Optical Transport Research Articles

Accurate characterization of full-chain infrared multispectral imaging features under an aerodynamic thermal environment.

The detection performance of infrared imaging systems during high-speed flight is significantly impacted by aero-optical and aero-thermal radiation effects. However, traditional numerical calculations struggle to balance accuracy and efficiency, and there is a lack of a comprehensive model for infrared imaging in an aerodynamic thermal environment. In this study, we propose a calculation method based on Cellular Automata (CA) ray tracing, which allows for parallel calculation of aero-optical and aero-thermal radiation effects by combining optical field transport rules with the cellular space obtained by interpolation under fluid-solid boundary constraints. Using this method, we extend the traditional imaging feature prediction model of the infrared imaging system to obtain an accurate characterization model of the full-chain imaging features adapted to the aerodynamic thermal environment. Finally, we investigate the characteristics of infrared multispectral imaging system in various spectral bands under the influence of aero-optical and aero-thermal radiation effects. With this full-chain imaging model, the key elements of the imaging system under aerodynamic thermal environment can be globally optimized.

Quasi‐1D Polymer Semiconductor–Diarylethene Blends: High Performance Optically Switchable Transistors

AbstractOptically switchable field‐effect transistors (OSFETs) are non‐volatile photonic memory devices holding a great potential for applications in optical information storage and telecommunications. Solution processing of blends of photochromic molecules and π‐conjugated polymers is a low‐cost protocol to integrate simultaneously optical switching and charge transport functions in large‐area devices. However, the limited reversibility of the isomerization of photochromic molecules due to steric hindrance when embedded in ordered polymeric matrices represents a severe limitation and it obliges to incorporate as much as 20% in weight of the photochromic component, thereby drastically diluting the electronic function, limiting the device performance. Herein, a comparative study of the photoresponsivity of a suitably designed diarylethene molecule is reported when embedded in the matrix of six different polymer semiconductors displaying diverse charge transport properties. In particular, this study focuses on three semi‐crystalline polymers and three quasi‐1D polymers. It is found that 1% w/w of 1,2‐bis(5‐(3,5‐di‐tert‐butylphenyl)‐2‐methylthiophen‐3‐yl)cyclopent‐1‐ene in a blend with poly(indacenodithiophene‐co‐benzothiadiazole) is sufficient to fabricate OSFETs combining photo‐modulation efficiencies of 45.5%, mobilities >1 cm2 V−1s−1, and photo‐recovered efficiencies of 98.1%. These findings demonstrate that quasi‐1D polymer semiconductors, because of their charge transport dominated by intra‐molecular processes, epitomize the molecular design principles required for the fabrication of high‐performance OSFETs.

100 Gbps quantum-secured and O-RAN-enabled programmable optical transport network for 5G fronthaul

We have successfully demonstrated the first 5G open radio access network (O-RAN)-enabled and quantum-secured optical network solution and tested its performance in a 5G fronthaul use case. Our proposed solution is unique in a way that it combines a quantum key distribution (QKD)-compatible on-demand programmable 100 Gbps Ethernet encryptor with multi-tenant network operation while satisfying the stringent timing requirements of the 5G O-RAN with ultra-low pipeline latency. Moreover, our encryption cores provide the fastest reconfiguration speeds with the highest transmission capacity. By using dynamic reconfiguration technology, encryption schemes can be switched between Advanced Encryption Standard (AES) variations AES-256, AES-192, and AES-128 and Camellia-256, XOR, or no-encryption configurations in 16.7 ms for encryption and 24.1 ms for decryption. Furthermore, the key slicing functionality was introduced to our system, allowing users to have their separate key storages within the field programmable gate array and different key exchange schemes or refresh rates per client, where a secret key rate of 1.6 keys/s per client for less than 10 Gb of encrypted data could be provided. With encryption, the lowest system latency of 817.6 ns was achieved. Without encryption, the system latency could be as low as 667.2 ns. When our proposed system was tested in 5G fronthaul where our design was placed between a 5G radio unit and a 5G distributed unit/central unit, and the traffic between the 5G customer premises equipment and 5G core user plane function was transported and encrypted by our system over 100 Gbps, no significant impact on network latency on the millisecond scale was observed. Our system’s 10 Gbps fronthaul interface was stressed with a large Ethernet frame (1500B) at a rate of ≈9.8Gbps with 300,000 Internet Control Message Protocol pings, and less than 1% data loss was observed.

