Abstract: This ultra-low-loss optical fiber comprises a core having a higher relative refractive index difference than silica and a cladding having a lower relative refractive index difference than silica. The relative refractive index difference of the core with respect to the refractive index of silica is 0.0030 to 0.0055, for example, and the relative refractive index difference of the cladding with respect to the refractive index of silica is ?0.0020 to ?0.0003. The ultra-low-loss optical fiber has the loss characteristic of simultaneously having optical losses of at most 0.324 dB/km at a wavelength of 1310 nm, at most 0.320 dB/km at a wavelength of 1383 nm, at most 0.184 dB/km at a wavelength of 1550 nm, and at most 0.20 dB/km at a wavelength of 1625 nm. The ultra-low-loss optical fiber is supercooled when the surface temperature of the optical fiber has a temperature range in a glass transition section during drawing.

Abstract: This ultra-low-loss optical fiber comprises a core having a higher relative refractive index difference than silica and a cladding having a lower relative refractive index difference than silica. The relative refractive index difference of the core with respect to the refractive index of silica is 0.0030 to 0.0055, for example, and the relative refractive index difference of the cladding with respect to the refractive index of silica is ?0.0020 to ?0.0003. The ultra-low-loss optical fiber has the loss characteristic of simultaneously having optical losses of at most 0.324 dB/km at a wavelength of 1310 nm, at most 0.320 dB/km at a wavelength of 1383 nm, at most 0.184 dB/km at a wavelength of 1550 nm, and at most 0.20 dB/km at a wavelength of 1625 nm. The ultra-low-loss optical fiber is supercooled when the surface temperature of the optical fiber has a temperature range in a glass transition section during drawing.

Abstract: An optical fiber for use in a metro network is provided. The optical fiber has a loss of 0.25 dB/km or less in the C-band and the L-band, a zero dispersion wavelength between 1560 nm and 1560 nm, and a dispersion slope of at least 0.074 ps/nm2/km at a wavelength of 1550 nm.

Abstract: A method for reducing the hydrogen sensitivity of an optical fiber is disclosed. The method includes a deuterium treatment step of exposing an optical fiber to a gas mixture including a deuterium, so that the optical fiber makes a contact with the deuterium, and a degassing step of degassing the optical fiber treated with the deuterium under a negative pressure condition.

Abstract: A photonic crystal fiber (PCF) preform, from which a photonic crystal fiber is manufactured, includes a rod-shaped substrate with holes longitudinally formed therethrough in a photonic lattice structure, and material layers having at least two different indices of refraction. The material layers are disposed in the holes, respectively. Distribution of index of refraction of the photonic crystal fiber preform is controlled by arrangement of the material layers. Consequently, an optical fiber with very low optical loss, very low optical nonlinearity and excellent transmission characteristics can be easily manufactured, and an optical fiber with various characteristics, differing depending upon the lattice structure, can be realized.

Abstract: An optical fiber for long-distance optical communication networks has a zero dispersion wavelength value in the range of 1560 to 1570 nm and a dispersion gradient value, at a wavelength band of 1550 nm, in the range of 0.055 to 0.075 ps/nm2/km.

Abstract: An optical fiber includes a core as a light signal transmission medium, a clad surrounding the core, a first coating layer which surrounds the clad and is formed of an UV-cured polymer material, and a second coating layer which surrounds the first coating layer and is formed of an UV-cured polymer material. The difference between the refraction index of the first coating layer and that of the second coating layer ranges from 0 (excluding 0) to 0.06.

Abstract: An optical fiber for an optical network is disclosed. The optical fiber includes a core having a core region having a first refractive index N1, and a refractive index depressed region surrounding the core region and having a second refractive index N2 that is lower than the first refractive index. A clad surrounds the core and having a third refractive index N4. The optical fiber has a zero-dispersion wavelength that is not less than 1555 nm and positioned in a wavelength range which does not exceed L-band. The optical fiber has negative dispersion values in C-band and positive dispersion values in L-band.

Abstract: A double-coated optical fiber and method includes providing a core that serves as a light transmission medium. A cladding surrounds the core and has a smaller reflective index than the core. A primary coating layer is formed of a UV-cured polymer around the clad, and a secondary coating layer is formed of a UV-cured polymer around the primary coating layer, to a thickness ranging from about 22 to 37.5 ?m in order to obtain a coating strip force ranging from about 1.0 to 1.63 N and a dynamic stress corrosion parameter ranging from 20 to 29. The primary and secondary coating layers can be formed by a wet on wet or wet on dry process.

