Fiber Attenuation Research Articles

Photobleaching Effect on Infrared Radiation-Induced Attenuation of Germanosilicate Optical Fibers at MGy Dose Levels

We investigated the radiation-induced attenuation (RIA) at 1550 nm under X-rays in two single-mode germanosilicate optical fibers (OFs): the Corning SMF-28e <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> and a homemade fiber manufactured by the Université Côte d'Azur in the framework of the CERTYF project. The RIA dependence on the injected power level of the probing signal is studied in order to analyze the photobleaching phenomenon at high doses [>100 kGy(SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> )]. The Corning SMF-28e <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> revealed no RIA variation with the signal power (microwatts-milliwatts range), proving to be a good candidate for distributed OF sensor (DOFS) applications, while the CERTYF OF showed a clear photobleaching effect. A fitting routine based on the second-order growth kinetics model of Griscom has been performed, which has shown good consistency with the experimental results and offered a quantitative evaluation of the photobleaching effect on the CERTYF OF.

Near‐IR Radiation‐Induced Attenuation of Aluminosilicate Optical Fibers

The X‐ray radiation‐induced attenuation (RIA) growth kinetics are studied online in different single‐mode aluminosilicate optical fibers in the near‐IR (NIR) domain to evaluate their potential in terms of dosimetry. The optical fibers differ by Al contents, core sizes, drawing parameters, and also by a preform deposition process. The data show no dependence of the RIA on all these parameters, a positive result for the design of point or distributed radiation detectors exploiting RIA to monitor the dose. The RIA growth rate is unchanged for dose rates changing from 0.073 to 6.25 Gy(SiO2) s−1, and the RIA linearly increases with the dose up to 2 kGy(SiO2). Small but noticeable RIA changes are observed when the irradiation temperature increases up to 50 °C during successive irradiation runs. Such results, and the post‐irradiation RIA recovery, have to be considered for the application, as they can affect the dose measurement accuracy. Finally, the spectral analysis shows no dependence of the spectral shape on the fiber and irradiation parameters. As a consequence, the data reported at 1310 and 1550 nm give information not only for the RIA kinetics at telecommunications and sensor wavelengths but also for the whole NIR range often used fiber‐based technologies.

High accuracy analysis of fiber-optic laser-induced breakdown spectroscopy by using multivariate regression analytical methods

Fiber-optic laser-induced breakdown spectroscopy (FO-LIBS), which delivers the laser energy through an optical fiber cable, is more suitable for remote analysis and applying in complex environment than traditional laser-induced breakdown spectroscopy (LIBS). However, since the laser fluence is limited by optical fiber loss and attenuation, FO-LIBS suffers more from spectral interference, matrix effect, and self-absorption effect. In this work, three multivariate quantitative analytical methods, including two linear models partial least squares (PLS) and sparse partial least squares (SPLS), one nonlinear model support vector machine (SVM), were utilized to carry out the quantitative analysis of four trace metal elements (Manganese (Mn), Chromium (Cr), Nickel (Ni), and Titanium (Ti)) in pig iron. And the quantitative analytical ability of linear model and nonlinear model was studied and compared. The results show that nonlinear SVM model has the best performance. Using the SVM model, the coefficients of determination (R2) of Mn, Cr, Ni, and Ti were 0.9705, 0.9849, 0.9882, and 0.9837, respectively, and the root mean squared errors of prediction (RMSEP) of Mn, Cr, Ni, and Ti were 0.0982 wt%, 0.0185 wt%, 0.0179 wt%, and 0.0178 wt%, respectively. This work demonstrates that nonlinear quantitative analytical methods can effectively overcome those nonlinear effects and improve the quantitative analytical accuracy of FO-LIBS

Impact of encryption and decryption techniques for high speed optical domain

This project proposes the design of ultrafast communication circuit which can enable the high speed secured data transmission at 50 Gb/s and 100 Gb/s by the use of distributed Raman amplifier, EDFA (Erbium – doped fiber amplifier), filter, single mode fiber along with Fiber Bragg Grating (FBG) and attenuators. The simulation of the suggested optical circuit involves the use of parameters of Raman amplifier and EDFA and other components included in the optical structure. The design also includes the use of encryption and decryption techniques to ensure secured communication. Thus, realization of these circuits at 50 Gb/s and 100 Gb/s will enable the future optical communication applications for ultrafast data transmission to large distances.

