerning comparative analysis vis-a-vis the hybrid (Fi-Wi)-single model, precisely serving as the baseline, unequivocally delineates the superior performance of the proposed methods across metrics of Q-factor, eye height, and logarithmic bit error rate-Q factor.

Thermographic observation of fast ion impact areas in the NBI ducts of TJ-II

Infrared thermography has been used to study the fast ion impact areas in the Co and Counter NBI ducts of TJ-II. Statistical results of the distribution of accumulated impacts on the walls of the duct have been obtained with an ion trajectory code. A more realistic description is obtained by coupling a beam simulation code to produce the ion birth point distribution. In this way, the main interception areas for both injectors have been found. Those areas constitute the Regions of Interest (ROI's) for the IR thermography system. The up-graded IR system, with its high definition MIR camera, enlarged window, and precision support and displacement mechanisms for camera and mirror, allows such ROI's to be captured. The optimal alignment parameters of the camera and mirror have been obtained with the optical simulation code ZEMAX, and the feasibility of the mechanical configuration in the crowded window environment has been checked with a CAD program, also used to simulate the field of view inside the ducts. Finally, infrared images of the ducts during beam pulses without magnetic field and with magnetic field have been compared, to obtain highlighted images of the fast ion impact areas in both ducts, showing the expected stellarator symmetry.

Neural Network-Based Detection of OCC Signals in Lighting-Constrained Environments: A Museum Use Case

This research presents a novel approach by applying convolutional neural networks (CNNs) to enhance optical camera communication (OCC) signal detection under challenging indoor lighting conditions. The study utilizes a smartphone app to capture images of an LED lamp that emits 25 unique optical codes at distances of up to four meters. The developed CNN model demonstrates superior accuracy and outperforms traditional methodologies, which often struggle under variable illumination. This advancement provides a robust solution for reliable OCC detection where previous methods underperform, particularly in the tourism industry, where it can be used to create a virtual museum on the Unity platform. This innovation showcases the potential of integrating the application with a virtual environment to enhance tourist experiences. It also establishes a comprehensive visible light positioning (VLP) system, marking a significant advance in using CNN for OCC technology in various lighting conditions. The findings underscore the effectiveness of CNNs in overcoming ambient lighting challenges, paving the way for new applications in museums and similar environments and laying the foundation for future OCC system improvements.

160 Gbps MMF/FSO system based on OAM beams and PV code under rainy weather

In this paper, a high-speed transmission system that combines a multimode fiber (MMF) with Free Space Optics (FSO) is proposed to accommodate the rapid growth of traffic. As Orbital Angular Beams Multiplexing (OAM) plays a crucial role in 6G networks by enhancing transmission capacity, four OAM beams (LG0,0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${LG}_{\\mathrm{0,0}}$$\\end{document}, LG0,20\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${LG}_{\\mathrm{0,20}}$$\\end{document}, LG0,40\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${LG}_{\\mathrm{0,40}}$$\\end{document}, and LG0,40\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${LG}_{\\mathrm{0,40}}$$\\end{document}) are utilized in this study. Additionally, the Optical Code Division Multiple Access (OCDMA) technique is employed, known for its high level of confidentiality and the ability to allow multiple channels to transmit data simultaneously. To ensure ubiquitous data transmission, two channels: MMF and FSO are used. Accordingly, in our proposed MMF/FSO system, we employ four OAM beams, with each carrying four OCDMA channels assigned distinct Permutation Vector (PV) codes. With a data transmission rate of 10 Gbps on each OCDMA channel, the overall capacity of the system amounts to 160 Gbps (10 Gbps × 4 OCDMA channels × 4 OAM beams). Moreover, the performance is investigated and evaluated using two scenarios. The first assumes an FSO range of 5 km and Clear Air (CA) weather conditions, with a variable MMF length. In contrast, the second scenario maintains a fixed MMF length of 1 km while altering the FSO span. Weather conditions like CA and rain conditions; Light Rain (LR), Medium Rain (MR), and Heavy Rain (HR) are considered while evaluating the system performance in the second case. The bit error rate (BER), travelling distances in the channel either MMF or FSO, and eye diagrams are among the metrics used for evaluation. They all provide information about the received signal performance. Finally, the obtained results for the proposed MMF/FSO system, utilizing OAM beams and PV codes, indicate that in the first scenario, the system can support a total capacity of 160 Gbps across all channels. The performance is noteworthy, with a BER below 10-5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${10}^{-5}$$\\end{document} and a wide eye opening, enabling successful transmission over 6.2 km (1.2 km MMF length + fixed 5 km FSO span). For the second scenario, the achievable distance is decreased due to the attenuation caused by rain. It becomes 2.62 km (1 km MMF + 1.62 km FSO span), 5.2 km (1 km MMF + 1.2 km FSO span), and 1.77 km (1 km MMF + 0.77 km FSO span), under LR, MR, and HR, respectively.

Performance analysis of 2D optical code division multiple access through underwater wireless optical medium

The performance of a two-dimensional optical code division multiple access (2D-OCDMA) system using an underwater wireless optical (UWO) medium is assessed in this work. The optical source is an LED with a working wavelength of 532 nm, and the optical detector is a p–i–n photodiode. When calculating the bit error rate (BER), the phase-induced intensity noise (PIIN), thermal noises, and shot sounds are taken into account. The user code address is set using 2D perfect difference (2D-PD) codes. Link distance, inclination angle, beam divergence angle, transmitter power, and the number of concurrent users are all taken into account when determining the BER performance. For various water media, such as pure sea water (PSW), clear ocean water (CLOW), and coastal ocean water (CSOW), the performance of the suggested system is examined.