Low Nonlinearity Long Haul Optical Transmission System

A long haul optical transmission system comprising:

• a transmitter comprising a modulated bit rate of at least 40 Gb/s;
• a receiver optically coupled to the transmitter with at least two composite optical fiber spans, each composite optical fiber span having a length of at least 50 km and comprising:
• a first optical fiber optically coupled to the transmitter and comprising, at a wavelength of 1550 nm, an effective area Aeff1 of greater than 120 μm2, an attenuation α1 of less than 0.180 dB/km, a nonlinear refractive index n21, and a length L1 of at least 30 km;
• a second optical fiber optical fiber optically coupled to the first optical fiber, wherein the second optical fiber has a length L2 of at least 20 km and wherein:
• when the second optical fiber has positive dispersion at a wavelength of 1550 nm, the composite optical fiber span has, at a wavelength of 1550 nm, an average attenuation of less than 0.180 dB/km;
• and
• when the second optical fiber has negative dispersion at a wavelength of 1550 nm, the composite optical fiber span has, at a wavelength of 1550 nm, an average dispersion with a magnitude from about 2 to about 5 ps/nm/km, an average attenuation of less than 0.205 dB/km, and each composite optical fiber span has an average dispersion slope with a magnitude less than about 0.02 ps/nm2/km;
• and wherein the system comprises at least one amplifier between each composite optical fiber span.