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.

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: 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 Forward Error Correction (FEC). A 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. The current reference voltage is maintained if the numbers of occurrence of errors for bits “1” and “0” are rendered equal to each other.

Abstract: An apparatus and method for extracting an optical clock signal are provided. The method includes splitting a predetermined polarization component from an input optical signal, selecting frequency components for clock signal extraction from the predetermined polarization component and amplifying the selected frequency components, rotating the amplified frequency components by a predetermined angle and then reflecting them, amplifying the reflected frequency components and removing noise from the amplified frequency components using a Fabry-Perot filter, and obtaining a beat frequency component from the frequency components from which noise has been removed using the Fabry-Perot filter to extract a clock signal. Accordingly, influence of the pattern of the input optical signal is reduced and the apparatus and method are provided at low price.

Abstract: Provided are an apparatus and a method for generating a CS-RZ optical signal. The apparatus includes: a classifier distributing an input signal into two NRZ (non-return-to-zero) signals with an identical transmission speed; a first signal transformer converting one of the two NRZ signals into a first RZ signal using a full-frequency clock; a second signal transformer converting the other one of the two NRZ input signals into a second RZ signal using a full-frequency clock; a phase adjuster adjusting the first and second RZ signals so that a delay time corresponding to half a period of the input signal exists between the first and second RZ signals; a bias unit adding different DC (direct current) bias voltages to the first and second RZ signals; and a dual electrode optical modulator transforming the two electrical RZ signals into an optical CS-RZ signal.

Abstract: Provided are a frequency extracting apparatus and a signal extracting system employing the same. The signal extracting system can reduce the effect of an input signal pattern by extracting two frequency components and beating them to extract a desired clock signal, and improve a signal-to-noise ratio of an extracted clock signal. The frequency extracting apparatus includes: a circulator for changing an output direction of an input signal; a reflective filter for extracting a desired frequency component among frequency components of the input signal; a wavelength and amplitude controlling unit; and the frequency amplitude controller.

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: An apparatus for synchronizing a clock using a source synchronous clock is disclosed. The apparatus includes: channel receivers for receiving a source synchronous channel; divider for dividing the source synchronous clock to a low frequency clock; selectors for selecting one of the divided source synchronous clock and a system clock as a reference clock; detectors for generating a phase difference signal; phase difference signal selectors for selecting a phase difference signal from the detectors and a phase difference signal from an internal logic; and voltage oscillators for transmitting a clock synchronized to a source synchronous channel to the external optical transmission system by generating a predetermined synchronous frequency according to the selected phase difference signal.

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: A clock extracting apparatus is provided. In the clock apparatus, two frequency components are made to have an equal magnitude by adjusting a temperature and current applied to an FP LD, and a clock signal is extracted by beating the two frequency components having the equal magnitude. The clock extracting apparatus includes: a circulator for changing a direction of an inputted optical signal; an adjuster for adjusting a characteristic and wavelength of a spectrum; and a clock extractor for selecting two frequency components having different magnitudes on the spectrum of the inputted optical signal, receiving an adjusted signals in which magnitudes of the two frequency components are made equal by the adjuster, making the two frequency components have an equal magnitude, and extracting a clock signal by beating the two frequency components having the equal magnitude.

Abstract: An apparatus and a method for generating an optical carrier is disclosed. The apparatus includes: a light source generating a pump light; a SBS generator for stimulated Brillouin scattering the pump light to generate a stokes light from the light source; an attenuator for controlling an amplitude of the pump light from the light source to generate an amplitude controlled pump light; and a detector for heterodyne beating the stokes light and the amplitude controlled pump light to generate an optical carrier.

Abstract: Provided is an apparatus for an optical clock extraction, which is capable of providing high optical amplification rate and more efficient noise cancellation by using a Fabry-Perot (FP) filter and an optical amplifier. In the apparatus, an optical circulator changes a direction of an inputted optical signal. The FP filter extracts different frequency components existing on a spectrum of the inputted optical signal and being spaced apart by a clock frequency, removes noise from a reflected and amplified optical signal, and transmits the resulting signal to the optical circulator. An optical amplifier performs a primary amplification to equalize two different frequency components outputted from the filter, and performs a secondary amplification on an optical signal reflected and fed back thereto. A reflector reflects the primarily-amplified optical signal to the optical amplifier.

