Optical Attenuation Research Articles

Design of a low power silicon-plasmonic hybrid electro-optic modulator relied on ITO

In this paper, a low power silicon-plasmonic hybrid electro-optic modulator relied on Indium Tin Oxide (ITO) has been proposed and designed. The proposed modulator is based on a three-coupled waveguide; two silicon waveguides and one hybrid plasmonic waveguide. A hybrid plasmonic horizontal waveguide with two ITO layers separates two silicon waveguides. Balancing between extinction ratio (ER) and insertion loss (IL) requires a trade-off when designing an optical modulator. The structure is proposed as a modulator that alleviates this trade-off. The structure has two ITO layers with an epsilon near zero (ENZ) effect for increasing light-matter interaction, maximizing optical mode's attenuating and disrupting the optical coupling. In the designed structure, amplitude modulation with high ER and, at the same time, low IL are obtained. The designed device is broadband with low power consumption. The ER, IL, and power consumption values were 16.05 dB, 0.3 dB, and 16.2 fJ. The finite-difference time-domain (FDTD) method is used to investigate the properties of the proposed modulator.

Broadband photonic tensor core with integrated ultra-low crosstalk wavelength multiplexers

Abstract The integration of artificial intelligence (AI) systems in the daily life greatly increases the amount of data generated and processed. In addition to the large computational power required, the hardware needs to be compact and energy efficient. One promising approach to fulfill those requirements is phase-change material based photonic neuromorphic computing that enables in-memory computation and a high degree of parallelization. In the following, we present an optimized layout of a photonic tensor core (PTC) which is designed to perform real valued matrix vector multiplications and operates at telecommunication wavelengths. We deploy the well-studied phase-change material Ge2Sb2Te5 (GST) as an optical attenuator to perform single positive valued multiplications. In order to generalize the multiplication to arbitrary real factors, we develop a novel symmetric multiplication unit which directly includes a reference-computation branch. The variable GST attenuator enables a modulation depth of 5 dB over a wavelength range of 100 nm with a wavelength dependency below 0.8 dB. The passive photonic circuit itself ensures equal coupling to the main-computation and reference-computation branch over the complete wavelength range. For the first time, we integrate wavelength multiplexers (MUX) together with a photonic crossbar array on-chip, paving the way towards fully integrated systems. The MUX are crucial for the PTC since they enable multiple computational channels in a single photonic crossbar array. We minimize the crosstalk between the channels by designing Bragg scattering based MUX. By cascading, we achieve an extinction ratio larger than 61 dB while the insertion loss is below 1 dB.

Automatic geographic atrophy segmentation using optical attenuation in OCT scans with deep learning.

A deep learning algorithm was developed to automatically identify, segment, and quantify geographic atrophy (GA) based on optical attenuation coefficients (OACs) calculated from optical coherence tomography (OCT) datasets. Normal eyes and eyes with GA secondary to age-related macular degeneration were imaged with swept-source OCT using 6 × 6 mm scanning patterns. OACs calculated from OCT scans were used to generate customized composite en face OAC images. GA lesions were identified and measured using customized en face sub-retinal pigment epithelium (subRPE) OCT images. Two deep learning models with the same U-Net architecture were trained using OAC images and subRPE OCT images. Model performance was evaluated using DICE similarity coefficients (DSCs). The GA areas were calculated and compared with manual segmentations using Pearson's correlation and Bland-Altman plots. In total, 80 GA eyes and 60 normal eyes were included in this study, out of which, 16 GA eyes and 12 normal eyes were used to test the models. Both models identified GA with 100% sensitivity and specificity on the subject level. With the GA eyes, the model trained with OAC images achieved significantly higher DSCs, stronger correlation to manual results and smaller mean bias than the model trained with subRPE OCT images (0.940 ± 0.032 vs 0.889 ± 0.056, p = 0.03, paired t-test, r = 0.995 vs r = 0.959, mean bias = 0.011 mm vs mean bias = 0.117 mm). In summary, the proposed deep learning model using composite OAC images effectively and accurately identified, segmented, and quantified GA using OCT scans.

