An optical transmission line includes a first optical fiber and a second optical fiber connected to the first optical fiber. The first optical fiber includes a core region formed at a center of the fiber and a cladding region formed around the core region. The cladding region includes air holes formed in a triangular lattice around the core region. The first optical fiber has a negative wavelength dispersion and a dispersion per slope of -200 nm to -50 nm at a wavelength of 1050 nm. The second optical fiber has a positive wavelength dispersion and the dispersion per slope of -800 nm to -50 nm at the wavelength of 1050 nm.