Measurement of UV-induced losses and thermal effects in photosensitive fibers using whispering gallery modes

When a photosensitive (PS) fiber is exposed to UV-irradiation, a permanent refractive index change is induced in the core. As a result, according to Kramers-Kronig relations, the absorption coefficient (α) is also increased. This increment of the absorption can lead to a significant heating of the fiber when it is illuminated by a moderate optical power. Thermal effects may produce spectral changes in some fiber devices, as for example Long Period Gratings (LPGs) or Fiber Bragg Gratings (FBGs) [1].