| 摘要 |
PROBLEM TO BE SOLVED: To suppress the occurrence of waveform distortion by eliminating the possibility of the induction of a nonlinear phenomenon even when the multiplexing number of wavelengths increases by adjusting the effective core diameter of an Er-doped optical fiber to a specific value or larger and constituting an optical fiber amplifier so that the zero dispersion wavelength may become a wavelength on the outside of a specific wavelength band. SOLUTION: In an Er-doped optical fiber which is used for constituting an Er-doped optical fiber amplifier for wavelength multiplex transmission, seven cores (having refractive indexes of nw ) 10 to which both Er and Al are added are formed in a clad 8 and an intermediate layer (having a refractive index Ni ) 9 is provided on the outer periphery of each core 10. Each core has a diameter D and the interval between each core is S. Fig. (b) shows the refractive index distribution in the optical fiber. The relative refractive-index difference between each core 10 and clad (having a refractive index nc ) 8 (or the intermediate layer 9) is expressed asΔn. Then the effective core diameter of the optical fiber at 1.55μm is adjusted to >=9μm and the zero dispersion wavelength is adjusted to a wavelength longer than 1.53-1.56μm by appropriately setting the values of theΔn, D, and S. |