Impact of encryption and decryption techniques for high speed optical domain

This project proposes the design of ultrafast communication circuit which can enable the high speed secured data transmission at 50 Gb/s and 100 Gb/s by the use of distributed raman amplifier, erbium–doped fiber amplifier (EDFA), filter, single mode fiber along with fiber Bragg grating (FBG) and attenuators. The simulation of the suggested optical circuit involves the use of parameters of Raman amplifier and EDFA and other components included in the optical structure. The design also includes the use of encryption and decryption techniques to ensure secured communication. Thus, realization of these circuits at 50 Gb/s and 100 Gb/s will enable the future optical communication applications for ultrafast data transmission to large distances.

Simultaneous transmission of clock and data signals in photonic-assisted WDM passive optical networks

This work reports on the use of a gain-switched vertical cavity surface-emitting laser (VCSEL) optical frequency comb (OFC) to generate multiple optical carriers for applications in future wavelength-division multiplexing (WDM) passive optical network (PON) systems. The VCSEL-based OFC system was tested for its ability to simultaneously transmit error-free data signals up to 30 Gbps, and a 50 MHz clock signal proposed to be used for latency monitoring of the network. The system was demonstrated over a fiber distance beyond 20 km. Four optical carrier signals were filtered from the generated OFC. Three of the four optical carriers were combined and amplitude-modulated with 5 and 10 Gbps on–off keying (OOK) data signals. The fourth optical carrier was amplitude-modulated with a 50 MHz clock signal. These four modulated optical carriers were multiplexed and transmitted over 21 km of standard single-mode fiber. When the three data-carrying optical carriers were modulated with 5 Gbps OOK data and multiplexed with the clock-carrying carrier, a negligible transmission penalty was achieved after fiber transmission. When these three data-carrying optical carriers were modulated with 10 Gbps OOK data and multiplexed with a clock-carrying carrier, a maximum transmission penalty of 4.8 dB was achieved after fiber transmission. The system was investigated at a minim bit error rate (BER) of 10 − 9 . A receiver sensitivity of less than − 11 d B m was achieved at both bit rates. The clock signal suffered little effect when transmitted with the three optical carriers at both 5 and 10 Gbps data rate. A power penalty of 15.37 dB, mainly due to fiber attenuation, was experienced in the clock after fiber transmission. Due to the unavailability of the numerical system to quantify the clock performance in terms of phase noise, the phase-noise results could not be provided. Nevertheless, the provided qualitative results were able to show that the transmitted clock integrity was able to be retained after being multiplexed with transmission on the 21 km fiber channel. For the first time, to the best of our knowledge, we have simultaneously reported on data and clock transmission results using a low-power, VCSEL-based OFC to realize a WDM-PON system. These results are attractive as they demonstrate and motivate the possibility of using gain-switched VCSELs as OFC sources in future WDM-PON networks requiring enhanced channel capacity and stringent network latency monitoring to realize intelligent, simple, and power-efficient PON networks.