Abstract: Disclosed is an optical-fiber preform having barrier layers to hydroxyl radicals, the optical-fiber preform comprising: a quartz tube in the form of a cylinder shape serving as a substrate for forming the optical-fiber preform; a first barrier layer for preventing hydroxyl radicals from permeating the optical-fiber preform and deposited onto the inner surface of the quartz tube; a second barrier layer having a permeation coefficient higher than the first barrier layer and deposited onto the first barrier layer; a third barrier layer having a permeation coefficient lower than the second barrier layer and deposited onto the second barrier layer; and, a core layer being located at the center of the optical-fiber preform.

Abstract: A method for reducing the hydrogen sensitivity of an optical fiber is disclosed. The method includes a deuterium treatment step of exposing an optical fiber to a gas mixture including a deuterium, so that the optical fiber makes a contact with the deuterium, and a degassing step of degassing the optical fiber treated with the deuterium under a negative pressure condition.

Abstract: An optical fiber for use in a metro network is provided. The optical fiber has a loss of 0.25 dB/km or less in the C-band and the L-band, a zero dispersion wavelength between 1560 nm and 1560 nm, and a dispersion slope of at least 0.074 ps/nm2/km at a wavelength of 1550 nm.

Abstract: Disclosed are a method and apparatus for overcladding a glass rod with a glass tube. The method includes (a) preparing a sealing tube, provided with a hole formed through the central portion thereof, (b) attaching the sealing tube to an upper end of the glass tube, (c) aligning the glass rod with the glass tube such that the glass rod is inserted into the sealing tube and (d) sealing an upper end of the sealing tube by heating an outer wall of the sealing tube.

Abstract: An optical fiber for long-distance optical communication networks has a zero dispersion wavelength value in the range of 1560 to 1570 nm and a dispersion gradient value, at a wavelength band of 1550 nm, in the range of 0.055 to 0.075 ps/nm2/km.

Abstract: A method of fabricating an optical fiber preform using an overcladding device and an optical-fiber-drawing method are provided. The overcladding device includes first and second chucks, an annular oxygen-hydrogen burner, a furnace, and a carriage for reciprocating between the first and second chucks positioned on a shelf, and a vacuum pump coupled to one of the chucks. According to the preform-fabricating method, primary and secondary preforms fixed to the first and second chucks are leveled respectively. The primary preform is inserted coaxially into the secondary preform. The secondary preform is pre-heated using the furnace and heated using the oxygen-hydrogen burner, thus softening the preforms. A first end of the secondary preform is sealed by heating the first end using the furnace, and the primary and secondary preforms are collapsed by forming a negative-pressure vacuum state inside the secondary preform through a second end of the secondary preform.

Abstract: A photonic crystal fiber capable of single-mode transmission and a preform thereof are disclosed. The photonic crystal fiber includes a substrate and a plurality of refraction index-adjusting material layers, each having a different refraction index, wherein the refraction index distribution of the fiber is the same as an electric field power distribution of incident light to be transmitted through the fiber. The photonic crystal fiber can minimize pulse dispersion caused by light loss and refraction-index deviation due to the incident light passing through a zone away from an actual core.

Abstract: Disclosed is a system for drawing an optical fiber for controlling polarization mode dispersion. A furnace is provided for uniformly heating an optical fiber preform in the drawing system mounted to an optical fiber draw tower. The furnace comprises: (a) a main body; (b) a sub-body placed coaxially with the main body and having a diameter smaller than that of the main body; and (c) an upper gas feeding section over the main body, wherein the upper gas feeding section includes a first hollow rotary body having at least one slit in the inner surface thereof along the longitudinal direction of an optical fiber and at least one opening extended in the direction of the center, whereby a gas artificially/periodically creates non-contact polarization to the optical fiber by the first hollow rotary body. Effective non-contact control can be carried out about polarization mode dispersion of the optical fiber.

Abstract: An optical fiber includes a core as a light signal transmission medium, a clad surrounding the core, a first coating layer which surrounds the clad and is formed of an UV-cured polymer material, and a second coating layer which surrounds the first coating layer and is formed of an UV-cured polymer material. The difference between the refraction index of the first coating layer and that of the second coating layer ranges from 0 (excluding 0) to 0.06.

Abstract: A method for drawing an optical fiber is provided in which a plurality of coating layers having a different viscosity is formed on the outer peripheral surface of a first optical fiber drawn from an optical fiber perform, then a second optical fiber with the coating layers formed thereon is drawn in a slanted direction relative to the drawing axis of the first optical fiber to form a third optical fiber incorporating a twist.

Abstract: A method and apparatus for drawing an optical fiber from an optical fiber preform is disclosed. The method includes the steps of: measuring an outer diameter of the optical fiber as being drawn from the preform and cooling the optical fiber; coating a sheath layer on the peripheral surface of the cooled optical layer; and curing the optical fiber coated with the sheath layer under a nitrogen atmosphere. The quantity of nitrogen charged into the nitrogen atmosphere may be controlled in such a manner that the sheath layer coated optical fiber has a strip force of not less than 1N.