Blockchain-based trust management collaborative system for transport multi-stakeholder scenarios

A trend in future networks (i.e., beyond 5G and 6G) is the increasing virtualization and disaggregation of networks (i.e., Open Radio Access Network, network function virtulization/software-defined networking, or disaggregated optical networks, among others). This trend leads to a multi-vendor situation appearing in the telco arena (i.e., hardware suppliers, software function providers, vendors, operators) that communications service providers will need to deal with. This multi-stakeholder scenario complicates provisioning and the established relationships among actors based on operation agreements that define the requirements, penalties, and prices that generate a certain level of trust among them. This new disaggregated scenario implies an increment of possibilities and relationships, requiring agreements to be created in a run-time way. As the agreement is generated ad hoc, selecting a provider is a crucial decision, and so, trust and transparency are keys to help with this decision. As trust is a human/subjective concept, it is necessary to find a way to convert it into an objective parameter that can be used in an analytical field such as network control and management. This paper aims to present a model to compute the reputation of a provider based on a set of specific and measurable parameters and the use of Blockchain to make all of the process transparent and reliable to all players involved. Furthermore, this paper shows the design for a Blockchain-based Trust Manager that can compute and distribute the reputation and trust parameters to define how trustworthy are the multi-stakeholders. Finally, an experimental validation is presented on top of an optical transport network.

Towards 6G: fast and self-adaptive dynamic bandwidth allocation for next-generation mobile fronthaul [Invited

6G networks will deliver dynamic and immersive applications that bridge the real and digital worlds. The next-generation passive optical access network is a potential optical transport solution for the fronthaul of open radio access networks. With this solution, uplink bandwidth is shared, and uplink latency performance is thus highly dependent on how bandwidth is allocated. Compounding this issue is that future mobile fronthaul (MFH) is expected to support a range of applications that could vary in terms of traffic patterns, bit rates, etc. In view of dynamic network conditions, we present in this paper a machine learning driven dynamic bandwidth allocation scheme that rapidly learns to optimize bandwidth allocation decisions to satisfy uplink latency requirements. The principle of operation of the scheme detailing the reinforcement and transfer learning framework is first described. Performance evaluation results implemented on a target empirical network are then presented. Results show that self-adaptive bandwidth decisions can be rapidly achieved in response to different traffic patterns, network loads, and line rates, consolidating the potential of the dynamic allocation scheme in supporting diverse applications in future MFH networks.

Engineered Wood: Sustainable Technologies and Applications

Natural wood has been used for construction, fuel, and furniture for thousands of years because of its versatility, renewability, and aesthetic appeal. However, new opportunities for wood are arising as researchers have developed ways to tune the material's optical, thermal, mechanical, and ionic transport properties by chemically and physically modifying wood's naturally porous structure and chemical composition. Such modifications can be used to produce sustainable, functional materials for various emerging applications such as automobiles, construction, energy storage, and environmental remediation. In this review, we highlight recent advancements in engineered wood for sustainable technologies, including thermal and light management, environmental remediation, nanofluidics, batteries, and structural materials with high strength-to-weight ratios. Additionally, the current challenges, opportunities, and future of wood research are discussed, providing a guideline for the further development of next-generation, sustainable wood-based materials.

Chemically assembled 2D-van der Waals WSe2-WC heterostructured photo-anodes for electrochemical devices

Structural, optical, nanomorphological, photoresponsive and electrochemical charge transport characteristics of chemically assembled 2D-layered Tungsten Selenide (WSe2)-Tungsten Carbide (WC) heterostructure were examined. WC exhibited an optical bandgap of ∼3.2 eV, which did not show any optical absorption in the visible spectrum, and WSe2 showed the same in the spectral range of 200 nm-950 nm with an optical bandgap of ∼1.3 eV. Chemical assembly of WSe2-WC heterostructure was made in which the weight fraction of WSe2 was varied to understand its role in WC. Among the 2, 4, 6 and 8 wt% of WSe2 in WC, we observed that 6 wt% exhibited a dominant absorption and fluorescence emission (∼600 nm). High-resolution transmission electron microscopic studies revealed the d-spacing values of 0.24 nm and 0.33 nm for WSe2 and WC, respectively. Further, the presence of W (4f), Se (2d) and C (1 s) were traced out and studied by X-ray photoelectron spectroscopy. Raman modes A1g and EAg1 at 150 cm−1 and 250 cm−1 asserted the presence of WSe2 in WC which exhibited A1g at 150 cm−1. In addition, the individual WSe2 and WC along with WSe2-WC heterostructures were subjected to X-ray diffraction to study the crystallite size and strain-induced broadening due to the lattice deformation that occurred at the WSe2-WC heterostructures. Incorporating WSe2 into WC increased the photo-responsive behaviour and facilitated the charge transport as envisaged from the electrochemical impedance spectroscopic studies.

