Patent ID: 7706055

Claim:
An optical module comprising: an amplification optical fiber amplifying light to be amplified by supply of pumping light, said amplification optical fiber including: a core extending along a predetermined axis and being doped with an amplification dopant for amplifying the light to be amplified; a first cladding provided on an outer periphery of said core and having a refractive index lower than that of said core; a second cladding provided on an outer periphery of said first cladding and having a refractive index lower than that of said core; and a third cladding provided on an outer periphery of said second cladding and having a refractive index lower than those of said first and second claddings, whereby said amplification optical fiber allows light to be amplified to propagate in a single-mode in said core thereof and allows the pumping light to propagate in a multi-mode in said core, said first cladding, and said second cladding thereof; an optical coupler optically connected to one end of said amplification optical fiber, said optical coupler supplying at least the pumping light into said amplification optical fiber; and an absorption optical fiber optically connected to the other end of said amplification optical fiber and absorbing the pumping light having passed through said amplification optical fiber, said absorption optical fiber including: a core extending along a predetermined axis so as to be optically connected to said core of said amplification optical fiber; a first cladding provided on an outer periphery of said core of said absorption optical fiber so as to be optically connected to said first cladding of said amplification optical fiber, and having a refractive index lower than that of said core of said absorption optical fiber; a second cladding provided on an outer periphery of said first cladding of said absorption optical fiber so as to be optically connected to said second cladding of said amplification optical fiber, and having a refractive index lower than that of said core of said absorption optical fiber, said second cladding of said absorption optical fiber being doped with an absorption dopant for absorbing the pumping light; and a third cladding provided on an outer periphery of said second cladding of said absorption optical fiber and having a refractive index lower than those of said first and second claddings of said absorption optical fiber, whereby said absorption optical fiber allows light to be amplified to propagate in a single-mode in said core thereof and allows the pumping light to propagate in a multimode in said core, said first cladding, and said second cladding thereof.