Electronics and Telecommunications Research Institute

Kwang Joon Kim

Jyung Chan Lee

Joon Ki Lee

Heuk Park

Seung Il Myong

Hyun Jae Lee

Jong Hyun Lee

Bong Kyu Kim

Moo Jung Chu

Youn Seon Jang

Min Soo Kim

Hee Sang Chung

Hwan Seok Chung

Won Kyoung Lee

Sun Hyok Chang

Ji Wook Youn

El Hang Lee

O Kyun Kwon

Jin Soo Han

Sae Kyoung Kang

Dae Ub Kim

Hae Geun Kim

Chan Gyo Han

Hye Young Kim

Jong Tae Song

Seok Ho Song

Seok Y Kang

Sang Kyu Lim

Sang Jo Park

Kyeong Eun Han

Hyuek Jae Lee

Kyung Sook Hyun

Sung Un Lee

Byoung-Sung Kim

Chan Sung Park

Jun Ki Lee

A parallel scheduling apparatus includes an information managing unit generating a first request information for scheduling, a first scheduling unit performing first scheduling and then generating first matching information on the basis of the first request information, and a second scheduling unit performing second scheduling on the basis of the first request information and the first matching information. The parallel scheduling has an advantage of improving the scheduling performance and lowering the implementation complexity, ensuring low delay and transmission fairness among VOQs at low input traffic, being applied to all scheduling algorithms that perform existing multi-iterations, and providing efficient scheduling in a packet switch having a long RTT time or having a very short time slot or cell size, such as an optical switch.

Parallel scheduling method and parallel scheduling apparatus

A Mode Division Multiplexed Passive Optical Network (MDM-PON) apparatus includes: a non-mode selective multiplexer which includes a first end where three or more single-mode optical fibers are spaced apart from each other by a predetermined distance, and a second end where cores of the three or more single-mode optical fibers are tapered such that a gap between the three or more single-mode optical fibers is narrower than the predetermined distance while the three or more single-mode optical fibers are spaced apart from each other by an equal distance; an optical line terminal (OLT) which is connected to the second end through a few-mode fiber, and transmits a downstream optical signal; and three or more optical network units (ONUs) which is connected to the first end through the three or more single-mode optical fibers, and transmits upstream optical signals.

Mode division multiplexed passive optical network (MDM-PON) apparatus, and transmission and reception method using the same

An active alignment method for a multi-channel optical transmitter and receiver is disclosed. The active alignment method for a multi-channel optical transmitter includes actively aligning an optical signal generator with an optical multiplexer based on optical outputs of a plurality of wavelengths from the optical signal generator and an optical output of the optical multiplexer, and actively aligning the optical multiplexer with a fiber optic coupler based on an optical output of the optical multiplexer and an optical output of the fiber optic coupler.

Active alignment method for multi-channel optical transmitter and receiver, which has an optical signal generator with an optical multiplexer, which has an optical signal generator with an optical multiplexer

A method and apparatus for controlling a wavelength tuning of an optical source in an optical communication system. An operating temperature of an optical source is controlled and monitored to shorten a wavelength tuning time of the optical source generated in an optical source generator. When the current operating temperature reaches a final target temperature, an operating current is supplied to the optical source generator, and transmission of the operating current to the optical source generator is controlled and monitored. When the operating current reaches a final operating current, the wavelength tuning of the optical source is terminated. The operating temperature is adjusted by distinguishing between a smaller amount of temperature change and a larger amount of temperature change to prevent oscillation at the point of reaching the final target temperature, thereby minimizing the time taken for the output wavelength tuning.

Method and apparatus for controlling wavelength tuning of optical source for optical communication

Provided are an acousto-optic filter and an optical code division multiple access (CDMA) system using the acousto-optic filter. The acousto-optic filer includes: an acousto-optic mode converter (AOMC) converting an optical signal of a specific optical frequency corresponding to a frequency of an electric signal of an optical signal of a first mode having a predetermined optical frequency band; and a mode stripper (MS) stripping an optical signal of the optical signal of the first mode that has been converted to a second mode.

