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The present technology provides large mode area optical fibers engineered to have normal dispersion around 1600 nm, enabling high power Raman amplification at eye safer wavelengths. The fibers can have a main core and one or more side cores disposed relative to the main core so that modes of the main core and the one or more side cores hybridize into supermodes with modified dispersion.
Optical dispersive soliton solutions for the fractional Lakshmanan–Porsezian–Daniel equation for optical fibers are studied in this paper considering the M-derivative of order χ. The analytical method considered here is based on the Jacobi elliptic function (JEF) anzätz method. We found new optical soliton solutions that are relevant for the dynamics inside optical fibers. Some constraints conditions arise between the parameters of the JEF soliton solutions. Typical behaviour of the soliton solutions obtained is depicted in some interesting simulations.
A system or method for a magnetic self-aligning coupling device for a fiber optic cable. The device includes a first end coupling comprising a first magnet and a second magnet. Both magnets include a mating surface and an annular ring defining an axial aperture. The aperture receives a distal end of a segment of fiber optic cable in a tight fit. The fiber optic cable has an exterior sleeve and a fiber core. The fiber core of the first segment and the second segment of the fiber optic cable are axially aligned by magnetic force in the first and second apertures to create a continuous fiber optic path. A method for detecting a security breach of a door using the self-aligning couplings is also described.
A system or method for a magnetic self-aligning coupling device for a fiber optic cable. The device includes a first end coupling comprising a first magnet and a second magnet. Both magnets include a mating surface and an annular ring defining an axial aperture. The aperture receives a distal end of a segment of fiber optic cable in a tight fit. The fiber optic cable has an exterior sleeve and a fiber core. The fiber core of the first segment and the second segment of the fiber optic cable are axially aligned by magnetic force in the first and second apertures to create a continuous fiber optic path. A method for detecting a security breach of a door using the self-aligning couplings is also described.
Optical Fibers - ASI Spring Newsletter
The work detailed in this report was supported under the In-Pile Instrumentation program for FY19. The work was conducted by researchers at Boise State University (BSU) and Idaho National Laboratory (INL). This report describes the out-of-pile testing that has been conducted to help guide sensor design and data interpretation by providing a robust understanding of out-of-pile fiber optic performance under different environmental factors. Highlighted in this report are two test configurations, transmission testing of optical fibers over a range of temperatures, and tensile testing of optical fibers identified through prior research as having potential for in-core use. The transmission temperature testing is conducted with high spectral resolution to study the influence of elevated temperatures on transmission. This testing has been conducted from room temperature up to 800ºC. The transmission testing was conducted by BSU at the Fiber Laser and Integrated photonics Research (FLaIR) laboratory. This testing will allow separation of radiation and temperature effects during in-core testing and allow for a more thorough understanding of radiation effects on fiber sensors. The tensile testing of optical fibers was conducted to provide a baseline for the strength of fiber optics. The fragile nature of glass fibers is a limitation in the deployment of fiber optics. Furthermore, intrinsic fiber optic sensors such as Fiber Bragg Gratings (FBG) add defects or damaged areas to the fiber which reduce its strength and can lead to broken sensors if not handled with care. The thermo-mechanical test facility enables the ability to quantitatively measure the strength of fibers with and without FBG’s over a temperature range. This information will be used to determine which types of FBG’s, and other sensors, are likely to survive the installation process. These tests will also be used to characterize the potential measurement range of fiber based strain sensors. The tensile testing was completed at INL in the HTTL Fiber Optics and Ultrasonic Technologies (FOUT) laboratory. Pure silica core (PSC) optical fibers have been shown to perform well in harsh environments. Transmission testing and tensile testing showed little change in fiber dynamic strength and transmission with elevated temperatures. There was no significant weakening of the fiber for temperatures up to 200ºC. Transmission at 1550 nm (a common wavelength used for optical sensors) showed minimal changes up to 800ºC with some improvement after 12 hours of annealing at 800ºC. This indicates that PSC optical fiber is a good candidate for in-pile testing.
