Multiple Optical Signals Research Articles

Recent Advances in Metallic Nanostructures-Assisted Biosensors for Medical Diagnosis and Therapy.

The field of nanotechnology has witnessed remarkable progress in recent years, particularly in its application to medical diagnosis and therapy. Metallic nanostructures-assisted biosensors have emerged as a powerful and versatile platform, offering unprecedented opportunities for sensitive, specific, and minimally invasive diagnostic techniques, as well as innovative therapeutic interventions. These biosensors exploit the molecular interactions occurring between biomolecules, such as antibodies, enzymes, aptamers, or nucleic acids, and metallic surfaces to induce observable alterations in multiple physical attributes, encompassing electrical, optical, colorimetric, and electrochemical signals. These interactions yield measurable data concerning the existence and concentration of particular biomolecules. The inherent characteristics of metal nanostructures, such as conductivity, plasmon resonance, and catalytic activity, serve to amplify both sensitivity and specificity in these biosensors. This review provides an in-depth exploration of the latest advancements in metallic nanostructures-assisted biosensors, highlighting their transformative impact on medical science and envisioning their potential in shaping the future of personalized healthcare.

The Design of a Fiber-Coupling Micro-Lens Array for an M × N Wavelength-Selective Switch.

The M × N port wavelength-selective switch (WSS) is a crucial device used for Reconfigurable Optical Add/Drop Multiplexors and optical switching nodes in optical communication systems. The primary function of an M × N port WSS is to simultaneously transmit and switch multiple input optical signals from input fiber ports to output fiber ports through spatial light coupling. The port array module in a WSS that is responsible for coupling the spatial beam with the fiber determines the important parameters of the M × N port WSS, such as the number of input/output ports and insertion loss. In this paper, VirtualLab Fusion software 2023.1 (Build 1.558), as a powerful physical optics simulation tool, is used to design and optimize a silicon micro-lens array that can achieve the high-precision coupling of a fiber array with a pitch of 1143 μm. Finally, the designed micro-lens is manufactured and experimentally demonstrates its good beam focusing ability with a 3 dB insertion loss. The designed micro-lens array coupling system, which delivers 28 focused spots of approximately 1mm in size (the beam has a 1/e2 diameter) after transmitting a distance of around 300 mm, effectively extends the number of WSS ports. This design method of the micro-lens array significantly amplifies the port count of the M × N port wavelength-selective switch, effectively expanding it to encompass an impressive 28 × 28 ports.

Last mile access-based FSO and VLC systems

Free-space optics (FSO) and visible light communication (VLC) are interesting solutions for last mile access due to their benefits over conventional wired and wireless communication systems, including easy installation, low latency, high bandwidth, and low cost. This study aims to present last mile access using hybrid FSO/VLC, addressing the shortcomings of each technology. A hybrid system might, for instance, use VLC to give last meter connectivity to specific buildings and FSO to provide high-bandwidth outdoor connectivity across vast distances. In this paper, three proposed scenarios are designed using Optisystem and Matlab software, employing pulse amplitude modulation with four levels (PAM-4). The first scenario involves designing the last mile of the FSO-VLC system. In contrast, the second uses wavelength division multiplexing (WDM) technology to increase the data transmission capacity by enabling multiple optical signals at various wavelengths. The last scenario entails using VLC systems and the non-orthogonal multiple access (NOMA) approach to accommodate several users simultaneously. The simulation results show that the proposed system can fulfill outdoor link distances of more than 10 km and indoor coverage of about 2 m with a bit-error rate (BER) of 1.5×10−32 for a 10 Gbps data rate. However, the proposed systems can achieve the same data rate with a reduced FSO distance under different turbulence and weather conditions.

Enhanced Multiwavelength Response of Flexible Synaptic Transistors for Human Sunburned Skin Simulation and Neuromorphic Computation.

