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

Abstract

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.

Theoretical Investigation of Thermal Effects in High Power Er3+/Yb3+‐ Codoped Double‐Clad Fiber Amplifiers for Space Applications

“…In this case, there is an energy transfer between two ions in higher excited states which impairs both the pumping efficiency and population inversion and gives an extra heat load into the doped core since point defects inside the doped silica matrix occur. Usually this effect is negligible in active fibers in regular environment, but it becomes predominant when the fiber is exposed to radiation, going from few dB/km to few dB/m losses …”

“…For space applications in which Erbium‐Doped Fiber Amplifiers (EDFA) are used, it is clearly identified that the radiation‐affected component is the Erbium‐Doped Fiber (EDF) itself . For most of these fibers, such as those containing aluminum (Al) or phosphorous (P) in their silica‐based cores, the point defects causing the attenuation improvement of both pump and signal light are related to the dopants chosen for facilitating the active ion incorporation rather than to defects related to rare‐earth ions . Such amplifiers suffer of gain‐saturation problems when the output power grows up, so the co‐doping with ytterbium Yb 3+ sensitizer ions is an efficient way to overcome this drawback.…”

“…Indeed, the presence of Yb 3+ ions provides an efficient indirect pumping mechanism for erbium, reduces the formation of Er 3+ cluster and the cooperative up‐conversion (CUP) among Er 3+ ions, extends the range of the possible pump wavelength band, increases the pump absorption around 975 nm of about two orders of magnitude larger than the non‐sensitized one. It has been also shown that the presence of the Yb 3+ ions did not increase the fiber radiation sensitivity, so the Er/Yb composition allows higher fiber gain compared to Er‐doped fibers …”

Systematic investigation of composition effects on the radiation-induced attenuation mechanisms of aluminosilicate, Yb-doped silicate, Yb- and Yb,Ce-doped aluminosilicate fiber preforms [Invited]

“…[3] gives a topical example). Then, the CC formation is due to ionizing radiations and it results into the so-called radiation-induced attenuation or RIA (see [4,5] for reviews of radiation effects). Space-based applications, where active fibers (in fiber optic gyroscopes or power laser sources) are simultaneously submitted to pumping and radiations, combine the PD and RIA issues and raise the question of their interaction.…”

“…Radiation-induced defects have been extensively studied by the means of optical absorption (OA), luminescence, electron spin resonance (ESR) techniques and their combination (see [5,[13][14] for reviews). Almost all intrinsic and dopant-related CCs that have been identified so far in silica-based glasses have OA bands in the VIS and UV ranges (only one phosphorus-related color center, the P1 center, has a peak absorption at 1570 nm) [4,5,13]. For most of them, structural models have been debated, generation processes have been proposed in terms of photoionization or carrier trapping, and thermal stability has been assessed by isochronal annealing experiments [13][14][15].…”