Characteristics Of Optical Signals Research Articles

Modeling and Calculation of Limit Magnitude Detection of Orbital Optoelectric Tracking System

In order to evaluate the tracking capability of optoelectric tracking for an orbital target, the limit magnitude detection performance calculation model and its calculation method are studied. Combining the optical signal characteristics of the tracked orbital target, the background, and the CCD noise, the framework of the limit magnitude calculation model of the system for dynamic target detection is constructed. The relationships between the limit magnitude and the signal-to-noise ratio threshold of the optical signal characteristics, the exposure time of the CCD camera, and the dark current of the CCD imaging are studied and analyzed while considering the sunlight illumination condition, so that the calculation function and its change curve are given. The limit magnitude detection capability of the system is verified by the simulated experiment and the synchronized tracking test, and the detection distance maximum error of the model calculation is 3.6 m. The results show that under certain illumination conditions, when the exposure time of the CCD camera is longer and the SNR threshold is lower, the limit magnitude detection performance of the system is better, and the tracking performance of the system is more stable.

Optical signal characteristics analysis of atmospheric disturbance density fields generated by high-speed aircraft

Aircraft disturbs the adjacent atmospheric environment in flight, forming spatial distribution features of atmospheric density that differ from the natural background, which may potentially be utilized as tracer characteristics to introduce new technologies for indirectly sensing the presence of aircraft. In this paper, the concept of a long-range aircraft detection based on the atmospheric disturbance density field is proposed, and the detection mode of tomographic imaging of the scattering light of an atmospheric disturbance flow field is designed. By modeling the spatial distribution of the disturbance density field, the scattered echo signal images of active light towards the disturbance field at long distance are simulated. On this basis, the characteristics of the disturbance optical signal at the optimal detection resolution are analyzed. The results show that the atmospheric disturbance flow field of the supersonic aircraft presents circular in the light-scattering echo images. The disturbance signal can be further highlighted by differential processing of the adjacent scattering images. As the distance behind the aircraft increases, the diffusion range of the disturbance signal increases, and the signal intensity and contrast with the background decrease. Under the ground-based observation conditions of the aircraft at a height of 10000 m, a Mach number of 1.6, and a detection distance of 100 km, the contrast between the disturbance signal and the background was 30 dB at a distance of one time from the rear of the fuselage, and the diffusion diameter of the disturbance signal was 50 m. At a distance eight times the length of the aircraft, the contrast decreased to 10 dB, and the diameter increased to 290 m. The contrast was reduced to 3 dB at a distance nine times the length of the aircraft, and the diameter was diffused to 310 m. These results indicate the possibility of long-range aircraft detection based on the characteristics of the atmospheric density field.

Global Receptive Field Designed Complex-Valued Convolutional Neural Network Equalizer for Optical Fiber Communications

In this paper, an improved complex-valued convolutional neural network (CvCNN) structure to be placed at the received side is proposed for nonlinearity compensation in a coherent optical system. This complex-valued global convolutional kernel-assisted convolutional neural network equalizer (CvGNN) has been verified in terms of Q-factor performance and complexity compared to seven other related nonlinear equalizers based on both the 64 QAM experimental platform and the QPSK numerical platform. The global convolution operation of the proposed CvGNN is more suitable for the calculation process of perturbation coefficients, and the global receptive field can also be more effective at extracting effective information from perturbation feature maps. The introduction of CvCNN can directly focus on the complex-valued perturbation feature maps themselves without separately processing the real and imaginary parts, which is more in line with the waveform-dependent physical characteristics of optical signals. Based on the experimental platform, compared with the real-valued neural network with small convolutional kernel (RvCNNC), the proposed CvGNNC improves the Q-factor by ∼2.95 dB at the optimal transmission power, while reducing the time complexity by ∼44.7%.

