Abstract: An optical transmission system includes an optical transmitting apparatus that includes a polarization controller configured to change a polarization state of a signal light at an operating frequency included in a frequency range at which polarization trackability is obtained on a receiving side, based on a notified monitoring result, the optical transmitting apparatus being configured to output the signal light having the changed polarization state, and an optical receiving apparatus that is provided on the receiving side and includes a monitoring control unit configured to receive the signal light having the changed polarization state and monitor transmission quality of the received signal light, the optical receiving apparatus being configured to notify the optical transmitting apparatus of the monitoring result.

Abstract: A pre-emphasis control method includes calculating an average value of transmission characteristics based on transmission characteristics of a plurality of light beams received by a receiver, and determining that, among signals of the plurality of light beams, a wavelength with a deviation from the average value is a wavelength at which control is to be performed, determining that the wavelength at which control is to be performed and a wavelength adjacent thereto are a group of wavelengths at which control is to be performed, obtaining an average of transmission characteristics of the group of wavelengths at which control is to be performed, and based on a difference between averaged transmission characteristics and respective transmission characteristics of the group of wavelengths at which control is to be performed, changing a light intensity output from each transmitter that transmits a group of wavelengths at which control is to be performed.

Abstract: An optical transmission system includes an optical transmitting apparatus that includes a polarization controller configured to change a polarization state of a signal light at an operating frequency included in a frequency range at which polarization trackability is obtained on a receiving side, based on a notified monitoring result, the optical transmitting apparatus being configured to output the signal light having the changed polarization state, and an optical receiving apparatus that is provided on the receiving side and includes a monitoring control unit configured to receive the signal light having the changed polarization state and monitor transmission quality of the received signal light, the optical receiving apparatus being configured to notify the optical transmitting apparatus of the monitoring result.

Abstract: A pre-emphasis control method includes calculating an average value of transmission characteristics based on transmission characteristics of a plurality of light beams received by the receiver, and determining that, among signals of the plurality of light beams, a wavelength with a deviation from the average value is a wavelength at which control is to be performed, determining that the wavelength at which control is to be performed and a wavelength adjacent thereto are a group of wavelengths at which control is to be performed, obtaining an average of transmission characteristics of the group of wavelengths at which control is to be performed, and changing a light intensity output from each transmitter that transmits a group of wavelengths at which control is to be performed based on a difference between averaged transmission characteristics and respective transmission characteristics of the group of wavelengths at which control is to be performed.

Abstract: A Raman amplifier repeater comprising a Raman excitation light production/answer signal superimposition unit for producing a first reply signal for a down-direction line with respect to a monitor control command, an answer signal production unit for producing a second reply signal with respect to the monitor control command, and a command reply switch for selectively using the first reply signal when an optical signal passing through a down-direction line on a second terminal station side is inputted as an answer signal with respect to the monitor control command and the second reply signal when the optical signal is not inputted through the second terminal station side down-direction line. With this configuration, high-quality monitor control is feasible even if a disconnection/break trouble occurs in an optical fiber in conducting the optical amplification repeating by the Raman amplification.

Abstract: A Raman amplifier repeater comprising a Raman excitation light production/answer signal superimposition unit for producing a first reply signal for a down-direction line with respect to a monitor control command, an answer signal production unit for producing a second reply signal with respect to the monitor control command, and a command reply switch for selectively using the first reply signal when an optical signal passing through a down-direction line on a second terminal station side is inputted as an answer signal with respect to the monitor control command and the second reply signal when the optical signal is not inputted through the second terminal station side down-direction line. With this configuration, high-quality monitor control is feasible even if a disconnection/break trouble occurs in an optical fiber in conducting the optical amplification repeating by the Raman amplification.

Abstract: A supervisory system in a wavelength division multiplexing communications network is provided with a first and a second terminal stations and a repeater unit. The first terminal station transmits a supervisory signal to the second terminal station. The second terminal station transfers the supervisory signal to the repeater unit to be monitored. Paths to a hub station A and a hub station B can be a single path by looping back a supervisory signal output from the hub stations A and B for issuing and terminating the supervisory signal at a first and a second branch stations connected through an optical wavelength multiplexing/demultiplexing unit. If the hub station B loops back a supervisory signal, the supervisory signal output from the hub station A can be returned to the hub station A again after circulating the path.

Abstract: A supervisory system in a wavelength division multiplexing communications network is provided with a first and a second terminal stations and a repeater unit. The first terminal station transmits a supervisory signal to the second terminal station. The second terminal station transfers the supervisory signal to the repeater unit to be monitored. Paths to a hub station A and a hub station B can be a single path by looping back a supervisory signal output from the hub stations A and B for issuing and terminating the supervisory signal at a first and a second branch stations connected through an optical wavelength multiplexing/demultiplexing unit. If the hub station B loops back a supervisory signal, the supervisory signal output from the hub station A can be returned to the hub station A again after circulating the path.

Abstract: A supervisory system in a wavelength division multiplexing communications network is provided with a first and a second terminal stations and a repeater unit. The first terminal station transmits a supervisory signal to the second terminal station. The second terminal station transfers the supervisory signal to the repeater unit to be monitored. Paths to a hub station A and a hub station B can be a single path by looping back a supervisory signal output from the hub stations A and B for issuing and terminating the supervisory signal at a first and a second branch stations connected through an optical wavelength multiplexing/demultiplexing unit. If the hub station B loops back a supervisory signal, the supervisory signal output from the hub station A can be returned to the hub station A again after circulating the path.

Abstract: A supervisory system in a wavelength division multiplexing communications network is provided with a first and a second terminal stations and a repeater unit. The first terminal station transmits a supervisory signal to the second terminal station. The second terminal station transfers the supervisory signal to the repeater unit to be monitored. Paths to a hub station A and a hub station B can be a single path by looping back a supervisory signal output from the hub stations A and B for issuing and terminating the supervisory signal at a first and a second branch stations connected through an optical wavelength multiplexing/demultiplexing unit. If the hub station B loops back a supervisory signal, the supervisory signal output from the hub station A can be returned to the hub station A again after circulating the path.

Abstract: A circulator guides wavelength multiplexed light that is received from a main transmission path to a 1st fiber grating. The 1st fiber grating reflects light of wavelength &lgr;1. Wavelength multiplexed light that has passed through the 1st fiber grating is guided to a 2nd fiber grating. The 2nd fiber grating reflects light of wavelength &lgr;n. The circulator guides the signal light that has been reflected from the 1st and 2nd fiber gratings to a branch transmission path. The length of the transmission path between the 1st and 2nd fiber gratings is determined based on the transmission rate or frequency of the signal that is transmitted using light of wavelength &lgr;n.

Abstract: An optical amplifying repeater is provided whereby a transfer signal generated in response to a monitor signal from an end office is generated and amplified by a rare earth element doped fiber, the modulation degree with respect to the optical output of the fiber being held constant, regardless of the frequency of the this transfer signal. This optical amplifying repeater has a rare earth element (such as erbium) doped fiber, an automatic adjusting loop 12, and a monitor and response unit, and is further provided with a modulation degree compensation part for the purpose of holding constant the transfer signal modulation degree with respect to the optical output of the fiber, regardless of the frequency of the transfer signal.