In biological species, optogenetics and bioimaging work together to regulate the function of neurons. Similarly, the light-controlled artificial synaptic system not only enhances computational speed but also simulates complex synaptic functions. However, reported synaptic properties are mainly limited to mimicking simple biological functions and single-wavelength responses. Therefore, the development of flexible synaptic devices with multiwavelength optical signal response and multifunctional simulation remains a challenge. Here, flexible organic light-stimulated synaptic transistors (LSSTs) enabled by alumina oxide (AlOX ), with a simple fabrication process, are reported. By embedding AlOX nanoparticles, the excitons separation efficiency is improved, allowing for multiple wavelength responses. Optimized LSSTs can respond to multiple optical and electrical signals in a highly synaptic manner. Multiwavelength optical synaptic plasticity, electrical synaptic plasticity, sunburned skin simulation, learning efficiency model controlled by photoelectric cooperative stimulation, neural network computing, "deer" picture learning and memory functions are successfully proposed, which promote the development for future artificial intelligent systems. Furthermore, as prepared flexible transistors exhibit mechanical flexibility with bending radius down to 2.5mm and improved photosynaptic plasticity, which facilitating development of neuromorphic computing and multifunction integration systems at the device-level.

Direct ink writing of three-dimensional Al2O3/polydimethylsiloxane photonic crystal heterostructures for terahertz frequencies

The photonic crystal heterostructures with multi-bandgap could manipulate multiple optical signals simultaneously, and have important applications in various multi-channel optical or optoelectronic devices. However, due to the limitations of materials and structure complexity, photonic crystal heterostructures for terahertz frequencies are rarely reported. Here, we report a facile and efficient approach to fabricate terahertz photonic crystal heterostructures (TPCHs) via direct ink writing (DIW) 3D printing technology. Al2O3/polydimethylsiloxane (PDMS) composite ink suitable for DIW has been developed. Al2O3/PDMS TPCHs with different structural parameters have been fabricated by DIW 3D printing. The results of simulation and experiments demonstrate that these TPCHs exhibit some special optical properties, such as bandgap deepening and dual-bandgap, compared with the conventional three-dimensional terahertz photonic crystals (3D-TPCs). The optical properties of TPCHs could be accurately regulated by varying the lattice constant of their compositional 3D-TPCs. The DIW 3D printing technology offers a new opportunity to create TPCHs with tailored photonic behavior for novel terahertz functional devices.

Multi-Degree-of-Freedom for Underwater Optical Wireless Communication with Improved Transmission Performance

Underwater optical wireless communication (UOWC) has great potential to provide high-speed and intensive communications over short ranges underwater. However, the mobility of the UOWC system is limited by the strict alignment requirements between the transceivers. In this paper, a multi-degree-of-freedom (MDOF) UOWC system with high flexibility and improved transmission performance is proposed and experimentally demonstrated based on the off-the-shelf light-emitting diode (LED) source. A hardware pre-equalization circuit is employed at the transmitter to extend the modulation bandwidth from 5.03 MHz to 50 MHz. At the receiving end, a Fresnel lens array is constructed to achieve efficient convergence of multiple incident optical signals from different directions. To improve the underwater signal transmission quality, we designed an additional digital signal recovery module after the trans-impedance amplifier. Finally, an experimental system is established with a 460 nm blue LED. The communication reliability of the system is verified by the measurement of the eye diagram and the bit error rate of the recovered signal at the receiving end. The experimental results show that optical signals from three different incident directions with a maximum data rate of 100 Mbps are reliably transmitted over a 1.2-m-long water tank using the non-return-to-zero on-off-keying modulation format.

Multimode Optomechanical Weighting of a Single Nanoparticle.

We demonstrate multimode optomechanical sensing of individual nanoparticles with a radius between 75 and 150 nm. A semiconductor optomechanical disk resonator is optically driven and detected under ambient conditions, as nebulized nanoparticles land on it. Multiple mechanical and optical resonant signals of the disk are tracked simultaneously, providing access to several pieces of physical information about the landing analyte in real time. Thanks to a fast camera registering the time and position of landing, these signals can be employed to weight each nanoparticle with precision. Sources of error and deviation are discussed and modeled, indicating a path to evaluate the elasticity of the nanoparticles on top of their mere mass. The device is optimized for the future investigation of biological particles in the high megadalton range, such as large viruses.

Identification of Water-Soluble Polymers through Discrimination of Multiple Optical Signals from a Single Peptide Sensor.

