Abstract: A wavelength converter for generating a wavelength tunable laser optical source in itself is disclosed. The wavelength converter includes a first semiconductor optical amplifier for generating an optical noise, generating and outputting a first optical source by amplifying the generated optical noise if an external current is applied, first and second distributed Bragg reflectors for reflecting only a component of a specified wavelength range among components of the optical noise and applying the reflected component to the first semiconductor optical amplifier, and a second semiconductor optical amplifier for receiving an optical source divided from the optical source reflected by and outputted from the first distributed Bragg reflector and an input data optical source, generating and outputting a second optical source by changing a phase of the divided optical source according to a digital signal from the input data optical source.

Abstract: An optical signal switching network having a transmitter and a receiver, wherein the transmitter includes a data generator for generating a data signal and a clock signal having the same frequency as the data signal; a clock attenuator for attenuating a frequency of clock signal generated in the data generator at a predetermined ratio; a signal synthesizer for synthesizing the data signal and the attenuated clock signal; a laser generator for generating a laser beam used to transmit the synthesized data signal and clock signal; and a modulator for coupling the synthesized data signal and clock signal to the laser beam and modulating the coupled signal, thereby providing the modulated optical signal to be transmitted to the receiver over an optical fiber

Abstract: A method for enhancing transmission efficiency of burst data by estimating a void between burst data and filling the void with new burst data in an optical burst switching (OBS) network. To this end, a node in the OBS network receives burst data (BD) aggregated from data packets, and a burst control packet (BCP) that is received prior to the BD by an offset time. The BCP contains information relating to the offset time and the BD. To predict the void between the BDs, a void filling time is defined within the offset time using the BCP. The present invention provides the method for determining whether to fill the void and filling the void by directly monitoring the BD over a preset time.

Abstract: A high-speed wavelength selectable optical source and a method thereof are disclosed. The wavelength selectable optical source includes at least one optical source having a multimode oscillation spectrum, a demultiplexer and an optical switch for extracting light having a certain selected wavelength. A certain wavelength can be selected among the multimode wavelengths using the demultiplexer and the optical switch, and thus the wavelength can discontinuously be tuned at high speed. Also, by making the light having the selected wavelength incident to the multimode optical source, the power of the output light can uniformly be maintained and maximized through injection locking.

Abstract: A wavelength converter for generating a wavelength tunable laser optical source in itself is disclosed. The wavelength converter includes a first semiconductor optical amplifier for generating an optical noise, generating and outputting a first optical source by amplifying the generated optical noise if an external current is applied, first and second distributed Bragg reflectors for reflecting only a component of a specified wavelength range among components of the optical noise and applying the reflected component to the first semiconductor optical amplifier, and a second semiconductor optical amplifier for receiving an optical source divided from the optical source reflected by and outputted from the first distributed Bragg reflector and an input data optical source, generating and outputting a second optical source by changing a phase of the divided optical source according to a digital signal from the input data optical source.

Abstract: An apparatus and method for effectively transmitting a packet data and a control data of path information about the packet data in an optical packet data switching network. The method includes grouping a plurality of wavelengths into at least two wavelength bandwidths, each wavelength bandwidth being composed of neighboring wavelengths, and transmitting the optical packet data and the control data with wavelengths of different wavelength bandwidths respectively. Since the wavelength to transmit the optical packet data and the wavelength to transmit the control data has a difference from each other, a node receiving optical data easily divides the packet data and the control data.

Abstract: Apparatuses and methods are provided which suppress a surge component occurring at an optical amplifier on an optical path through which an optical burst signal is transmitted. An optical amplifier may experience a surge due to the power variation of the optical burst signal that is fed to the optical amplifier. To suppress such a surge component, a power corresponding to a number of wavelengths of an optical burst signal to be input is calculated. The optical amplifier is instructed to generate an optical signal with a power corresponding to a difference between a set value and the calculated power. The generated optical signal and the optical burst signal to be input are coupled and output according to the instruction. Thus, the optical amplifier can receive the optical signal with the constant power and the surge component at the optical amplifier can be suppressed.

Abstract: Disclosed is an optical packet communication system using a wavelength-offset polarization-division multiplexing labeling. An optical signal transmitter which is provided at an ingress node positioned at a sending end in an optical packet switching network, generates and combines packet data and a label, and transmits the combined packet data and label to a core node, wherein the packet data and label have polarization directions perpendicular to each other and maintain a predetermined wavelength interval. A label swapping device detects the label from the combined packet data and label received from the optical signal transmitter, detects next moving position information of the packet data, for generating a new label, substitutes the detected label by the new label, combines the new label with the packet data, and transmits the combined packet data and new label to a next moving position.