Optical Signal Characteristics of Power Frequency Arc in Transformer Oil

Optical Signal Characteristics of Power Frequency Arc in Transformer Oil

Measurement and simulation of partial discharge using optical signal based on crystal fluorescent fiber

Partial discharge (PD) radiates optical signals in the process of discharge. By analyzing the characteristics of optical signals, the intensity of PD can be judged and the insulation status of equipment can be evaluated. The sensor for PD monitoring is prepared by the SiO2 cladding YAP:Ce crystal core fluorescent fiber (SYCF). In this work, the PD fault source with needle-plate electrodes model is established, the PD sensing responses between current transducer (CT) and SYCF are compared and the relationship between SYCF sensing responses and applied voltage is studied. The results indicate that the number of discharge optical pulses and applied voltage from 3 kV to 7 kV have a linear relationship with an R2 value of 0.96122, and the first pulse integral value of discharge signals and applied voltage from 3 kV to 7 kV have a linear relationship with a fit degree of 0.99223. The variation of electron density and N2 density between electrodes are studied by finite element simulation software. As the applied voltage increases, the electron density increases, and the time for streamer head to reach the cathode is gradually shortened. The density of N2 decreases and more photons will be produced. Through the analysis of theory, experiment and simulation, this research can provide a basis for measuring the intensity of PD by means of optical signals sensing by crystal fluorescent fiber.

Dual-mode aptasensors based on AuNPs and Ag@Au NPs for simultaneous detection of foodborne pathogens

Food safety detection is developing rapidly and with high throughput. Nanoparticles have obvious advantages in foodborne pathogens detection, among which gold nanoparticles (AuNPs) are widely used due to their stable chemical and optical properties. In this study, two kinds of aptasensors based on AuNPs were established. The first one was a visual detection method based on AuNPs lateral flow aptasensor, and the other one was a surface-enhanced Raman spectroscopy (SERS) aptasensor detection based on silver-core gold-shell nanoparticles (Ag@Au). The former allowed for visual readings, eliminated the need for machines, which achieved an initial diagnosis of three common pathogenic bacteria with a detection limit of 20–30 CFU/mL. The sensitivity of the latter can be improved by Ag@Au and the detection limit reached 2 CFU/mL, which can achieve high sensitivity and high-throughput detection. We systematically studied the structure, function and optical signal characteristics of AuNPs in detection, which can provide a favorable reference for the detection of foodborne pathogens in the future.

Detection technology of partial discharge in transformer based on optical signal

The detection of partial discharge (PD) in transformers is of great significance for preventing insulation defects from developing into insulation failures. Transformer partial discharge detection technology includes pulse current method, radio frequency measurement method, UHF method, ultrasonic detection method, gas chromatography, and optical detection method. Among them, the optical detection method has the characteristics of strong anti-electromagnetic interference ability, and the signal can be transmitted and received without loss. The optical detection method has unique advantages. In this paper, an optical signal measuring device for partial discharge inside the transformer is designed and fabricated, the typical insulation defect inside the transformer is simulated, and the optical signal characteristics of typical partial discharge are obtained. Compared with the pulse current method, it is found that the magnitude of partial discharge can be characterized by the integral of the optical signal. The characteristic of the optical signal phase resolved partial discharge (PRPD) spectrum of typical insulation defects is obtained. The PRPD spectrum of the optical signals of different defects is obviously different. It is feasible to draw the PRPD spectrum and identify the defect types according to the optical signal, which can be further applied to the identification of internal faults in transformers.

Optical arrangement method of lighting units in switchgear based on partial discharge luminosity distribution characteristics

Partial discharge optical measurement has the characteristics of high sensitivity and strong anti-interference, but its detection effect is greatly affected by the deployment position of the sensor. Therefore, based on the radiation characteristics and transmission characteristics of optical signals, the deployment position of sensors in equipment is optimized. In this paper, an optimal layout scheme of switch cabinet lighting unit based on the distribution characteristics of partial discharge photometric is proposed. Firstly, the optical simulation model of switchgear cable room is designed, and the discharge light source is set at the typical fault location. According to the optical simulation results, the position sensor with high response intensity is selected for different discharge light sources. In order to prove the effectiveness of the layout scheme, the discharge optical detection experiment of switch cabinet was carried out. The results show that the sensor can detect discharge effectively in the selected installation position.

