Advanced modulation formats like dual-polarization quadrature phase-shift keying (DP-QPSK) along with the digital coherent receiver are enabling optical networks to provide high spectral efficiency (SE) over long-haul transmission reach. The DP-QPSK based dense wavelength division multiplexing (DWDM) system with 37.5 GHz channel spacing can provide extra throughput of 33% compared to 50 GHz channel

In this paper, the expression for the SNR has been developed through the imaging model. It is concluded that the image SNR decreases with the increase of the number of light-emitting points of the target under the same hardware conditions and experimental parameters. Using uniform bright squares of different sizes as the target, the SNR of the reconstructed image is calculated. Simulation and prototype

Photometric stereo allows us to estimate the surface normal of an object based on its shading. In uncalibrated photometric stereo, the light source direction is unknown; thus, both the light source direction and surface normal should be estimated, which establishes an ill-posed problem with ambiguity in its solution. Consequently, assumptions should be made to uniquely determine the solution; however

To image distant and dim objects, this paper designs a sparse aperture optical system with a small F number and a large filling factor. The design process is divided into three steps. To start with, the curvature radius and spacing of the primary and secondary mirrors are calculated under the guidance of the paraxial imaging theory. Then, based on the primary aberration theory, the conic coefficients

A gradient-index (GRIN) array is used as an imaging unit in light-emitting diode (LED) printers. In this study, we measure tilts of GRINs in an array and analyze the intensity distribution of the image to clarify the tilting amount and to evaluate the relation between the GRIN tilt and the degradation of the image. The arrangement intervals of the GRINs are measured, and the GRIN tilts are calculated

An Upper Physical layer functional Split (UPS) for an Ethernet fronthaul network is modeled, and the frame delay and Frame Delay Variation (FDV) limitations are investigated. The results show that contention in Ethernet switch ports can cause an increase in the delay and FDV beyond proposed specifications for the UPS and other time-sensitive traffic types such as I/Q-type traffic. Time Aware Shaping

Up to now, laser self-mixing interferometry (SMI) has been widely applied to numerous scientific and industry fields. A easily negligible parameter, linewidth enhancement factor \(\alpha \), influences the inclination of SMI signals, and larger \(\alpha \) generally indicates more inclined fringes. It is demonstrated in the paper that solid-state lasers (SSL) have smaller linewidth enhancement factors

The radiation force calculated in the Rayleigh regime is investigated by comparison with the generalized Lorenz Mie Theory (GLMT). The basic concepts behind the Rayleigh regime and GLMT are introduced, and a numerical simulation is conducted to analyze the difference between these two methods. Several physical parameters are considered to evaluate their effect on the calculation accuracy of the Rayleigh

The saturated gain performance of the two-pump fiber optical parametric amplifier (2-P FOPA) in the presence of random dispersion fluctuation as well as fourth-order dispersion coefficient are investigated. The gain spectra of the 2-P FOPA is simulated by solving the coupled equations numerically, considering the dispersion fluctuations along the fiber as a stochastic process with a given standard

Multimode fibers (MMF) are enjoying a renewed attention boosted by recent advances in multimode complex nonlinear optics. Reason behind nonlinearity is occurred either due to intensity dependence of the medium refractive index or to inelastic-scattering phenomenon. The most commonly occurred non-linear effects in optical Multiple Input Multiple Output (O-MIMO) are the Kerr, Stimulated Brillouin Scattering

In hyperspectral imaging, the captured signal is often affected by saturation due to specular reflection or a peaky spectrum. In this paper, we propose a restoration method for saturated hyperspectral signals. Our algorithm is based on principal component analysis to obtain the reconstruction basis and then solve a linear constrained least square problem to calculate the coefficients of each basis

An accurate inversion technique in double integrating sphere (DIS) measurement is essential for determining the optical properties of biological tissue. Although there are several established techniques, the computational time and complexity for spectral analysis require some approximations of the anisotropy factor g and refractive index n. We aim to demonstrate an artificial neural network (ANN) based

