Abstract: There is provided a packaging unit for an optical fiber array using a planar lightwave circuit (PLC). An optical fiber array is fixed within a housing. The housing has first and second slots formed to face each other on the side periphery, and each of the first and second slots has opened ends to make the inner and outer walls of the housing communicate with each other. An optical fiber of the optical fiber array is inserted through first and second boots and then the first and second boots are inserted in the first and second slots of the housing.

Abstract: An optical fiber having a core that has a graded refractive index profile is disclosed. A clad surrounds the core and traps light within the core. A difference between differential mode delays (DMDs) at wavelengths of about 1300 nm and about 850 nm within the core is increased in a radial direction. The difference between the DMDs at both the wavelengths basically has a value equal to or less than 0.6 ns/km between a position corresponding to 50% of a radius of the core and a center of the core.

Abstract: Disclosed is a method for managing a foreign mobile subscriber in a visitor location register (VLR) of a mobile switching center (MSC) to provide a roaming service.

Abstract: Disclosed is a residual stress measuring system for measuring the residual stress in an optical fiber. The residual stress measuring system comprises a light source for generating light used to measure the residual stress, a lens system for converting the generated light into a plane wave, a polarimeter for transforming the converted light to an input polarized light, which is incident on the optical fiber, a rotational measuring section for rotating the optical fiber so as to enable the polarized light to transmit through the optical fiber in various directions, and a detector for detecting the residual stress from a phase shift of the transmitted light.

Abstract: An erbium-doped fiber amplifier and a wavelength division multiplexing optical transmission system equipped with the same are disclosed. The wavelength division multiplexing optical transmission system includes a transmission stage having a first C/L fiber amplifier for amplifying combined C and L-band optical signals, an optical repeater having at least one second C/L fiber amplifier for amplifying the optical signals transmitted from a single mode fiber of a predetermined length, and a dispersion compensating fiber of a predetermined length for compensating dispersions of the amplified optical signals. The system also includes a reception stage having a third C/L fiber amplifier for amplifying the optical signals transmitted from a single mode fiber of a predetermined length, and a receiver for separating the amplified optical signals from the third C/L fiber amplifier into C-band optical signals and L-band optical signals band by band and de-multiplexing the separated amplified optical signals.

Abstract: A gain-clamped semiconductor optical amplifier capable of providing constant gain for output optical signals at substantially all times is disclosed. In particular, the gain-clamped semiconductor optical amplifier according to the present invention comprises a active waveguide having an input and output side; clad layers surrounding the active waveguide; and a grating, which is formed partially at both end parts under the input and output sides of the active waveguide.

Abstract: A method for enabling a first terminal of a packet-based network to communicate with a second terminal connected to a remote access server includes the steps of: registering the aliases and IP addresses of the first terminal and the remote access server in the gatekeeper; letting the first terminal to send a message to the gatekeeper for requesting a connection with the second terminal; causing the gatekeeper to request the remote access server to connect with the second terminal even when the second terminal is not registered with the gatekeeper; causing the remote access server to request the second terminal to register its alias and IP address in the gatekeeper; and, establishing communication between the first and second terminals through the gatekeeper.

Abstract: The present invention discloses a method for fabricating silica glass using a sol-gel process, which includes a sol forming step for forming a sol by mixing a starting material, deionized water and an additive together; gelation step for gelatinizing the sol after filling a circular mold with the gel produced; gel drying step for separating the gel from the circular mold and drying the gel; setting step for placing the gel inside of a heat chamber and injecting helium gas into the heat chamber; and low heat treatment step for pressurizing and depressurizing an internal pressure of the heat chamber repeatedly for several times.

Abstract: Disclosed is a phase-demodulation method for minimizing the phase error of a communication signal. The phase-demodulation method for demodulating a phase-demodulated communication signal using a digital phase-demodulation algorithm includes the steps of: adding one sampling to the digital phase-demodulation algorithm represented by an equation F k ? ( x ) = ? k = 0 k - 1 ? C k ? x k , where k is the number of sampling times and Ck is a complex constant; and, demodulating the phase-demodulated communication signal. Accordingly, the phase-demodulation method minimizes the phase error generated when a noise is propagated in phase space during a demodulation time of the phase-modulated communication signal, using a minimum number of sampling times and a minimum number of calculation times.

Abstract: This invention provides an optical fiber block that includes an optical-fiber-alignment portion and a stress-reduction-depth portion. In the optical-fiber-alignment portion, a V groove array is arranged to accommodate the non-coated fiber portion of a ribbon fiber. The V groove array is formed by primary and secondary wet-etching processes on a silicon wafer, and further includes first V grooves at both sides and second V grooves different from the first V grooves disposed between the first V grooves. Meanwhile, the stress-reduction-depth portion is formed by another wet etching, extending to a predetermined depth from the optical-fiber-alignment portion, for reducing stress caused by a variation in the coating thickness of the optical fibers.

Abstract: An optical cross-connect system is disclosed that use reduces the number of AWGs (Arrayed-Waveguide Grating) as compared to prior art systems so that the hardware complexity is reduced while simultaneously reducing its production costs. The optical cross-connect system includes N×N AWGs for performing multiplexing/demultiplexing functions, an optical circulator for transmitting bidirectional signals via the AWGs, an optical coupler for interconnecting N individual ports of the AWGs, and an optical switching block connected to the optical coupler. One of the optical signals branched from the optical coupler is input to the optical switching block having a corresponding wavelength and distributed to a desired output terminal, and the other one of the optical signals is input to an optical switching block being out of an operable wavelength range and filtered by the optical switching block.

