Optical Attenuation Research Articles

The DNN-based DBP scheme for nonlinear compensation and longitudinal monitoring of optical fiber links

In this paper, a double-effect DNN-based Digital Back-Propagation (DBP) scheme is proposed and studied to achieve the Integrated Communication and Sensing (ICS) ability, which can not only realize nonlinear damage mitigation but also monitor the optical power and dispersion profile over multi-span links. The link status information can be extracted by the characteristics of the learned optical fiber parameters without any other measuring instruments. The efficiency and feasibility of this method have been investigated in different fiber link conditions, including various launch power, transmission distance, and the location and the amount of the abnormal losses. A good monitoring performance can be obtained while the launch optical power is 2 dBm which does not affect the normal operation of the optical communication system and the step size of DBP is 20 km which can provide a better distance resolution. This scheme successfully detects the location of single or multiple optical attenuators in long-distance multi-span fiber links, including different abnormal losses of 2 dB, 4 dB, and 6 dB in 360 km and serval combinations of abnormal losses of (1 dB, 5 dB), (3 dB, 3 dB), (5 dB, 1 dB) in 360 km and 760 km. Meanwhile, the transfer relationship of the estimated coefficient values with different step sizes is further investigated to reduce the complexity of the fiber nonlinear damage compensation. These results provide an attractive approach for precisely sensing the optical fiber link status information and making correct strategies timely to ensure optical communication system operations.

Fiber Optic Attenuation Analysis Based on Mamdani Fuzzy Logic in Gambir Area, Central Jakarta

In this study, the authors conducted an analysis of the quality of fiber optic network maintenance based on attenuation value and maintenance time using fuzzy Mamdani logic and simulated using Matlab software, to improve accuracy in drawing conclusions on maintaining quality. This study uses a quantitative method, in which the author obtains a summary of customer data from PT. Telkom Indonesia in a period of 4 months of observation from August to November 2021. In August there were 776 customers, in September there were 362 customers, in October there were 359 customers, and in November 445 customers who underwent Indihome fiber optic cable maintenance. The test results with the centroid method with an input Handling Time of 1.5 hours and an Attenuation of 15 dB, then the output Repair Quality is 5.5 or categorized as Good. The greater the attenuation value generated, the more time it takes to maintain the IndiHome internet network disturbance. This is due to the many technical maintenance of fiber optic cables carried out by technicians to adjust for damage/trouble in the field. It is expected that maintenance can be carried out routinely in order to avoid fatal internet disturbances on the customer's side, and maximize maintenance time according to the dosage determined by the company, which is less than 3 hours, taking into account the work performance of technicians and also the quality of maintenance.

Temperature Influence on the Optical Properties, Attenuation Coefficient, and Total Molecular Cross Section of Dhunge Dhara Drinking Water

This work aims to measure the different parameters of Dhunge Dhara water (DDW) such as absorbance, transmittance, mass attenuation coefficient (MAC), and molecular cross section (MCS) and experimentally compare the obtained values with those of pure water (PW) at various temperatures (5 °C to 90 °C) using a theremino spectrometer. Observation shows that the parameters vary with temperature and wavelength. The transmittance of DDW ranges from 18% to 85% and absorbance of the same ranges from 0.09 Au to 0.7 Au. Meanwhile, the transmittance of PW ranges from 40% to 98% and the absorbance of the same ranges from 0.09 Au to 0.39 Au. The MAC of PW ranges from 0.02 cm2g−1 to 0.6 cm2g−1, and that for DDW ranges from 0.2 cm2g−1 to 1.1 cm2g−1 at 30 °C. The MCS of PW ranges from to , and that of DDW ranges from to at 30 °C. In conclusion, DDW has an extremely high amount of impurities and total dissolved solids and is recommended to be filtered prior to use (drinking and cooking)

Propagation Losses Estimation in a Cationic-Network-Based Hydrogel Waveguide.