Quality Signal Degradation in Single-Channel Fiber Using 10 Gbps Bit Rate

Reliable data transmission capacity is a crucial factor in supporting high-data-rate communication for smart cities by implementing the Internet of Things. Optical fiber has become the most favorable transmission media by taking advantage of optical signals. However, when optical signals propagate through optical fibers, disturbances occur as the transmission distance increases. These disturbances affect the system performance indicated by the deteriorating transmission data quality in terms of the quality factor (Q-factor) and bit error rate. These parameters are vulnerable to certain factors that can alter signal transmissions such as fiber attenuation, group velocity dispersion (GVD), and self-phase modulation (SPM) as a nonlinear effect. In this study, the effects of these factors on a single-channel, single-mode fiber are investigated using a bit rate of 10 Gbps at various transmission distances and source power levels. The parametric study of attenuation, GVD, and SPM with non-return-to-zero (NRZ) modulation format are considered at various transmission distances, from 10 to 100 km, and input powers of 5 and 10 dBm are simulated using OptiSystem to characterize the parameters of Q-factor and received power. The results indicate that the performance of the system deteriorates as the transmission distance increases, and the dominant effect that impacts the performance is GVD. This result is useful for designing effective and precise fiber optic transmission for high-data-rate transmission.

Monte Carlo modeling of the influence of strong magnetic fields on the stem-effect in plastic scintillation detectors used in radiotherapy dosimetry.

To investigate the impact of strong magnetic fields on the stem-effect in plastic scintillation detectors (PSDs) using Monte Carlo methods. Prior to building the light guide model, the properties of the Čerenkov process in GEANT4 were investigated by simulating depth-dose and depth-Čerenkov emission profiles in water as functions of Čerenkov process input parameters. In addition, profile simulations were performed for magnetic field strengths ranging from 0T to 1.5T. A PMMA light guide was constructed in GEANT4 using data from the manufacturer and literature. Simulations were performed with the model as functions of depth and fiber-beam angle where the simulated stem-effect spectrum and the Čerenkov light ratio (CLR) were scored and compared to measured data in the literature. The light guide optical properties were iteratively adjusted until agreement between the simulated and measured data was achieved. Simulations were performed with the validated model as functions of depth and magnetic field strength and the simulated data were compared to measured data in the literature. The model was also used to evaluate the sensitivity of the CLR to the various optical properties of the light guide in different irradiation conditions. No significant changes in the depth-dose or depth-Čerenkov emission profiles were observed with step-size restrictions imposed by the Čerenkov process input parameters, which was attributed to the condensed history algorithm and transport parameters used in this work. Similar changes in the depth-dose and depth-Čerenkov emission profiles were observed with increasing magnetic field strength, which indicates the Čerenkov process is not adversely impacted by the presence of the magnetic field. Following optimization of the light guide optical properties, agreement within two standard deviations was observed between the simulated and measured optical data for all validation geometries considered. Agreement within one standard deviation was observed between the simulated and measured data for all depths and field strengths ≥0T whereas discrepancies were observed for magnetic field strengths <-0.35T. These significant differences were attributed to insufficient measurement data for this irradiation configuration during model validation. Of the light guide optical properties investigated, the fluorescence signal had the greatest impact on the CLR sensitivity to the magnetic field. No significant change in the Čerenkov emission per dose in water was observed for magnetic field strengths up to 1.5T. The nominal fiber fluorescence signal was found to have a significant impact on the CLR sensitivity to varying irradiation conditions where changes up to 11.7% were observed whereas the mirror reflectivity and fiber attenuation had a modest impact with maximum CLR changes of 2.6% and 1.2% relative to 0T, respectively. The results of this work suggest light guides with low fiber fluorescence should be used with PSDs for dosimetry measurements in magnetic fields to minimize the impact of the magnetic field on the CLR correction.

Investigative Modeling of Symmetric Fiber Bragg Grating as Dispersion Compensation for Optical Transmission System

Dispersion is a serious issue related to the integrity of data transmission in high-speed optical fiber communication systems. Fiber Bragg gratings (FBGs) are among the most important components used to reduce dispersion in these systems. FBGs are simple, and have low-cost filter for wavelength selection, low insertion loss and customized reflection spectrum, and wide bandwidth. This study investigates the optical transmission system performance of a symmetric FBG for dispersion compensation. Transmission scheme simulation is analyzed with different parameters based on an OptiSystem simulator. Symmetric FBG and avalanche photodetector are used to enhance the evaluation of an optical transmission system. Optical fiber length, attenuation coefficient, input power, bit rate, and FBG grating length parameters are also investigated in detail to determine system optimization. The developed simulation design demonstrated high gain, low noise figure, substantial output power, and high Q-Factor for long transmission distance of up to 60 km with 0.2 dB/km attenuation coefficient.

