Abstract: An optical pumping apparatus for few-mode fiber amplification is provided. The optical pumping apparatus includes an optical pump source configured to generate an optical pump; an optical power divider configured to divide an optical power of the optical pump from the optical pump source so as to output several optical pumps with uniformly distributed optical power; and a modal multiplexer configured to receive the optical pumps from the optical power divider through a plurality of single-mode fibers, multiplex the received optical pumps, apply a multiplexed optical pump to each mode of a few-mode fiber (FMF) amplifier, and adjust a gain difference among modes, wherein the FMF amplifier obtains a gain by amplifying an optical signal with the optical pump.

Abstract: An optical transmitting apparatus based on multicarrier differential phase shift keying. The optical transmitting may include a multicarrier generator to output two or more optical signals, each of which has a different wavelength; two or more optical modulators to receive the two or more optical signals, respectively, which have been output from the multicarrier generator, wherein each of the two or more optical modulators modulates phases of the two or more received optical signals by electrical signals that are applied in pairs.

Abstract: An optical transmitter including an optical modulator comprising a first modulator and a second modulator connected in parallel to each other in the form of a Mach-Zehnder interferometer, and a phase shifter connected to the second modulator in series, a high-speed generator configured to generate a single carrier signal or multi-carrier signals and apply the generated single carrier signal or multi-carrier signals to the optical modulator, and an output stabilizer configured to stabilize a final output optical signal of the optical modulator by controlling a bias of each of the first modulator, the second modulator and the phase shifter.

Abstract: Disclosed is an optical signal transmitting apparatus including: an optical carrier generator configured to generate a plurality of optical carriers and outputs the optical carriers to optical modulators corresponding to the optical carriers, respectively; a plurality of optical modulators configured to modulate the optical carriers, respectively, according to an input signal; and an optical combiner configured to couple a plurality of optical signals from the plurality of optical modulators.

Abstract: An optical transmission apparatus includes: a transmission light source configured to generate single-mode light of a specific wavelength; a power coupler configured to split the light generated by the transmission light source into a plurality of light sections; at least one modulator configured to modulate an electrical signal carrying different data into at least one optical signal using the light section from the power coupler; and a mode multiplexer configured to convert the modulated optical signal into a different mode, and to transmit the mode-converted optical signal to a fiber.

Abstract: An optical pumping apparatus for few-mode fiber amplification is provided. The optical pumping apparatus includes an optical pump source configured to generate an optical pump; an optical power divider configured to divide an optical power of the optical pump from the optical pump source so as to output several optical pumps with uniformly distributed optical power; and a modal multiplexer configured to receive the optical pumps from the optical power divider through a plurality of single-mode fibers, multiplex the received optical pumps, apply a multiplexed optical pump to each mode of a few-mode fiber (FMF) amplifier, and adjust a gain difference among modes, wherein the FMF amplifier obtains a gain by amplifying an optical signal with the optical pump.

Abstract: An optical transmitter including an optical modulator comprising a first modulator and a second modulator connected in parallel to each other in the form of a Mach-Zehnder interferometer, and a phase shifter connected to the second modulator in series, a high-speed generator configured to generate a single carrier signal or multi-carrier signals and apply the generated single carrier signal or multi-carrier signals to the optical modulator, and an output stabilizer configured to stabilize a final output optical signal of the optical modulator by controlling a bias of each of the first modulator, the second modulator and the phase shifter.

Abstract: A polarization control device in accordance with an exemplary embodiment of the present invention may include a first polarization converter for converting a polarization angle of an input optical signal in response to first control voltages, a second polarization converter for converting a polarization angle of an input optical signal in response to second control voltages, and a third polarization converter for converting an optical signal received from the first polarization converter or the second polarization converter into a first output optical signal having a linear polarization state and outputting the first output optical signal.

Abstract: An apparatus and method for controlling a multicarrier light source generator are provided. The apparatus includes N-light source input units configured to input light sources to a multicarrier light source generator that generates multicarrier light sources at a frequency interval of F [Hz], and a control unit configured to adjust the frequency interval of the multicarrier light sources generated from the multicarrier light source generator, by adjusting a frequency interval between the light sources input from the N-light source input unit as F/N [Hz].

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: Provided is a coherent optical receiving apparatus and an optical signal processing method. The coherent optical receiving apparatus may include an optical hybrid unit to generate an optical signal by combining a first optical signal inputted from an optical transmitting apparatus and a second optical signal inputted from a local oscillator, a polarization demuxer to demultiplex the optical signal outputted from the optical hybridizing unit, a frequency offset compensator to estimate a frequency offset of at least one of even-numbered samples and odd-numbered samples, and to compensate for a frequency offset of the even-numbered samples and a frequency offset of the odd-numbered samples using the at least one estimated frequency offset, and a carver distortion compensator to compensate for phase distortions of the samples for which the compensation for the frequency offset is performed, the phase distortions being generated by the optical transmitting apparatus.

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 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: Disclosed is an optical signal transmitting apparatus including: an optical carrier generator configured to generate a plurality of optical carriers and outputs the optical carriers to optical modulators corresponding to the optical carriers, respectively; a plurality of optical modulators configured to modulate the optical carriers, respectively, according to an input signal; and an optical combiner configured to couple a plurality of optical signals from the plurality of optical modulators.

Abstract: The multi-core optical fiber amplifier according to an exemplary embodiment of the present invention having the above configuration includes: a double clad multi-core optical fiber including a plurality of cores, an internal cladding enclosing the plurality of cores, and an external cladding enclosing the internal cladding; a pumping light source outputting pumping light; an optical fiber to which pumping light from the pumping light source is input; and a wavelength division multiplexing coupler coupling the optical fiber with the double clad multi-core optical fiber to apply the pumping light input to the optical fiber from the pumping light source to the double clad multi-core optical fiber.

Abstract: 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.

Abstract: Disclosed is an orthogonal frequency division multiplexing (OFDM) optical transmitter including a signal size adjustor for amplifying plural data signals modulated based on an OFDM scheme with different amplification rates so that each data signal is amplified according to a size of the corresponding data signal. Accordingly, it is possible to reduce a peak-to-average power ratio, and thus a nonlinear phenomenon generated in an optical line can be reduced and the quality of an OFDM optical signal can be improved.

Abstract: The present invention provides an interface apparatus between a dual-carrier optical transceiver and a WDM (wavelength division multiplexing) optical transmission line, including: an optical multiplexer configured to receive a first optical signal modulated by a first optical carrier and a second optical signal modulated by a second optical carrier from the dual-carrier optical transceiver, and multiplex the first optical signal and the second optical signal to output the signals to the optical transmission line; and an optical demultiplexer configured to receive the multiplexed optical signal from the optical transmission line and demultiplex the multiplexed optical signal to output the signals to the dual-carrier optical transceiver.

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: 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.