A method based on the photographic recording of the power distribution laterally diffused by cationic-network (CN) hydrogel waveguides is first checked against the well-established cut-back method and then used to determine the different contributions to optical power attenuation along the hydrogel-based waveguide. Absorption and scattering loss coefficients are determined for 450 nm, 532 nm and 633 nm excitation. The excellent optical loss values obtained (0.32-1.95 dB/cm), similar to others previously described, indicate their potential application as waveguides in different fields, including soft robotic and light-based therapies.

Polylactic acid tungsten trioxide reinforced composites: A study of their thermal, optical, and gamma radiation attenuation performance

In the current investigation, the gamma radiation shielding abilities, structure, and thermal and optical properties of Polylactic acid PLA have been tried to be developed by introducing tungsten trioxide WO3. PLA/WO3 composites were fabricated by a solution mixing method at different weights percent (1%, 3%, 5%, and 7%). SEM indicates the good dispersion of WO3 in the PLA matrix, and the X-ray diffraction (XRD) pattern displays the existence of recognizable peaks for PLA and WO3. The thermal properties were investigated by thermo-gravimetric analysis (TGA), which enhances the thermal stability of the PLA/WO3 composites more than pure PLA. The transmittance decreases with increasing the WO3 content in the PLA matrix while the absorption and extinction coefficients α and k as well as the refractive index, rise with the increase of the WO3 content in the PLA matrix. The radiation shielding parameters have been experimentally reported. The equipment used in the experiment consisted of a NaI detector as well as a variety of radioactive point sources that released photons with energy of 80, 238, 356, 662, 1173, 1333, and 2164 keV, respectively. Examining the linear attenuation coefficient (μ), the half-value layer (T0.5), and the radiation protection effectiveness of the PLA/WO3 composites was done in order to investigate the gamma radiation shielding capabilities of the materials (RPE). Pure PLA (free WO3) was found to have the lowest μ values, and it was discovered that increasing the WO3 content led to an improvement in the photon attenuation competency of the present epoxy. The T0.5 lengths of the PLA/WO3 composites were lowered when WO3 was added. This verified that adding WO3 increases the radiation absorption capabilities of the PLA/WO3 composites. The four different energies were tested. Based on the findings, it is possible to draw the conclusion that non-toxic, naturally occurring composites that are low in cost and have a high WO3 content could play an important part in enhancing the gamma-ray shielding capabilities of PLA/WO3 composites for low-energy radiation applications, which can used as protective cover for solar cell against harm radiation.

Rigid POSS Nanofiller Regulated the Interfacial Self‐assembly of Particles into 2D Monolayer Superlattice with Fixed Interparticle Spacing†

Comprehensive SummaryPlasmonic superlattices of nanoparticles (NPs) possess unique “surface lattice resonances” properties that facilitates their wide applications in plasmonic sensing, photocatalysis, and nanoscale light manipulation. However, it is still challenging to manufacture superlattices with precisely controllable NPs distance and break the size limitation of NPs. Herein, we provided an effective strategy to construct NPs superlattices via shape‐persistent polyhedral oligosilsesquioxane (POSS) molecular nanoparticles govern interfacial assembly. As a nanoscale molecule with diameter of 1.5 nm, the POSS‐SH molecule provides sufficient rigid steric hindrance and hydrophobic effect for tailoring the uniformity and controllable distance between NPs in superlattices. Interestingly, synergistically with hydrophilic ligands of polyethylene glycol (PEG‐SH) with optimized ratio, the rigid POSS ligands can effectively regulate the distance between NPs in a fixed range of 2.3—2.8 nm, which is independent of ligands molecular weight and particle size. Furthermore, the effective approach can be universal to anisotropic NPs for manufacturing monolayer films with high NPs density. We believe this nanoscale molecule tailored interfacial self‐assembly strategy can effectively break the size of NPs and assembly obstacles for superlattice monolayer film. Additionally, the definite distance between NPs in superlattices can minimize optical energy attenuation and facilitates the applications such as surface‐enhanced Raman spectroscopy and photocatalysis.

Deep learning-based optical coherence tomography image analysis of human brain cancer.

