The temperature dependence of the emission and absorption cross sections of Er and Yb ions in rare-earth-doped aluminosilicate optical fibers is experimentally investigated. The obtained results ...demonstrate that the McCumber theory accurately predicts the temperature-induced changes of the emission cross section spectrum up to 500 °C when the absorption spectra measured at the considered temperature is used for the calculations instead of the one acquired at ambient temperature. Finally, we also demonstrate that the various heating steps up to 500 °C are not affecting the fiber guiding properties and no permanent effect is observed on the emission and absorption cross section spectra measured at room temperature.
Raman-based Distributed Temperature Sensors (RDTS) allow performing spatially resolved (1 m) reliable temperature measurements over several km long Optical Fibers (OFs). These systems are based on ...the temperature dependence of the intensities of both the Stokes and anti-Stokes components of the Raman back-scattered signal. One of the specific issues associated with RDTS technology in radiation environments is the differential Radiation Induced Attenuation (RIA) between the two components that induces huge errors in the temperature evaluation. Such problem is particularly evident for commercially available single-ended DTS using one laser source. Double-ended configuration could be used to correct for the differential attenuation but are limited by RIA in terms of sensing range. In the present work, we show how a Radiation-Hardened-by-Design DTS (RHD-DTS) overcomes the observed radiation issues keeping the single-ended interrogation scheme. In the tested RHD-DTS two infrared excitation laser sources (~1550 nm and ~1650 nm) are employed: the wavelength of the Stokes component due to the first excitation source coincides with the wavelength of the second excitation; vice versa, the wavelength of the anti-Stokes component due to the second excitation source coincides with the wavelength of the first excitation. The overall result is that the two signal intensities are automatically corrected for the differential RIA all along the OF sensor length and the temperature measurements becomes robust against radiation effects. This study demonstrates the potential of such a sensor by reporting preliminary experimental results obtained with a prototype developed by Viavi Solutions exploiting radiation-sensitive or radiation-hardened optical fibers.
We investigated the behavior of a new class of erbium-doped fiber amplifier (EDFA) when exposed to 63 MeV protons. The EDFA is designed with a radiation hardened hole-assisted carbon coated (HACC) Er ...3 + -doped optical fiber. The particular structure of this HACC fiber allows to permanently incorporate an optimal amount of D 2 or H 2 gases into its core, reducing its radiation sensitivity without degrading the EDFA performances. Irradiations up to a fluence of 7.5 ×10 11 p/cm 2 confirm the excellent tolerance of this HACC-EDFA component. It exhibits a limited decrease of ~ 0.6 dB of its ~ 27 dB gain for this fluence corresponding to an ionization dose of 100 krad(Si). Such a device can then survive to the radiative environments associated with both today's space missions and future more challenging applications.
In this paper, we demonstrate and highlight a proof of concept for the feasibility of an innovative technique to regenerate on-site irradiated optical fiber links in nuclear facilities. Using ...Hole-Assisted optical fibers (HAOF), a longitudinal gas-loading is easy to perform thanks to the fibers' dedicated holes located in the outer part of the cladding. All along the fiber length, gas ( H2 or D2) diffuses from the holes into the silica matrix, interacts with radiation induced point defects and passivates them, reducing the Radiation Induced Attenuation (RIA) levels. The validity of our approach is demonstrated considering the changes occurring at infrared wavelengths during the H2 treatment of a MGy irradiated single mode Ge-doped HAOF. Within just a few hours, a reduction of about 50% is observed for the RIA at 1550 nm of the 10 MGy irradiated HAOF, acting only from one of its two ends. An additional study is done on a set of fibers with various core dopants (F, Ge, P) and without holes to give an overview of the pertinence of developing HAOF fibers with these dopants for various applications. Using HAOF and this recovery technique appears very promising for samples based on pure-silica, Ge or F-doped cores and operating in the ultraviolet-visible spectral domains such as plasma diagnostics. This approach exhibits another interesting feature which may be extension to higher dose ranges and lifetime of P-doped distributed dosimeters used in high energy physics facilities or nuclear power plants.
Fusion-based metallic additive manufacturing (AM) features complex material and heat transfer phenomena. These processes dynamics can be monitored using different techniques in order to assess the ...manufacturing quality or detect defects. Fiber Bragg Gratings written using femtosecond laser pulses (fs-FBGs) inside optical fibers allow temperature multipoint sensing by monitoring the reflected wavelength \lambda_{\mathrm{B}} of each wavelength-multiplexed sensor 1.
This article presents a new fractional order adaptive control scheme design based on sliding mode configuration for actuator failure compensation applied to a wing rock system with redundant ...actuators. The main objective of this work is to establish an adaptive control law that compensates faulty actuators by taking into account actuator redundancy and introducing fractional calculus. First, a non-integer sliding mode surface is defined. Next, an adaptive scheme is derived from the ideal control law to accommodate for the occurring failures during operation. Then, the stability analysis of the closed loop system is performed using the Lyapunov theory under certain assumptions on the system and the failures. Finally, simulations were carried out on a wing rock system subjected to various actuator failures scenarios in order to illustrate the effectiveness of the proposed control law.
In the two last decades, several research works proposed adaptive sliding mode control (SMC) algorithms to deal with fractional-order chaotic systems for control and synchronization. As a ...contribution to this investigation effort, this paper proposes a new adaptation law for fractional-order SMC addressing the synchronization problem for a class of nonlinear fractional-order systems with chaotic behavior. The main innovation in the proposed control design concerns the choice of a sliding surface with two adjustable parameters, leading easily to an efficient adaptation law for the SMC controller. Stability analysis of the proposed control scheme is performed using the Lyapunov stability theorem. As an illustration of the effectiveness of this synchronization strategy, a simulation example on the fractional-order Arneodo chaotic system is presented and discussed.
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