Dispersion-compensating fiber, and dispersion-compensating module and hybrid optical fiber link using the same

A dispersion-compensating fiber comprising:

• a central core segment;
• an intermediate core segment which is provided around the central core segment;
• a ring core segment which is provided around the intermediate core segment;
• and
• a clad which is provided around the ring core segment,
• wherein the refractive index profile of the dispersion-compensating fiber being such that the intermediate core segment has a lower refractive index than the central core segment, the ring core segment has a refractive index which is higher than that of the intermediate core segment and lower than that of the central core segment, and the clad has a refractive index which is lower than or equal to that of the ring core segment and higher than that of the intermediate core segment;
• and
• when the dispersion-compensating fiber is linked with a dispersion-shifted fiber which satisfies the following conditions:
• (A) single-mode transmission is actually achieved at a wavelength of 1.565 μm;
• (B) the zero dispersion wavelength is within the range of 1.55 μm±0.05 μm;
• (C) at all wavelengths of between 1.525 μm and 1.575 μm, chromatic dispersion is greater than or equal to −3.5 ps/nm/km and less than or equal to +3.5 ps/nm/km;
• (D) the dispersion slope at the zero dispersion wavelength is greater than or equal to +0.05 ps/nm2/km and less than or equal to +0.085 ps/nm2/km,
• the residual chromatic dispersion is below +1.5 ps/nm/km in all or part of the band of wavelengths from 1.565 μm to 1.625 μm.