Study of Variations in Mass Absorption Efficiency of Elemental Carbon Influenced by Different Measurement Techniques and Vehicle Emission

An inter-comparison study of mass absorption efficiency (MAE) of elemental carbon (EC) by different sampling modes and measurements was conducted at the School of the Environment (SE) and Station for Observing Regional Processes of the Earth System (SORPES) in Nanjing from November 2015 to October 2016. Compared with offline sampling, the underestimation in MAE of online sampling was mainly due to the decreased optical attenuation (ATN) from the losing EC, and the difference in MAEs of the two types of sampling was greatly influenced by secondary organic aerosol (SOA) formation. Based on five temperature protocols, which include four NIOSH-derived protocols and one IMPROVE-A protocol, dependence of MAE on the temperature protocol was investigated. The main reason for the change in MAE estimation was the difference in EC determination. The result showed that low peak inert mode temperature (Tpeak) produced a small amount of pyrolysis carbon, and this carbon fraction was typically classified as organic carbon (OC), resulting in overestimation of EC and thereby underestimation of MAE. In order to study the influence of vehicle emission of highway on MAE values of EC, the simultaneous observation at SE and SORPES was conducted. The mean MAE of SE was 8.5% lower than that of SORPES. EC concentration was estimated to decrease by 0.13 μg/m3 with an increment distance of 100 m. Good correlation was found between the differential ATN for the two sites and the proportion of secondary organic carbon (SOC) at SORPES (R2 = 0.71). These results indicated that high MAE at SORPES was expected to be relevant with the dry deposition of EC from vehicle emission and the lensing effect by SOA coating.

Photonic reservoir computer based on frequency multiplexing.

Reservoir computing is a brain-inspired approach for information processing, well suited to analog implementations. We report a photonic implementation of a reservoir computer that exploits frequency domain multiplexing to encode neuron states. The system processes 25 comb lines simultaneously (i.e., 25 neurons), at a rate of 20 MHz. We illustrate performances on two standard benchmark tasks: channel equalization and time series forecasting. We also demonstrate that frequency multiplexing allows output weights to be implemented in the optical domain, through optical attenuation. We discuss the perspectives for high-speed, high-performance, low-footprint implementations.

Influence of increasing SnO2 content on the mechanical, optical, and gamma-ray shielding characteristics of a lithium zinc borate glass system

A series of six samples were prepared based on the chemical composition of 65B2O3 + 20ZnO + (15-x)LiF + xSnO2 (where x = 0, 0.25, 0.5, 0.75, 1, and 1.25 mol%) to study the role of SnO2 on enhancing the optical and radiation attenuation capacity of the prepared glasses. The preparation of the glass series was performed using the melt quenching method at 1100 °C for 60 min. The density of the fabricated samples was measured using an MH-300A densimeter. The optical parameters of the fabricated glasses were calculated based on the spectrum recorded by a Cary 5000 UV–Vis–NIR double beam spectrophotometer in a wavelength range of 200 to 3000 nm. Furthermore, Monte Carlo simulation code and the XCOM online database were used to estimate the gamma-ray shielding capacity of the fabricated samples from 0.244 to 2.506 MeV. The results show enhanced gamma-ray shielding capacity due to the replacement of LiF by SnO2. The linear attenuation coefficient at 0.244 MeV was enhanced from 0.352 to 0.389 cm−1. The half-value thickness of the investigated glasses decreased from 1.967 to 1.784 cm when the increasing addition of SnO2 from 0 to 1.25 mol%.