The pollution of water environments is a worldwide concern. Not only marine pollution by plastic litter, including microplastics, but also the spillage of water-soluble synthetic polymers in wastewater have recently gained increasing attention due to their potential risks to soil and water environments. However, conventional methods to identify polymers dissolved in water are laborious and time-consuming. Here, we propose a simple approach to identify synthetic polymers dissolved in water using a peptide-based molecular sensor with a fluorophore unit. Supervised machine learning of multiple fluorescence signals from the sensor, which specifically or nonspecifically interacted with the polymers, was applied for polymer classification as a proof of principle demonstration. Aqueous solutions containing different polymers or multiple polymer species with different mixture ratios were identified successfully. We found that fluorophore-introduced biomolecular sensors have great potential to provide discriminative information regarding water-soluble polymers. Our approach based on the discrimination of multiple optical signals of water-soluble polymers from peptide-based molecular sensors through machine learning will be applicable to next-generation sensing systems for polymers in wastewater or natural environments.

Dyes Encapsulated Nanoscale Metal–Organic Frameworks for Multimode Temperature Sensing with High Spatial Resolution

Luminescent nanothermometers working with high resolution and multiple optical signals are a powerful tool for complex analysis with high accuracy and selectivity. Herein, we describe a novel strategy, for the first time, by encapsulating two types of luminescent dyes (4-Mu and Flu) into the pores of a nanoscale metal–organic framework (MOF) ZIF-8 for multimode temperature sensing. When the temperature rises, the maximum emission wavelength (λmax) of dye 4-MU in ZIF-8⊃4-MU&Flu redshifts, and the emission ratio (IFlu/I4-MU) of Flu and 4-MU in ZIF-8⊃4-MU&Flu shows good linear response to temperature, which indicate the high sensitivity of the nanothermometer with multimode temperature readout (Sm = 0.62% K–1 at 240 °C). Remarkably, the uniform nanoscale size distribution and good thermal stability of the nanosized MOF⊃dyes composites enable it to perform multimode temperature sensing with high spatial resolution, which is demonstrated by the temperature mapping. Therefore, this material shows a more-reliable temperature indication by utilizing the multiparameter readout and an excellent temperature distribution with high spatial resolution.

WDM Network Issues: QOT Impairments, Dynamic Bandwidth Allocation, Modeling and Monitoring Schemes based on ML

Machine Learning (ML) has recently drawn the interest of both academics and professionals in the optical networking area to solve several problems. This trend has been triggered largely by the vast amount of available data (i.e., signal strength metrics, network alerts, etc.) and the large range of optimization criteria available in today's optical networks (such as modulation format, light path routes, transport wavelength, etc.). WDM systems are popular in the telecommunications industry. It increases network bandwidth without laying more cable. WDM technology in optical communication transports multiple optical carrier signals on a single fibre using various wavelengths of laser light. Wavelength division multiplexing (WDM) is an efficient strategy for leveraging the wide bandwidth of optical fibres to meet the rapid rise in demand for bandwidth on the Internet. WDM plays an essential role in both core and access networks in the communication network and faces various issues like its network performance is affected due to QoT impairments, Dynamic Bandwidth Allocation problem, Modeling, and Monitoring issues. Physical impairments are an issue in WDM and can cause calls to be blocked if the transmission quality is calculated in terms of minimum bit-error-rate. Dynamic allocation of bandwidth in WDM provides a crucial challenge for the effective and equal usage of the passive optical network upstream bandwidth when supporting the QoS specifications of various traffic groups. Fast attack monitoring can prevent the failure of vast volumes of data on all-optical networks. So, monitoring and modeling in a WDM network is also a critical issue. To solve these issues in WDM networks, more intelligence resources in scalable optical networks are necessary. ML techniques are demonstrating superiority in solving these issues. In this paper, a small detail about the WDM network is presented. Then, some WDM issues like QOT impairments, Dynamic Bandwidth Allocation, and modeling and monitoring are discussed, and then, in the next section focus on some ML techniques for solving these issues are presented.

