Abstract: A method of producing an optical fiber preform includes preparing a glass preform that has a hole extending in a longitudinal direction formed on one end of the glass preform in such a manner that a length of the hole is equal to or less than half of an entire length of the glass preform, synthesizing a porous glass preform by depositing glass particles on an outer circumference of the glass preform having the hole formed on the end, and sintering the porous glass preform after arranging the porous glass preform in such a manner that the end having the hole formed thereon points downward and the hole is open to the air.

Abstract: A method of producing an optical fiber that has a hole extending in a longitudinal direction includes preparing a glass preform that has a hole extending in a longitudinal direction, synthesizing a porous preform layer by depositing silica-based glass particles on an outer circumference of the glass preform, dehydrating the porous preform layer, sintering the dehydrated porous preform layer under a reduced pressure so that the porous preform layer becomes a translucent glass preform layer that contains closed pores, and drawing a translucent glass preform that includes the glass preform and the translucent glass preform layer so that the translucent glass preform layer becomes a transparent glass layer.

Abstract: A method of producing an optical fiber preform includes preparing a glass preform that has a hole extending in a longitudinal direction formed on one end of the glass preform in such a manner that a length of the hole is equal to or less than half of an entire length of the glass preform, synthesizing a porous glass preform by depositing glass particles on an outer circumference of the glass preform having the hole formed on the end, and sintering the porous glass preform after arranging the porous glass preform in such a manner that the end having the hole formed thereon points downward and the hole is open to the air.

Abstract: An optical fiber includes a first core having a relative refractive index difference of larger than 0.36%, and a cladding. The optical fiber has fiber cut-off wavelength ?c of more than 1350 nm, cable cut-off wavelength ?cc of less than 1285 nm, bending loss at a wavelength of 1625 nm of not more than 10 dB/km when wound at a diameter of 20 mm, transmission loss at a wavelength range of 1285 to 1625 nm of not more than 0.40 dB/km, transmission loss at a wavelength of 1383 nm less than transmission loss at a wavelength of 1310 nm, and difference in transmission loss at a wavelength of 1383 nm of not more than 0.04 dB/km before and after exposure to hydrogen. The lower bending loss of the optical fiber provides an optical fiber cable for use in a WDM transmission in wavelength range of 1285 to 1625 nm.

Abstract: An optical fiber includes a first core having a relative refractive index difference of larger than 0.36%, and a cladding. The optical fiber has fiber cut-off wavelength &lgr;c of more than 1350 nm, cable cut-off wavelength &lgr;cc of less than 1285 nm, bending loss at a wavelength of 1625 nm of not more than 10 dB/km when wound at a diameter of 20 mm, transmission loss at a wavelength range of 1285 to 1625 nm of not more than 0.40 dB/km, transmission loss at a wavelength of 1383 nm less than transmission loss at a wavelength of 1310 nm, and difference in transmission loss at a wavelength of 1383 nm of not more than 0.04 dB/km before and after exposure to hydrogen. The lower bending loss of the optical fiber provides an optical fiber cable for use in a WDM transmission in wavelength range of 1285 to 1625 nm.

Abstract: Provided is an optical fiber that is in particular suitable for Raman amplification. An effective area at a wavelength of 1570 nm is in a range of 35 &mgr;m2 to 45 &mgr;m2, an absolute value of a dispersion slope at the wavelength is equal to or less than 0.04 ps/nm2/km, and a dispersion value at the wavelength is in a range of 5 ps/nm/km to 10 ps/nm/km. It is desirable that a refractive index profile contains at least one annular region between a center core and a cladding region.

Abstract: Provided is an optical fiber that is in particular suitable for Raman amplification. An effective area at a wavelength of 1570 nm is in a range of 35 &mgr;m2 to 45 &mgr;m2, an absolute value of a dispersion slope at the wavelength is equal to or less than 0.04 ps/nm2/km, and a dispersion value at the wavelength is in a range of 5 ps/nm/km to 10 ps/nm/km. It is desirable that a refractive index profile contains at least one annular region between a center core and a cladding region.

Abstract: Provided is an optical fiber that is in particular suitable for Raman amplification. An effective area at a wavelength of 1570 nm is in a range of 35 &mgr;m2 to 45 &mgr;m2, an absolute value of a dispersion slope at the wavelength is equal to or less than 0.04 ps/nm2/km, and a dispersion value at the wavelength is in a range of 5 ps/nm/km to 10 ps/nm/km. It is desirable that a refractive index profile contains at least one annular region between a center core and a cladding region.