OPTICAL FIBER AND OPTICAL COMMUNICATION SYSTEM USING THIS OPTICAL FIBER

摘要

The present invention resides in an optical fiber able to form an optical transmitting line for wavelength division multiplexing transmission in a wavelength band of 1.5 .mu.m using a Raman amplifier, and an optical communication system using this optical fiber. The optical fiber has an effective core area from 40 .mu.m2 to 60 .mu.m2 in a set wavelength band of at least one portion of a wavelength band of 1.5 .mu.m; a dispersion value from 4 to 10 ps/nm/km at a wavelength of 1.55 .mu.m; a dispersion slope set to a positive value equal to or smaller than 0.04 ps/nm2/km in a wavelength band of 1.55 .mu.m; and a zero dispersion wavelength equal to or smaller than 1.4 .mu.m. Further, a cutoff wavelength is set to be equal to or smaller than 1.5 .mu.m at a length of 2 m, and a bending loss is set to be equal to or smaller than 5 dB/m at a diameter of 20 mm in the wavelength band of 1.5 .mu.m. In a refractive index profile of the optical fiber, for example, a relative refractive index difference .DELTA.1 of a first glass layer as an innermost layer with respect to a reference layer, and a relative refractive index difference .DELTA.3 of the refractive index of a third glass layer as a third layer from an inner side with respect to the reference layer are set to be positive. Further, a relative refractive index difference .DELTA.2 of a second glass layer as a second layer from the inner side with respect to the reference layer is set to be negative.