A fiber optic sensor and a related method of manufacture are provided. The fiber optic sensor includes an embedded optical fiber contained within a metal diaphragm assembly, where the terminal end of the optical fiber is positioned opposite a diaphragm. The method includes forming a metal-embedded optical fiber by ultrasonic additive manufacturing and securing the metal-embedded optical fiber to a housing having a diaphragm that is opposite of the terminal end of the optical fiber. The sensor can provide extremely accurate pressure measurement at high temperatures and in highly corrosive media. An optical fiber-based pressure sensing system is also provided.
Fiber optic pressure sensors are desirable for nuclear applications because they are low mass/small size, immune to electromagnetic interference, high sensitivity, and have multiplexing and multimodal measurement capabilities. Much research and development has been conducted on developing fiber optic based sensors and they are now considered a class of standard instrumentation in many industries. Specifically, for pressure sensing, a wide range of fiber based sensors have been developed for various pressure ranges and environments. This vast body of research will be leveraged for the development of pressure sensors for nuclear applications. Four pressure measurement scenarios were considered which would benefit from a fiber optic based pressure sensor. These scenarios include pressure measurement in the fuel rod plenum, coolant pressure during LOCA testing, advanced coolant (helium, sodium, molten salt) pressure for flow loop operation, and high pressures resulting for direct fuel-coolant interaction. Each scenario has unique pressure, temperature, and material requirements for the sensor. From a survey of commercially available sensors and a literature review; it has been determined that an extrinsic Fabry-Perot interferometer approach is the most appropriate for the various measurement requirements. The experience and knowledge base for Fabry-Perot interferometers can be leveraged since they are the most common fiber optic based pressure sensors available commercially and found in literature. These pressure sensors rely on the interference of light in a gas filled cavity, which minimizes the impact of radiation induced attenuation and compaction on the measurement, compared to intrinsic sensing techniques. The measurement range of these sensors is based on the stiffness of the diaphragm that deflects under pressure. This allows for a suite of fiber based sensors to be developed by interchanging this diaphragm for the requirements of each application. Key material and design considerations have been identified for the development of a Fabry-Perot interferometry pressure measurement for nuclear applications. These include high temperature bonding between the glass fiber optic and metal housing, identifying diaphragm materials & geometry, and minimizing cross sensitivity to temperature or implementing compensation techniques found in literature. Overcoming these challenges will develop a pathway for a fiber optic based pressure sensor for nuclear applications, and additionally can be leveraged for other sensing application based on Fabry-Perot interferometers, such as temperature, strain (creep & deformation), vibration, and index of refraction.
Monitoring of energy infrastructure through robust yet economical sensing platforms is becoming an area of increased importance, with ubiquitous applications including the electrical grid, natural gas and oil transportation pipelines, H2 infrastructure (storage and transportation), carbon storage, power generation, and subsurface environments. Plasmonic and functional nanomaterial enabled fiber optic sensors show excellent promise for a wide range of sensing applications due to their versatility to be engineered for specific analytes of interest while retaining inherent advantages of the optical fiber sensor platform. Through the design of novel sensing layers, the optical transduction mechanism and wavelength dependence can also be tailored for ease of integration with low-cost interrogation systems enabling an inexpensive yet highly functional optical fiber sensing platform. In addition, recent advances in artificial intelligence and machine learning theoretical methods have been leveraged to simultaneously extract multiple parameters through multi-wavelength interrogation such that unique wavelengths can also serve as unique sensing elements, analogous to electronic nose sensor technologies. The concept of an optical fiber based “photonic nose” via multiple interrogation wavelengths and/or sensor nodes offers a compelling platform technology to realize multiparameter speciation of chemical analytes within complex gas mixtures. In this Perspective, we further generalize the notion of multiparameter sensing through the novel “photonic nervous system” concept based upon low-cost, functionalized optical fiber sensor probes monitoring a variety of distinct analyte classes (physical, chemical, electromagnetic, etc.) simultaneously to provide broad situational awareness via integrated sensors.