Fiber-optic Crack Sensing in Steel Structures and Buildings (Dept.E)

Fiber-optic sensing techniques have received a considerable interest in recent years. Optical fibers have several desired and advantageous attributes useful for sensor applications, including their ability to act as both sensing and information transmitting media. One of the specific aims of this paper is to build an optical system having the capability to measure the attenuation in optical fibers due to its macrobending, and compare (or calibrate) our results with other who used different systems in order to ensure that our system is suitable to use. The attenuation due to bending loss in optical-fiber at different bending radii of fiber, at different multiple circular Joops bending of liber, and at different optical frequencies transmitted through fiber, are insured experimentally by our optical system. The results for these measurements show that the attenuation (or bending loss) increases with decreasing the bonding radius, with increasing number of fiber turns and with increasing transmitted signal frequencies through the bended fiber. This optical system can be used as a sensitive sensor to measure the cracks in steel structures and buildings.

MODELING AND ANALYSIS OF FIVE REGIONS FIBER BRAGG GRATING USING OPTISYSTEM SOFTWARE SIMULATION

This paper describes the concept and simulation of an fiber Bragg grating. Simulation of the transmission system have been analized using simulator OptiSystem, based on different parameters. Show there parameters are investigated by simulating a communication device model and using the most suitable system settings which include input power (dBm), fiber cable length (km) and attenuation coefficient (dB / km) in the cable segment; Namely, signal strength (dB), noise power (dB), receiver output (watts). The power values (-5.299 dB) and (-2.6635 dB) are found in which regions, which decrease as the number of network regions in the fiber increases, thus increasing the density efficiency (16.316) and (75.5192) as well as the number of fiber regions (FBG).

Performance analysis of high speed backward compatible TWDM-PON with hybrid WDM–OCDMA PON using different OCDMA codes

In this paper, a backward compatible bidirectional 160/40 Gbps time and wavelength division multiplexing-passive optical network with hybrid wavelength division multiplexing optical code division multiple access PON (WDM–OCDMA PON) has been proposed. Six OCDMA codes have been used to enhance the security and users’ ability to access shared bandwidth of an optical network. In this “pay-as-you-grow” supported system, the fiber impairment effects have been effectively reduced. The performance of the proposed system has been analyzed for variable input power (4–19 dBm) and transmission distance (10–70 km) supporting 120 active users under the influence of fiber nonlinearities, attenuation, dispersion and noise. Based on the numerical calculations, the proposed system using modified quadratic congruence (MQC) code is shown to provide better performance compared to multi diagonal, hadamard, zero cross-correlation (ZCC), shift ZCC and flexible cross-correlation codes. To validate the numerical analysis, the simulation of the proposed system at 160/40 Gbps data rate for 70 km downstream and greater than 70 km upstream fiber link transmission at 10−9 BER limit for 68 active users have been successfully demonstrated. Also, it has been shown that MQC code provides optimum results at 10 dBm input power over 55 km distance and supports more than 120 active users with high gain of − 1.97 dB and low noise figure of 2 dB. Further, the comparative performance of the proposed system with the previous latest works in literature reveals a superior performance of the system.

Distributed Sensors Assisted by Modulated First-Order Raman Amplification

In distributed optical fibre sensors, the measurement range is typically limited to a few tens of kilometers due to the fibre attenuation and the input pump power limits imposed by the emergence of nonlinear effects. To overcome these problems, distributed amplification schemes have been investigated, generally employing continuous-wave pumping schemes. In this article, we propose the use of Raman amplification with an engineered intensity modulation. We show that this kind of assistance may provide, in principle, a close to perfect loss compensation along the fibre length. To find the optimal modulation profile, an analytical model is presented, and numerically, its performance is analyzed. Using a close to optimal pump modulation profile, we experimentally demonstrate a flat optical trace along 50 km of fibre with a minimal SNR penalty along the length. The result is favorably compared with the continuous-wave pumping case injecting the same average power. Thanks to this new approach, the sensitivity in the worst point is considerably better and the ASD noise floor is also reduced.