In this study, we discuss a new method to optimize the design of an omnidirectional gaze optical imaging system with ultrahigh resolution and long focus. An aspheric diffractive optical element is used in the optical system to offer more freedom, simplify the structure, and decrease the chromatic aberration. Owing to large image sensor arrays, the omnidirectional gaze photoelectric imaging system is

Both Fabry–Pérot interferometry and the DC electrochemical method have been simultaneously used for the first time to measure in situ the anodic current density (J) of aluminum oxide films in 0, 2, 4, 5, 6, 8 and 10% sulfuric acid solutions (H2SO4). The calculated values of J by Fabry–Pérot interferometry were verified by the DC electrochemical method, i.e., a potentiostat, and the AC electrochemical

The proposed adaptive power control based on the chaotic hurricane search optimization (A-CHSO) for elastic optical networks (EON)s dynamically and efficiently adjusts the power increasing (r0) parameter taking into account the quality of transmission (QoT), which is measured by the optical performance monitors (OPM)s. For sake of comparison, three alternative power assignment methods are analyzed

As optical fibre reaches deeper into passive optical network (PON) in fibre-to-the-x (FTTx) networks, maintaining the integrity of these networks is indeed imperative. Essentially, best practices have been established throughout the installation and verification of the fibre access network. Equally significant is monitoring the optical fibre performance degradation in-service to ascertain efficient

Based on software defined optical network and machine learning, the flexible resource management mechanism (ML-FRM) is proposed, which meets the resource requirements of different services in the optical data center networks. The machine learning is integrated to the SDON controller, which accomplishes the resource allocation algorithms according to the classification and clustering results. ML-FRM

This study presents the development and validation of a fibre Bragg gratings (FBGs)-based sensor system for the assessment of strain in the midpalatal suture in subjects using rapid palatal expanders (RPEs). The ex-vivo experiments were made by means of positioning two RPEs in a porcine palatal region. The RPEs used were the Hyrax, a tooth-borne expander and MARPE (microimplant-assisted rapid palatal

The temperature on the busbars of electric generators in the end-winding region needs to be monitored continuously. High temperature is associated with curvatures, seams, and poor ventilation. However, this solution has limitations, such as the number of measurement points. This article presents a reconstruction algorithm to estimate high-resolution signals, from readings of a distributed temperature

This study presents a theoretical model for polarisation manipulation using electronic polarisation controllers (EPCs) based on fibre squeezing. A method to calculate the EPC configuration in order to transform between two arbitrary states of polarisation (SOP) is presented. After, a technique to deterministically generate four SOPs for use in polarisation-encoded quantum communication systems is proposed

Commercial light-emitting diodes are a low-cost and energy-efficient solution for the implementation of optical wireless communication, known as visible light communication (VLC). This technology has a huge growing interest, being recently a research spotlight in the scientific community, especially due to the increasing popularity and rapid development of self-sustainable smart houses and the Internet

Visible light communication (VLC) is a promising candidate for future indoor wireless communication. Light emitting diodes (LEDs) are popular choices as transmitters for VLC, since they are energy efficient and have the ability to provide illumination and data transmission simultaneously. VLC is attractive for reasons such as security, the ability to use a licence free spectrum, and broad bandwidth

The rapid growth of digital services has led to a widespread deployment of opto-electronics that furnish the Internet as an efficient communication backbone. The electroabsorption-modulated laser (EML) is a representative example of a monolithic integrated electro-optic converter that has early become a commodity: it has been widely adopted in telecommunication networks in virtue of its cost- and energy-efficient

In this study, the authors present a single-band tunable metamaterial absorber in the 3.00–6.00 THz region. This absorption peak (90.00% amplitude) is excited by the cavity resonance at the resonance frequency of 4.55 THz. The cavity resonance mode is achieved in the spacer cavity formed by the metal/strontium titanate (STO)/SU-8 photoresist (SU-8)/STO/metal layers. The effect of structural parameters

