Optical fiber, optical amplifier, optical transmitting system and solid laser

PURPOSE:To obtain an optical fiber having excellent optical transmitting property and high efficiency by adding Dy ions to an optical material in high optical refractive area of an optical fiber having a high light refraction area and a low light refraction area each having a prescribed refractive index difference and capable of transmitting an optical signal in a specific wavelength area in a single mode. CONSTITUTION:The object optical fiber has a high optical transmitting property and a low optical transmitting property (0.01-1% refractive index), and transmits an optical signal of 800-1400nm wavelength area in a single mode. This optical fiber is obtained by adding 100-10000ppm divalent Dy (dysprosium) ions to an optical material (e.g. fluoride based or SiO2 based material) in the high optical refractive area. The figure shows energy level of a Dy ion and when an excited light having 830nm wavelength enters the optical fiber, an energy level of the Dy ion is transferred to absorption excitation level 105 and then transferred to a semistable excitation level 103 by a non-luminescence transition 121 by phonon release. Then, a light having 1.25-1.35nm wavelength is released and returned to a base level 102.