Measuring the shape of microbends in optical fibers.

We report on the distributed shape measurement of small deformations produced along the length of an optical fiber. The fiber contains multiple waveguiding cores, each inscribed with weak continuous Bragg gratings. The distributed Bragg-reflectivity data for the fiber cores, obtained from the optical backscatter reflectometry, are used to estimate the local curvature and the position of the fiber. We successfully demonstrate the sensing of periodic microdeformations-approximately 1 µm or less in amplitude and a few hundred µm in length. Such microbends are known to cause attenuation in optical fibers, and the approach presented here can enable a detailed measurement of these microbends in applications ranging from telecommunications cable design to biotechnology, robotics, manufacturing, aerospace, and security.

In-situ regeneration of P-doped optical fiber dosimeter

We demonstrate the feasibility of resetting and reusing dosimeters exploiting the measurement of the infrared radiation-induced attenuation (IR-RIA) in phosphosilicate optical fibers (OFs) to provide point or distributed dose measurements in radiation environments. To bleach the room temperature stable IR-RIA, we used the photobleaching (PB) phenomenon. The PB efficiency was evaluated for different wavelengths in the [400-1100] nm range. The best identified PB resetting condition consists in using a continuous-wave Argon-ion laser at 514 nm. This treatment successfully bleached ∼97% of the IR-RIA at 1550 nm of a 30 m-long P-doped single mode optical fiber X-ray irradiated at a dose of 100 Gy. Successive re-irradiations of the same OF sample, regenerated after each run, confirm that the dosimeter keeps the same calibration curve during the whole process.

Experimental Demonstration of Nonlinear Frequency Division Multiplexing Transmission With Neural Network Receiver

Nonlinear frequency division multiplexing (NFDM) communication systems that are based on the nonlinear Fourier transform (NFT), have seen a rapid improvement in performance and transmission reach over just a few years. However, such an improvement is now being slowed down by fundamental challenges such as fiber loss and noise. As the NFT theory is defined over a lossless transmission fiber, a strong research focus has been dedicated to either improve the lossless assumption for practical fibers, by adapting the theory to approximately account for the fiber loss, or by devising encoding schemes that increase the robustness of the NFT to the fiber attenuation. However, the proposed solutions provide only minimal benefits to the system performance, especially for long fiber spans as in deployed links. Alternatively, a detection strategy based on replacing a conventional NFT receiver with a time-domain Neural network (NN)-based symbol decisor has been numerically proposed. Here, we extend such an idea by validating it experimentally. In order to apply the method in an experimental environment, the impact of phase noise, and receiver frequency offset needs to be addressed. We, therefore, propose a novel time-domain receiver architecture that combines a two-stage iterative carrier recovery with a NN-based symbol decisor. The carrier recovery, itself based on aNN for phase estimation, is numerically, and experimentally characterized. The proposed receiver has been evaluated for single-polarization two-eigenvalue transmission at 1 GBd. A two-fold increase in the transmission reach is enabled by the NN receiver (≈1600 km) compared to a conventional NFT receiver (≈560 km) for a practical link using 80-km spaced erbium-doped fiber amplifier (EDFAs).

Recombinant Human Soluble Thrombomodulin Suppresses Monocyte Adhesion by Reducing Lipopolysaccharide-Induced Endothelial Cellular Stiffening.