Acousto-optic filter and optical CDMA system using the same

Provided are an optical transmission apparatus and method using a light source for wavelength division multiplexing (WDM) optical communication that employs a Fabry-Perot laser diode (F-P LD) whose output wavelength is locked by an externally injected incoherent light, a multifiber, and a waveguide grating router. The light transmission apparatus includes: an incoherent light source (ILS) outputting incoherent light; a plurality of circulators (CIRs) connected to the ILS, receiving the incoherent light from the ILS, and outputting first optical signals; a first waveguide grating router (WGR) outputting the first optical signals output from each of the CIRs to optical fibers corresponding to each of the CIRs, and outputting second optical signals input from the optical fibers to the corresponding CIRs; a plurality of second WGRs corresponding to each of the CIRs, and demodulating the second optical signals output from each of the plurality of CIRs; and a plurality of receivers connected to the plurality of the second WGRs, and inputting the demultiplexed optical signals output from the plurality of second WGRs. A plurality of light sources for WDM optical communication whose output wavelength is locked can increase size and economical efficiency of a light transmission system (subscriber). The N&#xd7;N WGR can produce a conventional light transmission system and accommodate many subscribers.

Optical transmission apparatus and method

Provided are an apparatus and a method for reducing a signal noise of an OCDMA receiver and an OCDMA receiver and method. The includes: a clock recovery unit extracting sine wave clock from an output signal of an OCDMA decoder including an MAI (multiple access interference) noise; a time gating unit separating an auto-correlation peak signal and the MAI noise from the output signal of the OCDMA decoder using the sine wave clock; and an optical interferometer removing an SI (signal interference) noise remaining in the auto-correlation peak signal.

Apparatus and method for reducing signal noise and OCDMA receiver and method

Disclosed herein is an apparatus for controlling a decision threshold voltage to an optical receiver, which is capable of automatically controlling the decision threshold voltage to the optical receiver appropriately to signal level decision on the basis of a low-frequency band signal component of an output signal from the optical receiver. The apparatus is adapted to control the level of the decision threshold voltage to the optical receiver, which converts an input optical signal into an electrical signal. To this end, the apparatus comprises a voltage detector for branching off part of the output signal from the optical receiver and detecting a corresponding voltage, a differential comparator for comparing the voltage detected by the voltage detector with a reference voltage inputted thereto and outputting the resulting differential voltage, a low pass filter for filtering the differential voltage from the differential comparator at a predetermined low frequency band and supplying the resulting voltage as the threshold voltage to the optical receiver, and a voltage controller for controlling the reference voltage to the differential comparator on the basis of a differential voltage between the threshold voltage from the low pass filter and a predetermined voltage corresponding to a predetermined minimum bit error rate.

Apparatus for controlling decision threshold voltage to optical receiver

The present invention relates to an apparatus and method for stabilizing a bias voltage for a pulse generating modulator, which can automatically detect an optimal bias voltage for an external modulator, which is used in RZ or CSRZ modulation of an optical transmission signal using NRZ data to generate a reference pulse optical signal, and maintain the optimal bias voltage. In the bias voltage stabilizing method of the present invention, an output signal of the external modulator, to which the bias voltage to be stabilized is applied, is detected, a drive clock signal applied to the external modulator is detected, a mean output value of the products obtained by the multiplication of the output signal and the clock signal is periodically examined, and the bias voltage is adjusted so that the mean output value becomes '0'.

Apparatus and method for stabilizing bias voltage for pulse generating modulator

Provided is an erbium-doped fiber amplifier reducing transient phenomena of a signal-to-noise ratio and a bit error rate in a dynamic wavelength division multiplexing system and an amplifying method using the erbium-doped fiber amplifier. The erbium-doped fiber amplifier includes: a polarization scrambler modulating a polarization state of an input signal to remove a polarization of the input signal; an amplifier amplifying the input signal from which the polarization has been removed; a detector reading powers of input and output signals of the amplifier; and an automatic gain controller controlling currents of the pump LDs according to the powers of the input and output signals read by the detectorto maintain the gain even if the power of input signal changes.

