Patent ID: 6937805

Claim:
A dispersion compensating fiber, comprising: a cladding; a central core region having a higher refractive index than that of said cladding; a depressed core region which is located around said central core region, and which has a lower refractive index than that of said cladding; and a ring core region which is located around said depressed core region and inside said cladding, and which has a higher refractive index than that of said cladding, wherein the radius of said ring core region is set in a range from 6.5 μm to 9.5 μm, the radius ratio of said depressed core region relative to said central core region is set in a range from 2.0 to 4.0, and the radius ratio of said ring core region relative to said depressed core region is set in a range from 1.1 to 2.0, wherein the relative refractive index difference of said central core region relative to said cladding is set in a range from +1.00% to +1.90%, the relative refractive index difference of said depressed core region relative to said cladding is set in a range from −0.60% to −1.00%, and the relative refractive index difference of said ring core region relative to said cladding is set in a range from +0.20% to +1.00%, and wherein at least one wavelength selected from the range from 1.53 μm to 1.63 μm, chromatic dispersion of said dispersion compensating fiber is in a range from −50 ps/nm/km to −150 ps/nm/km, the dispersion slope is in a range from −0.25 ps/nm 2 /km to −3.0 ps/nm 2 /km, the ratio of the dispersion slope relative to the chromatic dispersion is in a range from 0.005 nm −1 to 0.020 nm −1 , and said dispersion compensating fiber has a cut-off wavelength which substantially enables single mode transmission.