Real-time intraoperative delineation of cancer and non-cancer brain tissues, especially in the eloquent cortex, is critical for thorough cancer resection, lengthening survival, and improving quality of life. Prior studies have established that thresholding optical attenuation values reveals cancer regions with high sensitivity and specificity. However, threshold of a single value disregards local information important to making more robust predictions. Hence, we propose deep convolutional neural networks (CNNs) trained on labeled OCT images and co-occurrence matrix features extracted from these images to synergize attenuation characteristics and texture features. Specifically, we adapt a deep ensemble model trained on 5,831 examples in a training dataset of 7 patients. We obtain 93.31% sensitivity and 97.04% specificity on a holdout set of 4 patients without the need for beam profile normalization using a reference phantom. The segmentation maps produced by parsing the OCT volume and tiling the outputs of our model are in excellent agreement with attenuation mapping-based methods. Our new approach for this important application has considerable implications for clinical translation.

MEMS enabled suspended silicon waveguide platform for long-wave infrared modulation applications

Long-wave infrared (LWIR, 6–14 µm) is an important wavelength range as it covers abundant vibrational molecular fingerprints that can be used for gas/liquid sensing and absorption spectroscopy. Silicon waveguide-based passive photonic devices that offer advantages toward chip-scale miniaturization of photonic integrated circuits (PIC) and photonic sensors in LWIR have been explored. However, the modulation of Si-based guided-wave propagation in LWIR remains less reported. Here, we demonstrate a MEMS tunable directional coupler operating at a long-wave infrared wavelength range (6.4–7 µm) using suspended Si waveguides with subwavelength gratings. Leveraging the membrane transfer technology, the whole photonic waveguide device membrane is transferred onto a receiver substrate with a cavity that allows sufficient displacement for MEMS electrostatic actuation. The proposed device experimentally achieved an optical attenuation of −14.25 dB with 90 V DC bias voltage, while having a response time of 177 µs. In addition, the demonstration of using such a device for computational spectroscopy has been validated.

A novel bathymetry signal photon extraction algorithm for photon-counting LiDAR based on adaptive elliptical neighborhood

Ice Cloud and Land Elevation Satellite-2 (ICESat-2) uses a 532-nm laser with a strong seawater penetration ability, and can provide reliable water depth information for sea areas that in situ bathymetric data are lacking. However, because of the complexity of underwater terrain, background noise, optical signal attenuation in water, and other factors, there are still some obstacles to accurately extract bathymetry photons using ICESat-2 data This paper proposes an novel bathymetry signal extraction algorithm based on an adaptive elliptical neighborhood window. The direction-adaptive elliptical neighborhood strategy ensures the directionality and continuity of signal extraction. The size-adaptive neighborhood strategy satisfies the demand for extraction of both shallow, dense signals and deep, sparse signals. The kernel density estimation (KDE) based strategy for sea surface elevation extraction and above-water signal separation makes it possible to determine the sea surface elevation accurately while correctly separating the above-water photons. Four study areas with different environmental conditions in the Xisha Islands, the Bahamas, and the Gulf of Aden were selected, and the key results are as follows. (1) For a water-land interface area with dense noise, the proposed algorithm can effectively reduce the impact of land and accurately eliminate noise photons in shallow water. (2) For an extremely sparse signal in a deep-water area, which is difficult to process using classical algorithms, the proposed algorithm can accurately extract signal photons in water approximately 50 m deep while effectively extracting the dense signal photons in shallow water. (3) In the extraction results obtained using this algorithm, the signal strip has better continuity and smoothness than the classical algorithm and therefore can portray the seafloor terrain more completely. As the in situ water depth confirms, the overall mean absolute error (MAE) and mean relative error (MRE) of the water depth information extracted by the proposed algorithm are 0.79 m and 7.54%, respectively, which indicate high reliability.

Alteration in the optical, structural, and nuclear radiation attenuation characteristics of polyvinyl alcohol/lead oxide (PVA/PbO) films

Alteration in the optical, structural, and nuclear radiation attenuation characteristics of polyvinyl alcohol/lead oxide (PVA/PbO) films

Guiding losses estimation in hydrogel-based waveguides

A method based on the photographic recording of the power distribution laterally diffused by cationic electroactive network (CN)-based hydrogel waveguides is first checked against the well-established cut-back method and then used to determine the different contributions to the optical power attenuation along the hydrogel-based waveguide. Absorption and scattering loss coefficients are determined for 450 nm, 532 nm and 633 nm excitation.