Environment-Robust Polarization-Based Phase-Shift Dynamic Demodulation Method for Optical Fiber Acoustic Sensor

In this paper, an environment-robust polarization-based phase-shift dynamic demodulation method for optical fiber acoustic sensor is proposed. Through optical lever effect of polarization low-coherence interference and amplitude scaling differential cross multiplication (AS-DCM) algorithm, acoustic-source induced interference phase of the acoustic sensor can be demodulated in real-time with high precision. The maximum relative phase demodulation error was only 0.694% when the cavity length had an offset ∼4 μm. The maximum cavity length demodulation error was keeping less than 3.988 nm under the optical power reduced ten times, which demonstrated an ultra-stable demodulation for the largest permitted optical power attenuation range, to our best knowledge. The proposed method has a capability of tolerating large optical power attenuation and large cavity length random offset, providing an environment-robust way for optical fiber acoustic sensor working in extreme environments.

Sex-dependent jugular vein optical attenuation and distension during head-down tilt and lower body negative pressure.

Non‐contact coded hemodynamic imaging (CHI) is a novel wide‐field near‐infrared spectroscopy system which monitors blood volume by quantifying attenuation of light passing through the underlying vessels. This study tested the hypothesis that CHI‐based jugular venous attenuation (JVA) would be larger in men, and change in JVA would be greater in men compared to women during two fluid shift challenges. The association of JVA with ultrasound‐based cross‐sectional area (CSA) was also tested. Ten men and 10 women completed three levels of head‐down tilt (HDT) and four levels of lower body negative pressure (LBNP). Both JVA and CSA were increased by HDT and reduced by LBNP (all p < 0.001). Main effects of sex indicated that JVA was higher in men than women during both HDT (p = 0.003) and LBNP (p = 0.011). Interaction effects of sex and condition were observed for JVA during HDT (p = 0.005) and LBNP (p < 0.001). We observed moderate repeated‐measures correlations (r rm) between JVA and CSA in women during HDT (r rm = 0.57, p = 0.011) and in both men (rr m = 0.74, p < 0.001) and women (r rm = 0.66, p < 0.001) during LBNP. While median within‐person correlation coefficients indicated an even stronger association between JVA and CSA, this association became unreliable for small changes in CSA. As hypothesized, JVA was greater and changed more in men compared to women during both HDT and LBNP. CHI provides a non‐contact method of tracking large changes in internal jugular vein blood volume that occur with acute fluid shifts, but data should be interpreted in a sex‐dependent manner.

Synthesis and characterization of newly developed phosphate-based glasses through experimental gamma-ray and neutron spectroscopy methods: Transmission and dose rates

In this study, four new phosphate-based glasses with the compositions of CaO–Na2O–K2O–P2O5 (PN system), CaO–Na2O–K2O–Al2O3–P2O5 (PA system) and CaO–Na2O–K2O–Al2O3–SiO2–P2O5 (PS system) were synthesized and characterized through experimental gamma-ray and neutron spectroscopy methods. Glass densities were then measured experimentally and evaluated theoretically. Next, a high purity Germanium (HPGe) detector was used for determining the fundamental gamma-ray transmission parameters in 35.4–383 keV gamma-ray energies emitted from 133Ba source (Radioactivity: 3Ci). Additionally, the experimental setup was used to determine the equivalent dose (EAD) to get a better knowledge of fast neutron attenuation. Our findings indicate that experimental gamma-ray transmission measurements are consistent with standard theoretical data (EpiXS). Consequently, PA10 was shown to have higher gamma-ray and neutron attenuation capabilities when compared to the other glass samples studied. Our outcomes showed that increasing the molar contribution of Al2O3 to the phosphate-based glasses increased not only their transparency but also their gamma-ray and neutron attenuation capacities. It can be concluded that substituting Al2O3 for P2O5 is a functional and monotonic tool for improving the optical, gamma-ray, and neutron attenuation of phosphate-based glasses, which are being evaluated as prospective shielding materials for medical and industrial radiation facilities.