Modularized batch production of 12-inch transition metal dichalcogenides by local element supply

Two-dimensional (2D) transition metal dichalcogenides (TMDs) are regarded as pivotal semiconductor candidates for next-generation devices due to their atomic-scale thickness, high carrier mobility and ultrafast charge transfer. In analog to the traditional semiconductor industry, batch production of wafer-scale TMDs is the prerequisite to proceeding with their integrated circuits evolution. However, the production capacity of TMD wafers is typically constrained to a single and small piece per batch (mainly ranging from 2 to 4 inches), due to the stringent conditions required for effective mass transport of multiple precursors during growth. Here we developed a modularized growth strategy for batch production of wafer-scale TMDs, enabling the fabrication of 2-inch wafers (15 pieces per batch) up to a record-large size 12-inch wafers (3 pieces per batch). Each module, comprising a self-sufficient local precursor supply unit for robust individual TMD wafer growth, is vertically stacked with others to form an integrated array and thus a batch growth. Comprehensive characterization techniques, including optical spectroscopy, electron microscopy, and transport measurements unambiguously illustrate the high-crystallinity and the large-area uniformity of as-prepared monolayer films. Furthermore, these modularized units demonstrate versatility by enabling the conversion of as-produced wafer-scale MoS2 into various structures, such as Janus structures of MoSSe, alloy compounds of MoS2(1−x)Se2x, and in-plane heterostructures of MoS2-MoSe2. This methodology showcases high-quality and high-yield wafer output and potentially enables the seamless transition from lab-scale to industrial-scale 2D semiconductor complementary to silicon technology.

Jamming and depletion in extremely bidisperse mixtures of microscale emulsions and nanoemulsions.

While much attention has been given to jamming of granular and colloidal particles having monomodal size distributions, jamming of systems having more complex size distributions remains an interesting direction. We create concentrated, disordered binary mixtures of size-fractionated nanoscale and microscale oil-in-water emulsions, which are stabilized by the same common ionic surfactant, and measure the optical transport properties, microscale droplet dynamics, and mechanical shear rheological properties of these mixtures over a wide range of relative and total droplet volume fractions. Simple effective medium theories do not explain all of our observations. Instead, we show that our measurements are consistent with more complex collective behavior in extremely bidisperse systems, involving an effective continuous phase that governs nanodroplet jamming, as well as depletion attractions between microscale droplets induced by nanoscale droplets.

Resource-efficient protection scheme for optical service units in fifth-generation fixed networks

One of the visions of fifth-generation fixed networks (F5G) is to provide a guaranteed reliable experience (GRE). Optical transport networks (OTNs) represent a primary candidate technology to offer high-quality bandwidth in F5G and hence to support GRE. Unfortunately, current OTN technologies provide large-bandwidth tunnels for carrying aggregated (typically, Ethernet) traffic, and corresponding protection techniques in OTNs consume a lot of resources. The emergence of a new technology called an optical service unit (OSU), which subdivides the payload block of traditional optical data units into smaller units, allows for the development of more flexible and resource-efficient protection schemes. In this paper, we propose a new resource-efficient protection scheme for OSU-based OTNs called OSU protection (OSU-P), with the aim to save network resources while providing individual customized protection for each single user. OSU-P only reserves small-bandwidth protection/backup connections for protected services; then, when a failure occurs, the protection bandwidth is adjusted to the bandwidth required by the service during the switching process. This scheme can save a significant amount of network resources, but it may encounter resource conflicts between the protected services and other preemptable services after a failure occurs. Hence, we also propose a deterministic protection algorithm and a preemptable service provisioning algorithm based on overlapping risk avoidance, which can ensure successful recovery switching of protected services and the least impact on preemptable unprotected services after a network failure occurs. Simulation results show that, compared with traditional 1+1 and 1:1 protection schemes, OSU-P can reduce spare resources allocated for protection by about 30% and 11%, respectively, and reduce the blocking rate by about 27% and 10%, respectively. The performance of the proposed algorithms in terms of the percentage of unsuccessful protection and affected preemptable services is also verified.