Abstract: The present invention relates to transmitting a coded video signal, wherein the video signal is preferably an MPEG-4 video signal including a base layer and an enhancement layer. The present invention comprises a first coding unit for coding the video signal into a first stream, a second coding unit for coding the video signal into a second stream, a layer-combining multiplexing unit for combining the first and second streams into one stream; and a real-time transport protocol (RTP) packetization unit for packetizing the combined stream, wherein the packetized combined stream has an RTP header.

Abstract: A method of synchronizing a still picture with a moving picture stream is disclosed, which is suitable for supporting a multimedia service further using a still picture to provide separate video data as well as moving pictures and voice. The present invention includes the steps of generating a control data for synchronization of the still picture from a server, providing the control data to a client through a prescribed moving picture frame of the moving picture stream by the server, and synchronizing the still picture with the moving picture stream to display by the client.

Abstract: A method is provided for decoding digital image data in order to improve a picture quality of a reproduced image by performing a dequantizing in consideration of an input DCT coefficient having a laplacian distribution. The digital image data decoding method of a digital image data decoder may dequantize digital image data using a quantizer having characteristics of mapping an input DCT coefficient xij to a restoration level yij. This may occur by estimating a probability distribution function p(xij) of the input DCT coefficient xij, calculating a mass center Cm, and setting the mass center as a restoration level.

Abstract: A one-way valve for evacuating air from a collapsible, flexible, airtight bag using a vacuum source. After the air is removed from the airtight bag, the one-way valve prevents air from re-entering the bag. A flat annular silicon valve and a valve body without center hole is provided for precise closing of the valve.

Abstract: A multimedia streaming service system is provided that includes a VOD server to sequentially transmit a header (moov) and media data (mdat) of MP4 contents in a TCP packet and a client to transmit a streaming service request signal in HTTP to the VOD server. The client may accumulate the media data (mdat) received from the VOD server in a decoder buffer for a predetermined time, and reproduce the data on a real time basis. A guaranteed rate of QoS may be enhanced as compared to an RTP/UDP-based streaming method. A service delay time may be reduced as compared with a TCP-based downloading method, thereby implementing contents on a real time basis.

Abstract: An apparatus for downloading a multimedia file including a file converter configured to convert a larger multimedia file into a smaller multimedia file by deleting prescribed medial information based on a media format contained in the larger file. Further, the file converter converts the larger file into the smaller file by deleting multi bit-rate media not corresponding to a selected bit rate or by deleting enhancement layer video.

Abstract: A method for setting a motion vector of a digital video including calculating a final motion vector allocated to a resolution-reduced macroblock using two motion vectors having a highest correlation among each other out of motion vectors of four adjacent macroblocks.

Abstract: A tunable optical oscillator that generates optical signals at a band of micro- to millimeter-wave is provided. The tunable optical oscillator includes an electrical signal generator for generating an electrical signal at the predetermined band; a master laser that is driven by the electrical signal, and generates an optical signal having a first frequency; and a slave laser that is driven by an electrical signal, injected into the optical signal generated by the master laser, generates an optical signal having a second frequency, and mixes the received optical signal with the optical signal having a second frequency to be output. The tunable optical oscillator is capable of generating signals over a broadband including micro- to millimeter-wave and beyond, say, from tens of MHz to several THz. The generated signals by the optical oscillator have also frequency tunability over the range of tens of GHz with coarse tuning methods to tens of MHz with fine tuning methods.

Abstract: A tunable optical oscillator that generates optical signals at a band of micro- to millimeter-wave is provided. The tunable optical oscillator includes an electrical signal generator for generating an electrical signal at the predetermined band; a master laser that is driven by the electrical signal, and generates an optical signal having a first frequency; and a slave laser that is driven by an electrical signal, injected into the optical signal generated by the master laser, generates an optical signal having a second frequency, and mixes the received optical signal with the optical signal having a second frequency to be output. The tunable optical oscillator is capable of generating signals over a broadband including micro- to millimeter-wave and beyond, say, from tens of MHz to several THz. The generated signals by the optical oscillator have also frequency tunability over the range of tens of GHz with coarse tuning methods to tens of MHz with fine tuning methods.