Overview of radiation induced point defects in silica-based optical fibers

A comparison of the losses induced in step index multimode, graded index multimode and single mode fibers by pulsed radiation exposure has been made among 12 laboratories over a period of 5 years. The recoveries of the incremental attenuations from 10{sup -9} to 10{sup 1} s are reported. Although a standard set of measurement parameters was attempted, differences between the laboratories are evident; possible origins for these are discussed. 18 refs., 18 figs., 7 tabs.

Interlaboratory comparison of radiation-induced attenuation in optical fibers. Part 3: Transient exposures

Over the last years, fiber optic sensors have been increasingly applied for applications in environments with a high level of radiation as an alternative to electrical sensors, due to their: high immunity, high multiplexing and long-distance monitoring capability. In order to assess the feasibility of their use, investigations on optical materials and fiber optic sensors have been focusing on their response depending on radiation type, absorbed dose, dose rate, temperature and so on. In this context, this paper presents a comprehensive review of the results achieved over the last twenty years concerning the irradiation of in-fiber Long Period Gratings (LPGs). The topic is approached from the point of view of the optical engineers engaged in the design, development and testing of these devices, by focusing the attention on the fiber type, grating fabrication technique and properties, irradiation parameters and performed analysis. The aim is to provide a detailed review concerning the state of the art and to outline the future research trends.

Radiation Effects on Long Period Fiber Gratings: A Review.

Based on the experience acquired early from pioneering work at Stanford University and Thomson-CSF starting in the mid 70s, fiber optic gyro (FOG) R&D began at Photonetics in the late 80s to yield OCTANS, a FOG-based inertial strapdown system providing attitude and gyro compassing, at the end of the 90s. This FOG activity was spun out from Photonetics in October 2000 to create iXsea with only 16 people. The product line was rapidly expanded with PHINS, an inertial-grade INS (Inertial Navigation System) and later with MARINS, a strategic-grade INS, as well as with ASTRIX systems developed for satellites in cooperation with EADS-Astrium (today Airbus Defence & Space). In 2010, iXsea merged with several subsidiaries of its parent company, iXcore, to create iXblue. Among these subsidiaries were iXfiber, a maker of specialty fibers, and Photline, producing lithium-niobate integrated optics, hence allowing iXblue to fully master the key FOG components supply chain. Ten years later, the ‘adventure' is continuing and the former start-up is now quite a significant player in the inertial world, especially for high-grade applications. The cumulated number of high-performance 3-axis systems in service has grown to over 8,000, i.e. more than 25,000 FOG axes, with a bias stability ranging from 30 mdeg/h down to 15 μdeg/h, and an angular random walk (ARW) performance ranging from 8 mdeg/√h down to 40 μdeg/√h depending on the size of their sensing coils (3 m2 to 1000 m2) and on the application!

The fiber optic gyro 'adventure' at Photonetics, iXsea and now iXblue

In this contribution, a complete dissertation concerning the behavior of a Long Period Grating (LPG) inscribed in a B-Ge co-doped optical fiber by means of an excimer laser and exposed to proton irradiation during a recent extensive campaign performed at the European Organization for Nuclear Research (CERN) with a fluence of 4.4·1015 p∙cm−2 is provided. The experimental results have been thus combined for the first time to the best of our knowledge with numerical simulations in order to estimate the variations of the major parameters affecting the grating response during the ultra-high dose proton exposure. From the correlation between experimental and numerical analysis, the irradiation exposure was found to induce a maximal variation of the core effective refractive index of ~1.61·10−4, responsible of a resonance wavelength red shift of ~44 nm in correspondence of the highest absorbed radiation dose of 1.16 MGy. At the same time, a relevant decrease close to ~0.93·10−4 in the refractive index modulation pertaining to the grating was estimated, leading to a reduction of the resonant dip visibility of ~12 dB. The effect of the proton beam on the spectral response of the LPG device and on the optical fiber parameters was assessed during the relaxation phases, showing a partial recovery only of the wavelength shift without any relevant change in the dip visibility revealing thus a partial recovery only in the refractive index of the core while the reduction of the refractive index modulation observed during the irradiation remained unchanged.

/pdf/analysis-of-uncoated-lpgs-written-in-b-ge-doped-fiber-under-3mlcsqsovv.pdf

Analysis of uncoated LPGs written in B-Ge doped fiber under proton irradiation for sensing applications at CERN

In this topical review, the recent progress on radiation-hardened fiber-based technologies is detailed, focusing on examples for space applications. In the first part of the review, we introduce the operational principles of the various fiber-based technologies considered for use in radiation environments: passive optical fibers for data links, diagnostics, active optical fibers for amplifiers and laser sources as well as the different classes of point and distributed fiber sensors: gyroscopes, Bragg gratings, Rayleigh, Raman or Brillouin-based distributed sensors. Second, we describe the state of the art regarding our knowledge of radiation effects on the performance of these devices, from the microscopic effects observed in the amorphous silica glass used to design fiber cores and cladding, to the macroscopic response of fiber-based devices and systems. Third, we present the recent advances regarding the hardening (improvement of the radiation tolerance) of these technologies acting on the material, device or system levels. From the review, the potential of fiber-based technologies for operation in radiation environments is demonstrated and the future challenges to be overcome in the coming years are presented.

https://iopscience.iop.org/article/10.1088/2040-8986/aad271/pdf

Armelle Paveau

Papers

Recent advances in radiation-hardened fiber-based technologies for space applications