Abstract: The optical node connects N networks to each other (where N is an integer larger than one). Each of the N networks respectively includes a first transmission path and a second transmission path. The optical node includes a switching unit that connects the first transmission path of one network of the N networks to other (N-1) networks; a failure detector that detects failure in the first transmission path of the network; and a control unit that causes the switching unit to connect the second transmission path of the network to the other (N-1) networks when the failure is detected.

Abstract: In an optical transmission system utilizing bi-directional Raman amplification, propagation directions and wavelengths of Raman pumps are chosen such that four-wave mixing products among the pump wavelengths are minimized in a signal wavelength region.

Abstract: An optical transmitting apparatus is configured such that K pieces of output ports of optical path switching units whose input port is connected to k-th input transmission path are connected to first to K-th output transmission paths except for the k-th output transmission path and to the k-th input port of a dropping unit, and the optical path switching units and the dropping unit outputs light of wavelength which is part or all of WDM light received from said input port from a specific output port, and can output light having a wavelength different from that of the light output from said specific output port from an output port different from said specific output port. Accordingly, while largely reducing the number of optical fiber patch cords necessary in an optical transmitting apparatus and largely reducing the number of spare ports, the flexible expansion of apparatus function can be realized.

Abstract: The optical switch includes: an input port from which beam is input; a dispersing unit that disperses the beam input; a condensing unit that condenses the beam dispersed; a mirror that reflects the beam condensed; and a plurality of output ports from which the beam reflected is output. The mirror rotates around a first axis so that the beam reflected enters one of the output ports, and also rotates around an axis that is selected, according to that which output port the beam reflected enters, from any one of the first axis and a second axis perpendicular to the first axis so that an intensity of the beam output is attenuated.

Abstract: The degree of polarization of an optical signal is measured by a polarimeter and used for providing a feedback signal to adjust adaptive optics of a polarization mode dispersion compensator. The polarization properties of the polarimeter are determined with high accuracy to match the polarimeter through calibration and used to produce the feedback signal.

Abstract: A core unit arranged in a transmission path includes a through path for causing an input signal to an input port to pass through to an output port, a drop-side port 25a that drops the input signal having a predetermined wavelength, and an add-side port 25b that adds channel having a predetermined wavelength to the input light.

Abstract: Linear networks are divided into a plurality of regeneration repeating sections which have nodes having regeneration repeaters arranged therein at both ends, devices such as linear repeaters or OADMs are arranged at the nodes positioned in the regeneration repeating sections, a plurality of assumed paths assumed as a result of arranging the devices are extracted in the regeneration repeating sections, and transmission permission/inhibition is determined for each assumed path, and after that, the determined transmission permission/inhibition is displayed to allow a user to perform settings again.

Abstract: Different bands (C-band and L-band) are allotted respectively to an upstream optical signal and a downstream optical signal. In a transmission-path optical fiber for Raman amplification, the C-band optical signal is amplified by pumping light from a C-band pumping light source, and the L-band optical signal is amplified by pumping light from an L-band pumping light source. As a result of this configuration, the optical signals are Raman-amplified through backward pumping in both upstream and downstream directions, whereby negative effects, which could be exerted on the optical signals by forward pumping, can be avoided.

Abstract: An optical fiber transmission line including first, second and third optical fibers connected together so that light travels through the transmission line from the first optical fiber, then through the second optical fiber and then through the third optical fiber. The first, second and third optical fibers have first, second and third characteristic values, respectively. The second characteristic value is larger than the first characteristic value and the third characteristic value. The characteristic value of a respective optical fiber being a nonlinear refractive index of the optical fiber divided by an effective cross section of the optical fiber. Pump light is supplied to the transmission line so that Raman amplification occurs in the transmission line as an optical signal travels through the transmission line.

Abstract: An optical fiber transmission line including first, second and third optical fibers connected together so that light travels through the transmission line from the first optical fiber, then through the second optical fiber and then through the third optical fiber. The first, second and third optical fibers have first, second and third characteristic values, respectively. The second characteristic value is larger than the first characteristic value and the third characteristic value. The characteristic value of a respective optical fiber being a nonlinear refractive index of the optical fiber divided by an effective cross section of the optical fiber. Pump light is supplied to the transmission line so that Raman amplification occurs in the transmission line as an optical signal travels through the transmission line.

Abstract: In an optical transmission system utilizing bi-directional Raman amplification, propagation directions and wavelengths of Raman pumps are chosen such that four-wave mixing products among the pump wavelengths are minimized in a signal wavelength region.

Abstract: The present invention relates to a method for gain equalization, for example. First, an optical transmission line including an optical amplifier having a gain changing nonlinearly with wavelength is provided (step (a)). Secondly, gain equalization of the optical transmission line is performed so as to obtain a gain changing substantially linearly with wavelength (step (b)). Finally, gain equalization of the optical transmission line is performed so as to obtain a gain remaining substantially unchanged with wavelength (step (c)). According to this method, gain equalization of the optical transmission line is performed so as to obtain a gain changing substantially linearly with wavelength. Accordingly, variations in equalization error due to changes in system condition can be easily suppressed.

