Oki Electric Industry Co., Ltd.

Hiromi Tsuji

Masatoshi Kagawa

Hideyuki Iwamura

Kozo Fujii

The present invention provides a method of generating time-division multiplexed encoded transmission signals, including encoding optical pulse signals for each of a plural multiplexed channels and generating a transmission signal for each channel, performing time division multiplexing on first and second transmission signals and generating a 2-channel multiplexed signal modulating the multiplexed signal with a modulation signal having a frequency of (F&#x2212;&#x394;f) Hz, detecting a strength of a &#x394;f Hz frequency component of the multiplexed signal changing a time delay amount of the second transmission signal with respect to the first transmission signal, and determining a time delay amount at which a strength of the &#x394;f Hz frequency component is minimized and adjusting the transmission signals of the individual channels such that they are arranged at equidistant intervals on a time axis.

Method and apparatus for generating time-division multiplexed encoded transmission signal

In a clock signal extraction system, an optical modulator modulates an input optical signal having its clock frequency equal to a first or second frequency with a modulation electrical signal having its frequency equal to the average of the first and second frequencies to output a modulated optical pulse signal to a phase comparator, which receives a reference electrical signal generated by a reference signal generator and having its frequency half as high as a difference between the first and second frequencies to compare in phase the modulated optical pulse signal with the reference electrical signal to output a resultant phase comparison signal to a modulation electrical signal generator, which in turn outputs a modulation electrical signal to the optical modulator and clock signal generator, which generates a signal with the modulation and reference electrical signals mixed, and outputs the signal at first or second frequency as a clock signal.

System for extracting a clock signal from optical signal including plural clock frequencies and a method therefor

In an optical element integrated module, first through n-th optical data signals are externally input to first ports of first through n-th optical circulators and are input to first through n-th optical/optical converters via second ports. The first through n-th optical/optical converters modulate first through n-th optical short pulse trains in accordance with the first through n-th optical data signals. First through n-th modulated optical data signals are input to the second ports of the first through n-th optical circulators and are input to an optical time division multiplexing section. The optical time division multiplexing section generates optical time division multiplexed signals by time division multiplexing the first through n-th modulated optical data signals.

Optical element integrated module

A multi-rate clock signal extracting device includes a light modulator, a photoelectric converter, a band-pass filter unit, a phase comparison unit, a bit rate changeover switch and a modulating electric signal generating unit. The light modulator modulates a light signal according to a modulating electric signal as a mixing signal obtained by mixing an electric signal with frequency f/(2) and an electric signal with frequency &#x394;f so as to output it as a modulated light signal. The modulated light signal is converted into a first electric signal by the photoelectric converter. A second electric signal group with frequency (2)&#xd7;&#x394;f is generated from signal components with frequencies (2)&#xd7;&#x394;f included in the modulated light signal by the photoelectric converter and the band-pass filter unit so as to be input into the phase comparison unit. The bit rate changeover switch selects an electric signal corresponding to the bit rate of the light signal so as to input it into a modulating electric signal generating unit. The modulating electric signal generating unit outputs the modulating electric signal.

Multi-rate clock signal extracting method and multi-rate clock signal extracting device

An optical communication system which constructs, at low cost, a network that uses Time Division Multiplexing in at least one direction of the communication. The optical communication system includes an optical multiplexer/demultiplexer that mediates communication between a network unit and a plurality of terminal units. The optical multiplexer/demultiplexer regenerates a synchronization clock from a downstream signal light. In addition, the optical multiplexer/demultiplexer adjusts, using the regenerated synchronization clock, the delay times of a plurality of upstream signal lights received from the terminal units. The network unit and the terminal units do not need to control the timing of the upstream signal lights. Thus, the construction costs of the optical communication system are reduced.

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Tokyo, Japan

Hiromi Tsuji