OPTICAL FIBER FOR AMPLIFICATION AND OPTICAL FIBER AMPLIFIER USING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide an optical fiber for amplification which can easily reduce the difference in gains between LPmode and LPmode light beams, and an optical fiber amplifier using the same.SOLUTION: An optical fiber for amplification includes a core having an inner core 11i and an outer core 11o surrounding the outer circumferential surface of the inner core 11i. The relative refractive index difference Δof the inner core 11i to a cladding 12 is smaller than the relative refractive index difference Δof the outer core 11o to the cladding 12. The outer core 11o is entirely doped with erbium. The theoretical cutoff wavelength of an LPmode light beam is 1,565 nm or more. The theoretical cutoff wavelength of an LPmode light beam is 1,530 nm or less. The theoretical cutoff wavelength of the LPmode light beam is 980 nm or less.SELECTED DRAWING: Figure 2