Integrated Hybrid VO2–Silicon Optical Memory

Vanadium dioxide (VO2) is an interesting material for hybrid photonic integrated devices due to its insulator–metal phase transition. Utilizing the hysteresis of the phase transition in voltage-biased VO2, we demonstrate a compact hybrid VO2–silicon optical memory element integrated into a silicon waveguide. An optical pulse writes the VO2 memory, leading to an optical attenuation that can be read out by the optical transmission in a silicon waveguide. Our on-chip memory cell can be optically written with energy as low as 23.5 pJ per pulse and with a 10–90% rise time of ∼100 ns. This approach is promising for optical data storage in silicon photonic integrated circuits.

Optical attenuation characteristics of Lake Daye, Hubei Province based on remote sensing inversion of Landsat 8 OLI

水体光学衰减特性直接影响湖泊的清澈程度和沉水植被的生存，利用遥感技术获取湖泊光学衰减分布特性能极大提高效率.基于2017—2019年的原位调查数据，利用Landsat 8 OLI影像开发了大冶湖水体光学衰减系数（K_d）的遥感反演模型，并分析大冶湖水体K_d的多年时空分布特性与驱动机制，以期为大冶湖流域的修复与管理提供参考.结果表明：波段比二次模型K_d=9.61（B1/B4）²-2.41（B1/B4）-6.40效果最好，精度达到R²=0.79，MAPE=23.9%，RMSE=0.89 m^-1.大冶湖水体K_d值的主要影响因素为悬浮物和浊度等，其次为有色溶解性有机物和叶绿素a.大冶湖K_d值分布在空间上由西向东逐渐递减，但局部也受到风速、陆源输入、人为活动和微生物活动等的影响，季节上平均以夏季最高、冬季最低.2013年以来大冶湖水体K_d值整体呈现下降趋势.;The optical attenuation characteristics of water directly affect the clarity of lake and the survival of submerged macrophytes. Using the way of remote sensing to obtain the optical attenuation distribution characteristics of lakes can greatly improve the efficiency. Lake Daye, located in Huangshi City, Hubei Province, is a typical shallow lake in the middle reaches of the Changjiang (Yangtze) River. Based on the in-situ survey data from 2017 to 2019, the remote sensing inversion model of Lake Daye water optical attenuation coefficient (K_d) is developed by using Landsat 8 OLI images, and the multi-year temporal and spatial distribution characteristics and driving mechanism of K_d in Lake Daye are analyzed, so as to provide reference for the restoration and management of Lake Daye basin. The results show that:the band ratio quadratic model was the best model (K_d=9.61 (B1/B4) ²-2.41 (B1/B4) -6.40), and its accuracy was R²=0.79, MAPE=23.9%, RMSE=0.89 m^-1. The main influencing factors of K_d of Lake Daye were suspended solids and turbidity, followed by chromophoric dissolved organic matter and chlorophyll-a. Moreover, the K_d value of Lake Daye decreased gradually from west to east in space, but it was also affected by wind speed, land-based input, human activities and microbial activities in some parts. The average of K_d is highest in summer and lowest in winter. Since 2013, the K_d value of Lake Daye has shown an overall downward trend.

Non-Additive Effects of Ionizing Radiation and Hydrogen on Optical Fiber Attenuation

Optical fibers having various dopants (pure silica, fluorine, germanium and phosphorous) were consecutively exposed to ionizing radiation (gamma or beta) and hydrogen-rich environments. The attenuation spectra measured before, in-between and after the exposures displayed impacts of the radiation and hydrogen as optical loss factors. Their intermediate and ultimate losses were found to drastically depend upon the dopant type. The fibers with pure silica and fluorine-doped cores behaved as most immune to the applied conditions. The irradiated germanium-doped fibers were found to be much more sensitive to hydrogen than the as drawn fibers, which is explained by development of radiation-induced reactive sites in the fiber, that further promote interactions with hydrogen. In contrast, the irradiated phosphorous-doped fiber displayed a strong hydrogen-induced bleaching at longer wavelengths (&gt;1000&#x00A0;nm), which was attributed to hydrogen reacted at P1 defect sites. A carbon coating present on one of the studied P-doped fibers was shown to prevent the bleaching.

