Dispersion-shifted fiber

A dispersion-shifted fiber having:

• a zero-dispersion wavelength within the range of 1.4 .mu.m to 1.7 m;
• and
• a cutoff wavelength of 1.6 .mu.m or more at a 2 m length of said dispersion-shifted fiber
• wherein said dispersion-shifted fiber comprises a core region and a cladding region disposed around an outer periphery of said core region, said core region including:
• a first core having a predetermined refractive index;
• and
• a second core disposed around an outer periphery of said first core, said second core having a lower refractive index than said first core, and
• wherein said cladding region includes:
• a first cladding disposed around an outer periphery of said second core, said first cladding having a lower refractive index than said second core;
• and
• a second cladding disposed around an outer periphery of said first cladding, said second cladding having a higher refractive index than said first cladding.

A dispersion-shifted fiber having:

• a zero-dispersion wavelength within the range of 1.4 .mu.m to 1.7 .mu.m;
• and
• a cutoff wavelength of 1.6 .mu.m or more at a 2 m length of said dispersion-shifted fiber,
• wherein said dispersion-shifted fiber comprises a core region and a cladding region disposed around an outer periphery of said core region, said core region including:
• a first core having a predetermined refractive index;
• a second core disposed around an outer periphery of said first core, said second core having a lower refractive index than said first core;
• and
• a third core disposed around an outer periphery of said second core, said third core having a higher refractive index than said second core, and
• wherein, when said core region has an outer diameter of 2a, said dispersion shifted fiber satisfies the following requirement:
• ##EQU10## wherein r is a distance from a center of said dispersion-shifted fiber in a radial direction thereof;
• .DELTA.n(r) is a relative refractive index difference with respect to said cladding region at the position apart from the center of said dispersion-shifted fiber at the distance r;
• and
• .DELTA.n.sub.max is a maximum relative refractive index difference in said core region with respect to said cladding region.

A dispersion-shifted fiber having:

• a zero-dispersion wavelength within the range of 1.4 .mu.m to 1.7 .mu.m;
• and
• a cutoff wavelength of 1.6 .mu.m or more at a 2 length of said dispersion shifted fiber,
• wherein said dispersion-shifted fiber comprises a core region and a cladding region disposed around an outer periphery of said core region, said core region including;
• a first core having a predetermined refractive index;
• a second core disposed around an outer periphery of said first core, said second core having a lower refractive index than said first core;
• and
• a third core disposed around an outer periphery of said second core, said third core having a higher refractive index than said second core, and
• wherein said cladding region includes:
• a first cladding disposed around an outer periphery of said third core, said first cladding having a lower refractive index than said third core;
• and
• a second cladding disposes around an outer periphery of said first cladding, said second cladding having a higher refractive index than said first cladding.

A dispersion-shifted fiber having:

• a zero-dispersion wavelength within the range of 1.4 .mu.m to 1.7 .mu.m;
• and
• a cutoff wavelength of 1.6 .mu.m or more at a 2 length of said dispersion shifted fiber,
• wherein said dispersion-shifted fiber comprises a core region and a cladding region disposed around an outer periphery of said core region, said core region including:
• a first core having a predetermined refractive index;
• a second core disposes around an outer periphery of said first core, said second core having a lower refractive index than said first core;
• a third core disposed around an outer periphery of said second core, said third core having a lower refractive index than said second core;
• and
• a fourth core disposed around an outer periphery of said third core, said fourth core having a higher refractive index than said third core, and
• wherein, when said core region has an outer diameter of 2a, said dispersion-shifted fiber satisfies the following requirement:
• ##EQU12## wherein r is a distance from a center of said dispersion-shifted fiber in a radial direction thereof;
• .DELTA.n(r) is a relative refractive index difference with respect to said cladding region at the position apart from the center of said dispersion-shifted fiber at the distance r;
• and
• .DELTA.n.sub.max is a maximum relative refractive index difference in said core region with respect to said cladding region.

A dispersion-shifted fiber having:

• a zero-dispersion wavelength within the range of 1.4 .mu.m to 1.7 .mu.m;
• and
• a cutoff wavelength of 1.6 .mu.m or more at a 2 m length of said dispersion-shifted fiber,
• wherein said dispersion-shifted fiber comprises a core region and a cladding region disposed around an outer periphery of said core region, said core region including:
• a first core having a predetermined refractive index;
• a second core disposed around an outer periphery of said first core, said second core having a lower refractive index than said first core;
• a third core disposed around an outer periphery of said second core, said third core having a lower refractive index than said second core;
• and
• a fourth core disposed around an outer periphery of said third core, said fourth core having a higher refractive index than said third core, and
• wherein said cladding region includes:
• a first cladding disposed around an outer periphery of said fourth core, said first cladding having a lower refractive index than said fourth core;
• and
• a second cladding disposed around an outer periphery of said first cladding, said second cladding having a higher refractive index than said first cladding.