Raman fiber optic amplifier with reduced dispersion

A Raman fiber optic amplifier comprising:

• a first fiber having a signal input end and an output end opposite the signal input end;
• a second fiber having a signal output end and an input end opposite the signal output end, wherein said input end is coupled to the output end of the first fiber;
• and
• a pump light source coupled to the first and the second fibers in such a manner as to achieve Raman amplification with respect to a light signal applied to the signal input end of the first fiber and output from the signal output end of the second fiber;
• wherein lengths of the first and the second fibers are determined so that the fibers have substantially equal relative dispersion slopes and exhibit dispersions of substantially equal magnitude and opposite sign at a wavelength of the light signal, the fiber having a positive dispersion comprises a generally cylindrical core, an outer cladding, and a refractive index profile with respect to the outer cladding, and
• (a) the core has a diameter of between 3 and 6 microns (μm) and a difference (Δn) between the refractive index of the core and the outer cladding is between 0.015 and 0.035;
• (b) the index profile includes a trench region adjacent the circumference of the core;
• and
• (c) the trench region has a width of between 1 and 4 μm and a Δn of between −0.005 and −0.015 with respect to the outer cladding.