Electronics and Telecommunications Research Institute

Kwang-Joon Kim

Hwan-Seok Chung

Sun-Hyok Chang

Sang-Soo Lee

Jong-Hyun Lee

O-Kyun Kwon

Kyung-Sook Hyun

El-Hang Lee

Ji-Wook Youn

Hyo-Hoon Park

Seung-Il Myong

Byueng-Su Yoo

Jyung-Chan Lee

Seok-Ho Song

Hye-Yong Chu

Yong-tae Kim

Kyeong-Eun Han

Bong-Kyu Kim

Seung-Hwan Kim

Wang-Joo Lee

Kye-Hyun Ahn

Yun-Hee Cho

Hee-Sang Chung

Sung-Un Lee

Sung-hoon Kwak

Sun-hyok Chang

Kyeong-eun Han

An OFDM receiver for compensating for I/Q imbalance is provided. The OFDM receiver includes an I/Q demodulator demodulating a received signal into a baseband in-phase (I) channel signal and a baseband quadrature (Q) channel signal, and an I/Q imbalance compensator compensating for imbalance between the I-channel signal and the Q-channel signal in a time domain. Accordingly, it is possible to solve the I/Q imbalance and suppress degradation in the performance of the OFDM communication device.

OFDM receiver and method for compensating for I/Q imbalance

An apparatus for receiving optical signals in DQPSK and method of controlling a phase offset in receiving optical signals for DQPSK is provided. An original optical signal modulated in DQPSK is received. The original optical signal is delayed by one bit to make a delay optical signal such that an interference on the original optical signal and the delay optical signal is performed. A control signal is generated by use of an interference result between the original optical signal and the delay optical signal. A phase offset for the interference between the original optical signal and the delay optical signal is controlled by use of the generated control signal. In receiving optical signals, the phase offset between the delay optical signal and the original optical signal is precisely controlled, thereby optimizing the transfer characteristics of an optical delay interferometer.

Apparatus for receiving optical signal and method of controlling phase offset for differential quadrature phase shift keying

Provided are methods of transmitting and receiving a multicast or broadcast frame in an optical line terminal (OLT) and an optical network unit (ONU) for a wavelength division multiplexing (WDM)-passive optical network (PON), a WDM-PON system, and an OLT for a WDM-PON. The method of transmitting a multicast or broadcast frame in an OLT for a WDM-PON includes converting and splitting a multicast or broadcast frame input using a single wavelength into a plurality of wavelengths, combining the split wavelengths, and outputting the multicast or broadcast frame. In this way, a multicast or broadcast frame can be transmitted and received, thereby providing a single copy broadcast (SCB) function in a WDM-PON.

Methods of transmitting and receiving multicast or broadcast frame in OLT and ONU for WDM-PON, WDM-PON system, and OLT for WDM-PON

Provided is an optical network in which a wavelength division multiplexing-based optical transmission scheme is implemented. An apparatus for cross-connecting an optical path includes a path switch including a plurality of input terminals receiving optical signals from other nodes, and a plurality of output terminals sending the optical signals to the other nodes, the path switch switching the path of the optical signal so that the optical signal input via one of the input terminals is output to one of the output terminals; and a wavelength converter converting a wavelength of the optical signal input via the input terminal and outputting the wavelength-converted optical signal to the output terminal according to a switching result of the path switch. Thus, inefficient use of a network resource due to wavelength collision can be prevented, the path can be automatically cross-connected and thus quickly established, path switching and branch combination can be performed irrespective of wavelength, and switching can be performed irrespective of direction.

Apparatus and method for cross-connecting optical path in wavelength division multiplexing system

Disclosed are a digital equalization apparatus for a coherent optical receiver and a digital equalization method for a coherent optical receiver, capable of compensating for chromatic dispersion and polarization impairment through a digital signal processing, and capable of performing a clock recovery and a data recovery through a digital symbol synchronization. The digital equalization apparatus and the method compensate for various impairments occurring on an optical path in a digital manner and achieve synchronization through a simple structure.

Digital equalization apparatus and method for coherent optical receiver

An Ethernet device having multiple lanes and a method of operating the lanes are provided. In one general aspect, it is possible to allocate a dummy block to each of one or more lanes such that the lanes do not selectively participate in communications. In addition, on a receiving side, the dummy block can be removed from among the genuine data blocks to enable data to be decoded. In this case, an Ethernet device on a transmission side and an Ethernet device on a receiving side can exchange information of a lane to which the dummy block is allocated by use of a lane status message, and the lane status message may be based on a link fault message specified by Ethernet standards.

Ethernet device and lane operating method

Provided is a channel assignment method in a wavelength-division-multiplexed transmission system. The channel assignment method includes obtaining information about signal modulation schemes from a plurality of optical transmitters, and assigning channels to the respective optical transmitters in consideration of the obtained information about the signal modulation schemes. Accordingly, in transmission of channels of different modulation formats, cross phase modulation is minimized, thereby reducing inter-channel interference.

Channel assignment method and apparatus for wavelength-division-multiplexed transmission system

Provided is a multi-ring network operating method of cross-connecting at least two ring networks, the method including connecting an input working ring and an input protection ring of a ring network to an output working ring and an output protection ring of another ring network and then performing cross-connection between the same or different ring networks by using a multi-dimensional cross-connect apparatus. In the multi-ring operating method, a plurality of ring networks can be connected regardless of the protection method used by the ring networks, and the original protection method of each ring network can remain after they are connected.

