Abstract: There is provided an alloy-coated optical fiber and a fabricating method thereof. In the alloy-coated optical fiber, a core is formed of a light transmitting material, a clad surrounds the outer circumferential surface of the core, and an indium-tin-silver coating layer is formed around the outer circumferential surface of the clad.

Abstract: There is provided a dispersion-managed fiber preform and a fabricating method thereof preform by modified chemical vapor deposition (MCVD). A core and a clad having the refractive index distribution of an optical fiber with a positive dispersion value are uniformly deposited in a glass tube. The preform with the positive dispersion value is heated at every predetermined period with a torch and the heated preform portions are etched to have a negative dispersion value. Then, the preform alternately having positions with the positive dispersion value and positions with the negative dispersion value along the length direction is collapsed.

Abstract: A multi-cladding optical fiber, a long-period optical fiber grating written in the optical fiber, and a writing method thereof are provided. The multi-cladding optical fiber includes a core made of germanium-doped silica (GeO2—SiO2), for guiding light, an inner cladding made of fluorine-doped silica (F—SiO2), the inner cladding having a refractive index smaller than that of the core and surrounding the core, and an outer cladding made of silica, the outer cladding having a refractive index smaller than that of the core and larger than that of the inner cladding and surrounding the inner cladding. Therefore, an optimized optical fiber can be designed. That is to say, an optical fiber having desired characteristics can be fabricated by adjusting at least one of the parameters including the amount of F doped into the inner cladding, the thickness of the inner cladding, the amount of GeO2 doped into the core, the composition of SiO2 in the outer cladding and the drawing tension of the optical fiber.

Abstract: An optical fiber for wavelength division multiplexing (WDM) communications, includes: an inner core having a predetermined refractive index, formed to 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 gets 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, and a cladding formed on an outer side of the outer core to have a third predetermined radius.

Abstract: There is provided an apparatus and method for fabricating a holey optical fiber. An optical fiber with air holes of a predetermined size and shape along the length of the optical fiber is drawn by supplying nitrogen gas into air holes through one end of a holey optical fiber preform while heating the other end of the preform.

Abstract: Disclosed is an apparatus for measuring a residual stress and a photoelastic effect of an optical fiber, which includes: a light source; a rotary type optical diffuser distanced from the light source in a predetermined distance for suppressing the spatial coherence of a light radiated in the light source; an optical condenser for condensing the radiated light passed through the optical diffuser into a spot where the optical fiber is located; a polarizer for polarizing the light passed through the optical condenser into a 45° linear polarized light from an axis of the optical fiber; a polarization analyzer, installed at 90° angle with respect to the polariscope and attached closely with the optical fiber, to prevent the penetration by the background image of the optical fiber; an optical fiber strain unit including a strain sensor for straining the optical fiber on the polarization analyzer toward a longitudinal direction and measuring the strain on the optical fiber; an object lens for magnifying the

Abstract: A cooler of an optical fiber draw tower, situated below a melting furnace for melting a preform for an optical fiber, for cooling the optical fiber drawn from the preform melted in the melting furnace, includes at least one heat exchanger installed with a predetermined length surrounding the optical fiber drawn from the melting furnace, for cooling the drawn optical fiber. The heat exchanger is formed of a thermoelectric cooler (TEC) for taking electrical energy through one heat absorbing surface to emit heat to the other heat emitting surface and has a tubular shape in which the heat absorbing surface of the TEC surrounds the optical fiber drawn from the melting furnace along the drawing direction by a predetermined length, and the drawn optical fiber is cooled as it passes through the tubular TEC. Also, the cooler further includes an auxiliary cooler attached to the heat emitting surface of the TEC, for cooling the emitted heat.

Abstract: An optical fiber for use in a fiber Bragg grating and a fiber Bragg grating using the same are provided. The optical fiber includes a core made of a material obtained by adding germanium oxide (GeO2) to silica (SiO2), for guiding light, and a cladding made by adding a material having a negative thermal expansion coefficient to silica (SiO2), the cladding having a refractive index lower than that of the core. Therefore, the change in Bragg wavelength depending on temperature can be minimized by forming the optical fiber using a material having a negative thermal expansion coefficient.

Abstract: There are provided an optical fiber rod overcladding apparatus and method, and an optical fiber drawing method. In the preform rod overcladding method, a preform rod is clamped in a top chuck and leveled, and a glass tube is mounted in a bottom chuck and leveled. The preform rod is coaxially inserted into a glass tube. Then, the glass tube is preheated by the furnace and heated by the burner until the glass tube reaches a softening point. The preform rod is completely sealed in the glass tube by sucking air in a clearance between the preform rod and the glass tube by application of a negative vacuum pressure. Thus, a preform is completed.

Abstract: In the interest of producing high-strength splice connections between silica-based glass fibers a method of using a tri-particle flow of gases for flame fusion is disclosed. An outer relatively high-velocity flow of oxygen surrounds an intermediate, lower-velocity flow of chlorine or oxygen which in turn surrounds a central flow of H.sub.2, D.sub.2, NH.sub.3, or ND.sub.3.Particularly high strengths are achieved when a central flow of hydrogen or deuterium and an intermediate flow of chlorine are used in such a fashion as to heat fiber ends to be spliced to temperatures of 500 degrees C. and beyond only after these ends have been enveloped by chlorine.

Abstract: An apparatus (30) for cooling a lightguide fiber (21) drawn from a molten portion of a glass preform (22) located in a furnace (23). The apparatus (30) has an upper chamber (34) and a lower chamber (36) each having a small opening in the lower portions thereof. The upper chamber (34) has a heat transfer liquid (35) therein and the lower chamber (36) is pressurized to prevent liquid from passing through the opening. The hot fiber (21) is cooled by the liquid as it is drawn through liquid (35) without physical contact with the periphery of the openings.

Abstract: A single mode lightguide fiber having a trapezoidal shaped refractive index profile. In a particular embodiment the ratio of the upper base to the lower base is less than 0.3.

Abstract: This invention involves optical fiber which supports essentially only a single guided mode, perhaps degenerate, at the transmission wavelength, usually between 0.6 and 1.7 microns. The index of refraction of the core material is graded in the radial direction so as to yield an optical fiber with very low total dispersion and therefore high bandwidth. Specific embodiments include, in addition to the low dispersion characteristic, improved field confinement, and therefore permit lower clad-to-core ratios then heretofore believed practical. Additional advantages which accrue as a result of the greater field confinement include lower cabling, microbending, and curvature-induced losses.

Abstract: A glass fiber is drawn through a rotating body of flowable coating material to apply the material thereon and then is further drawn through a throat section of an open ended cage formed by a plurality of wire strands forming a hyperboloid of rotation. As the glass fiber is drawn through the throat section the previously applied flowable material contacts the wire strands causing a vortex of material which centers the fiber in the throat and distributes the material uniformly and concentrically thereon.

Abstract: A glass fiber is drawn through a rotating body of flowable coating material to apply the material thereon and then is further drawn through a throat section of an open ended cage formed by a plurality of wire strands forming a hyperboloid of rotation. As the glass fiber is drawn through the throat section the previously applied flowable material contacts the wire strands causing a vortex of material which centers the fiber in the throat and distributes the material uniformly and concentrically thereon.