Abstract: A method and apparatus for minimizing system deterioration caused by polarization effects (e.g., a polarization-dependent gain (PDG), a polarization-dependent loss (PDL), and a polarization mode dispersion (PMD)). The apparatus performs a signal modulation process to enable one bit to simultaneously contain two orthogonal polarization components, resulting in a minimum DOP (Degree Of Polarization). If a signal undergoes the PMD, the apparatus converts an NRZ (Non Return to Zero) signal into an RZ (Return to Zero) signal, resulting in minimum inter-symbol interference caused by the PMD. The apparatus can improve a performance of an optical signal during the PMD operation, whereas a conventional PMD compensation technique has been designed to remove system deterioration caused by only the PMD.

Abstract: The present invention relates to an optical fiber access network, and more particularly, to a multi-purpose optical fiber access network capable of accepting all services provided by hybrid wireline/wireless access network.

Abstract: Disclosed is a fiber optic cable for a wavelength division multiplexing (WDM) optical transmission system including a plurality of connected optical fibers, wherein each of the connected optical fibers is formed of a plurality of optical fibers respectively exhibiting different dispersion values and different dispersion slopes in a predetermined operating wavelength range while having different lengths and different effective areas, the optical fibers being connected to one another in an optional order.

Abstract: The present invention relates to a method and apparatus for automatically monitoring an optical signal-to-noise ratio in which an arbitrarily polarized optical signal including an unpolarized ASE noise is inputted to a rotating quarter-wave plate and then to a rotating linear polarizer so that a maximum power and a minimum power of the signal outputted from the rotating linear polarizer can be detected, and the detected maximum power and minimum power is used for automatically monitoring the optical signal-to-noise ratio.

Abstract: A method and apparatus for minimizing system deterioration caused by polarization effects (e.g., a polarization-dependent gain (PDG), a polarization-dependent loss (PDL), and a polarization mode dispersion (PMD)). The apparatus performs a signal modulation process to enable one bit to simultaneously contain two orthogonal polarization components, resulting in a minimum DOP (Degree Of Polarization). If a signal undergoes the PMD, the apparatus converts an NRZ (Non Return to Zero) signal into an RZ (Return to Zero) signal, resulting in minimum inter-symbol interference caused by the PMD. The apparatus can improve a performance of an optical signal during the PMD operation, whereas a conventional PMD compensation technique has been designed to remove system deterioration caused by only the PMD.

Abstract: Disclosed herein is a wavelength-division-multiplexed metro optical network. The network comprises a transmitting unit having direct modulating transmitters and a multiplexer for multiplexing the optical signals and transmitting the multiplexed signal, and a receiving unit having a demultiplexer for receiving the multiplexed signal from the multiplexer, demultiplexing the received signal and outputting the demutiplexed signals, and receivers for receiving the demutiplexed signals. The network further comprises an optical fiber connected between the multiplexer and the demultiplexer. The optical fiber has a negative dispersion value of from −1 ps/nm/km to −3.3 ps/nm/km at a wavelength of 1550 nm, and a positive dispersion inclination.

Abstract: Disclosed is an apparatus for monitoring an optical signal-to-noise ratio in a WDM optical network. The apparatus includes an orthogonal polarization component module for receiving an optical signal and outputting it after removing a signal component thereof at a specific frequency band; and calculation means for measuring both average signal and noise component intensity of the optical signal outputted from the orthogonal polarization component module. By removing a signal component at a specific frequency bandwidth and passing only a noise component through, it is possible to easily measure the noise intensity within a signal bandwidth that cannot be measured in general. A frequency band is set within a signal bandwidth, and the signal intensity is minimized at the set frequency band, so that it is possible to measure the optical signal-to-noise ratio even for a signal whose amplified spontaneous emission noise spectrum is not flat, irrespective of the signal pattern length.

Abstract: The present invention provides a method and an apparatus for monitoring optical signal to noise ratio (OSNR) in a wavelength division multiplexing optical transmission system. The present invention utilizes a polarization nulling method and a tunable optical bandpass filter in order to reliably monitor the OSNR by considering a finite polarization nulling ratio, polarization mode dispersion and non-linear birefringence of the optical system in real time measurement of the OSNR. Further, the tunable optical bandpass filter is controlled to filter all wavelength bands of wavelength division multiplexed signals. Since the invention may monitor a plurality of demultiplexed optical signals with a single apparatus, the overall cost of the OSNR monitoring equipment is significantly reduced.

Abstract: A multiplexing/demultiplexing apparatus used in wavelength division multiplexed passive optical subscriber networks comprises a multiplexing/demultiplexing means each having a natural number N input and output ports, wherein wavelength divided signals in one direction inputted through the N−1 input ports are multiplexed onto one output port, and simultaneously wavelength division multiplexed signals in the other direction inputted through the remainder one input port are demultiplexed onto the remainder N−1 output ports. According to the present invention it is possible to implement economical and efficient wavelength division multiplexed passive optical subscriber networks, by including two WGR's, one at the central office and one at the remote node to perform simultaneous multiplexing and demultiplexing of signals in upstream and downstream, and employing an erbium-doped fiber amplifier to be able to use a low-cost light source such as a light-emitting diode.

Abstract: The invention relates to method and apparatus that automatically monitors each channel's optical signal-to-noise ratio (OSNR) using optical filter and polarization extinction method in wavelength division multiplexing (WDM) scheme-based optical transmission systems.