This study aims at optimising the graphene coverage in a microresonator for the design of an efficient modulator by using a combination of graphene induced losses and phase shift. The graphene integration in the ring can provide tunability by means of altering the loss and coupling coefficient by changing the graphene coverage or its chemical potential. The fundamental parameters of graphene integrated

An accurate power output prediction of the photovoltaic system is pivotal to eliminate the extra cost and the negative impact in the utility grid integrated with photovoltaic power sources. The power output of a photovoltaic system is predicted by introducing a long short-term memory method. Moreover, the influence of noise data on prediction results is eliminated with the empirical mode decomposition

In this study, the authors have theoretically investigated the effects of metallic nanoparticles (NPs) on the performance of nanowire-based plasmonic photodetectors. For this goal, they propose a novel structure for plasmonic photodetectors in which the metallic NPs are deposited on a semiconductor nanowire sandwiched between two ohmic contacts. To calculate the eigenstates of the system, they have

The liquid-infiltrated photonic crystal fibre (LI-PCF) is proposed for guiding terahertz radiation. Geometrical asymmetry is achieved by introducing a large ellipse in the core. By filling the ellipse with liquid cocaine, the optical properties of the photonic crystal fibre (PCF) are theoretically examined using finite element method-based COMSOL multiphysics software. At an operating frequency of

In this work, a self-oscillating parametric optical frequency comb generator is proposed and experimentally demonstrated. It consists of an electroabsorption modulated laser (EML) based dual-loop optoelectronic oscillation loop and a parametric frequency mixer. In the experiments, a 20 GHz radio-frequency signal is produced to drive the EML. The output pulses from the EML are amplified to work as pump

This study investigates the performance of a decode-and-forward-relay-based hybrid free space optical (FSO)/radio frequency (RF) system with selection combining. The proposed hybrid system considers an FSO sub-system as a default transmission option and RF sub-system is utilised when FSO is in outage. For the proposed system, the outage threshold signal-to-noise ratio (SNR) is an important parameter

Amplify-and-forward cooperative underwater optical wireless communication employing optical improved quadrature spatial modulation (OIQSM) is proposed in this study. It uses multiple signal constellations, thereby improving the system performance. It uses multiple lasers but it activates only a few of them depending on the message bits and can transmit double modulated symbols in a single symbol interval

In recent times, several applications requiring highly accurate indoor positioning systems have been developed. Since the global positioning system is unavailable/less accurate in the indoor environment, alternative techniques such as visible light positioning (VLP) are considered. The VLP system benefits from the wide availability of illumination infrastructure, energy efficiency and the absence of

A novel C + L band hybrid erbium-doped fibre amplifier (EDFA) using a two-stage configuration was proposed and demonstrated experimentally. The amplifier is composed of a 0.5-m long hafnium bismuth erbium co-doped fibre (EDF) to provide gain within the C-band and a 4-m long zirconia-based EDF to provide gain within the L-band. The proposed amplifier was examined based on the multi-wavelength input

We propose a superimposing interferogram method to enhance the sensitivity and interference definition of spatial-phase-shift interferometers. The proposed method uses a multi-slit array as a redesigned field stop for the spatial-phase-shift interferometer. The widths of the apertural and blocked areas correspond to half the wavelength of the fringe pattern on the imaging plane and determine the wavelength

We live in a colorful world, and it is important for us to receive visual information from colors in situations such as when we read a map. However, such important color-based information cannot be accurately received by some people. These people generally have some type of color vision deficiency such as protanopia or deuteranopia. It is important to realize their difficulties in recognizing differences

Hollow-core photonic crystal fibers (HCPCFs), a form of optical conveyer belts, have been used to guide particles for many years. However, only the translational motions of a guided particle can be manipulated. In contrast to traditional types, we demonstrate a new form of optical conveyor belts based on a polarization-maintaining hollow-core photonic crystal fiber (PMHCPCF). Because of the constant