Endothelial cellular stiffening has been observed not only in inflamed cultured endothelial cells but also in the endothelium of atherosclerotic regions, which is an underlying cause of monocyte adhesion and accumulation. Although recombinant soluble thrombomodulin (rsTM) has been reported to suppress the inflammatory response of endothelial cells, its role in regulating endothelial cellular stiffness remains unclear. The purpose of this study was to investigate the impact of anticoagulant rsTM on lipopolysaccharide (LPS)-induced endothelial cellular stiffening. We show that LPS increases endothelial cellular stiffness by using atomic force microscopy and that rsTM reduces LPS-induced cellular stiffening not only through the attenuation of actin fiber and focal adhesion formation but also via the improvement of gap junction functionality. Moreover, post-administration of rsTM, after LPS stimulation, attenuated LPS-induced cellular stiffening. We also found that endothelial cells regulate leukocyte adhesion in a substrate- and cellular stiffness-dependent manner. Our result show that LPS-induced cellular stiffening enhances monocytic THP-1 cell line adhesion, whereas rsTM suppresses THP-1 cell adhesion to inflamed endothelial cells by reducing cellular stiffness. Endothelial cells increase cellular stiffness in reaction to inflammation, thereby promoting monocyte adhesion. Treatment of rsTM reduced LPS-induced cellular stiffening and suppressed monocyte adhesion in a cellular stiffness-dependent manner.

Steady-State X-Ray Radiation-Induced Attenuation in Canonical Optical Fibers

The so-called canonical optical fibers (OFs) are samples especially designed to highlight the impact of some manufacturing process parameters on the radiation responses. Thanks to the results obtained on these samples, it is thus possible to define new procedures to better control the behaviors of OFs in radiation environments. In this article, we characterized the responses, under steady-state X-rays, of canonical samples representative of the most common fiber types differing by their core-dopants: pure silica, Ge, Al, and P. Their radiation-induced attenuation (RIA) spectra were measured online at both room temperature (RT) and liquid nitrogen temperature (LNT), in the energy range [~0.6-~3.0] eV (~2100-~410 nm), highlighting the RIA growth kinetics during the fiber exposure up to an accumulated dose of ~200 Gy(SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) at a constant dose rate of 100 mGy/s at RT. At LNT, the deposited doses varied between 100 and 180 Gy, with a time-dependent dose rate. In order to understand the origin of the excess losses and the difference between the RIA spectral shapes observed at the two temperatures, spectral decomposition of the optical losses has been performed using a set of Gaussian absorption bands related to the already known point defects. As a result, if the RIA in the visible domain is quite well understood, the knowledge of the RIA origin in the near-IR remains incomplete, justifying new and deeper studies to clarify the response of the fibers under steady-state irradiation.

Bragg Gratings Inscribed in Solid-Core Microstructured Single-Mode Polymer Optical Fiber Drawn From a 3D-Printed Polycarbonate Preform

This paper reports the first microstructured solid-core fiber drawn from a 3D-printed preform and the first fiber Bragg gratings inscribed in a fiber of this type. The presented fiber is made of polycarbonate and displays single-mode behavior. The fiber attenuation was the lowest reported so far for a POF drawn from a 3D-printed preform across a broad range of wavelengths. In addition, extensive fiber characterization results are presented and discussed including: fiber attenuation, mode simulations, dynamic thermomechanical analysis and thermo-optic coefficient. Fiber Bragg gratings are successfully inscribed in the produced fiber using three different lasers: a continuous wave helium-cadmium laser, a pulsed femtosecond frequency doubled ytterbium laser and ultra-violet nanosecond krypton fluoride laser. Mechanical testing of the fiber showed that the 3D printing approach did not introduce any unexpected or undesirable characteristics.

Research on a quantitative method for three-dimensional computed tomography of chemiluminescence.

To develop a more advanced 3D computed tomography of the chemiluminescence method, the first quantitative 3D diagnosis was realized. The nonlinearity coefficient, the nonuniformity coefficient of the camera response, and various optical fiber attenuation coefficients were obtained through correction experiments. The conversion relationship between the number of photons released by the target object per unit time and the camera gray value at a specified solid angle was also calibrated. To verify the quantitative reconstruction equation, 3D reconstructions of a methane-air flat flame and a simulated phantom were performed for comparison. The method can overcome artificial distortions caused by uncorrected reconstruction.