Optical system and method having low loss and non-linear effects

A high-speed optical communications system comprising:

• a transmission line having first and second spans, each of the first and second spans having at least one single-mode fiber, the fiber of the first span having a negative dispersion with an absolute value of between about 4 ps/nm/km and 7 ps/nm/km at 1560 nm and the fiber of the second span having a positive dispersion at 1560 nm, the positive dispersion of the second span compensating the negative dispersion of the first approximately zero, wherein the length of the first span is greater than the length of the second span;
• a transmitting device for adding a signal to the transmission line, the transmitting device being coupled to one end of the transmission line;
• and
• a receiving device for receiving the signal sent by the transmitting device, the receiving device being coupled to another end of the transmission line.

A method of transmitting a signal over a transmission line having first and second spans of single mode optical fiber, the method comprising the steps of:

• adding the signal to the transmission line;
• transmitting the signal over the first span of optical fiber having a negative dispersion with an absolute value of between about 4 ps/nm/km and 7 ps/nm/km at 1560 nm;
• compensating for the negative dispersion of the first span by guiding the signal over the second span of optical fiber having a positive dispersion at 1560 nm, the total dispersion over the transmission line being compensated to approximately zero, wherein the length of the first span is greater than the length of the second span;
• and
• dropping the signal from the transmission line.

A high negative dispersion single-mode optical transmission fiber having a core and a cladding, the core comprising:

• an inner core having a first refractive index difference between about 0.0100 and 0.0160;
• a first glass layer surrounding the inner core and having a substantially constant refractive index difference, the first refractive index difference of the inner core being greater than the second refractive index difference of the first glass layer;
• a second glass layer surrounding the first glass layer and having a third refractive index difference between about 0.0030 and 0.0080;
• and wherein the cabled fiber has a cutoff wavelength less than about 1500 nm and a value of dispersion between about −8.0 ps/nm/km and −3.0 ps/nm/km at a wavelength of about 1560 nm.