We demonstrate distributed measurement of the polarization beat length along single-mode optical fibers (SMFs) using slope-assisted Brillouin optical correlation-domain reflectometry (BOCDR) with high spatial resolution, long measurement range, high sampling rate, and single-end accessibility. The beat lengths of SMFs wound on mandrels with radii of 10.5, 7.5, and 3.4 cm are measured to be 36.0, 18

Two-point resolution for ordinary microscopy was studied in a bright background under partially coherent light. The basic equation was derived from the unified theory of image intensity for two point-like objects for bright and dark backgrounds. For an extended Rayleigh’s criterion, it is shown that the two-point resolution in a bright background is noticeably different from that in a dark background

The optical three-dimensional (3D) measurement technique based on the laser stripe has become increasingly important in additive manufacturing, which is necessary to extract the laser stripe accurately. In welding, the wrong laser stripe centers due to the high-brightness noise are usually extracted, which causes serious measurement error. In this paper, a laser stripe extraction algorithm based on

Applications of digital micromirror device for lidar are overviewed. A large Lagrange invariant value makes DMD as one of the attractive beam steering transmitter and receiver solutions for a time-of-flight lidar, especially with its an extended angular throw by synchronized pulsed laser illumination.

We have established a holographic particle tracking velocimetry (HPTV) technique based on compressed sensing (CS) for measurement of the velocity field of microflows in this study. In conventional HPTV, where the scattered light field is reconstructed via backpropagation calculations, the particle image spreads greatly in the depth direction and it is then difficult to perform three-dimensional three-component

In the astronomical speckle interferometry, low-light CCD cameras such as the electron bombarded/multiplying CCDs (EB/EMCCDs) are being widely used for taking the faint speckle images. The detector noise affects the power spectral estimate of the astronomical object as well as the speckle noise does. The estimation errors of the object power spectrum are results of the propagation of the random fluctuations

We report on a high-power continuous-wave (CW) intracavity frequency-doubled laser at 670.8 nm, which is produced by the second-harmonic generation of a diode side-pumped Nd:YAP crystal laser with a type-II noncritically phase-matched LBO crystal. A maximum output power up to 13 W at 670.8 nm is obtained with an optical-to-optical \((808\mathrm{ nm}\to 671\mathrm{ nm})\) efficiency of 2.4%. The beam

This study presents the design and analysis of energy-efficient visible light communication-based downlink and uplink using a thin-film corner cube retroreflector (TCCR). The uplink establishment from the user device (UD) to base station (BS) is achieved with the retroreflection of the downlink light beams using TCCR in UD. It eliminates the requirement of active optical source in the UD that reduces

The authors experimentally demonstrated the generation of mode-locked pulses from all-fibre erbium-doped fibre laser cavity by using organic material, Alq 3 , as a saturable absorber (SA). The SA film was integrated into a ring fibre laser cavity to act as a mode-locker. A mode-locking operation was achieved in three different experiments with pulse width/repetition rate of 1.26 ps/3.36 MHz, 970 fs/3

In the present paper, the bit error rate (BER) performance of hybrid power line communication (PLC) and multiple-input multiple-output (MIMO) visible light communication (VLC) system (HPMV) has been investigated using line-of-sight (LOS) and LOS plus first reflection (L-R1) signals for room size of 5 m × 5 m × 3 m (configuration A) and 7.5 m × 7.5 m × 3.5 m (configuration B). In the work, Rayleigh

Photo-current characteristics in close space sublimation processed multi-facetted Cadmium Telluride (CdTe) micro-granular films were studied under AM1.5, blue and green laser illuminations to assess the energy dependent charge transport characteristics. Photo-current under AM1.5 illumination (100 mW/cm 2 ) resulted in three times more than dark current while it was observed 2.4 and 2.5 times more in

In this study, we analyze the combined effect of TMD/Perovskite/2D Material on the performance of SPR biosensor using Kretschman configuration. In order to optimize the parameters, we compare the results of each material falls in the family of TMD/Perovskite/2D respectively and finally applied in the proposed sensor. It is observed that the combined structure based on black phosphorus, a 2D material