In Vivo Imaging of the Breast Surgical Cavity Using Optical Coherence Tomography Attenuation Imaging

In Vivo Imaging of the Breast Surgical Cavity Using Optical Coherence Tomography Attenuation Imaging

Non-invasive Delay State Calibration of Silicon Optical Switching Delay Line

Silicon optical switching delay line (OSDL) chip, which composed of optical switches cascaded with optical waveguides of different lengths, has the merits of broadband true time delay and high delay accuracy, and is one of the key components in microwave photonic beamforming system. Due to the inevitable manufacturing errors of silicon photonic chips, the driving voltages of the &#x201C;through&#x201D; and &#x201C;cross&#x201D; states of each optical switch in OSDL need to be calibrated separately to ensure properly switching among different delay states. In general, additional optical power monitor taps or variable optical attenuators (VOAs) can be added into OSDL to achieve the switching voltage calibration processes of all the optical switches. However, adding additional optical power monitor taps after each optical switch will increase the extra loss of the delay line, also the I&#x002F;O ports will be greatly increased. Introducing silicon VOAs based on carrier injection in each delay stage of the silicon OSDL will increase the manufacturing cost and control complexity. Therefore, a simple and non-invasive calibration technique for all the optical switches in OSDL chip is greatly needed. Here, based on the interferograms induced by the cascade unbalanced Mach-Zehnder interferences formed in OSDL, we propose a simple and effective calibration method for silicon OSDL chip without introducing additional components. As a proof of concept, we calibrated and measured all the delay states of a 5-Bit silicon OSDL chip, and the measured results agree well with those obtained with optical power monitor taps.

Sistem Pedukung Keputusan Pemilihan Lokasi Pemasangan Wifi.Id Pada PT. Telkom Indonesia ( Witel Bekasi )

Abstract: Wifi.id is a broadband access network that is a medium for enjoying high-speed internet services up to 100 Mbps and various other multimedia services. Wifi.id is a place where we can access the internet with a good network that was built to meet the needs of the community to surf at high speed and pay at an affordable price. This Wifi.id service can only be found in a few places because this Wifi.id service is only installed in places where the location meets the standards. The purpose of this study is to find out locations that meet the right standards for installing wifi.id services because in placing wifi.id installation locations the right considerations and decisions are needed. In this study, researchers used several criteria, namely Fiber Optic, Spec Distance, Fiber Optic Attenuation, and location density. The method used in this study is the SAW method which can make decisions to find out the appropriate location for installing Wifi.id services in an effective way for complex problems.&#x0D; &#x0D; Keywords: Distance, Fiber Optic, Internet, Location, SAW, Wifi.id

Metrological evaluation of the influence of the detection gate width on a single photon detector through optical attenuation

In this paper, we propose a method for evaluating the impact of the detection gate width of an InGaAs/InP single-photon avalanche diode detector by analyzing the probability of detecting 0 or 1 photon as a function of the optical attenuation and the consequent variation of the average number of photons per gate measured by the detector (μ¯). With a detection efficiency η of 15 % and a dead time of 1 µs, considering gate widths of 4 ns, 8 ns, 12 ns, 16 ns, and 20 ns, an adequate optical power range for calibrating a single-photon avalanche diode detector was obtained in the range of 0.15 nW to 10 nW, with linear behavior and low measurement uncertainty of calibration curve fittings for 4 ns and 8 ns gate widths, respectively, associated with products μ¯η of 0.32 × 10-4 to 190 × 10-4 and 2.90 × 10-4 to 140 × 10-4.

