OPTICAL FIBER, PROCESS FOR PRODUCING THE SAME AND OPTICAL AMPLIFIER

摘要

An optical fiber comprising first core part (1) having rare earth ions added thereto, second core part (2) disposed around the circumference of the first core part (1) and having rare earth ions added thereto and a refractive index lower than that of the first core part (1), and clad part (3) disposed around the circumference of the second core part (2) and having a refractive index lower than that of the second core part (2), wherein the concentration of rare earth ions added to the second core part (2) is higher than the concentration of rare earth ions added to the first core part (1). As a result, while relieving any efficiency deterioration by concentration quenching, a reduction of fiber length is effected to thereby attain suppressing of the intensity of FWM cross talk in optical amplification.