Abstract: An optical receiver includes a converter configured to convert, into an electrical signal, an optical signal including error correction information, the optical signal being received from a transmitting side; a corrector configured to correct an error on the electrical signal, based on the error correction information; a threshold controller configured to control a threshold value discriminating a power of the electrical signal, based on a result of the error correction; a table configured to form therein data of a relationship between the threshold value and a power of an optical noise occurring when the optical signal is amplified within an optical transmission path; and a deriving unit configured to obtain the power of the optical noise corresponding to the threshold value from the table.

Abstract: An optical receiver includes a converter configured to convert, into an electrical signal, an optical signal including error correction information, the optical signal being received from a transmitting side; a corrector configured to correct an error on the electrical signal, based on the error correction information; a threshold controller configured to control a threshold value discriminating a power of the electrical signal, based on a result of the error correction; a table configured to form therein data of a relationship between the threshold value and a power of an optical noise occurring when the optical signal is amplified within an optical transmission path; and a deriving unit configured to obtain the power of the optical noise corresponding to the threshold value from the table.

Abstract: A signal detection method used in an optical receiver apparatus detects the variation of an optical input level from the presence or absence of a clock signal and appropriately controls a dispersion compensator, thereby enabling the presence or absence of an input signal to be correctly determined. The signal detection method includes: detecting the level of input light of an optical amplifier, storing the level of the detected input light, comparing the level of the stored previous input light with the level of current input light, detecting the level variation of the input light by the comparison to detect the state change of the presence or absence of an optical signal, performing a dispersion compensation on the input light, and extracting a clock from an optical input. When the level variation of the input light is detected, the presence or absence of the optical signal of the input light is determined from the presence or absence of the clock signal.

Abstract: To obtain automatic gain control with high accuracy by including first and second light monitors, a reference light supplying unit supplying reference light of which wavelength is set within a gain band of a distributed Raman amplification and out of a wavelength band of main signal light to the optical transmission path, a first reference light monitor monitoring a power of the reference light input to the optical transmission path from one end side thereof, a second reference light monitor monitoring the power of the reference light output from the other end side of the optical transmission path, and a controlling unit controlling supply of pump light in a pump light supplying unit as well as supervising a state of the optical transmission path, based on monitor results from the first and second light monitor and the monitor results in the first and second reference light monitors.

Abstract: A light amplifying device including a Raman amplifier to Raman-amplify a signal light by inputting excitation lights of a plurality of wavelengths to a transmission path through which the signal light propagates, a plurality of measuring units measuring powers of light output from the Raman amplifier in a plurality of wavelength bands included in an amplification band of the Raman amplifier, a calculating unit calculating a ratio of the respective powers measured by at least two of the plurality of measuring units, and a control unit controlling a power ratio of the respective excitation lights input to the transmission path by the Raman amplifier based on the ratio calculated by the calculating unit.

Abstract: A Raman amplification apparatus includes a pumping light supplying section, a main signal wavelength light level acquisition section, a monitoring signal wavelength light level acquisition section, a function information storage section for storing, as function information, information regarding functions for deriving a noise amount and a gain by Raman amplification with regard to a monitoring signal wavelength light with respect to pumping light power supplied from the pumping light supplying section, and a transmission characteristic derivation section for deriving a transmission characteristic on an optical transmission line based on information acquired by the main signal wavelength light level acquisition section and the monitoring signal wavelength light level acquisition section and the function information stored in the function information storage section, and Raman gain is derived with high accuracy in comparison with the conventional technique.

Abstract: A Raman amplifier inputs pump light into an optical fiber (transmission path) through which an optical signal passes, to amplify the optical signal. An optical receiving unit is provided downstream of the Raman amplifier and monitors the power of the optical signal amplified by the Raman amplifier. A calculating unit determines Raman amplification gain based on the power of the optical signal monitored by the optical receiving unit, and calculates the power of a noise component included in the optical signal based on the gain. The calculating unit, in real-time, calculates the power, which varies in complicated manners depending on conditions, and outputs information concerning to the power to another apparatus at a frequency on the order of milliseconds.

Abstract: The WDM optical transmission system using distributed Raman amplification, before starting operation of main signal light, transfers a plurality of lights having different wavelengths to that of the main signal light (for example Raman amplification pump lights or the like) between first and second optical transmission devices connected to opposite ends of a transmission line, monitors transmission line input and output power for each light, calculates a transmission line loss in each wavelength using the monitor results, and specifies a type of the transmission line based on a loss wavelength characteristic that can be estimated from the calculation result. Then the power of pump light provided to the transmission light is optimized in accordance with the type of transmission line.