Multi-ring network operating method and system

An apparatus and method for protection switching of an optical channel at each node in an optical network based on wavelength division multiplexing optical transmission technology are provided. The method can be applied to any node having at least two optical fiber inputs and outputs. The apparatus includes: a splitter receiving an electrical signal and splitting the received electrical signal into a plurality of electrical signals which are substantially identical to the received electrical signal; an output switching unit selecting output paths of the electrical signals split by the splitter according to an optical channel path control command of the optical network; and a plurality of optical transponders being assigned to the respective output paths of the electrical signals, converting the electrical signal input by the selection of the output switching unit to an optical signal, and transmitting the converted optical signal to another node of the optical network.

Apparatus and method for protection switching of optical channel

In a wavelength allocation method in a wavelength division multiplexing network, a 3R wavelength converter having a limited wavelength conversion range is disposed according to a wavelength conversion band of each node, at least one path set between transmitting/receiving nodes is selected, routing paths corresponding to the number of the selected at least one path set between the transmitting/receiving nodes having a request for a new optical path generation are extracted, it is determined whether there is a wavelength consecutive segment set that satisfies a maximum transmission distance for guaranteeing transmission quality of an optical signal and that includes one consecutive wavelength among the extracted routing paths, and a path using a first-fit wavelength is selected from paths of each wavelength consecutive segment and the wavelength is allocated when determining that there is a wavelength consecutive segment set.

Dynamic wavelength allocation device using 3R wavelength converter having limited wavelength conversion range and method thereof

Provided are a method and an apparatus for detecting the fault of an optical switch. The apparatus includes an optical monitoring signal generator, a coupler, a splitter, a plurality of optical detecting and output power transition sensing units, and a fault determiner. The optical monitoring signal generator generates optical monitoring signals having different wavelengths from optical signals including data to be transmitted. The coupler optically couples the optical monitoring signals to the optical signals including data to be transmitted and inputs the coupled optical signals to an optical switch. The splitter splits the optical monitoring signals from optical signals output from the optical switch. The plurality of optical detecting and output power transition sensing units detect output power transitions of the split optical monitoring signals. The fault determiner receives information on setting the optical switch from an external source, compares the information with the detected output power transitions of the split optical monitoring signals, and determines whether the optical switch malfunctions depending on whether the information coincides with the detected output power transitions of the split optical monitoring signals.

Method and apparatus for detecting optical switch fault by monitoring optical output transitions

The optical performance monitoring apparatus includes a first optical distributor for distributing a WDM optical signal branched from an optical transmission line, a plurality of wavelength selectors, each for selecting a predetermined wavelength optical signal from the optical signal distributed, a plurality of first optical detectors, each for detecting power of the predetermined wavelength optical signal for a corresponding one of channels selected by the wavelength selectors; and a signal processor for measuring the power for each channel of the WDM optical signal, a total ASE noise power, and an optical signal-to-noise ratio for each channel from the digital value.

Optical performance monitoring apparatus for a WDM optical communication system

An apparatus and a method for modulating the optical intensity, with the noises suppressed by using a linear optical modulator, are disclosed, so that the characteristics of signals transmitted from an optical communication system can be improved, and that the resolution of the measured physical quantities can be improved in an optical measuring instrument. The method is carried out in the following manner. That is, the magnitude of frequency is measured by utilizing pilot signals and electrical signals to transfer negatively fed-back signals to an optical intensity modulator. The phase is delayed by generating pilot signals so as to suppress an amplitude noise from the pilot signal caused by nonlinear modulation at the optical intensity modulator. A linear modulation is carried out on the phase-delayed signals and on optical signals from an external source to provide a linear component. The bias voltage is adjusted in accordance with the negatively fed-back signals, and an optical intensity modulation is carried out on the linearly modulated signals and on the added signals, the added signals having been formed by combining the data signals and the pilot signals.

Apparatus and method for modulating optical intensity with amplitude noise suppressed by using linear optical modulator

The present invention is to provide an automatic gain-controlled optical fiber amplifier, comprising: a first optical branch for branching a portion of an optical signal inputted into the optical fiber amplifier; a second optical branch for branching a portion of an optical signal outputted from the optical fiber amplifier; an optical distributor for receiving the optical signal of an input side branched partially by the first optical branch and for outputting it separately; a first wavelength selector for receiving the optical signal of a one side distributed by the optical distributor and for selecting a predetermined wavelength optical signal; a second wavelength selector for receiving the optical signal of an output side branched partially by the second optical branch and for selecting the predetermined wavelength optical signal; a signal processor for receiving the optical signal of a second side distributed by the optical distributor and the predetermined wavelength optical signal selected by the first and second optical wavelength selector and for measuring a total power of an input signal and a number of input channels; and a controller for generating a control signal according to the total power of the input signal and the number of input channels measured by the signal processor.

Automatic gain-controlled optical fiber amplifier

For a multiple transmission communication system, how to individually isolate the transmitted lights and then to distribute to the terminals has been primary concerns to be solved. In the photodetector structure, an absorption layer may be configured as either multiple quantum well structures corresponding to operational wavelengths, or filter-based structure, allowing to select wavelengths in a 1:2:4:8 ratio as an absorptance for each wavelength. In case of using such four-fold lights, the determination as to which wavelength among four-fold wavelengths can be made based upon the total amounts of the current flow in such a photodetector. The photodetector employing such schemes is provided from the present invention.

Growing community of inventors

Daejeon-si, South Korea

Kwang-Joon Kim