Low Loss 16-Channel Photodetector Array Receiving Module With Fine Tuning Ability

A 16-channel photodetector array receiving module with good performance as low loss, fine tuning and high reliability is manufactured in our laboratory. The whole module was consisted with a silica arrayed waveguide grating chip (AWG), a thermo-optical type variable optical attenuator (VOA), a photodetectors (PDs) array with direct-current (DC) bias circuit, all components were integrated via 3D package method. In the article, the structure parameters of Y branch and edge couplers were optimized for lower loss. In order to realize excellent tuning ability, Titanium was selected as heating material for precisely tuning and its electric attenuation range could reach at a level more than 20 dB. Periodically segmented waveguide coupler designed in passive chips could minimize coupling loss less than 0.4 dB/coupling. The high-performance receiving module could effectively improve detection quality and significantly enlarge capacity in communication system.

Comparison of Raman, Brillouin, and Rayleigh Distributed Temperature Measurements in High-Rate Wells

With the maturity of and demand for fiber-optic sensing technology growing steadily over the last few years across multiple basins, operators are seeking fiber-optic sensing solutions that address the technology challenges associated with the life-of-field monitoring of subsea developments. Single-ended distributed temperature sensing (DTS) measurements have been acquired for decades now, typically using Raman optical time-domain reflectometry (OTDR) on multimode fiber. However, for topside interrogation of subsea completions, Raman DTS performs poorly. This is due to the available optical power budget and the potential wavelength dependency of optical attenuation across multiple connectors and splices comprising the optical subsea infrastructure. Any wavelength-dependent attenuation as the signals pass through connectors, splices, and optical feedthrough systems will generate step changes in the measured Raman DTS temperature profile. Brillouin OTDR can provide a DTS alternative that overcomes these challenges and operates on single-mode fiber. Brillouin OTDR operates with a large dynamic range to measure a wavelength (frequency) shift of the Stokes/anti-Stokes components that is proportional to both strain and temperature. Since downhole cables are manufactured with optical fibers suspended in a gel and with appropriate extra fiber length (EFL), any fiber strain relaxes, and the Brillouin wavelength shift is an absolute temperature measurement. An additional alternative is also explored here. We typically associate coherent Rayleigh OTDR with distributed acoustic sensing (DAS) on single-mode fibers, but low frequencies also contain a relative temperature dependence. The low-pass filtering of DAS data can then be used as a form of Rayleigh DTS with appropriate data processing. In this paper, we report on a comparison of Raman, Brillouin, and Rayleigh DTS simultaneously acquired in the same high-rate producer and injector wells. We validate that, with appropriate cable design, Brillouin DTS can be simultaneously operated on the same single-mode fiber with DAS and can deliver absolute temperature measurements suitable for production analysis. We also use a laboratory experiment to show that Rayleigh DTS provides an accurate measure of temperature changes comparable in precision to a traditional thermocouple. We conclude with a discussion about the implementation of this DAS-DTS solution for sensing subsea completions.

Three-Dimensional Polymer Variable Optical Attenuator Based on Vertical Multimode Interference with Graphene Heater.

Low-power-consumption optical devices are crucial for large-scale photonic integrated circuits (PICs). In this paper, a three-dimensional (3D) polymer variable optical attenuator (VOA) is proposed. For monolithic integration of silica and polymer-based planar lightwave circuits (PLCs), the vertical VOA is inserted between silica-based waveguides. Optical and thermal analyses are performed through the beam propagation method (BPM) and finite-element method (FEM), respectively. A compact size of 3092 μm × 4 μm × 7 μm is achieved with a vertical multimode interference (MMI) structure. The proposed VOA shows an insertion loss (IL) of 0.58 dB and an extinction ratio (ER) of 21.18 dB. Replacing the graphene heater with an aluminum (Al) electrode, the power consumption is decreased from 29.90 mW to 21.25 mW. The rise and fall time are improved to 353.85 μs and 192.87 μs, respectively. The compact and high-performance VOA shows great potential for a variety of applications, including optical communications, integrated optics, and optical interconnections.

