Behavior of strain-assisted self-trapped holes in pure-silica optical fibers upon pulsed-X-ray irradiation

Abstract Radiation-induced absorption (RIA) in a pure-silica fiber (PSF) was investigated at four wavelengths λ = 659, 828, 1310, and 1550 nm after seven X-ray pulses on the scale 1 μs–2 s. The behavior of RIA due to strain-assisted self-trapped holes (STHs) and of RIA at 1310 and 1550 nm was analyzed. The 1.63- and 1.88-eV strain-assisted STH bands were found to decay nearly completely after seven pulses with the total dose of just 440 Gy. Contrary to the previous assumptions, the 1.63- and 1.88-eV STH bands proved not to be responsible for RIA at the communication wavelengths (1.31 and 1.55 μm) upon pulsed-X-ray irradiation. The real origin of RIA at the communication wavelengths was identified, namely, the recently discovered STH bands centered near 1 eV. RIA due to STHs of other classes and types was found to emerge at the expense of the decayed strain-assisted STHs.