Research on Optimization Policy Routing Technology of Optical Fiber Communication Network

With the development of global informatization, information has penetrated into every corner of human society. With the popularization of Internet, the transmission bandwidth of information becomes more and more important. Nowadays, people’s demand and dependence on information are becoming stronger and stronger. It is urgent to expand the capacity of wide area backbone communication network, and the optical network composed of wavelength division multiplexing (WDM) can just take this role. In WDM network, it can transmit multiple optical signals of different wavelengths in one fiber at the same time. WDM has the advantages of large transmission capacity, strong technical adaptability, simple implementation and easy expansion. In addition, WDM optical network can also make full use of the huge bandwidth of optical fiber itself to carry out high-speed transmission. Now, the optical network using WDM technology has become the backbone network of long-distance transmission. This paper studies the optical fiber communication system and analyzes the structure of the optical fiber network. For the optical network, how to find the appropriate routing is a very important technology. After analyzing all kinds of basic routing technologies, this paper proposes a new policy based routing technology, and carries out relevant experiments. The experimental results show that the new routing technology has some advantages compared with the old routing technology.

Microfluidic synthesis of robust carbon dots-functionalized photonic crystals

Robust hybrid microbeads with multiple optical signals have garnered widespread interests for various applications. However, the inefficient physical combination and the potential toxicity of raw materials (heavy metal-based quantum dots) have limited their sustainable development. Herein, we report a microfluidic strategy to achieve the continuous production of environmentally friendly carbon dots (CDs)-functionalized photonic crystal (PC) microbeads. The efficient mass and heat transfer on microscales and the covalent bonding crosslink between CDs and poly (methyl methacrylate-butyl acrylate-methacrylic acid) (P(MMA-BA-MAA)) colloid particles ensure effective assembly of CDs-P(MMA-BA-MAA) PC microbeads in the microchannel. Benefiting from this, the CDs-P(MMA-BA-MAA) hybrid microbeads behave stable fluorescence properties, together with highly saturated and angle-independent structural color, which can overcome the optical information confusion and distortion. Meanwhile, the obtained CDs-P(MMA-BA-MAA) hybrid microbeads show dual optical signal responsiveness through the variation of fluorescence and structural color under different ionic environment. Based on this, we realize the dual ionic sensing by constructing CDs-P(MMA-BA-MAA) hybrid microbeads arrays, which broadens the application of optical hybrid microbeads. In addition, we also prepare robust hybrid film and flexible lamp belt. The obtained robust CDs-functionalized PC hybrid microbeads with various attractive optical properties have a broad prospect in optical display, sensors, biological coding and antireflection coatings.

Design of low‐power all‐optical networks under the constraint of four‐wave mixing

SummaryIn this paper, we propose a static lightpath establishment method to design low‐power all‐optical networks under the constraint of four‐wave mixing (FWM). Since the FWM causes nonlinear interchannel crosstalk, it degrades the communication quality of optical signals. The FWM crosstalk effect becomes strong in a fiber as the number of passing optical signals increases. Therefore, we should reduce the number of optical signals passing through the same fiber from the perspective of the FWM. Meanwhile, in order to enhance the power efficiency of optical amplifiers, which are deployed at each optical fiber, it is preferred that multiple optical signals are transmitted in the same fiber. In order to decrease the power consumption while keeping high communication quality, the proposed method statically selects routes, wavelengths, and fibers for each traffic demand, considering the FWM crosstalk effect and the usage efficiency of the optical amplifiers. We show the performance of the proposed method through numerical experiments.

Research on Testing of Optical Fiber Wavelength Division Multiplexing System

In order to meet the requirement of long-distance high-speed data bus for information transmission in vehicles, optical fiber wavelength division multiplexing (FWDM) technology is used to realize the transmission of multiple optical signals by connector. Although wavelength division multiplexing technology has been widely used in the field of communication, the adaptability of the real-time control system needs to be further studied. In this paper, a prototype of the optical fiber wavelength division multiplexing system is tested and the test results are preliminarily studied, which provides a basis for evaluating transmission reliability margin and analyzing system failure.