Here, the authors propose a new approach for realising wideband and polarisation-independent antireflection coating, based on a metamaterial composed of a subwavelength array of metallic pillars with a square cross-section. The effective impedance of the array can be duly adjusted by the size and distance of the pillars. As such, the authors design the effective impedance of the antireflection coating

This work examined the possibility of overcoming narrow band optical absorption of organic dyes in the range of 350–700   nm via surface plasmon effect mediated by RF-sputtered tungsten (W) thin film on mesoporous TiO 2 for dye-sensitised solar cells (DSSCs) application. The UV–visible spectroscopic measurement showed optical absorption of W-film in the spectral range of 350–700   nm with a dominant

This study experimentally demonstrates a Q-switched fibre laser using a new tungsten tri-oxide (WO 3 )-based saturable absorber (SA). Using the drop and casting approach, we managed to prepare a thin film that contained WO 3 powders in polyvinyl alcohol. A small bit of the film was used to form an SA which was placed in a ytterbium-doped fibre laser cavity to generate a Q-switched laser. The laser

A new device architecture of an all-optical logic inverter (AOLI) has been proposed in this study. The AOLI functions based on stimulated Raman scattering (SRS) in silicon nanocrystal embedded slotted photonic crystal waveguide (SPCW). The operating power and footprint size of the proposed device have significantly been scaled down to ∼1.5 mW and , respectively, by combining the benefits of giant SRS

A small portion of an optical fibre clad was removed and coated with methylamine hydroiodide by a slurry deposition process to develop an evanescent wave optical fibre ammonia sensor. The experiment was performed for a few volatile organic compounds in order to understand the selectivity and sensitivity. Prior to the gas sensing measurement, the methylamine hydroiodide sample was characterised using

In optical fibre communication system, improved modulation schemes have been proposed to increase capability and high bit rate transmission. One such technique is optical duobinary modulation, which can able to broadcast high-speed optical signals over bandwidth-limited channels. The conventional modulation schemes employ the non-return-to-zero modulation and return-to-zero modulation technique. These

Non-linearities introduced by power amplifiers in communication systems have been a subject of interest for industry and academia for a long time. On one hand, the search for increased range intrinsically incites operators to boost input power. On the other hand, this leads to stronger non-linear phenomena in amplifiers, which in turn increase the bit error rate. The situation led to the emergence

Evolution and accessibility of smart-phones have led to a huge demand in network bandwidth. The ubiquitous use of smart-phones in high-speed trains poses a unique challenge in delivering high-speed internet service on board. This challenge can be overcome by employing free-space optics, an alternative to radio-frequency technology. Previous coverage models for ground–train communications employed single

A novel liquid-core photonic crystal fibre (LC-PCF) based on the Zeonex substrate has been proposed for sensing the varying concentration of kerosene in petrol and diesel fuels in terahertz frequencies. Fuel sample infiltration is achieved by designing a single hexagon in the porous core region. The LC-PCF has been numerically studied using a finite element method. By filling the core hexagon with

Rich scattering of ultraviolet signals enables the non-line-of-sight outdoor wireless connectivity and eliminates the line-of-sight requirement of free-space optical links. Besides scattering losses, ultraviolet signals also suffer from the atmospheric turbulence-induced fading. One of the strong fading mitigation techniques is the spatial diversity, which has been extensively studied in the context

We propose an image reconstruction technique of a color 3-D object to perform image refocusing by combining information from bright-field image and digital holography. The key concept is first to reconstruct the 3-D object using compressive holography. Next, a binary mask is created to separate objects and transparent voxels. Then, the mask is used to assist the 3-D color object reconstruction from

For images with insufficient visibility, image processing is required. Retinex theory is often implemented for image contrast enhancement for images with this characteristic. This paper proposes a multi-scale retinex-based contrast enhancement method using the illumination component; this method could preserve the naturalness of color images. In the proposed method, illumination was first modified