Abstract: A device for compensating for PMD occurring in a transmission optical fiber in an optical transmission system. An output beam from an optical fiber link changes its polarization state by a polarization controller (PC) to be applied to a PBS. A first polarization component passes through a variable delay line, rotates by a predetermined angle, and is inputted to the PBS. A portion of a second polarization component is transmitted by a predetermined mirror. The reflected second polarization component is applied to the PBS to be combined with the first polarization component inputted to the PBS. The transmitted second polarization component passes through a photo-detector and a BPF. The filtered signal is inputted to a PC controller to select the smaller value among the currently and previously measured power values.

Abstract: A channel allocation method of channels having different transmission speeds in a wavelength division multiplexing (WDM) system is provided. The channel allocation method in a multirate optical transmission system includes selecting a channel having the lowest transmission speed from not allotted channels, allotting the selected channel to the longest wavelength band of empty wavelength bands, and determining whether not allotted channels exist in order to repeatedly perform selecting the channel having the lowest transmission speed from the not allotted channels and allotting the selected channel to the longest wavelength band of the empty wavelength bands, until all the channels are allotted.

Abstract: Provided are a polarization mode dispersion (PMD) compensator and method for automatically and rapidly compensating PMD occurring in an optical transmission fiber in a high-speed optical transmission system. The polarization mode dispersion compensator includes a separator and a differential time delay remover. The separator aligns orthogonal first and second polarization components of a received optical signal with respect to two orthogonal axes of a polarization beam splitter using optical signal information output via a second path of a first path and the second path of the two outputs of the polarization beam splitter, splits the first and second polarization components, and transmits the first polarization component via the first path and the second polarization component via the second path. The differential time delay remover receives the first and second polarization components that have been split to remove a differential time delay between the first and second polarization components.

Abstract: Provided are an optical fiber amplification method and apparatus for controlling a gain. Initial values including target gains of first and second amplifications for an optical amplifier amplifying the input light signal are set. Power of the input light signal is measured and the power of first and second backward pump lights proceeding in the opposite direction to the input light signal is controlled based on the measured power. The input light signal is firstly amplified and a first amplification gain of the amplified light signal is calculated. Power of a first forward pump light proceeding in the same direction as the input light signal is controlled so that the first amplification gain can be substantially equal to the target gain of the first amplification. The firstly amplified light signal is secondly amplified and a second amplification gain with respect to the input light signal is calculated.

Abstract: Disclosed herein is an Erbium-Doped Fiber Amplifier (EDFA) used in a WDM (Wavelength Division Multiplexing) transmission system. In accordance with the present invention, a variation of the intensity of the output optical signal in the optical fiber amplifier, which results from an gain imbalance due to different wavelength distribution caused by the gain inhomogeneity characteristics, can be prevented by examining the laser diode sensitive to the gain inhomogeneity characteristics in the erbium-doped optical fiber amplifier, constructing the filter having spectrum characteristics capable of suppressing the gain imbalance of the optical signal outputted from the optical fiber amplifier, and driving the sensitive laser diode using the electrical signal obtained by branching some of the input optical signal and passing the branched optical signal through the filter and driving other laser diodes with a constant voltage value.

Abstract: Disclosed herein is an inhomogeneity tunable erbium-doped optical fiber amplifier with a long wavelength band and method of blocking a backward amplified spontaneous light emission in the same. The optical fiber amplifier includes a control device situated between a first amplification stage and a second amplification stage for controlling an isolation rate of a backward amplified spontaneous light emission being propagated from a second amplification stage to the first amplification stage. The method blocks a backward amplified spontaneous light emission in a two-stage inhomogeneity tunable erbium-doped optical fiber amplifier with a long wavelength gain band, in which the backward amplified spontaneous light emission being propagated from a second amplification stage to a first amplification stage is blocked, and an isolation rate of the backward amplified spontaneous light emission is controlled according to the intensity of an optical signal inputted to the first amplification stage.

Abstract: Provided are an optical signal receiving apparatus whose optimum receiving performance is maintained regardless of a change in the power of an optical signal, and a method using the same. The apparatus includes an optical coupler for dividing an input optical signal at a predetermined ratio to produce first and second divided signals, a photoelectric converter for converting the first divided signal into an electric signal, an amplifier for amplifying the electric signal within a predetermined range centering on a reference voltage, a reference voltage controlling unit for detecting the power of the second divided signal, predicting the power of the first divided signal, and controlling the amplitude of the reference voltage in accordance with the predicted power, and a clock & data recovery unit for recovering a clock signal and data from a signal output from the amplifier.

Abstract: Disclosed herein is an Erbium-Doped Fiber Amplifier (EDFA) used in a WDM (Wavelength Division Multiplexing) transmission system. In accordance with the present invention, a variation of the intensity of the output optical signal in the optical fiber amplifier, which results from an gain imbalance due to different wavelength distribution caused by the gain inhomogeneity characteristics, can be prevented by examining the laser diode sensitive to the gain inhomogeneity characteristics in the erbium-doped optical fiber amplifier, constructing the filter having spectrum characteristics capable of suppressing the gain imbalance of the optical signal outputted from the optical fiber amplifier, and driving the sensitive laser diode using the electrical signal obtained by branching some of the input optical signal and passing the branched optical signal through the filter and driving other laser diodes with a constant voltage value.

Abstract: An improved long wavelength-band EDFA (L-band EDFA) is disclosed. The EDFA includes an input terminal for receiving signal light, a pumping unit for pumping a 1,530 nm wavelength band pumping light, a WDM coupler for multiplexing the signal light and the pumping light, and an EDF pumped by a 1,530 nm wavelength band pumping light for amplifying the signal light. Compared with conventional 1,480 nm pumping, the EDFA pumped by 1,530 nm band pumping have about two times higher power conversion efficiency.

Abstract: Disclosed herein is an inhomogeneity tunable erbium-doped optical fiber amplifier with a long wavelength band and method of blocking a backward amplified spontaneous light emission in the same. The optical fiber amplifier includes a control device situated between a first amplification stage and a second amplification stage for controlling an isolation rate of a backward amplified spontaneous light emission being propagated from a second amplification stage to the first amplification stage. The method blocks a backward amplified spontaneous light emission in a two-stage inhomogeneity tunable erbium-doped optical fiber amplifier with a long wavelength gain band, in which the backward amplified spontaneous light emission being propagated from a second amplification stage to a first amplification stage is blocked, and an isolation rate of the backward amplified spontaneous light emission is controlled according to the intensity of an optical signal inputted to the first amplification stage.

Abstract: An improved long wavelength-band EDFA (L-band EDFA) is disclosed. The EDFA includes an input terminal for receiving signal light, a pumping unit for pumping a 1,530 nm wavelength band pumping light, a WDM coupler for multiplexing the signal light and the pumping light, and an EDF pumped by a 1,530 nm wavelength band pumping light for amplifying the signal light. Compared with conventional 1,480 nm pumping, the EDFA pumped by 1,530 nm band pumping have about two times higher power conversion efficiency.