On-Chip 4×10 GBaud/s Mode-Division Multiplexed PAM-4 Signal Transmission

Emerging 5G mobile networks and cloud computing applications are driving the demand for an ever-increasing capacity of short-reach optical communications. To meet this demand, mode-division multiplexing (MDM) has been proposed to scale up the bandwidth density by leveraging the spatial modes of an optical waveguide for transmitting multiple optical signals. On the other hand, the use of multi-level pulse amplitude modulation (PAM) can also increase the transmission bandwidth. Therefore, on-chip MDM in conjunction with PAM is an approach to enhance the transmission capacity in a photonic integrated circuit. In this paper, we report a silicon photonic integrated four-channel MDM circuit for high data rate on-chip communications with a low channel crosstalk and small insertion loss. To make the circuit have a small size that supports broadband operation, a mode multiplexer and demultiplexer are realized with the use of cascaded asymmetrical directional couplers on rib waveguides. By incorporating the MDM circuit in an optical communications system, the transmission of a 4 x 10 GBaud/s OOK and PAM-4 signal is experimentally demonstrated. The performance in terms of eye diagrams and power penalties is evaluated. The power penalties for the four-channel OOK transmission are 4.31, 2.38, 1.44 and 3.5 dB at a BER of 10−9. For the four-channel PAM-4 transmission, the power penalties are 7.98, 1.10, 0.66 and 5.14 dB. The required received optical power at a BER (<3.8 × 10−3) of the 7% overhead-hard decision FEC is −2.6 dBm. The key advantage of the approach is that high-capacity on-chip communications is enabled by the photonic integrated MDM circuit with a small footprint. Since the MDM circuit is implemented on a silicon photonic platform, the system holds high potential for full integration on a single chip.

Free Space Optical Communication in Long-Reach Unidirectional Ring-Architecture Fiber Network

In the work, a ring-constructed wavelength-division-multiplexing (WDM) access system for delivering multiple free space optical (FSO) wireless signals is investigated. To reach the FSO transmission through single-mode fiber (SMF) connection, the optical wireless unit (OWU) and remote OWU are designed in the WDM network. The downstream and upstream WDM FSO channels could be transmitted in unidirectional propagation with the same wavelength. Hence, the presented ring-based WDM network not only can transmit the FSO signal, but also can circumvent the Rayleigh backscattering (RB) interferometric beat noise. In addition, according to the experimental results, the SMF and FSO transmission lengths can reach 50 km and 500 to 1000 m at the forward error correction (FEC) level without using optical amplification and dispersion compensation, respectively, when four WDM wavelengths are exploited experimentally for demonstration.

Toward Practical Digital Phase Alignment for Coherent Beam Combining in Multi-Aperture Free Space Coherent Optical Receivers

In free space optical communication systems, multi-aperture coherent optical receivers based on digital coherent beam combining (D-CBC) technique can provide exceptionally high sensitivity and are more robust to the atmosphere turbulence compared with the single aperture receivers with the same collection area. D-CBC relies on the digital phase alignment algorithm (PAA) to align the different versions of signals in phase. However, due to the limited working frequency and space of the digital signal processing (DSP) circuits, the main obstacle to realizing real-time phase alignment of multiple high-speed optical signals is the computation complexity. Therefore, we need to minimize the computation complexity while guaranteeing a satisfactory performance. In this paper, we investigate the relationship between the computation complexity and the combining loss (CL) for both maximum ratio combining (MRC) and equal gain combining (EGC) based D-CBC. Universal analytical expressions are deduced that allow easy minimization of the computation complexity for both MRC and EGC based receivers according to the prescribed CL and input optical signal-to-noise ratios (OSNRs). The analytical expressions are validated by extensive numerical simulations. It is demonstrated that the computation complexity is mainly determined by the quality of the signal with a larger OSNR in MRC, while it is determined by the overall quality of the signals in EGC. When EGC is replaced with MRC, the computation complexity can be reduced by more than 55% at the same CL when the OSNR difference between the signals to be combined is above 10dB. The maximum computation complexity increases exponentially with decreasing input OSNR lower limit and the smaller the CL, the steeper the slope. Furthermore, when the prescribed CL is relaxed from 0.1 to 0.5dB, the maximum computation complexity can be reduced by about 80%. The results provide useful guidelines toward practical phase alignment on a real-time platform.

