An optical communication device includes an excitation light source that outputs excitation light, a multiplexer that multiplexes signal light and the excitation light outputted from the excitation light source, a first nonlinear optical medium into which the multiplexed excitation light and the signal light are inputted, and a second nonlinear optical medium that is coupled to the first nonlinear optical medium in series and has an optical property different from that of the first nonlinear optical medium.

An optical fiber includes: a core; a depressed layer surrounding the core; and a cladding surrounding the depressed layer. A refractive index profile of the core is an α-th power distribution having an index α of 1.0 or more and 2.9 or less. A relative refractive index difference Δ.sup.− of the depressed layer with respect to the cladding has an absolute value |Δ.sup.−| that is 0.05% or more and 0.15% or less. A ratio r1/r2 of a radius r1 of the core to an outer radius r2 of the depressed layer is 0.35 or more and 0.60 or less. A cable cutoff wavelength λcc of 22 m is less than 1.26 μm. A mode field diameter at a wavelength of 1.31 inn is larger than 8.6 inn and smaller than 9.5 μm.

An optical fiber includes: a core; a depressed layer surrounding the core; and a cladding surrounding the depressed layer. A refractive index profile of the core is an -th power distribution having an index of 1.0 or more and 2.9 or less. A relative refractive index difference .sup. of the depressed layer with respect to the cladding has an absolute value |.sup.| that is 0.05% or more and 0.15% or less. A ratio r1/r2 of a radius r1 of the core to an outer radius r2 of the depressed layer is 0.35 or more and 0.60 or less. A cable cutoff wavelength cc of 22 m is less than 1.26 m. A mode field diameter at a wavelength of 1.31 inn is larger than 8.6 inn and smaller than 9.5 m.

An optical communication device includes an excitation light source that outputs excitation light, a multiplexer that multiplexes signal light and the excitation light outputted from the excitation light source, a first nonlinear optical medium into which the multiplexed excitation light and the signal light are inputted, and a second nonlinear optical medium that is coupled to the first nonlinear optical medium in series and has an optical property different from that of the first nonlinear optical medium.

In a glass material, a full width at half maximum of a first sharp diffraction peak of an X-ray scattering spectrum is 5.9 nm.sup.1 or less.