Abstract: Disclosed is a method for fabricating planar light waveguide circuits, wherein the circuit has a structure that includes a substrate comprised of a core and under-clad layers, an optical circuit, and a plurality of arrayed waveguides coupled thereon. More specifically, the method includes the steps of layering a hard layer on the core layer for forming a mask pattern of the planar light waveguide circuit; forming the mask pattern on the hard layer; layering a photoresist layer on a branch of the optical circuit and the arrayed waveguides of the mask pattern; forming a vertical taper structure on the photoresist layer using a gray scale mask; and, etching the core layer using the photoresist layer with the vertical taper structure and the mask pattern.

Abstract: Disclosed is an optical module of an isolator structure including a semiconductor laser, a polarizer, and a Faraday rotator. The laser outputs a first linearly-polarized beam of a predetermined polarization mode. The polarizer is positioned to face an end of the laser, and its polarization axis is tilted at a 45° angle with respect to the polarization direction of the first beam. The Faraday rotator is disposed between the laser and the polarizer, and rotate the polarization direction of the first beam by 45° to substantially coincide with the polarization axis of the polarizer, and then output it to the polarizer, and to rotate a second beam from the polarizer by 45°, wherein the second beam has a polarization mode polarized perpendicular to the first beam, and then output it to the semiconductor laser.

Abstract: A photomask is disclosed for the fabrication of an optical fiber block including a first section provided with slit arrays adapted to form an optical fiber alignment region of the optical fiber block while having a uniform slit pitch, partition portions arranged between adjacent ones of the slit arrays while having a pitch larger than the slit pitch, and end portions arranged outside the slit arrays while having a pitch larger than the slit pitch. The photomask also includes a second section adapted to form a stress-reducing recessed region of the optical fiber block etched to a desired depth from the level of the optical fiber alignment region. The photomask also includes auxiliary slit arrays arranged at an interface between the first and second sections. The auxiliary slit array includes at least one slit.

Abstract: An optical fiber alignment system for mounting optical fiber arrays on an optical fiber block having a plurality of grooves on its upper surface according to the present invention comprises jig assemblies including a first jig for propping up a part of the optical fiber arrays and a second jig for adsorbing and fixing the other part of the optical fiber arrays using a plurality of vacuum holes formed on the upper side; X-Y-Z-?X-?Y-?Z stages for translating and rotating the jig assemblies in 3D to align the optical fiber arrays on the block; a vision unit including an image detector to monitor the alignment process of the optical fiber arrays and a display for displaying the image signal on a screen; and, an vision unit translator for translating the vision unit in 3D.

Abstract: Disclosed is an optical fiber coating device for coating the outer circumference of the optical fiber with the coating material, in which the coating device is provided with and a gas provider for providing an environmental gas within the coating device, and a cooler for cooling down the environmental gas provided to the coater from the gas provider.

Abstract: Disclosed is a PIN photodiode used for a light-receiving element for optical communication. The PIN photodiode comprises a gate electrode structure consisting of a gate insulation layer and a gate electrode pad which prevent a bonding layer from being excessively depleted in the lateral direction at the time of applying a negative electric voltage to an electrode that is in contact with the bonding layer. The PIN photodiode allows the control of the electrostatic capacitance of the element by controlling the depletion level of the bonding layer in the lateral direction using the gate electrode pad. Therefore, it is possible to suppress the increase of the electrostatic capacitance and to achieve a high-speed operating property.

Abstract: Disclosed are a flip-chip bonding structure for improving the vertical alignment of an optical device relative to a PLC and a flip-chip bonding method for achieving this structure. The flip-chip bonding structure includes: a semiconductor substrate; a lower-clad layer formed on the upper surface of the semiconductor substrate, wherein the lower-clad layer is depressed on a designated area for mounting an optical device; vertical alignment structures formed on a part of the upper surface of the depressed area of the lower-clad layer and determining a vertical alignment position of the optical device on the semiconductor substrate; electrodes formed on another part of the upper surface of the depressed area of the lower-clad layer; a solder bump formed on the upper surfaces of the electrodes; and, an optical device bonded to the substrate by a flip-chip bonding method using the solder bump.

Abstract: Disclosed is a wavelength-division-multiplexer/demultiplexer using a parabolic horn-type waveguide provided with a grating for demultiplexing a multiplexed optical signal to channels, an input waveguide for inputting the optical signal to the grating, and output waveguides for outputting the optical signals demultiplexed by the grating, wherein the output waveguide comprises a first sub-waveguide having a parabolic horn shape, in which its width is gradually increased in a progressive direction of the optical signal; and a second sub-waveguide having a straight-line shape, in which its width is uniformly maintained in the progressive direction of the optical signal passing through the first sub-waveguide.

Abstract: A packaging device for alignment between a planar lightguide circuit and an optical-fiber block is disclosed. The device includes a planar lightguide circuit and a single optical-fiber block. The planar lightguide circuit includes an input port of an input waveguide, a plurality of output ports of output waveguides, arranged on the same surface as the input port of the input waveguide, and at least one dummy waveguide arranged abutting the outermost end of the output waveguides. An output port of the dummy waveguide is arranged on the same surface. The single optical-fiber block includes a plurality of ports corresponding to the input/output ports. The input/output ports are coupled in alignment with the input port of the input waveguide and the output ports of the output waveguides. The invention enables making a single processed alignment of the input/output ports of the planar lightguide circuit and the single input/output ports.