Optical fiber amplifier that can attain sufficient gain shift effect, small noise property and high operation efficiency at the same time even in two-wavelength excitation tm dopant optical fiber amplifier, and optical amplifier having the same

Abstract

A laser amplifier includes a gain medium of a glass fiber, a first exciting light source, a second exciting light source, and another first exciting light source. The gain medium of the glass fiber includes rare earth dopant in a host medium. Ions of the rare earth dopant has an energy level structure including a ground level and a pair of laser upper level and laser lower levels between which a stimulated transition is to be produced after production of a population inversion between the pair of laser upper and laser lower levels. The pair of laser upper and laser lower levels being higher than the ground level. The first exciting light source is coupled to the input side of the glass fiber for introducing first exciting light to the glass fiber to produce the population inversion. The second exciting light source is coupled to the input side of the glass fiber for introducing second exciting light source to the glass fiber to raise ions of the rare earth dopant from the ground level to the laser lower level. The second exciting light has a wavelength band different from a wavelength band of the first exciting light. The other first exciting light source is coupled to the output side of the glass fiber for introducing the first exciting light to the glass fiber. A two-way excitation is performed on the glass fiber.