DNN-based optical performance monitoring and its application for soft failure localization by multipoint estimation

In current optical communication networks, it is becoming increasingly important to use optical performance monitoring (OPM), which monitors the transmission characteristics of optical signals, to detect early degradation of features that may affect communication quality. This paper describes a method to realize OPM by training a deep neural network (DNN) with data obtained from digital coherent transceivers. In addition, we propose a dataset generation method, Data Augmentation using Differential Image (DADI), to enable the DNN to train with fewer data. We demonstrate that this method simultaneously classifies the optical signal to noise ratio and polarization mode dispersion with high accuracy. Furthermore, we apply DNN-based OPM to detect and localize soft failure in a multi-span environment. We develop a method to identify the location of soft failure by collecting information from DNN-based OPM estimated at multiple points in multi-span optical transmission links. We demonstrate that the method correctly localizes the soft failure with more than 90% accuracy on average (min, 85%; max, 98%) under single-channel experimental conditions.

Spatiotemporal Fourier transform with femtosecond pulses for on-chip devices

On-chip manipulation of the spatiotemporal characteristics of optical signals is important in the transmission and processing of information. However, the simultaneous modulation of on-chip optical pulses, both spatially at the nano-scale and temporally over ultra-fast intervals, is challenging. Here, we propose a spatiotemporal Fourier transform method for on-chip control of the propagation of femtosecond optical pulses and verify this method employing surface plasmon polariton (SPP) pulses on metal surface. An analytical model is built for the method and proved by numerical simulations. By varying space- and frequency-dependent parameters, we demonstrate that the traditional SPP focal spot may be bent into a ring shape, and that the direction of propagation of a curved SPP-Airy beam may be reversed at certain moments to create an S-shaped path. Compared with conventional spatial modulation of SPPs, this method offers potentially a variety of extraordinary effects in SPP modulation especially associated with the temporal domain, thereby providing a new platform for on-chip spatiotemporal manipulation of optical pulses with applications including ultrafast on-chip photonic information processing, ultrafast pulse/beam shaping, and optical computing.

The application of fluorescent optical fiber in partial discharge detection of Ring Main Unit

Ring Main Units (RMU) are commonly used in the power system. At present, there is no example of partial discharge (PD) detection in RMU by optical method. In this article, the PD in RMU was detected by optical method. Meanwhile, the characteristics of the optical signals and the influential factors have been analyzed. The phase, amplitude and quantity characteristics of the PD optical signals in the positive and negative half cycle was analyzed and listed and we can find the PD optical signals under four typical insulating defects have their own characteristics; if the output of the PMT have not reach it saturation value, the maximum amplitude of the optical signals will increase with the increase of the applied voltage while the average amplitude of the optical signals did not always increase except the insulation gap defect; besides, the number of the optical signals also have a positive relationship with the applied voltage. When the optical receiving length quadruple, the initial PD voltage (IPDV) of optical method has decreased about 14.7% while the number of PD optical signals has increased about 1046.5%; when the pressure changing from 0.1 MPa to 0.14 MPa, the IPDV has increased about 83.65% while the signals number has decreased about 36.23%; when the distance between the optical fiber and the defect model changing from 2.5 cm to 7.5 cm, the IPDV has increased about 9.3% while the signals number has decreased about 65.7%.

