The radiation-induced loss of single mode fibers with undoped and Ge-doped core material was measured at 1300 nm and 1550 nm in the time range from 0.1 seconds to approximately less than 500,000 seconds at room temperature (plus 25 degrees Celsius). With the Ge-doped fiber, measurements were also made at minus 50 degrees Celsius and plus 80 degrees Celsius. The ratio of the losses at 1300 nm and 1550 nm increased at plus 25 degrees Celsius with both fiber types within about 10 seconds to a maximum value of approximately equal to 2 (Ge-doped) or approximately equals 2.7 (undoped). Then the ratio decreased continuously and became less than 1 (equals higher loss at 1550 nm) after about 35,000 - 70,000 seconds (Ge-doped) or approximately greater than 350,000 seconds (undoped). After approximately equal to 500,000 seconds a value of approximately equal to 0.75 was reached with the Ge-doped fiber, with an observable tendency to fall further. At minus 50 degrees Celsius the ratio increased up to about 2.2 and remained constant (as if frozen) during the whole irradiation time of 500,000 seconds. At plus 80 degrees Celsius, however, the radiation- induced loss at 1550 nm was higher at the beginning and became lower than the one at 1300 nm only after an irradiation time of approximately greater than 104 seconds. Additionally the annealing time of loss was measured after the end of irradiation for varying irradiation times between about 3 seconds and 400,000 seconds. The results can qualitatively explain the radiation-induced loss curves at 1300 nm and 1550 nm as well as their ratio.