Radiation tests on optical materials: Presentation held at Radiation Test Workshop 2016, Seville, Spain, 31st March - 1st April 2016

The talk will give a general introduction on testing optical materials for use in radiation environments. A special emphasis is given to thin optical coatings, optical fibers, and fiber Bragg gratings. Here the test procedures are much more challenging than for bulk materials. The challenges are, amongst others, conflicting standards, often online tests and the necessity to use several different radiation sources. The talk will give an overview of test standards, especially concerning optical fibers, and a discussion of the influence of parameters such as dose rate, temperature etc

Basic characterization of optical fibers: Paper presented at International Symposium on Reliability of Optoelectronics for Systems, ISROS 2019, November 26-29, 2019, Toulouse, France

In the present contribution we remind some of the basic information that can be obtained on silica glass employing radiation induced attenuation, electron paramagnetic resonance and photoluminescence spectroscopies. In details, it is shown how each of these techniques, can support the characterization, the qualification and the study of the glasses. Such multi-experimental approach has proved to be useful in previous cases and as a consequence still represents a fundamental tool for optical fibers investigation that cannot be neglected

Gamma irradiation test of Ge-doped single-mode optical fiber at cryogenic conditions

Optical fibers are used routinely in harsh environments for signal transmission or sensing applications. Whereas the individual challenges originating from very high or very low temperatures, vacuum or ionizing radiation were extensively studied, the effects of combinations of these conditions were not investigated widely. In this paper we report on a detailed analysis of gamma irradiation tests done on Germanium-doped single-mode fibers at very low temperatures of 16 K. The drastic change in radiation response is shown with varying temperatures through measurements with discrete light sources and a spectral measurement system. To monitor the temperature in the fibers, Fiber-Bragg-Gratings (FBG) were used and their response under radiation observed. The findings will be valuable for determination of the temperature dependence of the point-defect formation as well as for specialized applications at low temperatures, such as accelerators or deep space missions

Radiation testing of optical coatings: Better testing with simulations

Radiation testing of thin optical coatings for space requires different approaches compared to bulk optical components or other material samples. In contrast to thicker samples, already particles of lower energy and thus lower range in the material will deposit high levels of dose in functional areas. In this paper we will discuss those differences and show ways to develop optimized test strategies

Photobleaching effects in multi-mode radiation resistant optical fibers

This work investigates radiation induced attenuation under gamma ray exposure in various multimode fibers intended for deployment in CERN accelerators. It reports photobleaching under injection of optical signals and characterizes the signal power influence

Future radiation testing: Adapt or fail: Paper presented at 69th International Astronautical Congress, Bremen, Germany, October 1-5, 2018

Radiation testing of active electronic and active as well as passive photonic devices is a major challenge for nearly all space applications. Methods were developed and standards defined, leading to an accepted way to qualify components for a reliable operation under space radiation conditions. However, many new aspects with respect to space radiation appeared that can potentially overturn decades of “best practice” and existing standard procedures. We may need to define radically new approaches, because in several cases traditional testing methods might or will fail or will not be applicable. Three major radiation effect types in electronic and photonic devices exist: total ionizing dose damage, displacement or non-ionizing dose damage, and effects induced by single particles hitting a sensitive volume

Irradiation of radiation-tolerant single-mode optical fibers at cryogenic temperature

Radiation effects at cryogenic temperature are investigated in two radiation-tolerant Fluorine-doped single-mode fibers originating from two different manufacturers. This paper presents measurements at room temperature (297 K) and at cryogenic temperature (16 K) of the radiation induced attenuation at 1312 nm and 1570 nm for both fibers. In addition to the massive increase of the optical attenuation at 16 K, the fiber is found to be in a frozen state where thermal bleaching and defect recombination no longer occurs. However, a long-term recovery, including the heating of the fiber from cryogenic temperature to room temperature, anneals a large amount of the defects created and brings the fiber back to almost its initial performance

The Relevance of Point Defects in Studying Silica-Based Materials from Bulk to Nanosystems

The macroscopic properties of silica can be modified by the presence of local microscopic modifications at the scale of the basic molecular units (point defects). Such defects can be generated during the production of glass, devices, or by the environments where the latter have to operate, impacting on the devices’ performance. For these reasons, the identification of defects, their generation processes, and the knowledge of their electrical and optical features are relevant for microelectronics and optoelectronics. The aim of this manuscript is to report some examples of how defects can be generated, how they can impact device performance, and how a defect species or a physical phenomenon that is a disadvantage in some fields can be used as an advantage in others

Large-Scale Procurement of Radiation Resistant Single-Mode Optical Fibers for CERN

2400 km of special radiation resistant optical fibres were procured by CERN (European Organization for Nuclear Research), for the installation of more than 55 km of optical fibre cables in the accelerator complex underground during the Long Shutdown 1 (LS1). In the frame of this large-scale industrial production, a thorough quality assurance plan (QAP) was put in place and followed at each step of the process. In-depth qualification of optical fibres preceded the 17-month procurement process. All supplied batches were tested for their resistance to radiation, leading to more than 65 quality control irradiation tests. During the cable assembly process and the installations works, a full traceability down to the optical fibre level was ensured. The actions put in place in the frame of the QAP led to successful installation works and to full respect of the LS1 planning