Patent ID: 7164834

Claim:
A dispersion-compensating fiber comprising: (a) a first core region that includes the center axis and that has a refractive index of n 1 ; (b) a second core region that surrounds the first core region and that has a refractive index of n 2 ; (c) a third core region that surrounds the second core region and that has a refractive index of n 3 ; and (d) a cladding region that surrounds the third core region and that has a refractive index of n 4 ; the first core region having a refractive-index profile, and the refractive index n 1 denoting the maximum value in the profile; the refractive index n 2 having the relationship n 1 >n 2 ; the refractive index n 3 having the relationship n 2 <n 3 ; the refractive index n 4 having the relationship n 3 >n 4 ; the first core region having a relative refractive-index difference of at least 2.0% and at most 3.3% with reference to the refractive index n 4 ; the second core region having a relative refractive-index difference of at least −1.5% and at most −0.2% with the same reference as above; the third core region having a relative refractive-index difference of at least 0.2% and at most 0.5% with the same reference as above; the dispersion-compensating fiber having a figure of merit of at least 200 ps/nm/dB and an absolute value of relative dispersion curvature of at most 10 −4 nm −2 both at a wavelength of 1550 nm.