Single mode optical fiber and manufacturing method therefor

A manufacturing method for a single mode optical fiber, comprising steps of:

• forming a glass rod having a core section and a first cladding section having a refractive index lower than that of the core section;
• vapor phase depositing for a second cladding on the first cladding;
• sintering the glass rod having the first and second claddings to produce a glass preform;
• and
• performing the drawing operation on the glass preform to produce an optical fiber;
• wherein the ratio of the diameter of the first cladding section to the diameter of the core section is >4.8;
• the OH concentration of the core section and the first cladding section are not more than 0.1 ppm;
• and the OH concentration of the second cladding section is not more than 100 ppm.