Abstract: An apparatus for compensating a polarization mode dispersion including a polarization adjusting means for adjusting polarization states of an optical beam having a differential group delay based on a polarization adjusting feedback control signal; a polarization beam splitting means for splitting principal states of polarization of the adjusted optical beam into a first polarization and a second polarization; a time delaying means for the first polarization based on a time delay feedback control signal; a polarization adjustment controlling means for controlling the polarization adjusting means based on a polarization adjusting feedback control signal; a time delay controlling means for controlling the time delaying means based on a time delay controlling feedback signal; and an electric combining means for combining a time-compensated first polarization and the second polarization transmitted through the optical tap.

Abstract: Provided are an apparatus for optimizing bias voltage of an electro-optic modulator, a method therefor, and an optical transmission system using the method. The present research provides a bias voltage optimizing apparatus of an electro-optic modulator that can stabilize bias voltage supplied to the electro-optic modulator through automatic bias voltage initialization control by considering the point that the form of an optical output signal and the intensity of a clock component are changed according to the bias voltage of the electro-optic modulator, a method therefor and an optical transmission system using the method.

Abstract: A switching apparatus for switching an optical channel overhead in an optical supervisory channel is disclosed. The switching apparatus can suppress a terminated optical channel defect occurred by a defect of upper layers of the optical channel or a defect of the optical channel transmitter and also can maintain the corresponding optical channel at the wavelength converted optical transport network system. Furthermore, an apparatus for forwarding an optical channel maintenance signal is disclosed too. The apparatus includes the switching apparatus and transmits only an add and drop optical channel maintenance signal information to the CPU and generate the LOS suppression signal with respect to the optical channel according to the occurrence of malfunction, thus directly transmitting the suppression signal to the corresponding optical channel unit.

Abstract: Disclosed is a device and method for optical supervisory channel framing in an optical transport network system including at least one of an optical transmission section, an optical multiplex section, and an optical channel section. A maintenance signal is generated according to a first LOS (Loss OF Signal) signal generated from at least one of the optical transmission section, the optical multiplex section, and the optical channel section. The maintenance signal and a frame-related channel such as a message communication channel are multiplexed to generate an optical supervisory channel frame. The optical supervisory channel frame is output to another device including a repeater and a terminal system through a single supervisory channel.

Abstract: The present invention provides a method for correcting a shift of an output wavelength of a light source. The output wavelength shift correcting method derives simple equations through experimental processes, predicts a shift degree of the output wavelength with respect to a varied input current using the equations whenever a drive current is reset later, and adjusts a drive temperature according to the predicted shift degree, thus correcting the shift of the output wavelength. The output wavelength shift correcting method is advantageous in that it provides a method of locking an output wavelength of each light source without continuously operating a wavelength locker or a wavelength measuring device, thus reducing the operating cost of the optical communication system.

Abstract: The present invention provides a clock extraction apparatus and method for an optical signal. The clock extraction apparatus includes optical branching means, optical filtering means, and clock extraction means. The optical branching means branches an optical signal, which has been transmitted from a transmitting end to a receiving end, into a plurality of optical signals to be transmitted to a plurality of paths. The optical filtering means simultaneously reflects the center wavelength and a specific side peak wavelength of the optical signal, which has been transmitted to a first path of the plurality of paths, to the optical branching means, the specific side peak wavelength being spaced apart from the center wavelength by a clock frequency. The clock extraction means extracts a clock by detecting and bandpass filtering the beating signal from the center wavelength and the specific side peak wavelength reflected to the optical branching means.

Abstract: An apparatus for generating a Carrier-Suppressed Return-to-Zero (CS-RZ) signal is disclosed. The apparatus includes a mixer, a Low Pass Filter (LPF), a driver amplifier and a single external modulator. The mixer generates a modulator input by mixing data with a half clock signal. The LPF band-limits the modulator input data into low frequency band data. The driver amplifier amplifies the modulator input data generated by the mixing of the mixer and the band-limiting of the LPF. The external modulator generates CS-RZ signal, in which the phases of adjacent pulses have been inverted, by applying bias voltage to the modulator input data to be placed at the null point of the transfer function of the external modulator.

