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Title: Fiber Bragg gratings in the radiation environment: Change under the influence of radiolytic hydrogen

Abstract

The change of the transmission spectra of fiber Bragg gratings written in the optical fibers, whose silica cores are doped with either germanium or nitrogen, is studied experimentally under the influence of gamma-radiation. The transmission spectra in the neighborhood of the resonance (Bragg) wavelengths were regularly recorded “in-situ” in the course of irradiation during 24 days. For this purpose, uncoated gratings were placed in a pool near the spent fuel rods of a nuclear reactor. The fibers with the gratings written in them were in immediate contact with water. The estimated total absorbed radiation dose of the fibers is approximately 5 MGy. Molecular hydrogen, which is produced by radiolysis of water and penetrates into the core of silica fiber, is found to interact with the defects of Ge-doped silica induced by gamma-radiation, thereby causing a strong impact on the parameters of the spectrum of the Bragg gratings. On the contrary, in the case of gratings inscribed in N-doped silica fibers, the hydrogen molecules interact with defects induced in the course of laser UV exposure during the grating writing only. The possible subsequent formation of additional defects in N-doped silica under the influence of gamma-radiation has no substantial impact on the transmissionmore » spectra of Bragg gratings, which remained stable. The obtained results suggest that a small amount of molecular hydrogen resided in the fiber core is the main source of radiation instability of Ge-doped fiber Bragg grating sensors in radiation environments. These hydrogen molecules can remain in the Bragg gratings, in particular, after the inscription process in the hydrogen-loaded fibers.« less

Authors:
;  [1]; ;  [2]
  1. Kotel'nikov Institute of Radio-Engineering and Electronics of RAS, 11-7 Mokhovaya Str., Moscow 125009 (Russian Federation)
  2. Prolog LLC, PO Box 3007, Obninsk, the Kaluga Region 249033 (Russian Federation)
Publication Date:
OSTI Identifier:
22494766
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 118; Journal Issue: 7; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ABSORBED RADIATION DOSES; BRAGG REFLECTION; DEFECTS; DOPED MATERIALS; GAMMA RADIATION; GERMANIUM; GRATINGS; HYDROGEN; NITROGEN; OPTICAL FIBERS; RADIATION EFFECTS; SILICA; SPECTRA; SPENT FUELS; WAVELENGTHS