All-Optical Format Conversion of 2-Dimensional MQAM to MPSK Based on Nonlinear Mach-Zehnder Interferometer With Wavelength Preservation

An all-optical format conversion scheme of 2-dimensional multiple-quadrature amplitude modulation (MQAM) to multiple-phase shift keying (MPSK) signals is proposed and numerically simulated by using the nonlinear Mach-Zehnder interferometer (MZI) configuration with wavelength preservation. The input octal-quadrature amplitude modulation (8QAM) signal is generated through the phase modulator (PM) and amplitude modulator (AM) and injected into the nonlinear MZI configuration. The designed nonlinear MZI configuration includes two 3 dB optical couplers (OCs), a piece of high nonlinear fiber (HNLF) and a variable optical attenuator (VOA) in the upper interfering arm and a piece of standard single mode fiber (SSMF) or tunable optical delay line (TODL) and a variable phase shifter (VPS) in the lower interfering arm. The converted octal-phase shift keying (8PSK) signal can be obtained from the nonlinear MZI configuration through vector superposition between the input optical signal and itself with some nonlinear phase shift. The needed asymmetric nonlinear phase shift is mainly induced by the big nonlinear index difference between HNLF and SSMF. The error vector magnitude (EVM) and bit error rate (BER) performance of the scheme are calculated before and after format conversion with the different input and receiver optical-signal-noise-ratios (OSNRs). The scheme can be used in the intermediate node to connect the different networks which adopt 8QAM and 8PSK signals, respectively.

Asymptotic optical attenuation in sea water

A simple method is proposed for calculating the asymptotic attenuation coefficient K∞ of sea water. The method is based on the scaling analysis of the radiative transfer equation within the small-angle approximation. From the scaling, it follows that K∞ is analytically expressed in terms of the absorption coefficient, the transport scattering coefficient, and two dimensionless numeric constants (scaling exponents) depending on a specific scattering phase function. For a given phase function, the scaling exponents can be determined by numerical calculations of the downwelling irradiance. We test the method on a number of oceanlike scattering models. A direct numerical integration of the radiative transfer equation is carried out with the DISORT code for the Petzold, Morel et al., Fournier–Forand and Kopelevich phase functions. Our numerical results agree perfectly with the small-angle scaling and allow us to establish an explicit expression for K∞ for each phase function. We find that the scaling exponents depend rather weakly on the specific angular profile of the phase function and can be taken equal to their values for the Henyey–Greenstein function (this approximation leads to a relative error in the value K∞ less than 5%). So that, within a few percent accuracy, the coefficient K∞ is governed only by the absorption and transport scattering coefficients and is described by a universal formula.

A compact beamformer of diversity multiplexing of multiple modes by utilizing few-mode long-period fiber gratings

In this paper, a few-mode true delay beamforming network with two mode combinations is proposed to obtain continuously adjustable time delay. The excitation of LP modes is realized by using few-mode long-period fiber gratings (LPFGs), and the time delay differences between LP modes are controlled by two 2 × 2 optical switches. The system integrates three channels into one, and then demultiplexes LP modes through a mode selective photonic lantern. At first, the relationships of the distance between few-mode LPFGs are derived so that the beamformer can be rationally designed by them. Then, the amplitude errors of the antenna elements, radio-frequency gain and noise figure of each channel of the system affected by the conversion rates of few-mode LPFGs and the LP mode coupling of few-mode fibers and mode selective photonic lantern are also given. Finally, the experimental measurements show that variable optical attenuators can effectively eliminate the above effects, which further proves the feasibility of the beamformer.