Space division multiplexing in standard multi-mode optical fibers based on speckle pattern classification

In optical communications the transmission bandwidth of single mode optical fibers is almost fully exploited. To further increase the capacity of a telecommunication link, multiplexing techniques can be applied across 5 physical dimensions: amplitude, quadrature, polarization, frequency and space, with all but the latter being nearly exhausted. We experimentally demonstrate the feasibility of an original space division multiplexing technique based on the classification of speckle patterns measured at the fiber’s output. By coupling multiple optical signals into a standard multimode optical fiber, speckle patterns arise at the fiber’s end facet. This is due to quasi-random interference between the excited modes of propagation. We show how these patterns depend on the parameters of the optical signal beams and the fiber length. Classification of the speckle patterns allows the detection of the independent signals: we can detect the state (i.e. on or off ) of different beams that are multiplexed in the fiber. Our results show that the proposed space division multiplexing on standard multimode fibers is robust to mode-mixing and polarization scrambling effects.

All-optical signal processing technologies in flexible optical networks

All-optical signal processing has always been critical assistance for the flexible optical networks (FONs) development which realizes various signal processing functions in all-optical domain avoiding electronic bottlenecks. The sustained demands for the transmission capacity and network functions drive the optical networks to enlarge the bandwidth, extend formats and increase network structures. The optical vectors are multiplexed in four domains at least in practical which are amplitude, phase, polarization and wavelength, and more multiplexing technologies are under researching. Moreover, various kinds of optical networks are employed to fulfill the constantly emerging applications such as core, metro and access networks. Facing the higher-order modulation formats, multiple multiplexing technologies and more and more complicated network structure, the future FON needs to have the feature of modulation format transparency, bandwidth transparency, wavelength transparency (3T), multi-function, multi-channel, multi-network (3M), self-perceiving, self-learning, self-adapting (3S). The transmission capacity, network flexibility and efficiency will always be the critical index for the whole network performance. The all-optical signal processing technologies have great potential in realizing the FON with the feature of 3T, 3M and 3S to process the multiple multiplexing optical signals and the problems among various optical networks. In this paper, the future FON features including 3T, 3M and 3S are introduced in detail, and the key issues in the ultra-large-capacity FON (e.g., 400G FON) are analyzed including transmission distance, flexible connecting and performance monitoring. Then, the crucial all-optical signal processing technologies and the principle and important applications of the phase-sensitive amplifier are introduced. Finally, the current existing problems and future developing trend for the all-optical signal processing technologies are discussed.

The Interactions Between Bright Light and Competing Defocus During Emmetropization in Chicks.

The environment comprises multiple optical signals that affect eye growth. We aimed to determine if the inhibitory effects of myopic defocus and bright light (BL) against myopia are additive in the presence of the myopia-genic hyperopic defocus. In experiment 1, three groups of 24 chicks each were fitted with the following multizone dual-power lenses (pl): pl/-10 D (50:50 area), +10/-10 D (50:50 area), and +10/-10 D (33:67 area) monocularly for 6 days. Half of each group were raised under normal illumination of 500 lux, 12/12-hour light/dark cycle, whereas the remainder were exposed to 6-hour BL of 40 klx and 6-hour 500 lux during the light cycle. In experiment 2, 38 chicks wore +10/-10 D (33:67 area) lenses monocularly for 8 days and were exposed to one of four light intensities for 6 hours per day-500 lux, 10 klx, 20 klx, or 40 klx-and received 500 lux for the remainder of the light cycle. In experiment 1, interocular difference in refractions after 6 days for the three groups were -3.6 D, +2.0 D, and -4.2 D, respectively, under normal light and were -0.9 D, +4.2 D, and +0.67 D under BL, manifesting as a shorter anterior segment and vitreous chamber. In experiment 2, the effect of BL increased with light intensity in the +10/-10 D (33:67) group, with a significant difference in refraction between the 10 klx and 20 klx groups (interocular difference -2.75 ± 2.76 D vs. 1.70 ± 2.40 D, P < 0.01), but plateaued between 20 klx and 40 klx (1.70 ± 2.40 D vs. 1.70 ± 0.35 D, P > 0.05). The protective effects of myopic defocus and BL against experimental myopia were additive. The inhibitory effect of BL against myopia was dose dependent at 10 klx and above but plateaued at 20 klx.