Citation Formats

Butov, Oleg V., E-mail: obutov@mail.ru, Golant, Konstantin M., Shevtsov, Igor' A., and Fedorov, Artem N. Fiber Bragg gratings in the radiation environment: Change under the influence of radiolytic hydrogen. United States: N. p., 2015. Web. doi:10.1063/1.4928966.
Butov, Oleg V., E-mail: obutov@mail.ru, Golant, Konstantin M., Shevtsov, Igor' A., & Fedorov, Artem N. Fiber Bragg gratings in the radiation environment: Change under the influence of radiolytic hydrogen. United States. doi:10.1063/1.4928966.
Butov, Oleg V., E-mail: obutov@mail.ru, Golant, Konstantin M., Shevtsov, Igor' A., and Fedorov, Artem N. Fri . "Fiber Bragg gratings in the radiation environment: Change under the influence of radiolytic hydrogen". United States. doi:10.1063/1.4928966.
@article{osti_22494766,
title = {Fiber Bragg gratings in the radiation environment: Change under the influence of radiolytic hydrogen},
author = {Butov, Oleg V., E-mail: obutov@mail.ru and Golant, Konstantin M. and Shevtsov, Igor' A. and Fedorov, Artem N.},
abstractNote = {The change of the transmission spectra of fiber Bragg gratings written in the optical fibers, whose silica cores are doped with either germanium or nitrogen, is studied experimentally under the influence of gamma-radiation. The transmission spectra in the neighborhood of the resonance (Bragg) wavelengths were regularly recorded “in-situ” in the course of irradiation during 24 days. For this purpose, uncoated gratings were placed in a pool near the spent fuel rods of a nuclear reactor. The fibers with the gratings written in them were in immediate contact with water. The estimated total absorbed radiation dose of the fibers is approximately 5 MGy. Molecular hydrogen, which is produced by radiolysis of water and penetrates into the core of silica fiber, is found to interact with the defects of Ge-doped silica induced by gamma-radiation, thereby causing a strong impact on the parameters of the spectrum of the Bragg gratings. On the contrary, in the case of gratings inscribed in N-doped silica fibers, the hydrogen molecules interact with defects induced in the course of laser UV exposure during the grating writing only. The possible subsequent formation of additional defects in N-doped silica under the influence of gamma-radiation has no substantial impact on the transmission spectra of Bragg gratings, which remained stable. The obtained results suggest that a small amount of molecular hydrogen resided in the fiber core is the main source of radiation instability of Ge-doped fiber Bragg grating sensors in radiation environments. These hydrogen molecules can remain in the Bragg gratings, in particular, after the inscription process in the hydrogen-loaded fibers.},
doi = {10.1063/1.4928966},
journal = {Journal of Applied Physics},
number = 7,
volume = 118,
place = {United States},
year = {Fri Aug 21 00:00:00 EDT 2015},
month = {Fri Aug 21 00:00:00 EDT 2015}
}
  • Ultrafast infrared induced fiber Bragg gratings in a hydrogen-loaded SMF-28 fiber are shown to exhibit complex and, what we believe to be, novel spectral evolutions. It is believed that the induced grating peak profile in the fiber is nonsinusoidal as a result of the nonlinear absorption required to modify the material. Rouard's method is used to show that the observed spectral evolution is a consequence of the saturation of the nonsinusoidal index change profile.
  • In-fiber Bragg and long-period gratings as well as Mach-Zehnder interferometers based on germanium- and nitrogen-doped silica fibers have been investigated under {gamma}-rays. The majority of the experimental results suggest that both types of gratings in both types of fibers are stable with respect to {gamma}-ray doses of up to 1.47 MGy.
  • Chirped fiber Bragg gratings control the pulse width and energy in Kerr mode-locked erbium fiber soliton lasers. We create high-energy pulses by providing large amounts of excessive negative dispersion, which increases the pulse width while keeping the nonlinearity of the cavity constant. With a chirped fiber grating of 3.4-ps{sup 2} dispersion, 3-ps pulses with an energy content higher than 1 nJ are generated at a repetition rate of 27 MHz. By controlling the polarization state in the cavity, we obtain a tuning range from 1.550 to 1.562 {mu}m.
  • Environmentally stable high-power erbium fiber soliton lasers are constructed by Kerr or carrier-type mode locking. We obtain high-energy pulses by using relatively short fiber lengths and providing large amounts of negative dispersion with chirped fiber Bragg gratings. The pulse energies and widths generated with both types of soliton laser are found to scale with the square root of the cavity dispersion. Kerr mode locking requires pulses with an approximately three times higher nonlinear phase shift in the cavity than carrier mode locking, which leads to the generation of slightly shorter pulses with as much as seven times higher pulse energiesmore » at the mode-locking threshold. {copyright} {ital 1995} {ital Optical} {ital Society} {ital of} {ital America}.« less
  • We report the use of distributed fiber Bragg gratings to monitor thermal conditions within a simulated nuclear reactor core located at the Early Flight Fission Test Facility of the NASA Marshall Space Flight Center. Distributed fiber-optic temperature measurements promise to add significant capability and advance the state-of-the-art in high-temperature sensing. For the work reported herein, seven probes were constructed with ten sensors each for a total of 70 sensor locations throughout the core. These discrete temperature sensors were monitored over a nine hour period while the test article was heated to over 700 deg. C and cooled to ambient throughmore » two operational cycles. The sensor density available permits a significantly elevated understanding of thermal effects within the simulated reactor. Fiber-optic sensor performance is shown to compare very favorably with co-located thermocouples where such co-location was feasible.« less