Influence of Different Structure and Specification Parameters on the Propagation Characteristics of Optical Signals Generated by GIL Partial Discharge

Partial discharge (PD) leads to the generation of electrical, acoustic, optical, and thermal signals. The propagation characteristics of optical signals in gas insulated metal-enclosed transmission lines (GIL) are the basis of optical detection research. This paper simulates the propagation of PD optical signals in GIL through modeling GIL with different structures and specification parameters. By analyzing the optical parameters on the probe surface and the detection points when the PD source position is different, the influence of the difference in specifications caused by the voltage level on the propagation of the GIL PD optical signal is studied. The results show that the GIL cavity structure will affect the faculae distribution and the relative irradiance (RI) of the detection surface; the PD source position has a huge impact on the faculae distribution on the detection surface, but has little influence on the RI; as the voltage rises, the faculae distribution on the detection surface becomes more obvious, and the mean of RI decreases. The above results have the reference value for the manufacture of GIL equipment and the research of PD optical detection. When the specular reflection coefficient of surface material is smaller and the diffuse reflection coefficient is larger, the outline of the light spot is clearer, the proportion of brighter parts is larger, and the maximum value of the RI is larger.

Comprehensive Eye Diagram Analysis: A Transfer Learning Approach

A deep transfer learning (TL)-based comprehensive eye diagram analysis and diagnosis scheme that can output essential eye diagram parameters, estimate fiber link length, calculate Q-factor, and diagnose device imperfection-induced impairments is proposed. TL can be used to extract system information and optical signal characteristics contained in eye diagrams and apply the learned knowledge and extracted features obtained from source tasks to related target tasks. As a source task, the proposed method estimates the transmission distance of a fiber link using convolutional neural network (CNN)-based eye diagram recognition. The feature extraction layers of the CNN are transferred to six target tasks involving the recognition of cross percentage, levels “0” and “1,” eye height and width, and Q-factor. Using TL reduces the total training times for on-off keying (OOK) and pulse amplitude modulation (PAM4) formats by $>$ 95% and 60%, respectively. We also investigated six common PAM4 impairments caused by transmitter imperfection by setting the impairment category identification as source task and the impairment-degree diagnoses as target tasks. The TL methods consistently outperformed non-TL methods, with higher accuracies and significantly reduced training times. The proposed impairment diagnosis technique should be useful in impairment healing and fault correction.

Monitoring Skin Trauma Healing in Mice Using Second-Harmonic Generation Combined with Optical Coherence Tomography

Convenient methods for rapidly evaluating wound healing could help clinicians to select effective treatment measures for patients within an appropriate time frame. In this study, we explored the use of second-harmonic generation (SHG) combined with optical coherence tomography (OCT) to monitor the healing state of wounds, including the macro-morphology and optical signal characteristics of regenerated tissue. Wounds were imaged and monitored using OCT and SHG on healing days 3, 5, 7, 14, 21, and 28. The accumulation and maturation of newly formed collagen during the healing process was detected using SHG in real time. Additionally, changes in the OCT signal and attenuation coefficient in wounds before and after trauma were measured using the single-scattering OCT model. The wound closure percentage, the SHG intensity of collagen, and the attenuation coefficient of the wounds were analyzed using correlation analysis, which produced correlation coefficients of R 1 2 = 0.944, R 2 2 = 0.9776, and R 3 2 = 0.9354, respectively. In theory, it is feasible to replace the wound closure percentage with the SHG intensity of collagen and the attenuation coefficient to evaluate wound healing. The OCT and SHG combination could be used to diagnose wound healing in real time.

Fine Control of Photoluminescence and Optical Waveguiding Characteristics of Organic Rubrene Nanorods Using Focused Electron-Beam Irradiation

We demonstrate the fine control of the nanoscale photoluminescence (PL) and optical waveguiding characteristics of light-emitting organic rubrene nanorods (NRs) through focused electron-beam (E-beam) irradiation. Nanoscale laser confocal microscope PL intensity and spectra of the focused E-beam-treated compartments of the rubrene NR drastically varied with E-beam dose, and yellow-white light emission from those compartments with a specific E-beam dose was observed. In optical waveguiding experiments, the propagation characteristics of optical signals along the single NR were dependent on the crystalline structure of the rubrene. For the E-beam treated NR, the waveguiding PL signals along the crystalline a-axis had relatively higher output, indicating the major axis for the optical energy transfer. Additionally, the waveguiding characteristics such as decay constant along the crystalline b-axis and c-axis of the NR considerably varied at the boundary of the E-beam treatment.

