OPTICAL TRANSMISSION LINE

摘要

An optical transmission line which is so constructed as to reduce a dispersion for a signal light with a wavelength band of 1.55.mu.m and realize excellent transmission characteristics and suitable for WDM transmission, comprising one or more transmission units provided between a transmitter - a receiver, a transmitter - a repeater, a repeater - a repeater and a repeater - receiver. Each transmission unit has a dispersion shift optical fiber which is a transmission medium and a mode elimination device which reduces the optical power of the higher order modes other than the basic mode of a signal light propagated through the dispersion shift optical fiber. Particularly, the dispersion shift optical fiber has an incident end to which the signal light is incident and an emission end from which the signal light is emitted, has a dispersion whose absolute value is not larger than 5 ps/nm/km for a light with a wavelength of 1550 nm and a cut-off wavelength longer than the wavelength of the signal light at a fiber length of 2m. The mode elimination device is so constructed as to suppress the optical power of a higher order mode to 1/10 or smaller, more preferably to 1/40 or smaller, of the basic mode optical power in order to satisfy single mode condition in relation to the fiber length.