Abstract: An optical adding and dropping device includes a drop section including an input port and having a through port and a plurality of drop ports set as output ports, a first multiplexer adapted to multiplex light from the through port and light from a plurality of add ports, and a spectrum foot removing section provided on the input side of the first multiplexer and adapted to remove a foot of a spectrum of light to be inputted from the add ports to the first multiplexer. The optical adding and dropping device can be configured at a low cost while it has adding and dropping functions.

Abstract: An optical adding and dropping device includes a drop section including an input port and having a through port and a plurality of drop ports set as output ports, a first multiplexer adapted to multiplex light from the through port and light from a plurality of add ports, and a spectrum foot removing section provided on the input side of the first multiplexer and adapted to remove a foot of a spectrum of light to be inputted from the add ports to the first multiplexer. The optical adding and dropping device can be configured at a low cost while it has adding and dropping functions.

Abstract: In an optical amplifier of the invention, a WDM signal light is separated into N components by a demultiplexer after which each component is amplified by N optical amplifier sections, and the output light level of each optical amplifier section is controlled to a constant level by respective control circuits and multiplexed in a multiplexer. At this time, in the demultiplexer, the bandwidth of the signal light output from each of the output ports is designed to have a different value, so that inter-wavelength deviation in the optical output level that occurs in each of the optical amplifier sections, falls within a preset range. Moreover, the constant output control of each control circuit is performed by individually adjusting the gain of each of the optical amplifier sections in relation to fluctuations in the power level without channel number changes of the WDM signal light input to the demultiplexer.

Abstract: In an optical amplifier of the invention, a WDM signal light is separated into N components by a demultiplexer after which each component is amplified by N optical amplifier sections, and the output light level of each optical amplifier section is controlled to a constant level by respective control circuits and multiplexed in a multiplexer. At this time, in the demultiplexer, the bandwidth of the signal light output from each of the output ports is designed to have a different value, so that inter-wavelength deviation in the optical output level that occurs in each of the optical amplifier sections, falls within a preset range. Moreover, the constant output control of each control circuit is performed by individually adjusting the gain of each of the optical amplifier sections in relation to fluctuations in the power level without channel number changes of the WDM signal light input to the demultiplexer.

Abstract: An optical amplifier of a wavelength-division multiplexing transmission system that includes a pre-stage optical amplifying unit and a post stage optical amplifying unit. The pre-stage optical amplifying unit has a rare-earth element doped optical fiber and a pump light source for inputting a pump light to the rare-earth element doped optical fiber. The post-stage optical amplifying unit has a second rare-earth element doped optical fiber and a pump light source for inputting a pump light to the second rare-earth element doped optical fiber. The pre-stage optical amplifying unit and the post-stage optical amplifying unit are optically connected by a detachable optical coupling device. In addition, a gain equalizing unit, positioned on an output side of the optical fibers, compensates for wavelength-dependency of a gain characteristic of the optical fibers.

Abstract: The present invention aims at providing an optical amplifying apparatus constituted by combining Raman amplifiers, in which deterioration of a signal/noise ratio of output light is prevented to thereby improve the transmission characteristic of signal light, and an optical communication system utilizing such an optical amplifying apparatus. To this end, the optical amplifying apparatus according to the present invention comprises: first optical amplifying means for supplying excitation light to a Raman amplifying medium to thereby Raman amplify signal light; second optical amplifying means for amplifying the signal light output from the first optical amplifying means; and controlling means for controlling an operating state of the first optical amplifying means or the second optical amplifying means, so that a signal/noise ratio of the signal light to be output from the second optical amplifying means is kept substantially constant.

Abstract: An optical amplifying apparatus for widening the input dynamic range and lowering noises. The optical amplifying apparatus comprises a first optical amplifier, an optical attenuator, a second optical amplifier and a controller. The first optical amplifier changes the target value of output light when the variance amount of input light reaches a predetermined value. The controller changes the attenuation amount of attenuator in accordance with a difference between the target value and the changed target value of the output light level of the first optical amplifier, when the target value of the output light level of the first optical amplifier is changed.