Erbium doped fiber amplifier for reducing transient phenomena of OSNR and BER in dynamic WDM system and amplifying method thereof

The present invention relates to an apparatus and method for automatically correcting a bias voltage for a carrier suppressed pulse generating modulator using the phase distribution of the output pulses, which automatically detects an optimal bias voltage for the carrier suppressed pulse generating modulator and stabilizes the bias voltage. In the bias voltage automatic correction method and apparatus of the present invention, an optimal bias voltage for the modulator is set to a bias voltage that is obtained when mean power of an optical signal output from the modulator is highest. The varying direction of the bias voltage is detected on the basis of the phase variations in the output optical signal of the modulator according to the bias voltage variations is detected, and the bias voltage is corrected oppositely to the varying direction of the bias voltage.

Apparatus and method for automatically correcting bias voltage for carrier suppressed pulse generating modulator

A tunable high-order Bessel low pass filter which is applied to a multi-rate duobinary generation system of an optical communication system. The tunable Bessel low pass filter comprises a variable inductor circuit including a plurality of variable inductors connected in series between an input signal terminal and an output signal terminal and controlled respectively by corresponding inductance control signals, a variable capacitor circuit including a plurality of variable capacitors connected respectively between corresponding connection nodes of the plurality of variable inductors of the variable inductor circuit and a ground terminal and controlled respectively by corresponding capacitance control signals, and a variable capacitor/inductor controller for outputting the corresponding capacitance control signals to the variable capacitors of the variable capacitor circuit and the corresponding inductance control signals to the variable inductors of the variable inductor circuit on the basis of preset values according to a given data rate, respectively. When the data rate of an application system is changed, the tunable Bessel low pass filter controls its filtering characteristics most appropriately to the changed data rate, so as to extend its application range and enhance performance and efficiency of the application system.

Tunable high-order bessel low pass filter

Disclosed is a multiwavelength locking method and apparatus using an acousto-optic tunable filter in an optical communication system including optical transport networks, in which output wavelengths of light sources are monitored under the condition in which pilot signals are applied to the acousto-optic tunable filter, so as to lock the wavelengths of the light sources, thereby eliminating an wavelength instability of the light sources for an improvement in transmission characteristics. The acousto-optic tunable filter receives light beams of N different frequencies respectively outputted from N light sources, along with N pilot signals having different frequencies, and converts respective frequencies of beam components of the output beam corresponding to the N pilot signals, thereby outputting N frequency-converted output beams to be applied to a photo-detector. N electrical signals respectively corresponding to the frequencies of the pilot signals are outputted from the photo-detector, separated from one another while corresponding to the light sources, respectively, and then used to compensate for respective output wavelengths of the light sources, thereby enabling the corresponding light sources to output locked wavelengths, respectively.

Multiwavelength locking method and apparatus using acousto-optic tunable filter

Disclosed herein is an inhomogeneity tunable erbium-doped optical fiber amplifier with a long wavelength band and method of blocking a backward amplified spontaneous light emission in the same. The optical fiber amplifier includes a control device situated between a first amplification stage and a second amplification stage for controlling an isolation rate of a backward amplified spontaneous light emission being propagated from a second amplification stage to the first amplification stage. The method blocks a backward amplified spontaneous light emission in a two-stage inhomogeneity tunable erbium-doped optical fiber amplifier with a long wavelength gain band, in which the backward amplified spontaneous light emission being propagated from a second amplification stage to a first amplification stage is blocked, and an isolation rate of the backward amplified spontaneous light emission is controlled according to the intensity of an optical signal inputted to the first amplification stage.

Inhomogeneity tunable erbium-doped fiber amplifier with long wavelength gain band and method of blocking propagation of backward amplified spontaneous light emission in the same

An optical packet header processing apparatus for processing a header of an optical packet expressing an address of a destination node to control a switching operation of an optical packet switch. The optical packet header processing apparatus comprises a beam splitter for splitting the optical packet header into a predetermined number of optical packet header elements, and a plurality of time interval detectors. Each of the time interval detectors receives a corresponding one of the optical packet header elements from the beam splitter and outputs a detect optical pulse if a pair of optical pulses having a predetermined time interval therebetween are present in the received optical packet header element. A plurality of optical pulse detectors are adapted to convert the detect optical pulses from the time interval detectors into electrical signals and transfer the converted electrical signals to the optical packet switch, respectively. Therefore, the optical packet switch determines the destination node in response to the electrical signals from the optical pulse detectors and outputs the optical packet to an output port corresponding to the determined destination node.

Growing community of inventors

Daejeon, South Korea

Kwang Joon Kim