Abstract: A signal detection method used in an optical receiver apparatus detects the variation of an optical input level from the presence or absence of a clock signal and appropriately controls a dispersion compensator, thereby enabling the presence or absence of an input signal to be correctly determined. The signal detection method includes: detecting the level of input light of an optical amplifier, storing the level of the detected input light, comparing the level of the stored previous input light with the level of current input light, detecting the level variation of the input light by the comparison to detect the state change of the presence or absence of an optical signal, performing a dispersion compensation on the input light, and extracting a clock from an optical input. When the level variation of the input light is detected, the presence or absence of the optical signal of the input light is determined from the presence or absence of the clock signal.

Abstract: A Raman amplification apparatus includes a pumping light supplying section, a main signal wavelength light level acquisition section, a monitoring signal wavelength light level acquisition section, a function information storage section for storing, as function information, information regarding functions for deriving a noise amount and a gain by Raman amplification with regard to a monitoring signal wavelength light with respect to pumping light power supplied from the pumping light supplying section, and a transmission characteristic derivation section for deriving a transmission characteristic on an optical transmission line based on information acquired by the main signal wavelength light level acquisition section and the monitoring signal wavelength light level acquisition section and the function information stored in the function information storage section, and Raman gain is derived with high accuracy in comparison with the conventional technique.

Abstract: A Raman amplifier inputs pump light into an optical fiber (transmission path) through which an optical signal passes, to amplify the optical signal. An optical receiving unit is provided downstream of the Raman amplifier and monitors the power of the optical signal amplified by the Raman amplifier. A calculating unit determines Raman amplification gain based on the power of the optical signal monitored by the optical receiving unit, and calculates the power of a noise component included in the optical signal based on the gain. The calculating unit, in real-time, calculates the power, which varies in complicated manners depending on conditions, and outputs information concerning to the power to another apparatus at a frequency on the order of milliseconds.

Abstract: To obtain automatic gain control with high accuracy by including first and second light monitors, a reference light supplying unit supplying reference light of which wavelength is set within a gain band of a distributed Raman amplification and out of a wavelength band of main signal light to the optical transmission path, a first reference light monitor monitoring a power of the reference light input to the optical transmission path from one end side thereof, a second reference light monitor monitoring the power of the reference light output from the other end side of the optical transmission path, and a controlling unit controlling supply of pump light in a pump light supplying unit as well as supervising a state of the optical transmission path, based on monitor results from the first and second light monitor and the monitor results in the first and second reference light monitors.

Abstract: A light amplifying device including a Raman amplifier to Raman-amplify a signal light by inputting excitation lights of a plurality of wavelengths to a transmission path through which the signal light propagates, a plurality of measuring units measuring powers of light output from the Raman amplifier in a plurality of wavelength bands included in an amplification band of the Raman amplifier, a calculating unit calculating a ratio of the respective powers measured by at least two of the plurality of measuring units, and a control unit controlling a power ratio of the respective excitation lights input to the transmission path by the Raman amplifier based on the ratio calculated by the calculating unit.

Abstract: The WDM optical transmission system using distributed Raman amplification, before starting operation of main signal light, transfers a plurality of lights having different wavelengths to that of the main signal light (for example Raman amplification pump lights or the like) between first and second optical transmission devices connected to opposite ends of a transmission line, monitors transmission line input and output power for each light, calculates a transmission line loss in each wavelength using the monitor results, and specifies a type of the transmission line based on a loss wavelength characteristic that can be estimated from the calculation result. Then the power of pump light provided to the transmission light is optimized in accordance with the type of transmission line.

Abstract: A light amplifying device including a Raman amplifier to Raman-amplify a signal light by inputting excitation lights of a plurality of wavelengths to a transmission path through which the signal light propagates, a plurality of measuring units measuring powers of light output from the Raman amplifier in a plurality of wavelength bands included in an amplification band of the Raman amplifier, a calculating unit calculating a ratio of the respective powers measured by at least two of the plurality of measuring units, and a control unit controlling a power ratio of the respective excitation lights input to the transmission path by the Raman amplifier based on the ratio calculated by the calculating unit.