Measurement of bubble/slug velocity and size in vertical pipe based on optical cross-correlation method

Based on the principle of the cross-correlation, the method for measuring the velocity and size of bubbles in transparent gas-liquid two-phase flow in a vertical pipe is proposed by taking optical attenuation signal as the object. This method is used to measure the bubble velocity and size of transparent gas-liquid two-phase flow in vertical pipeline of two-phase flow experimental platform, and compared with synchronous measurement by image method. The experimental results show that the relative deviation of velocity and size between optical cross-correlation measurement and image method is less than 3% and 5%, respectively. The optical cross-correlation method can be used to measure the bubble velocity and size parameters of transparent gas-liquid two-phase flow in the vertical pipe without contact, and this method is suitable for industrial applications.

Penerapan Quality of Service (QoS) pada Fiber to the Home (FTTH) di Graha Sudirman Indramayu

Graha Sudirman housing started its construction in 2012, Graha Sudirman itself is located in thecenter of Indramayu city. Graha Sudirman housing has implemented an internet network to support ITbasedsmart housing. In this case, it is still based on simple fiber optics. This network has limitations interms of QoS on the client side. One of the initiators of IT-based smart housing is the housing coordinator,namely Mr. Khaerul Anam. In this Community Service program, we try to apply FTTH technology inGraha Sudirman housing to support IT-based smart housing. This service is expected to assist partners inimplementing IT-based smart housing programs both in terms of infrastructure and applications. From theresults of the implementation, the fiber optic attenuation output in each house ranges from -13dB to -25dB,this is due to many factors ranging from the type of fiber cable to the splicing or installation process. Forspeed, from -13dB to -25dB, you can still get 902 Mbps of bandwidth. This speed will decrease if it exceeds-29dB and above, even for connections it can be lost.

Improved Cherenkov Imaging across a Wide Range of Skin Pigmentation Levels for the Inclusion of Diverse Patient Populations

<h3>Purpose/Objective(s)</h3> Cherenkov imaging has recently emerged as a tool to visualize radiation dose and detect treatment incidents in real-time. The principle relies on the proportionality between Cherenkov light emission and dose deposited within tissue, introducing an additional opportunity to use the image information as a 2D surface dose map. The Cherenkov-dose relationship is affected by tissue optical properties, and recent studies have utilized routine CT-scans to correct for optical attenuation due to fibroglandular and adipose tissues, and blood volume, in the breast. However, the bulk of the reported <i>in vivo</i> data is limited to light-skinned patients due to limitations of geographical demographics. It is well documented that melanin is an optical absorber of Cherenkov photons, yet no prior <i>in vivo</i> work has been done to characterize the effect of different skin tones on Cherenkov dosimetry. We hypothesize that skin color information can be used to correct Cherenkov images for optical attenuation relating to melanin absorption across a diverse patient population. <h3>Materials/Methods</h3> A multi-institutional partnership was developed aiming to collect data from a more diverse patient population. A time-gated, intensified CMOS camera installed in the ceiling of a treatment room collects Cherenkov images of breast RT patients during their treatment. A standard color camera module is mounted adjacent to the Cherenkov camera to collect a color background image. Following a process developed with phantom studies, the two images are co-registered together in post-processing, RGB values are extracted from the skin over the treatment regions to calculate the relative skin luminance, L, and this value is compared to the optical emission from the corresponding Cherenkov image. A linear regression model is then used to assess the proportionality between L and Cherenkov emission intensity. <h3>Results</h3> The Cherenkov imaging system is being deployed in a clinic with a catchment area demographic of 67.4% Non-Hispanic White, an increase in diversity from 89.4% at the home institution. A clear relationship exists between skin color information and Cherenkov intensity, which cannot be determined like the bulk tissue properties from the CT scan alone. We found that L, derived from a wide range of melanin concentrations, is linearly proportional to Cherenkov intensity (R² = 0.98). Each Cherenkov image can be corrected based on skin luminance to improve the Cherenkov-dose relationship across various skin types. <h3>Conclusion</h3> The effect of both inter- and intra-patient skin color variations on the Cherenkov intensity can be corrected by using a linear regression model to increase the linearity between Cherenkov and deposited dose. This work will be used to improve our current CT-correction algorithm for all skin types and presents a major step towards expanding the inclusivity of Cherenkov imaging as a dosimetric tool for every patient.