Radiation induced attenuation in pure silica polarization maintaining fibers

Abstract Radiation-induced attenuation (RIA) at λ = 1.55 μm is studied in polarization-maintaining (PM) pure-silica-core optical fibers of the Panda-type under γ-irradiation and upon pulsed-X-ray-irradiation. For the first time, the RIA spectrum is compared under γ-irradiation in a Panda and in a non-PM fiber drawn from the same preform before embedding the stress-applying rods. It is found out that the chief RIA origins in the near-IR range in both fibers are an extremely short-lived band centered at ~1 eV and the tails of the classical bands due to strain-assisted self-trapped holes (STHs) at 1.63 and 1.88 eV. The former band is found to be many times more intense in the Panda; the latter bands, somewhat more intense in the non-PM fiber. The ~1-eV band proved to be composed of two Gaussian sub-bands centered at 0.95 and 1.12 eV. Under γ-irradiation, the composite ~1-eV band is found to be photobleached virtually fully by 1.55-μm light of 5-mW power, which results in manifold reduction of the total RIA. Upon pulsed irradiation, RIA in Pandas at large post-pulse times (>1 ms–1 s) is found to fall off below the record low level demonstrated elsewhere by a non-PM pure-silica-core fiber. This fact is explained as being due to a smaller concentration of strain-assisted STHs in Pandas than in non-PM fibers. The concentration of strain-assisted STHs in Pandas is shown to increase with increasing the value of birefringence.