Measurement-device-independent continuous variable quantum key distribution protocol operation in optical transport networks

Measurement-device-independent continuous variable quantum key distribution protocol operation in optical transport networks

Electrical manipulation of lightwaves in the uniaxially strained photonic honeycomb lattices under a pseudomagnetic field

The realization of pseudomagnetic fields for lightwaves has attained great attention in the field of nanophotonics. Like real magnetic fields, Landau quantization could be induced by pseudomagnetic fields in the strain-engineered graphene. We demonstrated that pseudomagnetic fields can also be introduced to photonic crystals by exerting a linear parabolic deformation onto the honeycomb lattices, giving rise to degenerate energy states and flat plateaus in the photonic band structures. We successfully inspire the photonic snake modes corresponding to the helical state in the synthetic magnetic heterostructure by adopting a microdisk for the unidirectional coupling. By integrating heat electrodes, we can further electrically manipulate the photonic density of states for the uniaxially strained photonic crystal. This offers an unprecedented opportunity to obtain on-chip robust optical transports under the electrical tunable pseudomagnetic fields, opening the possibility to design Si-based functional topological photonic devices.

Relevance and utility of the in-vivo and ex-vivo optical properties of the skin reported in the literature: a review [Invited

Imaging non-invasively into the human body is currently limited by cost (MRI and CT scan), image resolution (ultrasound), exposure to ionising radiation (CT scan and X-ray), and the requirement for exogenous contrast agents (CT scan and PET scan). Optical imaging has the potential to overcome all these issues but is currently limited by imaging depth due to the scattering and absorption properties of human tissue. Skin is the first barrier encountered by light when imaging non-invasively, and therefore a clear understanding of the way that light interacts with skin is required for progress on optical medical imaging to be made. Here we present a thorough review of the optical properties of human skin measured in-vivo and compare these to the previously collated ex-vivo measurements. Both in-vivo and ex-vivo published data show high inter- and intra-publication variability making definitive answers regarding optical properties at given wavelengths challenging. Overall, variability is highest for ex-vivo absorption measurements with differences of up to 77-fold compared with 9.6-fold for the in-vivo absorption case. The impact of this variation on optical penetration depth and transport mean free path is presented and potential causes of these inconsistencies are discussed. We propose a set of experimental controls and reporting requirements for future measurements. We conclude that a robust in-vivo dataset, measured across a broad spectrum of wavelengths, is required for the development of future technologies that significantly increase the depth of optical imaging.

Quantifying Charge Carrier Localization in PBTTT Using Thermoelectric and Spectroscopic Techniques.

Chemically doped poly[2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT) shows promise for many organic electronic applications, but rationalizing its charge transport properties is challenging because conjugated polymers are inhomogeneous, with convoluted optical and solid-state transport properties. Herein, we use the semilocalized transport (SLoT) model to quantify how the charge transport properties of PBTTT change as a function of iron(III) chloride (FeCl3) doping level. We use the SLoT model to calculate fundamental transport parameters, including the carrier density needed for metal-like electrical conductivities and the position of the Fermi energy level with respect to the transport edge. We then contextualize these parameters with other polymer-dopant systems and previous PBTTT reports. Additionally, we use grazing incidence wide-angle X-ray scattering and spectroscopic ellipsometry techniques to better characterize inhomogeneity in PBTTT. Our analyses indicate that PBTTT obtains high electrical conductivities due to its quickly rising reduced Fermi energy level, and this rise is afforded by its locally high carrier densities in highly ordered microdomains. Ultimately, this report sets a benchmark for comparing transport properties across polymer-dopant-processing systems.

PERENCANAAN SISTEM OPTICAL TRANSPORT NETWORK (OTN) PADA SISTEM TRANSMISI DWDM

An OTN consists of a set of optical network elements connected by a fiber-optic link. OTN can provide the use of transport, multiplexing, routing, management, supervision and resilience of optical channels. OTN (Optical Transport Network) itself is a technology that can increase network bandwidth and reliability by building network functions into optical networks. . An OTN consists of a set of optical network elements connected by a fiber-optic link.

Multichannel valley topological beam splitter based on different types of domain walls

Topological photonics has made great progress from physical concept verification to new technical applications, and valley topological photonic crystal (TPCs) are one of the most important candidates for future applications in functional devices because of large bandwidth and lossless optical transport. However, due to the limitations of the design method and structure arrangement, the multichannel valley topological beam splitter (BS) has not yet been much explored. Here, we reveal the different robustness of four types of domain walls in valley TPCs. Benefiting from the differences in domain walls, we numerically present and experimentally demonstrate a highly integrated multichannel valley topological BS in the microwave regime. Compared with traditional BSs, it has the advantages of being more robust and compact and having more output ports and higher integration. The reported multichannel topological BS opens an avenue to engineer the flow of light and offers effective design approaches for integrated photonic device miniaturization.

