Optical amplification apparatus

An optical amplification apparatus comprising:

• a first amplification optical fiber including:
• a first core that is doped with an active element using a first active element doping concentration distribution, and
• a first cladding layer disposed outside of the first core, the first cladding layer having a refractive index lower than a refractive index of the first core;
• a second amplification optical fiber that is connected to the first amplification optical fiber in a longitudinal direction of the first amplification optical fiber, the second amplification optical fiber including:
• a second core that is doped with the active element using a second active element doping concentration distribution that is different from the first active element doping concentration distribution, the second core being optically connected to the first core of the first amplification optical fiber, and
• a second cladding layer disposed outside of the second core, the second cladding layer having a refractive index lower than a refractive index of the second core,
• a first pumping light source that generates a first pumping light and allows the first pumping light to enter either of the first cladding layer in the first amplification optical fiber and the second cladding layer in the second amplification optical fiber;
• and
• a second pumping light source that generates a second pumping light and allows the second pumping light to enter either of the first cladding layer in the first amplification optical fiber and the second cladding layer in the second amplification optical fiber,
• wherein
• the first pumping light has a first wavelength,
• the second pumping light has a second wavelength at which an absorptance of light by the active element is lower than an absorptance of light at the first wavelength,
• the first pumping light source allows the first pumping light to enter the first cladding layer of the first amplification optical fiber from an opposite side of the first amplification optical fiber to the second amplification optical fiber,
• the second pumping light source allows the second pumping light to enter the first cladding layer of the first amplification optical fiber from an opposite side of the first amplification optical fiber to the second amplification optical fiber, and
• the first amplification optical fiber has such a length that a portion of the second pumping light transmits therethrough.