Abstract: The present invention provides a cross-gain modulation type optical wavelength converter having a high extinction ratio and a wide input dynamic range, which is capable of preventing an extinction ratio from lowering and allowing an input dynamic range to widen. The XGM type optical wavelength converter of the present invention allows a probe light to be cross-gain modulated by a pump light one more time using two SOAs, and allows the width of the modulation of the probe light to be further broadened, thereby improving the extinction ratio after wavelength conversion. Simultaneously, the XGM type optical wavelength converter detects the intensity of an optical signal inputted to the optical wavelength converter and automatically controls the intensity of the probe light on the basis of the detected intensity of the input optical signal, thereby providing a wide input dynamic range.

Abstract: A synchronous transfer mode (STM)-256 adder/dropper which provides a communication path between STM-64 optical channels in an apparatus of multiplexing STM-64 optical channels into STM-256 electrical signals, is provided. The STM-256 adder/dropper transmits STM signals by multiplexing the STM signals at a low speed and simultaneously provides a communication path between lower channels.

Abstract: Disclosed herein is a method of optimizing an output signal of an optical receiver using FEC and an optical receiving system using the method. In the method of the present invention, optical signals transmitted through an optical cable are converted into digital data of bits “1” and “0” on the basis of a reference voltage, and errors generated during transmission of the optical signals are corrected using the FEC. The method includes extracting numbers of occurrence of errors for bits “1” and “0” recovered through the FEC. Thereafter, the extracted numbers of occurrence of errors for bits “1” and “0” are compared with each other. A reference voltage used to judge levels of the signals to be level “1” or “0” is controlled if the numbers of occurrence of errors for bits “1” and “0” are not equal to each other.

Abstract: The present invention provides a cross-gain modulation type optical wavelength converter having a high extinction ratio and a wide input dynamic range, which is capable of preventing an extinction ratio from lowering and allowing an input dynamic range to widen. The XGM type optical wavelength converter of the present invention allows a probe light to be cross-gain modulated by a pump light one more time using two SOAs, and allows the width of the modulation of the probe light to be further broadened, thereby improving the extinction ratio after wavelength conversion. Simultaneously, the XGM type optical wavelength converter detects the intensity of an optical signal inputted to the optical wavelength converter and automatically controls the intensity of the probe light on the basis of the detected intensity of the input optical signal, thereby providing a wide input dynamic range.

Abstract: The present invention provides a method for correcting a shift of an output wavelength of a light source. The output wavelength shift correcting method derives simple equations through experimental processes, predicts a shift degree of the output wavelength with respect to a varied input current using the equations whenever a drive current is reset later, and adjusts a drive temperature according to the predicted shift degree, thus correcting the shift of the output wavelength. The output wavelength shift correcting method is advantageous in that it provides a method of locking an output wavelength of each light source without continuously operating a wavelength locker or a wavelength measuring device, thus reducing the operating cost of the optical communication system.

Abstract: A method and apparatus for optical clock recovery using optical filters with fixed reflective wavelengths is provided. In the apparatus, a first filter receives an optical signal and extracts one out of two spectral lines corresponding to two side peaks that are second in magnitude to a peak and exist at both sides of a peak on the spectrum of the received optical signal. A second filter extracts a spectral line corresponding the largest peak on the spectrum of the received optical signal. An attenuator equalizes the power levels of the two spectral lines extracted by the first and second filters. A beating generation unit receives signals corresponding to the two equalized spectral lines and generates beating between the equalized spectral lines, thereby recovering a clock component.

