Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: Disclosed herein is a communication terminal which has an adequate structure for keys so as to sufficiently fulfill various communication services, to thereby make the communication terminal compact, and can control operation of the keys so as to minimize a data input error of the keys. The communication terminal includes a first housing, a second housing which is oppositely coupled to the first housing, and a control unit which interrupts operation of a data input part provided at either the first housing or the second housing according to movement of the second housing with respect to the first housing.

Abstract: 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.

Abstract: A charging method of a mobile terminal is provided. The method comprises detecting brightness of ambient light around the mobile terminal by an illumination sensor of the mobile terminal; activating a charging circuit for charging a battery of the mobile terminal when the detected brightness is more than a first value; measuring a generated current of a solar cell; and deactivating the charging circuit when the generated current of the solar cell is below a second value.

Abstract: A wavelength-division apparatus and a wavelength combining apparatus are provided. Each of the wavelength-division apparatus and the wavelength combining apparatus includes a transparent block having one surface which is coated with an anti-reflective coating layer and the other surface which is coated with a partial transmitting coating layer. Each of the anti-reflective coating layer and the partial transmitting coating layer is coupled to a plurality of wavelength-selective filters that separate optical signals of different wavelengths through different paths other than a transmission path or a receiving path. Thus, the optical signals of the respective wavelengths output through the different paths can be used for various purposes such as monitoring the signal intensity and/or the signal quality.

Abstract: An OFDM optical transmitter and optical transmission method is provided. The OFDM optical transmitter includes a signal converter controlling amplitude of each of data signals according to a position of each of the data signals and converting the controlled data signal into a time-domain signal. Accordingly, it is possible to generate optical OFDM carriers which are uniform in size.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A timestamping apparatus and method are provided. The timestamping apparatus implements timestamping on a synchronization message at a physical layer when the synchronization message is transmitted to the physical layer. At an application layer of the timestamping apparatus, a bit stream including a start indicator bit informing a start of a pseudo random number sequence, the pseudo random number sequence, and an end indicator bit informing an end of the pseudo random number sequence is generated to check whether or not a message received from the physical layer is the synchronization message, and is inserted as signature information of the synchronization message. At the physical layer of the timestamping apparatus, the signature information included in the synchronization message is detected, and timestamping information is generated when the signature information is detected.

Abstract: Disclosed are a portable terminal including, a terminal body having a display, a solar cell disposed on at least one region of the terminal body and configured to convert sunlight into electric energy for charging a battery, a sensing unit configured to detect a quantity of state relating to the electric energy generated from the solar cell, and a controller configured to control brightness of the display based upon the quantity of state detected by the sensing unit, and a method for controlling a display thereof.

Abstract: 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.

Abstract: Provided are a local area network (LAN) emulation method and an information storage medium. The LAN emulation method provides a LAN emulation function in an arrayed-waveguide grating (AWG)-based wavelength division multiplexing (WDM)-passive optical network (PON) using a mode bit and a logical link identifier (LLID).

Abstract: 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.

Abstract: 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.

Abstract: An optical transmitting apparatus is disclosed. The optical transmitting apparatus outputs a signal having the same phase characteristics as a Return-to-Zero Differential Phase-Shift-Keying (RZ-DPSK) signal by using a single phase modulator. Accordingly, it is possible to generate RZ-DPSK signals without using a separate RZ modulator.

Abstract: An optical transmission apparatus for high-speed optical signal transmission is provided. The optical transmission apparatus includes an optical modulator which includes first and second modulators of a Mach-Zehnder (MZ) interferometer type which are connected in parallel, and an output stabilizer which controls biases for the first modulator, the second modulator and the optical modulator and stabilizes a final output optical signal of the optical modulator. The optical transmission apparatus can perform a stable optical signal output.

Abstract: Provided is a digital signal synchronization device of a coherent optical receiver. The digital signal synchronization device includes a digital signal processing unit to perform synchronization on a digital signal of an output optical signal generated by interfering an optical signal received through an optical fiber with an optical signal of laser output from a local oscillator and to perform decoding using the synchronized digital signal, and a digital signal managing unit to monitor the digital signal processing unit to output data of the optical signal normally, which has been received through the optical fiber, according to the synchronized digital signal.