Patent ID: 7369731

Claim:
An optical amplifying apparatus comprising: an optical fiber for amplification comprising: a core region extending along a predetermined axis, and a single cladding region which is in direct contact with an outer periphery of said core region and whose outer periphery is an outer periphery of said optical fiber for amplification; a pumping light supplier for supplying pumping light to said optical fiber for amplification; and a first connection fiber provided between said optical fiber for amplification and an entrance fiber provided on a light entrance end side of said optical fiber for amplification, said first connection fiber having a mode field diameter larger than a mode field diameter of said entrance fiber but smaller than a mode field diameter of said optical fiber for amplification, wherein said core region is doped with a rare-earth element, said core region having an outer diameter of 10 μm or more but 30 μm or less, and a relative refractive index difference of 0.5% or more but 2.0% or less with respect to said single cladding region, and wherein said single cladding region has a refractive index lower than that of said core region, said cladding region having an outer diameter of 75 μm or more but 200 μm or less.