Optical: systems and elements – Optical amplifier – Optical fiber
Reexamination Certificate
1998-05-29
2002-06-04
Hellner, Mark (Department: 3662)
Optical: systems and elements
Optical amplifier
Optical fiber
C359S337000, C359S349000
Reexamination Certificate
active
06400498
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an optical signal repeating and amplifying device and an optical level adjusting device which are applied to the optical WDM transmission.
BACKGROUND OF THE INVENTION
The optical WDM transmission system that optical signals with different wavelengths are transmitted in the lump through one optical fiber allows a large-capacity optical transmission. In particular, owing to the development of high-gain and high-power optical amplifiers, such as an erbium-doped optical fiber amplifier, a long-distance and large-capacity optical transmission can be realized. In repeating optical signals in the optical transmission, to amplify the optical signals unalteredly without converting into electrical signals can contribute effectively to the miniaturization of repeating station, thereby reducing the cost of transmission. At present, to realize a further long-distance optical transmission by using a multiple-stage optical repeating and amplifying has been expected.
However, conventional optical signal repeating and amplifying device and optical level adjusting device have some problems described below.
First, due to the limitation on output power of optical amplifier, the optical power per one wave is limited when the number of optical signals multiplexed is increased. Thereby the transmission distance is also limited to be short.
Second, with an increase in the number of repeating amplifiers, the difference in optical level between wavelengths due to the gain deviation of optical amplifier is increased and an ASE noise generated from optical amplifier is also increased. Thereby the reception sensitivity must be reduced. Further, in connecting multiple-stage optical amplifiers, the optical level may be greatly different between wavelengths because optical amplifiers have different gains depending on wavelength.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide an optical signal repeating and amplifying device that the reception sensitivity can be enhanced by removing an ASE noise, the total optical intensity of optical signals to be output after wavelength-multiplexing can be increased, and the level of wavelength lights in WDM optical signal can be equalized.
It is a further object of the invention to provide an optical level adjusting device that the optical level of each wavelength can be adjusted into an arbitrary value.
According to the invention, an optical signal repeating and amplifying device, comprises:
an optical amplifier which amplifies an optical signal to be input thereto and then outputs it; and
an optical filter means through which only one wavelength light of the optical signal to be output from the optical amplifier is passed.
According to another aspect of the invention, an optical signal repeating and amplifying device, comprises:
a first optical demultiplexer-multiplexer which demultiplexes a wavelength-multiplexed optical signal into a plurality of wavelength lights;
a plurality of optical transmission lines through which the plurality of wavelength lights from the first optical demultiplexer-multiplexer are separately transmitted; and
a second optical demultiplexer-multiplexer which multiplexes the optical signals transmitted through the plurality of optical transmission lines into a wavelength-multiplexed optical signal and outputs it.
According to another aspect of the invention, an optical signal repeating and amplifying device, comprises:
an optical circulator through which a wavelength-multiplexed optical signal to be input to the input port is output from the input-output port and a wavelength-multiplexed optical signal to be input to the input-output port is output from the output port;
an optical demultiplexer-multiplexer which demultiplexes the wavelength-multiplexed optical signal from the optical circulator into a plurality of wavelength lights and multiplexes a plurality of wavelength lights into a wavelength-multiplexed optical signal;
a plurality of optical transmission lines through which the demultiplexed plurality of wavelength lights to be output from the optical demultiplexer-multiplexer are separately transmitted; and
a plurality of optical reflecting mirrors which reflect separately the demultiplexed plurality of wavelength lights transmitted through the plurality of optical transmission lines to turn them back.
According to another aspect of the invention, an optical signal repeating and amplifying device, comprises:
an optical demultiplexer-multiplexer which demultiplexes a wavelength-multiplexed optical signal into a plurality of wavelength lights and multiplexes a plurality of wavelength lights into a wavelength-multiplexed optical signal;
a plurality of optical transmission lines through which the demultiplexed plurality of wavelength lights to be output from the optical demultiplexer-multiplexer are separately transmitted; and
an optical dividing and coupling means through which each of the plurality of wavelength lights transmitted through each of the plurality of optical transmission lines is re-input to the optical demultiplexer-multiplexer while by-passing a different one of the optical transmission lines without overlapping with another wavelength light.
According to another aspect of the invention, an optical signal repeating and amplifying device, comprises:
a first optical demultiplexer-multiplexer which demultiplexes a wavelength-multiplexed optical signal into a plurality of wavelength lights;
a plurality of optical filters through which the plurality of wavelength lights from the first optical demultiplexer-multiplexer are separately passed; and
a second optical demultiplexer-multiplexer which multiplexes the optical signals passed through the plurality of optical filters into a wavelength-multiplexed optical signal and outputs it.
According to another aspect of the invention, an optical signal repeating and amplifying device, comprises:
an optical divider which divides a wavelength-multiplexed optical signal into a plurality of lights;
a plurality of optical filters through which the plurality of wavelength lights from the optical divider are separately passed; and
an optical coupler which couples the optical signals passed through the plurality of optical filters into a wavelength-multiplexed optical signal and outputs it.
According to another aspect of the invention, an optical signal repeating and amplifying device, comprises:
an optical circulator through which a wavelength-multiplexed optical signal to be input to the input port is output from the input-output port and a wavelength-multiplexed optical signal to be input to the input-output port is output from the output port;
an optical demultiplexer-multiplexer which demultiplexes the wavelength-multiplexed optical signal from the optical circulator into a plurality of wavelength lights and multiplexes a plurality of wavelength lights into a wavelength-multiplexed optical signal;
a plurality of optical filters through which the demultiplexed plurality of wavelength lights to be output from the optical demultiplexer-multiplexer are separately passed; and
a plurality of optical reflecting mirror which reflect separately the demultiplexed plurality of wavelength lights passed through the plurality of optical filters to turn them back.
According to another aspect of the invention, an optical signal repeating and amplifying device, comprises:
an optical circulator through which a wavelength-multiplexed optical signal to be input to the input port is output from the input-output port and a wavelength-multiplexed optical signal to be input to the input-output port is output from the output port;
an optical divider-coupler which divides the wavelength-multiplexed optical signal from the optical circulator into a plurality of lights and couples a plurality of lights into a wavelength-multiplexed optical signal;
a plurality of optical filters through which the divided plurality of lights to be output from the optical divider-coupler are separately passed; and
a plurality of optical reflecting mirrors w
Henmi Naoya
Shimomura Hirofumi
NEC Corporation
Scully Scott Murphy & Presser
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