Temperature dependence of radiation-induced attenuation of optical f ibers

Abstract

We investigate the temperature dependence of radiation-induced attenuation (RIA) at 1 310 nm for a Ge/P co-doped fiber after a steady-state γ-ray irradiation. A γ irradiation facility 60 Co source is used to irradiate the fiber at a dose rate of 0.5 Gy/min, satisfying a total dose of 100 Gy. The test temperature ranges from -40 to 60• C by 20• C, and the RIA of the fiber is obtained using a power measuring device. The experimental result demonstrates that RIA exhibits a steady, monotonic, and remarkable temperature dependence after approximately 48 h of accelerated annealing at 70• C. The optical fiber irradiated with a high dose and annealed sufficiently can be used as a temperature sensor.OCIS The recent advancements in photonic technologies have provided new applications for optical fibers involving radiation environment, such as fibre optic gyroscope (FOG) [1,2] and fiber optics amplifiers [3,4] in space. The presence of highly energetic radiation in this environment, however, may induce additional optical attenuation greatly. Radiation-induced attenuation (RIA) is primarily caused by the trapping of radiolytic electrons and holes at defect sites in the fiber, i.e., formation of color centers [5,6] . In addition, a number of studies have indicated that the RIA of an optical fiber is sensitive to temperature [7,8] . Various studies have demonstrated that RIA decreases with increasing temperature, with the exception of fibers containing phosphorus (P) [9] . This phenomenon is mainly because of thermal annealing of color centers, which eliminates more of the damage at an elevated temperature [10] . For a P-doped fiber, researchers have considered this exception by transforming the phosphorus oxygen hole center (POHC) into the P1 center [11,12] . In this letter, the temperature behavior of the RIA of a Ge/P co-doped fiber after steady-state γ-ray irradiation and a series of annealing treatments was tested to demonstrate the temperature dependence of color center absorption. Our tests only considered the temperature, avoiding the influence of other factors, such as radiation dose and dose rate.Only one type of fiber was studied in our experiments, Ge/P co-doped both in core and cladding. The cladding and coating diameters of this fiber were 80 and 165 µm. This 300-m-long fiber was produced with a loss constant of 0.8 dB/km at 1 310 nm.Our experiments involved three steps. First, the temperature behavior of the fiber loss was tested in two temperature cycles before irradiation to compare the RIA temperature effect. Second, the tested fiber was subjected to radiation to satisfy a total dose of 100 Gy, and then set aside for approximately 4 d at room temperature for primary annealing. Two temperature cycling tests were conducted for the RIA temperature characteristic testing, in which the test condition was the same as the initial conditions. Finally, the fiber underwent an accelerated annealing process at 70• C, which was 10• C higher than the maximal test temperature, until the attenuation variation was less than ...