Charge transport through molecular ensembles: Triphenylamine-based organic dyes

Based on the recently synthesized triphenylamine-based organic dyes [https://doi.org/10.1021/acsami.1c11547], several small molecules that can be considered as organic semiconducting materials in photovoltaic devices were theoretically modeled. It is found that these designed dyes with the donor-π conjugated bridge-acceptor (D-π-A) framework show high charge transport properties in the dye-synthesized solar cells (DSSCs). Divers types of π-bridges are explored and the structural, electronic, optical, and charge transport characteristics of considered organic small molecules are studied. Our results revealed the effect of π-bridge in tuning the charge transport properties of the studied dyes. Especially, it is found that the thiazole-based moieties as the most favorable candidate for π-bridges, can be used in the D-π-A backbone of the synthesized dye to improve the photovoltaic performance of the organic semiconductors. For designed organic dyes, the low electron reorganization energies and high intra-molecular coupling created by π-stacking give rise to improved electron and hole mobilities. This approach can be used for improving the semiconducting character of organic dyes in photovoltaic devices.

Experimental investigation on transmission system of dual-polarization mode-division-multiplexing signals with few-mode erbium-doped fiber amplifiers

The transmission capacity of optical fiber communication can be effectively improved by the combination of dual-polarization (DP) high-order modulation format with mode division multiplexing (MDM) technology. We build up an experimental system for amplification and transmission of DP-MDM signals with orthogonal mode combination (OMC) and identical mode combination (IMC). The MDM transceiver units are composed of mode-selective photonic lanterns (MSPLs) and few-mode polarization controllers (FMPCs). The few-mode erbium-doped fiber amplifier (FM-EDFA) used here is constructed by homemade isolation and wavelength division multiplexers (IWDMs). The amplification and transmission experiments for 100 Gb/s dual-polarization quadrature phase shift keying (DP-QPSK) MDM signals are carried out by the commercial optical transport network (OTN) platform. An effective method of optimally receiving DP-MDM signals are presented by appropriately controlling the FMPC in the MDM receiver unit. The experimental results show that, (1) OMC DP-MDM signals have a better performance than IMC cases in differential modal gain (DMG), which provides a new means to reduce the DMG; and (2) under the optimization conditions, OMC and IMC DP-MDM systems possess a close receiver sensitivity, but the former has a larger optical power margin than the latter by 2.2 dB.

Compact single fiber optical tweezer–micropipette system for completely noninvasive cell sorting

Bridging optical tweezers and microfluidics can form a multifunctional platform, which can overcome the difficulties of precise manipulation in hydrodynamic flow in a noninvasive method. However, when integrated into a microfluidic chip, the fiber optic tweezer loses its flexibility. Here, we propose a compact single fiber optical tweezer–micropipette system. It can sort particles by differences in shape and refractive index in a completely noninvasive way while retaining the flexibility, high selectivity, and precision of a fiber optical tweezer. Compact microfluidic channels are formed by combining two different-diameter micropipettes. The internal diameter of the circular microfluidic channel is less than 30 μm. Furthermore, we calculated the trapping and pushing regions of Yeast and Chlorella and achieved the separation of Yeast from Chlorella in the experiments. We did 90 sets of tests on the sorting accuracy of single fiber optical tweezer (SFOT). SFOT was able to distinguish between two types of particles in each test. With the advantages of high selectivity, high accuracy, low optical power consumption, and compact structure, such methods can be used in the fields of optical separation, cell transportation, cell sorting, and single-cell analysis.

A review of the Geant4 simulation platform for applications involving optical-based sensing and dosimetry

Geant4 is a versatile simulation platform for numerous applications involving transport of ionizing radiation, including ionizing photons. Moreover, the physics needed for tracking optical photons is also embedded in the Geant4 simulation toolkit. From its introduction two decades ago there have been a variety of reports concerning the use of the Geant4 code in optical photons transport applications. Further to this, in particular for the interests herein, characterizations of radioluminescence radiation detectors have also been conducted. Noting the rapid development of such detectors, reliant on light collection and detection, there has been an implicit need for optimization of the different components forming the respective optical devices. Compared to ionizing radiation transport modeling less attention has been paid to this capability among the radiation physics community and Geant4 users. This review first describes in brief terms the physics built into Geant4 to provide for the transport of optical photons. This is followed by a retrospective on reported applications, discussion of the strengths and deficiencies of optical transport analyses by Geant4 and contemplation of possible future applications.