Abstract: The output level of pumping light supplied from a pumping light source is varied using a variable attenuator, which is controlled by a variable attenuator driver circuit. By separating a portion containing the pumping light source from a portion containing an amplification medium, it becomes possible to prevent heat emitted by the pumping light source from adversely affecting the amplification medium. By arranging the portion containing the pumping light source such that a pumping light source or sources can be added when necessary, optical transmission system requirements of having more pumping light sources for system upgrade can be accommodated readily. By packaging portions containing amplification media, an optical amplifier can be made small.

Abstract: The present invention aims at providing an optical amplifying apparatus constituted by combining Raman amplifiers, in which deterioration of a signal/noise ratio of output light is prevented to thereby improve the transmission characteristic of signal light, and an optical communication system utilizing such an optical amplifying apparatus. To this end, the optical amplifying apparatus according to the present invention comprises: first optical amplifying means for supplying excitation light to a Raman amplifying medium to thereby Raman amplify signal light; second optical amplifying means for amplifying the signal light output from the first optical amplifying means; and controlling means for controlling an operating state of the first optical amplifying means or the second optical amplifying means, so that a signal/noise ratio of the signal light to be output from the second optical amplifying means is kept substantially constant.

Abstract: An optical amplifier of a wavelength-division multiplexing transmission system that includes a pre-stage optical amplifying unit and a post stage optical amplifying unit. The pre-stage optical amplifying unit has a rare-earth element doped optical fiber and a pump light source for inputting a pump light to the rare-earth element doped optical fiber. The post-stage optical amplifying unit has a second rare-earth element doped optical fiber and a pump light source for inputting a pump light to the second rare-earth element doped optical fiber. The pre-stage optical amplifying unit and the post-stage optical amplifying unit are optically connected by a detachable optical coupling device. In addition, a gain equalizing unit, positioned on an output side of the optical fibers, compensates for wavelength-dependency of a gain characteristic of the optical fibers.

Abstract: The output level of pumping light supplied from a pumping light source is varied using a variable attenuator, which is controlled by a variable attenuator driver circuit. By separating a portion containing the pumping light source from a portion containing an amplification medium, it becomes possible to prevent heat emitted by the pumping light source from adversely affecting the amplification medium. By arranging the portion containing the pumping light source such that a pumping light source or sources can be added when necessary, optical transmission system requirements of having more pumping light sources for system upgrade can be accommodated readily. By packaging portions containing amplification media, an optical amplifier can be made small.

Abstract: The output level of pumping light supplied from a pumping light source is varied using a variable attenuator, which is controlled by a variable attenuator driver circuit. By separating a portion containing the pumping light source from a portion containing an amplification medium, it becomes possible to prevent heat emitted by the pumping light source from adversely affecting the amplification medium. By arranging the portion containing the pumping light source such that a pumping light source or sources can be added when necessary, optical transmission system requirements of having more pumping light sources for system upgrade can be accommodated readily. By packaging portions containing amplification media, an optical amplifier can be made small.

Abstract: The output level of pumping light supplied from a pumping light source is varied using a variable attenuator, which is controlled by a variable attenuator driver circuit. By separating a portion containing the pumping light source from a portion containing an amplification medium, it becomes possible to prevent heat emitted by the pumping light source from adversely affecting the amplification medium. By arranging the portion containing the pumping light source such that a pumping light source or sources can be added when necessary, optical transmission system requirements of having more pumping light sources for system upgrade can be accommodated readily. By packaging portions containing amplification media, an optical amplifier can be made small.

Abstract: The output level of pumping light supplied from a pumping light source is varied using a variable attenuator, which is controlled by a variable attenuator driver circuit. By separating a portion containing the pumping light source from a portion containing an amplification medium, it becomes possible to prevent heat emitted by the pumping light source from adversely affecting the amplification medium. By arranging the portion containing the pumping light source such that a pumping light source or sources can be added when necessary, optical transmission system requirements of having more pumping light sources for system upgrade can be accommodated readily. By packaging portions containing amplification media, an optical amplifier can be made small.