Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1997-12-09
2001-01-23
Pascal, Leslie (Department: 2733)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S199200, C359S199200
Reexamination Certificate
active
06178022
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an optical transmitter and an optical receiver for optical time division multiplexing transmission where an optical signal is transmitted time-division-multiplexed.
BACKGROUND OF THE INVENTION
The high-speed transmission of signal has been reaching a limitation of operation speed of electrical circuit. Thus, it is difficult to further increase the velocity of transmitted signal. Currently, a next-generation ultra-high-speed and large-capacity communication means using an optical signal processing technique where an optical signal is processed as it is has been researched at some research institutions.
Also, as an effective one of the next-generation ultra-high-speed and large-capacity communication means, an optical time-division multiplexing system, where an optical pulse signal is generated by intensity-modulating short-pulse light with a very short pulse width and an optical time-division-multiplexed signal for ultra-high-speed and large-capacity communication is produced by multiplexing several optical pulse signals while giving a bit of time difference, has been researched.
However, in the conventional optical transmitter and optical receiver for optical time-division multiplexing transmission, means for identifying each channel in order to extract the optical pulse signal of each channel from the optical time-division-multiplexed signal transmitted to the optical receiver is not discussed. Namely, at present, only means for conducting the optical time-division multiplexing and demultiplexing are mainly researched and means for conducting the channel selection is not suggested.
This is because, at present, only the optical time-division multiplexing system with means for achieving main functions as the next-generation optical communication system has been researched and the research does not reach a stage to discuss the system after achieving the main functions.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide an optical transmitter for optical time-division multiplexing transmission where an optical signal of each channel in an optically-time-division-multiplexed signal to be transmitted can be identified to receive a predetermined channel.
It is another object of the invention to provide an optical receiver for optical time-division multiplexing transmission where an optical signal of each channel in an optically-time-division-multiplexed signal to be transmitted can be identified to receive a predetermined channel.
According to the invention, an optical transmitter for optical time-division multiplexing transmission where optical signals are intensity-modulated by data signals and then time-division-multiplexed to output an optical time-division-multiplexed signal, comprises:
means for superposing a low-frequency signal with a frequency proper to each of channels to be multiplexed on each of the optical signals corresponding to the each of channels by conducting a small quantity of intensity modulation.
According to another aspect of the invention, an optical transmitter for optical time-division multiplexing transmission, comprises:
data signal sources corresponding to a plurality of channels;
a plurality of means for outputting an optical signal corresponding to the data signal sources;
means for outputting a channel identification signal with a channel frequency proper to each of the plurality of channels to the optical signal corresponding to the plurality of optical signal outputting means;
a plurality of means for superposing the channel identification signal on the optical signal by using intensity modulation to output a channel-frequency-multiplexed optical signal; and
means for optically-time-division-multiplexing the channel-frequency-multiplexed optical signal to output an optically-time-division-multiplexed signal.
According to another aspect of the invention, an optical transmitter for optical time-division multiplexing transmission, comprises:
data signal sources corresponding to a plurality of channels;
means for outputting a channel identification signal with a channel frequency proper to each of the plurality of channels;
means for adding a data signal output from a corresponding one of the data signal sources and the channel identification signal to output a channel-identification-signal-superposed signal;
a pulse light source to output pulse light with a constant repetition period;
an optical modulator for intensity-modulating the pulse light by the channel-identification-signal-superposed signal to output a channel-frequency-superposed optical signal; and
means for optically-time-division-multiplexing the channel-frequency-superposed optical signal to output an optically-time-division-multiplexed signal.
According to another aspect of the invention, an optical receiver for optical time-division multiplexing transmission, the optical receiver receiving an optically-time-division-multiplexed signal from an optical transmitter for optical time-division multiplexing transmission where optical signals are intensity-modulated by data signals and the time-division-multiplexed to output an optically-time-division-multiplexed signal, the optical transmitter comprising means for superposing a low-frequency signal with a frequency proper to each of channels to be multiplexed on each of the optical signals corresponding to the each of channels by conducting a small quantity of intensity modulation, comprises:
means identifying each of the channel by detecting the low frequency when the optically-time-division-multiplexed signal received is demultiplexed to each of the channels.
According to another aspect of the invention, an optical receiver for optical time-division multiplexing transmission, the optical receiver receiving an optical time-division-multiplexed signal from an optical transmitter for optical time-division multiplexing transmission, the optical transmitter comprising data signal source corresponding to a plurality of channels, a plurality of means for outputting an optical signal corresponding to the data signal sources, means for outputting a channel identification signal with a channel frequency proper to each of the plurality of channels to the optical signal corresponding to the plurality of optical signal outputting means, a plurality of means for superposing the channel identification signal on the optical signal by using intensity modulation to output a channel-frequency-multiplexed optical signal, and means for optically-time-division-multiplexing the channel-frequency-multiplexed optical signal to output an optically-time-division-multiplexed signal, comprises:
means for identifying each of the channel by detecting the low frequency when the optical time-division-multiplexed signal received is demultiplexed to each of the channels.
According to another aspect of the invention, an optical receiver for optical time-division multiplexing transmission, the optical receiver receiving an optical time-division-multiplexed signal from an optical transmitter for optical time-division multiplexing transmission, the optical transmitter comprising data signal sources corresponding to a plurality of channels; means for outputting a channel identification signal with a channel frequency proper to each of the plurality of channels; means for adding a data signal output from a corresponding one of the data signal sources and the channel identification signal to output a channel-identification-signal-superposed signal; a pulse light source to output pulse light with a constant repetition period; an optical modulator for intensity-modulating the pulse light by the channel-identification-signal-superposed signal to output a channel-frequency-superposed optical signal; and means for optically-time-division-multiplexing the channel-frequency-superposed optical signal to output an optically-time-division multiplexed signal, comprises:
means for identifying each of the channel by detecting the low frequency when the optical time-division multiplexed signal received is demultiple
NEC Corporation
Pascal Leslie
Phan Hanh
Young & Thompson
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