GAIN EQUALIZER, LIGHT AMPLIFIER AND OPTICAL FIBER COMMUNICATION SYSTEM

摘要

PROBLEM TO BE SOLVED: To control gain characteristics of a gain medium by alleviating the wavelength dependency of a gain in the gain medium. SOLUTION: An optical fiber amplifier is manufactured by using an erbium- doped coated optical fiber 1 in which long-period fiber gratings 21 functioning as a gain equalizer are written in plural parts in a core by ultraviolet laser. In respective fiber gratings 21, ultraviolet laser is radiated from the outside of a coating layer of the coated optical fiber 1 to provide periodic modulation to the refractive index in the core. In the coated optical fiber 1, since the fiber gratings 21 compensate for the wavelength dependency of the gain to flatten it, the uniform amplification can be efficiently realized in the wide zone.