A using remodulation filterless scheme of generating frequency 32-tupling millimeter-wave based on two DPMZMs

In this paper, we introduce a filterless system for generating frequency 32-tupling millimeter waves (mm waves) by using two dual-parallel MZMs (DPMZM). A 5 GHz RF signal is used to modulate DPMZM-1. After the first beat, a 20 GHz signal for remodulating DPMZM-2 is generated. Unnecessary sidebands are suppressed by the following methods in the structure of DPMZM-2. Firstly, the ±(4n-2)th-order optical sidebands are suppressed by controlling the phase difference between two Mach-Zehnder modulators (MZMs). Then, the 0th-order sideband is offset by adjusting the value of optical attenuator (OA) and optical phase shifter (OPS). Finally, the 1st and 7th-order optical sidebands nearly disappear by adjusting the modulation index of DPMZM-2 is 3.94. Remaining sidebands enter the photodetector beat frequency to obtain frequency 32-tupling mm waves. Simulation results show that its optical sideband suppression ratio (OSSR) is 27.7 dB and radio frequency sideband suppression ratio (RFSSR) is 27.96 dB, which is consistent with the theory. Using 5 GHz RF signal to drive the DPMZM-1, 160 GHz mm-wave signal was obtained. Furthermore, analyzes the effects of modulation index, optical power and attenuator value on the system performance, optimize the system performance to the best state.

Optical Waveguide Sensors for Measuring Human Temperature and Humidity with Gel Polymer Electrolytes.

In this work, multimodal responsive optical waveguide sensors using a stable cross-linking gel polymer electrolyte are successfully designed and fabricated by bottom metal-printing technology. Temperature and humidity sensing characterization based on the polymer electrolyte is simulated and analyzed. The multimodal responsive properties of the photonic chip are defined based on the analysis of ion relaxation dynamics: optical phase variable to monitor temperature and optical attenuation variable to detect humidity. In the supervising temperature (36.0-38.0 °C) and relative humidity (45-65%) range, the temperature and humidity sensitivities of the device are measured as 0.5π rad/°C and 1.14 dB/% RH, respectively. The fast-response time for both temperature and humidity of the multifunctional sensor can be obtained as 4.21 ms and 1.32 s, respectively. These findings provide a feasible scheme for the design and application of temperature and humidity sensors in potential medical treatment. From gel polymer electrolytes to multimode monitoring applications, the application exploration of high stability and ultrafast response multimode waveguide sensors is gradually being carried out. This study has great significance for the comprehensive monitoring of sophisticated human physical signs by multimodal responsive waveguide sensors.

A radiation–temperature coupling model of the optical fiber attenuation spectrum in the Ge/P co-doped fiber

A radiation–temperature coupling model of optical fiber attenuation spectrum has been developed. The spectrum in Ge/P co-doped fiber ranging from 800 nm–1600 nm at different temperatures and doses was measured and decomposed according to the configurational coordinate model based on which the power-law model was employed to predict the intensity of the color center absorption band at different doses. And the fiber loss in space was predicted by the model. This work will benefit the application of fibers in a complicated radiation environment.

A New and Simple Frequency Quadrupling Millimeter-Wave Signal Generation Enabled by a Single Mach-Zehnder Modulator Without Optical Filter

In this work, we have designed and proposed a new optical method to realize the generating of frequency quadrupling millimeter-wave (mm-wave) only employing one Mach-Zehnder modulator (MZM), and no any optical filter is needed. Compared with the previously reported quadruple frequency scheme, this work greatly simplifies the structure of the system, and makes the performance better and the cost lower. In the scheme, the MZM is operated at peak bias point, which is applied to retain the even order optical sidebands and wipe off the odd order optical harmonics. By tuning-up the optical shifter and optical attenuator (OATT) to control the zeroth order optical carrier returns zero, only ±2nd order optical tones are generated. We demonstrated and discussed the presented scheme feasibility based on the detailed mathematical formula derivation and numerical simulation, the simulation results of which show that employing a sinusoidal radio frequency (RF) source with frequency at 10 GHz to drive a push-pull MZM, a 40 GHz millimeter-wave (mm-wave) signal can be obtained. In the work, the performance of the generated quadrupling signal is that the optical sideband suppression ratio (OSSR) is 34.8 dB and the radio frequency sideband suppression ratio (RFSSR) can reach 27.2 dB.