Abstract: There are provided a plurality of optical adjusting sections, a wavelength-multiplexing section, and a control section. The plurality of optical adjusting sections, which are provided for respective wavelength bands, amplifies light beams in the respective wavelength bands. The wavelength-multiplexing section wavelength-multiplexes amplified light beams in the respective wavelength bands. The control section controls the outputs of the respective optical amplifying sections so that optical powers of the respective wavelength bands will become approximately identical at a predetermined point when wavelength-multiplexed light of the light beams in the respective wavelength bands travels to the predetermined point. This configuration makes it possible to eliminate optical power deviations between wavelength bands that would otherwise occur when an optical signal of a plurality of wavelength bands is transmitted, and to thereby make optical SNRs uniform.

Abstract: A distributed optical amplifier comprises an optical amplifying medium for distributed optical amplification, light supplying means for supplying a pump light to said optical amplifying medium, a pump light detecting part for detecting optical power of said pump light, adjusting means for adjusting an incident power of the light amplified with said optical amplifying medium, and control means for adjusting incident optical power of said light according to an output of said pump light detecting means. Because of this, the present invention can be controlled with a simplified structure of an optical power of an pump light, and an optical power of light to be amplified. A distributed optical amplifier as such can, for example, be applied in optical transmission systems.

Abstract: There is provided in an optical amplifier device used for a system in which a power transfer takes place from comparatively short wavelength signal to a comparatively long wavelength signal. The device includes an amplifier stage coupled to an optical transmission medium, a monitor monitoring a status of a first band; and a pump light source unit supplying at least one first pump light to the optical transmission medium on the basis of the status of the first band monitored, so that the above at least one first pump light supplies additional power to longer wavelength channels related to the status of the first band.

Abstract: The present invention relates to a method for gain equalization, for example. First, an optical transmission line including an optical amplifier having a gain changing nonlinearly with wavelength is provided (step (a)). Secondly, gain equalization of the optical transmission line is performed so as to obtain a gain changing substantially linearly with wavelength (step (b)). Finally, gain equalization of the optical transmission line is performed so as to obtain a gain remaining substantially unchanged with wavelength (step (c)). According to this method, gain equalization of the optical transmission line is performed so as to obtain a gain changing substantially linearly with wavelength. Accordingly, variations in equalization error due to changes in system condition can be easily suppressed.

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 gain equalizer which equalizes gain versus wavelength characteristics of an optical amplifier. The gain versus wavelength characteristics of the optical amplifier include first, second and third gain peaks in a wavelength band with the second gain peak being between the first and third gain peaks. The optical amplifier amplifies an input signal in accordance with the gain versus wavelength characteristics to produce an output signal. The gain equalizer includes first, second and third optical filters having first, second and third transparency characteristics, respectively. The first, second and third transparency characteristics are periodic waveforms having different periods related to the wavelength difference between the first and third gain peaks. The second transparency characteristic is a periodic waveform having a period equal to 1/(2n) of the period of the waveform of the first transparency characteristic.

Abstract: The present invention provides a WDM transmission system that can multiplex/demultiplex and transmit wavelength division multiplexing signals, where signal lights have a different signal bandwidth, in a status without much deterioration of transmission quality. For the WDM signals P0, 10 Gbit/s signals with a 25 GHz bandwidth are arrayed in odd channels on a grid with a 50 GHz interval, and 40 Gbit/s signals with a 75 GHz bandwidth are arrayed in even channels. The WDM signals P0 are demultiplexed by the interleaver 1, then are demultiplexed by the interleavers 2 and 3. The central frequency of the transmission bands-of the ports A1 and B1 are shifted from the central frequency of the 10 Gbit/s signals so that the overlapping portion of the transmission band of the ports A1 and B1 substantially match the signal band of the channel ch [4i-2] (i is an integer of 1 or higher). By this, only 40 Gbit/s signals in the channel ch [4i-2] are output from the port B1.

Abstract: An object of the invention is to realize a low cost, low loss multi-directional optical branching apparatus with a simple configuration, capable of outputting WDM signal lights of uniform power in three or more directions. To this end, the multi-directional optical branching apparatus of the invention is provided with 2×N optical multiplexing/demultiplexing devices for N (N≧3) optical transmission paths, and a branch port connecting section that connects in one to one between the respective branch ports. The apparatus demultiplexes respectively the WDM signal light input from an input side optical path of each of the optical transmission paths into N−1 wavelength groups, and then multiplexes each of the demultiplexed groups with optical signals of different wavelength groups from other directions, to output to an output side optical path of a predetermined optical transmission path.