Hydrogen loading to the optic fibers for fiber grating sensors

Fibers with different depths of hermetically coated carbon are hydrogen loaded and radiated, and it's found that too thick of carbon layer around fiber can't bring best radiation-resistant properties, because the thick carbon layer would make the entering of hydrogen difficult although it can help to stop the hydrogen escaping. We also research the duration of saturated hydrogen loading under the temperature of 30 degrees C, 50 degrees C and 80 degrees C respectively, and it's found that after 150h, 100h and 48h, the fibers' photo sensitivities tend to be flat. Besides, in order to research the period of validity of hydrogen, some hydrogen loaded fibers are idle for from 1 day to 1 months before etched. The additional loss of these fibers are tested and compared.