Abstract: An optical receiver in an optical communication system, and more particularly, to a method and an apparatus for optimizing a decision level of a signal output from an optical receiver to obtain a minimum bit error rate (BER) by measuring output characteristics of the optical receiver and adjusting a reference voltage of the optical receiver based on a measurement result. The provided method includes measuring the strength of an electric signal at a modulated frequency out of the frequency elements of the output electric signal in the optical receiver, generating a reference voltage based on the strength data of the electric signal, inputting the reference voltage to the optical receiver and re-measuring the strength of the electric signal output from the optical receiver to determine whether the strength of the signal is minimum, and maintaining the reference voltage when the strength of the signal is minimum and adjusting the reference voltage in other cases.

Abstract: An apparatus for and a method of generating pointers for identifying structure boundaries of data for leased lines such as T1/E1 in an asynchronous transfer mode (ATM) adaptation layer Type 1 (AAL1) through an ATM layer.

Abstract: Provided are an asynchronous transfer mode, passive optical network (ATM-PON) slave device and a method for transmitting data in the ATM-PON slave device. The device includes an asynchronous transfer mode, passive optical network (ATM-OPN) slave device, the device including a received frame processing unit for receiving and transmitting data; a UTOPIA receiving unit for receiving the data from the received frame receiving unit, storing the data in a FIFO queue, and transmitting the data to an ATM layer; a UTOPIA transmitting unit for receiving the data from the ATM layer, storing the data to at least two FIFO queues according to the rank of data, and transmitting the data; and a transmission frame processing unit for receiving the data from the UTOPIA transmitting unit and transmitting the data to an optical line termination (OLT). Accordingly, one optical network unit (ONU) can have a plurality of traffic containers, and a minimal modification is made to the existing G.983.

Abstract: A method for transmitting and receiving leased line data, an apparatus for transmitting leased line data, and an apparatus for receiving leased line data are provided. The method includes storing received leased line data in a FIFO; packing the leased line date stored in the FIFO into the payload of a DSL frame; and transmitting the packed DSL frame. According to the method, leased line data can be transparently transmitted by adding minimum function blocks to the DSL modem, and with the simple circuit structure, the blocks can be integrated into one chip such that no additional external circuits are needed and a low-priced DSL modem chip that can transmit leased line data can be implemented.

Abstract: The present invention relates to a method for dynamically allocating bandwidth under a media access control (MAC) protocol between an optical line termination (OLT) and a group including a plurality of optical network units (ONUs) in an ATM-PON. In order to meet quality of service (QoS) requirement, the dynamic bandwidth allocation method is capable of determining bandwidth to be allocated to each of the ONUs on the basis of information about traffic indicators of connections established to each of the ONUs and about the number of non-real time cells waiting in each of the ONUs, resulting in an enhancement in utilization efficiency of an upstream transmission channel and enabling an effective transmission.

Abstract: A clock distribution device for a multiband modem which is capable of recovering a clock from a received signal of a highest-performance one of multiple bands and applying the recovered clock for clocks of the other bands. The clock distribution device recovers a clock from a received signal and distributes the recovered clock to multiple bands. That is, the clock distribution device is adapted to recover a symbol clock or sampling clock of a certain band from a received multiband signal, generate a high-frequency clock on the basis of the recovered clock, generate a highest-frequency clock among clocks necessary to each of the multiple bands on the basis of the generated high-frequency clock, and generate and distribute all the clocks necessary to each of the multiple bands on the basis of the generated highest-frequency clock.

Abstract: Disclosed herein is a variable length packet switching system. The variable length packet switching system includes at least two switching means, a plurality of multiplexing units and a plurality of demultiplexing units. The switching means switch ATM cells or variable length packet data in parallel. The multiplexing means are arranged upstream of the switching means for multiplexing data inputted from a line card to the switching means in packet units and dividing a packet into packets of a number corresponding to the number of the switching means. The demultiplexing means are arranged downstream of the switching means for combining packets inputted after being switched in parallel by the at least two switching means and outputting the combined packet converted into a format adequate to the line card.