Extraction Method of the Contrast Feature of Ship Wake Images

Since how to evaluate the ship wake images quality quantitatively and effectively, and achieve the purpose of the extraction of ship wakes optical signal characteristics rapidly, is an important base task for the ship optics-wakes elimination technology now. The method about quality evaluation of ship wake images is studied in this paper based on the contrast model. According to the characteristics of the obvious contrast between wake area and seawater background area in ship wake images, this paper uses the contrast parameter as the index of wake image quality evaluation, and also as the characterization of the strength of ship wakes optical signal characteristic. An experiment about the extraction of contrast feature and its results show that the contrast parameters can not only reflect the subjective visual perception of the human eye on the wake images actual quality, but also better reflect the application essence of the wake image processing. And the contrast parameters can describe the intensitys changing rules of ship wakes optical signal characteristics reliably and quantitatively.

Complex dispersion relation of a double chain of lossy metal nanoparticles

We study the propagation characteristics of optical signals in waveguides composed of a double chain of metallic nanoparticles embedded in a dielectric host. We find that the complex Bloch band diagram for the guided modes, derived by the Mie scattering theory including material losses, exhibits strong differences with respect to the previously studied single chain. The results of the model are validated through the finite element solution of the Maxwell equations.

Feasibility of using Bose-Einstein condensates for filtering optical pulses

The feasibility of using the extreme slowing down of light in Bose-Einstein condensates of alkali metal atoms as a means of improving the spectral characteristics of optical signals is studied. The basis of this approach is the resonant character of the slowing down of electromagnetic pulses in these media. In other words, signals with frequency characteristics close to the intervals between levels in the energy spectrum of alkali metal atoms in a Bose-Einstein condensate are slowed down the most. The filtering of electromagnetic signals is described in terms of a microscopic theory for the response of a gas of hydrogenlike atoms to a weak external electromagnetic field. The possibility in principle of signal filtering is demonstrated using the example of an electromagnetic pulse with a normal (gaussian) spectral intensity distribution propagating through a rarefied gas of alkali metal atoms in a Bose-Einstein condensate state. We study in detail the use of the shift in the hyperfine Zeeman levels of sodium atoms in a homogeneous, external, constant magnetic field with an appropriate choice of the Zeeman sublevel populations of the ground states of these atoms. Conditions are determined such that, when an optical signal propagates through a condensate, it is possible to isolate components of that signal with strictly defined frequencies from residual low intensity noise. It is also shown that if the resulting filtered signal is repeatedly passed through a condensate with a different value of the magnetic field, noise can essentially be eliminated entirely from the optical signal.

Dispersive properties of linear chains of lossy metal nanoparticles

We study the propagation characteristics of optical signals in waveguides composed of linear periodic arrangements of metallic nanoparticles embedded in a dielectric host. We find the complex Bloch band diagram for the guided modes including material losses by employing Mie scattering theory as well as coupled dipole approximations. The results of the model are validated through finite element solution of the Maxwell’s equations.

Measurement of the Characteristics of Optical Signals Varying in Time Based on Registration of the Doubled Spectrum with Geometrical Displacement in Spectral Plane

A solution to the phase problem in optics is considered within the context of the analysis of time-dependent signals. The analysis concerns, in particular, determination of the amplitude and phase structure of signals and processes of ultrashort duration. The operation of the scheme is based on the registration of two spectra of the investigated radiation separated spatially. The first spectrum corresponds to the signal directly, while the other one is formed by summation of two spectra shifted geometrically with respect to each other by a distance of the order of a spectral device resolution. The description of the summarized spectrum contains the frequency derivative. The information obtained allows one to determine the amplitude and phase structure of the signal.