Optical fiber for wavelength division miltiplexing communications

An optical fiber for wavelength division multiplexing (WDM) communications, comprising:

• an inner core having a predetermined refractive index, formed to have a first predetermined radius from a central axis of the optical fiber;
• an outer core having a refractive index which is lower than the refractive index of the inner core and getting linearly smaller from its inner side to its outer side, formed on an outer side of the inner core to have a second predetermined radius;
• an inner cladding formed on an outer side of the outer core to have a third predetermined radius;
• and
• an outer cladding having a refractive index which is lower than the refractive index of the inner cladding and gets linearly smaller from its inner side to its outer side, formed on an outer side of the inner cladding to have a fourth predetermined radius;
• the optical fiber having a dispersion value in a range of 2.0 to 4.0 psnm−1 Km−1 in a 1550 nm wavelength band.

A method for decreasing the sensitivity of a WDM optical fiber to influence from external stress and tension, said fiber having an inner core having an inner side and an outer side, an outer core and an inner cladding formed on the outer side of the outer core, said method comprising:

• selecting a fiber with a dispersion value from 2.0 to 4.0 ps nm−1 Km−1 at a wavelength of 1550 nm;
• selecting the inner core to have a predetermined refractive index Ri;
• and
• selecting the outer core to have a refractive index Ro such that (i) Ro<Ri, and (ii) Ro decreases linearly from the inner side of the outer core to the outer side of the outer core;
• and
• an outer cladding having a refractive index that becomes linearly smaller from its inner side to its outer side, formed on an outer side of the inner cladding.

In a method for transmitting via an optical fiber a plurality of optical signals of different wavelengths in the 1550 nm wavelength band, the method comprising feeding the plurality of signals to a fiber comprising:

• an inner core having a predetermined refractive index Ri;
• an outer core having an inner side and an outer side, said outer core having a refractive index Ro such that Ro<Ri;
• a cladding formed on the outer side of the outer core;
• Ro decreasing linearly from the inner side of the outer core to the outer side of the outer core;
• an inner cladding formed on an outer side of the outer core;
• and
• an outer cladding that becomes linearly smaller from its inner side to its outer side, formed on an outer side of the inner cladding;
• the improvement comprising:
• the fiber having a dispersion value in a range of 2.0 to 4.0 ps nm−1 km−1 in said 1550 nm wavelength band.

In an optical fiber for WDM communication, comprising:

• an inner core having a predetermined refractive index Ri;
• an outer core having an inner side and an outer side, said outer core having a refractive index Ro such that Ro<Ri;
• and
• an inner cladding formed on the outer side of the outer core;
• the improvement comprising:
• said fiber having means for decreasing the sensitivity of the fiber to influence from external stress and tension;
• and
• an outer cladding having a refractive index that becomes linearly smaller from its inner side to its outer side, formed on an outer side of the inner cladding.

A method for manufacturing a wave division multiplexing (WDM) optical fiber in which sensitivity to influence from external stress and tension is lessened, said method comprising the steps of:

• (1) providing an inner core with a predetermined refractive index Ri, said inner core having an outer surface;
• (2) depositing an outer core on the outer surface of the inner core, said outer core having an outer-core inner side and an outer-core outer side, said outer core having a predetermined refractive index Ro, where Ro<Ri and Ro decreases linearly from the outer-core inner side to the outer-core outer side, whereby Ro has a minimum value Ro-min at the outer-core outer side;
• (3) forming an inner cladding on the outer-core outer side, said inner cladding having a predetermined refractive index Ric less than Ro-min;
• (4) forming an outer cladding on the inner cladding, said outer cladding having a predetermined refractive index Roc, less than Ric;
• and
• (5) carrying out the steps of the method so as to provide a WDM optical fiber that has a dispersion value from 2.0 to 40 ps nm−1 km−1 at a wavelength of 1550 nm;
• whereby a WDM optical fiber having a reduced sensitivity to influence from external stress and tension is provided.