Abstract: An apparatus monitoring frequency of WDM signals using pilot tone and two interleaved solid etalon filters for efficient management and maintenance of wavelength division multiplexing optical transmission network is provided. Desirably, the apparatus for optical frequency monitoring includes splitting means, a plurality of optical filtering means, optical detecting means, and frequency detecting means. The splitting means splits optical signal and the optical signal includes pilot tone. The plurality of optical filtering means filters an output of the splitting means with particular passband. The optical detecting means converts an output of the optical filtering means into electrical signal. The frequency detecting means detects an intensity of the pilot tone from an output of the optical detecting means and calculates optical frequency.

Abstract: This invention relates to a multicast-capable optical cross-connect with layered modularity. Due to its layered modularity, this invention can be applied to many differently structured networks and provides easier maintenance than conventional optical cross-connects and efficient preparation for network evolution or node upgrade. By exploiting its simple elementary switches, multicast-capable optical cross-connect with layered modularity minimizes the switching time. For a given node, M input fiber ports supply multiplexed optical signals from other nodes in the network and m input fiber ports supply multiplexed optical signals generated from the node. M+m 1×M optical power splitters 311, 312, 313, 314, 315 distribute multiplexed input signals. A drop link module 331 selects signals to be dropped at the node where the optical cross-connect is installed. M transmission link modules 321, 322, 323 select signals to be transmitted to other nodes out of input signals.

Abstract: A bidirectional add/drop optical amplifier used in wavelength division multiplexing (WDM) optical networks to suppress the power change resulting from the adding and dropping of optical signals using an all optical gain control includes two fiber Bragg gratings (FBGs) and a bidirectional add/drop optical amplifier module composed of an Arrayed Waveguide Grating (AWG) and two bidirectional optical amplifiers. The filtered amplified spontaneous emission (ASE) lights are lased with the two FBGs and then used to adjust the gain of the bidirectional amplifiers.

Abstract: The monitoring of the qualities of the optical signal transmitted from a light amplifying relay and nodes of transmission networks. An object of the present invention is to provide an apparatus and method for correct monitoring the qualities of the optical signal. While conventional methods monitor the qualities of the optical signal solely by the intensity of the optical signal, the present invention provides an apparatus and method for extracting the clock component of data from the optical signal transmitted and measuring the magnitude and then detecting the presence or absence of the signal and the error rate upon receiving the deteriorated signal due to the chromatic dispersion. The present invention comprises the simple measuring apparatus having a optical coupler 1, a signal conversion means 2, a narrow optical detector 3, a super high frequency rectifier 4 and a voltage detector 5.

Abstract: The optical signal-to-noise ratio (OSNR) of optical signals that are demultiplexed into a plurality of optical channels by a wavelength-division multiplexing (WDM) optical transmission system is monitored by an apparatus which outputs the optical signals of each optical channel on a first path and a second path, and measures the signal intensity of each of the optical signals on the first path. The apparatus selectively passes an AC component of each of the optical signals on the second path and processes the AC component by converting the AC component into a digital signal and performing a fast fourier transform on the digital signal. The apparatus measures the noise intensity of the processed AC component on the second path. The OSNR of each optical signal is calculated by comparing the measured signal intensity of each of the optical signals and the measured noise intensity of the processed AC component of each of the optical signals.

Abstract: A cold-start wavelength-division-multiplexed (WDM) optical transmission system uses a synchronized etalon filter, DFB lasers and passive optical demultiplexers. The DFB lasers are tested under normal operating conditions and wavelength-selected for each channel. The wavelength selection is such that the laser operates within one half of the channel spacing from the standardized wavelength. For the cold-start operation, each laser is able to automatically find its operating wavelength without any prior knowledge of its operating conditions for the standardized wavelength. In addition, this system simultaneously adjusts the output power of each laser to a desired value.

Abstract: The present invention relates to a method and apparatus for automatically monitoring an optical signal-to-noise ratio in which an arbitrarily polarized optical signal including an unpolarized ASE noise is inputted to a rotating quarter-wave plate and then to a rotating linear polarizer so that a maximum power and a minimum power of the signal outputted from the rotating linear polarizer can be detected, and the detected maximum power and minimum power is used for automatically monitoring the optical signal-to-noise ratio.

Abstract: The present invention relates to a bidirectional add/drop optical amplifier used in wavelength division multiplexing (WDM) optical networks.

Abstract: This invention is to construct a bidirectional WDM add/drop amplifier module for transmitting WDMS in bidirection and for adding/dropping a signal in bidirection at each node in a WDM network system using a single N×N multiplexer. The bidirectional WDM add/drop amplifier module 100 comprises an 8×8 arrayed-waveguide grating 110. The 8×8 arrayed-waveguide grating 110 has, at each side, a WDMS input end L4 or R4, a WDMS output end L8 or R8, three separated signal input ends L1, L2 and L3, or R5, R6 and R7, and three separated signal output ends L5, L6 and L7, or R1, R2 and R3. One L2 or R6 of the separated signal input ends is designated as an added signal input end, one L6 or R2 of the separated signal output ends is designated as a dropped signal output end, and the separated signal output ends L5 and L7, or R1 and R3 except for the dropped signal output end connected to the signal input ends L1 and L3, or R5 and R7 at the same side.

Abstract: The present invention relates to a sliding-frequency guiding filter which is capable of guiding soliton pulses to hundreds of different resonant frequencies by designing the device so that the filter can automatically offset its peak resonant frequency from the frequency of incoming soliton pulses. The sliding-frequency guiding filter comprises the followings: a coupler to tap some of incoming soliton signals; a wafer whose one half is coated by multilayered dielectric on both sides while leaving the other half uncoated, where the soliton signals tapped through the coupler is directed to coated half and uncoated half of the wafer, respectively; and, a thermoelectric cooler attached to the coated side of the wafer. The sliding-frequency guiding filter, made of the same design, can be applied throughout the soliton transmission line instead of the numerous filters all operating at different resonant frequencies.