| 摘要 |
<p>In an optical communication and the like, a light amplifying optical fiber is capable of amplifying an optical signal having a wavelength in the vicinity of at least 1.57 to 1.62 mu m by a high gain. A cladding (5) is formed on the side of an outer peripheral portion of a core (1) to which erbium is added, and a refractive index of the cladding is smaller than that of the core (1). A relative refractive index difference " DELTA " of the core (1) with respect to the cladding (5) is made equal to 0.3 % or larger, and also equal to 1 % or smaller. While a composition of the core (1) is made of Er-Al2O3-GeO2-SiO2, a composition of the cladding (5) is made of SiO2, erbium is added to the entire region of the core, and concentration of this erbium is selected to be 1,000 wtppm, and also a cut-off wavelength of the optical fiber is selected to be 1,400 nm. While the cut-off wavelength of the optical fiber is made constant, since the relative refractive index difference " DELTA " is selected to be an optimum value, a diameter of the core may become an optimum value. Lowering of the gain caused by a bending loss of the optical fiber can be avoided, and an erbium absorption amount per unit length of the optical fiber can be increased, and further, a gain per unit length of the optical fiber can be increased <IMAGE></p> |