This work presents the computational evaluation of a new model for relative humidity sensor based on the principle of intermodal interference using a square-section no-core tapered optical fiber compared to a classical cylindrical tapered optical fiber sensor. Attempting at a new application of this type of sensor, simulations were carried out in the range of up to 60% of relative humidity, the main interest range of the pharmaceutical industry. Several materials were used in its modeling and an analysis was developed in its constructive dimensions, in order to verify the influence of each of them on the sensor performance.
A new technique for measuring the spatial and temporal structure of the poloidal field is presented, whereby the magnetic field causes the polarization of light traveling through an optical fiber to rotate via the Faraday effect by an amount proportional to the strength of the field oriented along the fiber. In fiber optic pulsed polarimetry, changes in the polarization of the backscatter light from the fiber are detected, thereby permitting measurement of the field as a function of position along the fiber. In this proof-of-principle experiment, specially prepared single-mode fibers with weak fiber Bragg gratings were installed in the poloidal direction on the outside of the thermal blanket on DIII-D. Light at 532 nm from a mode-locked Nd:YAG laser was injected into the optical fibers. The laser repetition rate was 895 kHz with a pulse length of <10 ps, resulting in ~1 μs temporal resolution. A photodetector system measured the Stokes polarization components necessary to determine the amount of polarization rotation. For this experiment, bandwidth limitations of the detectors resulted in a spatial resolution of ≈2 cm. The measured temporal and spatial distributions of the poloidal field are consistent with inductive probe measurements and Elastodynamic Finite Integration Technique reconstructions of the spatial distribution. Furthermore, this demonstrates the ability of this technique to provide real-time detection of the temporal and spatial variations of the poloidal field. Besides revealing more detailed information about the plasma, this new diagnostic capability can also help in detecting instabilities in real time, thereby enabling enhanced machine protection.
Distributed temperature monitoring can provide useful insights into the thermal conditions in the continuous caster tundish that can affect operating stability and cast quality, such as preheat conditions, superheat uniformity, fill height, and refractory wear. In the current study, fiber optic sensors were embedded into the refractory lining of a lab-scale tundish to record the temperature profiles during dry-out, preheating, and direct molten steel exposure to demonstrate sensor performance. Additional trials were performed with fiber optic sensors embedded in an industrial tundish used in production. Furthermore, the results demonstrate that fiber optic sensors using Rayleigh technology can provide accurate distributed temperature measurements in refractory lined vessels and provide useful information about the process.
In this paper, we propose a method for fabricating a U-bend optical fiber magnetic field sensor. The working principle of the sensor is based on the use of bending to induce a whispering gallery mode. In experimental testing, a U-shaped optic fiber probe was fabricated using a lamping process and then coated on its surface with ferroferric oxide (Fe{sub 3}O{sub 4}), which served as the magnetic field sensing layer. The intensity of an applied magnetic field was then controlled by the vertical distance between an NbFeB magnet and the sensor. The magnetic field was monitored using a Gauss meter. As the external magnetic field was applied to the sensor, it produced magnetic attraction with the Fe{sub 3}O{sub 4}. The magnetic field intensity was increased from 0 to 900 Gauss, which in turn caused the magnetic attraction to become larger. This in turn caused the optic fiber sensor to deform, inducing changes in the bending radius. Therefore, the wavelength shifted toward a short wavelength and the transmission loss was gradually increased. The results show that the sensitivity of the sensor in the magnetic field experiment was − 0.00130 nm/Gauss and the linearity (R{sup 2}) was 0.888, while the corresponding average loss sensitivity was 0.00028 dB/Gauss and the corresponding linearity (R{sup 2}) was 0.942.