Abstract: An apparatus and method for monitoring an optical signal are provided. In the apparatus, a polarization adjusting unit converts the state of polarization of an optical signal. A polarization beam splitter splits the optical signal into a first polarization component and a second polarization component perpendicular to each other. An optical intensity measuring unit measures the optical intensity of the first polarization component. A feedback control unit controls the polarization adjusting unit so that the first and second polarization components are aligned to the two axes of the polarization beam splitter. A scrambler scrambles the optical signal input to the transmission optical fiber. According to the apparatus and method, optical signal-to-noise ratio (OSNR) can be measured accurately.

Abstract: The present invention discloses an apparatus for suppressing stimulated Brillouin scattering and the method thereof that a threshold fiber input power is raised in order to prevent loss of an inputted light by stimulated Brillouin scattering being generated in a case that a signal having a strong intensity is inputted to the optical fiber and so a light signal having more strong intensity can be inputted to the optical fiber. The apparatus for suppressing the SBS includes a plurality of first transmission unit, each of which has a wavelength separation, for transmitting information signals through a signal channel; and a second transmission unit for generating and transmitting a supervisory signal of which a modulation frequency and an intensity generates a phase modulation to the plurality of information signals, through a supervisory channel.

Abstract: An apparatus for synchronizing a clock using a source synchronous clock is disclosed. The apparatus includes: channel receivers for receiving a source synchronous channel; divider for dividing the source synchronous clock to a low frequency clock; selectors for selecting one of the divided source synchronous clock and a system clock as a reference clock; detectors for generating a phase difference signal; phase difference signal selectors for selecting a phase difference signal from the detectors and a phase difference signal from an internal logic; and voltage oscillators for transmitting a clock synchronized to a source synchronous channel to the external optical transmission system by generating a predetermined synchronous frequency according to the selected phase difference signal.

Abstract: Provided are a clock component generating apparatus using an asymmetrical distortion of NRZ (non-return to zero) signal and an optical transmission and reception system employing it. The clock component generation apparatus can make an NRZ optical signal have large clock component by asymmetrically distorting the rising and the falling waveform of the NRZ signal utilized in an optical communication system. This apparatus includes asymmetrical pull-up circuit for producing a pull-up function and pull-down circuit for pull-down function to thereby generate a clock component in the distorted NRZ data signal. The invention may advantageously be applied to an optical transmission and reception system.

Abstract: Provided are a multi-protocol signal processing apparatus for a next-generation Synchronous Digital Hierarchy (NG-SDH) transponder, and a method thereof. The multi-protocol signal processing apparatus for an NG-SDH transponder, which includes: a sub-signal processing unit for classifying and processing multi-protocol sub-signals based on kinds; an interfacing unit for making interface between the sub-signal processing unit and an optical signal generating unit the same for the multi-protocol sub-signals to use the multi-protocol sub-signals in Synchronous Digital Hierarchy (SDH) flexibly with no regard to the kinds of the multi-protocol sub-signals; and the optical signal generating unit for generating SDH optical signals by aggregating the multi-protocol sub-signals having a predetermined capacity which are transmitted through the interfacing unit into SDH signals, performing framing, and performing optical/electrical (O/E) conversion on the SDH signals in an optical module.

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: The present invention relates to an apparatus and method for extracting an optical clock using filters and an amplifier. The object of the present invention is to provide an extraction of neighboring frequency components using wavelength fixed optical filters and an amplifier. In accordance with an aspect of the present invention, there is provided an apparatus for extracting an optical clock to extract a clock from the optical signal provided with plurality of peaks on a spectrum, including a first filter for extracting a central frequency component, a second filter for extracting a frequency component adjacent to the first frequency component, the amplifier for amplifying amplitude of the second frequency component until the amplitude of the second frequency component becomes the same as that of the first frequency component and the receiver for extracting a clock to do beating the first frequency component and the second frequency component.

Abstract: An apparatus and a method for generating an optical carrier is disclosed. The apparatus includes: a light source generating a pump light; a SBS generator for stimulated Brillouin scattering the pump light to generate a stokes light from the light source; an attenuator for controlling an amplitude of the pump light from the light source to generate an amplitude controlled pump light; and a detector for heterodyne beating the stokes light and the amplitude controlled pump light to generate an optical carrier.