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We experimentally study the effect of ionizing radiation on the properties of long-period gratings fabricated in two pure-silica-core fibers with the arc-discharge technique. It is observed that the spectra of the gratings remain almost unchanged after being subjected to doses in excess of 0.5 MGy. The results also show that the gratings' temperature and strain sensitivities are not affected by gamma radiation. OCIS codes: 050.2770, 060.2340, 060.2400, 260.5210, 350.5610.

We evaluated the performances of the hydrogen-loading technique to reduce the radiation-induced absorption in optical fibers in the visible part of the spectrum. A reduction factor as large as one order of magnitude can be obtained in high dose-rate regime. Based on a spectral deconvolution method, we showed that hydrogen preferentially interacts with NBOHC defects while the number of POR defects is not affected. Index Terms--Attenuation, hardening, hydrogen, optical absorption, fiber, radiation.

Wavelength-division multiplexed fiber-optic links could find applications in various radiation environments. Space industry, for example, could benefit from radiation-tolerant high-speed optical links for the next generation of observation satellites. For application in the nuclear energy industry, the use of passive optical devices also needs to be evaluated at high dose rates and total doses. Our previous results have shown that the in-fiber Bragg grating filters are key components in the radiation-resistant passive optical links, as they showed a remarkably high radiation-acceptance level in terms of total absorbed dose. The dose-rate dependencies also needed to be evaluated. We therefore gamma-irradiated fiber Bragg grating filter at several dose rates ranging from 1 to 25 kGy/h. We show, for the first time, that the dose rate does not affect the full-width at half-maximum of the Bragg peak and that the saturating Bragg peak shift remains. Index Terms--Fiber Bragg grating, fusion reactor, grating, nuclear radiation effects, optical fiber effects, optical fiber sensing.

Thermonuclear reactors will require permanent monitoring under high-gamma dose rates and high neutron flux. We propose to get rid of the digital data transmission limitations in highly radioactive environments by implementing an analog fiber-optic link based on directly modulated vertical-cavity surface-emitting laser (VCSELs). In this paper, we introduce an architecture for highly radiation-tolerant instrumentation data links based on the intrinsic wavelength division multiplexing capabilities of fiber-optic data transmission. The potential radiation acceptance level of the analog fiber-optic link is estimated on the basis of irradiation results on individual COTS photonic components such as VCSELs, fiber-optic passive multiplexers, and optical fibers. Index Terms--Fusion reactors, nuclear radiation effects, optical communication, optical fibers, semiconductor lasers.

We measured the change of the refractive index over a wide wavelength range in Ge- and N-doped high purity (fiber optics grade) silica glasses subjected to gamma irradiation. The radiation-induced change of the refractive index tends to be greater in the infrared part of the spectrum compare to the values measured in the UV-visible part of the spectrum. By means of the Kramers–Kronig relations, we estimate that a weak broadening of the optical vibration band of the silica network adds to this effect. The paper also discusses the difference observed in the spectral behavior of the induced refractive index change for both types of doped glass. [ABSTRACT FROM AUTHOR]