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: Disclosed is a multimode optical fiber having a structure to reduce scattering loss which includes a core divided into a central region having the optimal refractive index according to an optimal core shape index minimizing the scattering loss of the multimode optical fiber, and a peripheral region having the refractive index lower than that of the central region; and a cladding enclosing the core and having the refractive index lower than the lowest refractive index of the core.

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: An optical fiber preform having a substrate tube, a cladding layer and a core layer further includes a first barrier layer deposited by a material having a low OH diffusion coefficient between the substrate tube and the cladding layer, wherein the first barrier layer is for substantially preventing OH contained in the substrate tube from being diffused into the cladding layer. The optical fiber preform further includes a second barrier layer formed by depositing a material having a low OH diffusion coefficient between the cladding layer and core layer, for substantially preventing OH which has been diffused into the cladding layer from the substrate tube from being diffused further into the core layer.

Abstract: Disclosed is a high efficiency burner and an apparatus for over-cladding an optical fiber pre-form using the same. The high efficiency burner heating an optical fiber pre-form includes burner covers, burner bodies arranged between the burner covers, and fuel dischargers arranged in at least two rows between the burner bodies, and divided by a partition, respectively.

Abstract: An optical fiber having a multi-step core structure, and a method of fabricating the same, are provided. The optical fiber includes a central core having a predetermined radius a1 from an central axis and a refractive index n1, a first outer core having a radius a2 and a refractive index n2 smaller than the refractive index n1 and surrounding the central core, a second outer core having a radius a3 and a refractive index n3 smaller than the refractive index n2 and surrounding the first outer core, and a cladding having a radius a4 and a refractive index n0 smaller than the refractive index n3 and surrounding the second outer core, i.e., a1<a2<a3<a4 and n1>n2>n3>n0. The diameter of the core is increased by making the refractive index distribution of the core multi-stepped, thus providing easy fabrication. The optical fiber has a low dispersion value in a 1550 nm wavelength, thus making superspeed long distance transmission possible.

Abstract: A furnace minimizes the lowering of the quality of optical fibers, especially those lowerings of the quality that stems from variations of the conditions inside of the furnace. These variations can occur when a preform is connected to an auxiliary quartz rod of differing diameters. Also, the furnace has an inlet sleeve which minimizes fluctuations in flow speed of the inert gases and the pressures inside the furnace.

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: An apparatus for fabricating an optical fiber coated with metal, constructed with a crucible for melting the optical fiber preform to draw an uncoated optical fiber, a diameter measuring device for measuring the diameter of the uncoated optical fiber to regulate it, a metal coater for coating the uncoated optical fiber with metal to prevent penetration of moisture, a temperature controller for controlling the inside temperature of the metal coater, a post-cooler for cooling the metaled optical fiber from a high temperature, a capstan for drawing the optical fiber from the optical fiber preform by applying a rotational force against a portion of the metaled optical fiber, and a spool for winding the metaled optical fiber. The metaled optical fiber includes a core for transmitting light, a cladding on the core having lower refractive index than the core, and a metal coating formed on the cladding for preventing penetration of moisture.