Photochromic effect in germanosilicate fibers at very low intensities in the blue-green domain

The photochromic behavior of silica-based fibers irradiated in the blue-green domain is presented. The temperature influence during and after illumination is investigated. To explain the initial decrease of the transmitted light, a physical model is proposed based on Ge(1), Ge(2), and Ge(3) color centers under a new assumption: the simultaneous creation of Ge(l) and Ge(3) or Ge(2) and Ge(3). Then this model is discussed theoretically. Strange oscillating behavior in a fiber subjected to power steps is also presented.