Fabrication of OH-free, single-mode fiber by using slurry casting and rod-in-tube method

We present a new simple and low-cost process for fabricating low-loss single-mode fiber (SMF) cladding preforms by a modified slurry casting method, in which the cladding preform and a core rod obtained separately with the VAD method are assembled by a rod-in-tube method. The fabricated SMF showed almost the same loss characteristics as a standard SMF with a minimum loss of 0.19 dB/km at 1550 nm and an OH-free loss spectrum, which were realized with an OH reduction process in a slurry casting based cladding. This OH reduction method plays an important role in preventing OH diffusion into the core and inner cladding.