Method of fabricating optical fiber preform and method of fabricating optical fiber

A method of fabricating an optical fiber comprising:

• depositing a first cladding having an outer diameter D so as to surround a core having an outer diameter d to make a porous core rod of D/d≧4.0, by using a vapor-phase axial deposition method;
• dehydrating the porous core rod to reduce an OH group concentration in the porous core rod to 0.8 ppb or less by weight;
• vitrifying the porous core rod after the dehydrating the porous core rod step to make a core rod;
• stretching the core rod;
• depositing a second porous cladding around the core rod after the stretching step by using a vapor-phase deposition method;
• dehydrating the second porous cladding to reduce an OH group concentration to 50 ppm or less by weight;
• vitrifying the second porous cladding after the dehydrating the second porous cladding step to make an optical fiber preform;
• and
• drawing the optical fiber preform to make an optical fiber,
• wherein the optical fiber formed via said drawing step has a transmission loss at a wavelength of 1.38 μm less than a transmission loss at a wavelength of 1.31 μm both before and after exposure to a 1% H2 atmosphere at room temperature for 4 days.