Embedding fiber optics in metal components could enable new capabilities such as active monitoring of spatially distributed strain. Ultrasonic additive manufacturing is a suitable technique for embedding fiber optics because it allows fibers to be embedded in metals without melting and without the use of epoxy. However, for harsh environments that could have high temperatures or high radiation doses, traditional polymer-coated fibers cannot survive for extended periods of time. This work demonstrates successful embedding of commercially available copper-, nickel-, and aluminum-coated fibers into aluminum without any observable damage to the fiber. Copper-coated fibers embedded in copper show adequate light transmission, although residual strain could not be resolved. With further processing improvements, fibers embedded in copper or other high-temperature materials could enable even higher temperature operation. Optical transmission and spatially distributed strain were measured in the fibers embedded in aluminum. Measurements were taken after embedding and during heating to temperatures greater than 500 °C. Within the embedded region, both the copper- and aluminum-coated fibers showed strain that matched the expected strain in the surrounding aluminum matrix during heating. This suggests a strong interfacial bond strength that exceeds the maximum estimated fiber strain of 1.2% (871 MPa tensile stress). Furthermore this demonstration of embedded fibers that can survive high temperatures and remain bonded to the metal matrix is the first step toward embedded fiber optic sensors for harsh environment applications.
A system and method for forming a low cost optical sensor array. The sensor includes an optical fiber; a first nanocomposite thin film along at least a portion of the optical fiber for interrogating a first parameter through a correlated signal having a first wavelength; and a second nanocomposite thin film along at least a portion of the optical fiber for interrogating a second parameter through a correlated signal having a second wavelength different from the wavelength of the first parameter.
Fiber-optic based sensors will be needed for in situ monitoring of degradation products in various components of nuclear weapons. These sensors typically consist of a transducer located at the measurement site whose optical properties are modulated by interaction with the targeted degradation product. The interrogating light source and the detector for determining sensor response are located remotely. These two subsystems are connected by fiber optic cables. LLNL has developed a new technology, aerogel clad optical fibers, that have the advantage of accepting incident rays over a much wider angular range than normal glass clad fibers. These fibers are also capable of transmitting light more efficiently. These advantages can lead to a factor of 2-4 improvement in sensitivity and detection limit.
Measurement of the magnetic fields surrounding magnetic fusion energy (MFE) devices, such as tokamaks, is critical for characterizing and monitoring the plasma inside these devices, and it is especially important for detecting plasma instabilities, which can lead to the plasma damaging the inside of these devices. This program successfully demonstrated a new type of magnetic field diagnostic that is capable for the first time of measuring simultaneously the spatial and temporal magnetic field distributions of MFE devices in real-time and with high resolution. This is a capability not feasible with existing magnetic field diagnostics and, moreover, the technique we developed provides other advantages, such as less susceptibility to noise, the ability to operate during both pulsed and steady-state plasma conditions, the ability to detect relatively weak poloidal fields, and potentially lower costs. This new capability of being able in real-time to detect anomalies in the magnetic field distribution corresponding to the onset of plasma instabilities offers the ability to automatically shut down the MFE device before the plasma can damage the machine. Hence, this machine protection capability can be vital for future fusion power stations. Our technique uses optical fibers where changes in the polarization of the laser light traveling through the fiber provide a direct measurement of the magnetic field at any point along the fiber. The small size of the fibers allows them to be easily installed either outside or inside the MFE vacuum vessel, and in any direction one wishes (e.g., poloidal or toroidal). We demonstrated the basic capabilities of our new diagnostic during a proof-of-principle experiment performed on the General Atomics DIII-D tokamak, and published the results in: W. D. Kimura, D. S. Dhillon, S. Munaretto, E. J. Strait, D. Du, S. Loranger, J.-S. Boisvert, and R. Kashyap, “Measurements of DIII-D poloidal field by fiber-optic pulsed polarimetry,” Rev. Sci, Inst. 89, 10J102 (2018).