The effect of y radiation (Co60) on optical fibers is studied for investigations to remote measurement in irradiating environments. The spectral characteristics of PCS and AS silica fibers, PCS "wet" and AS "wet" and "superwet" are compared. An automatic computerized system for measurement "in situ" is used between 0.4 and 1,1 micron. Radiation-induced effects are examinated at 840 nm on PCS, AS with silicone, AS with epoxy (200 and 400/600m) up to 5.108 rads. Samples of "dry", wet", "superwet" and "doped fluor" silica are studied up to 1,3.109 rads between 0,3 and 2,5 μm. The photobleaching, the radiation hardening and the breakage of PCS and AS-silicone after 107 rads are recognized. The spectral characte-ristics of a band at 610-630 nm, a spectral deformation at 945 nm for "wet" fibers and a peak of the radiation-induced attenuation are observed. The kinetic of the 630 nm defect in silica fibers and silica samples is also investigated.