Matsushita Electric Industrial Co., Ltd.

Panasonic Corporation

Nippon Telegraph and Telephone Corporation

Toru Shiozaki

Masaru Fuse

Satoshi Furusawa

Tsuyoshi Ikushima

Kuniaki Utsumi

Katsumi Iwatsuki

Mitsuhiro Teshima

Shigeru Kuwano

Yoshikazu Ishii

Hiroaki Asano

Hitoshi Uematsu

A data communication apparatus wherein stealthiness is enhanced by significantly increasing the time required for a wiretapper to decrypt an encrypted text. The data communication apparatus is constituted by connecting a data transmitting apparatus and a data receiving apparatus via a transmission path. The data transmitting apparatus receives a first predetermined initial value (key information) and information data, generates a multi-valued signal, the level of which varies substantially in a random number manner, and converts the multi-valued signal to a modulated signal of a predetermined modulation format for transmission. The data receiving apparatus demodulates the modulated signal to output the multi-valued signal, and then reproduces the information data from the multi-valued signal and a received second predetermined initial value (key information).

Data communication apparatus

A data communication system that enhances concealment by significantly increasing the time required for a wiretapper to decrypt a cipher text. The data communication system is constituted by connecting a data transmitting apparatus () to a data receiving apparatus () via a transmission path (). In the data transmitting apparatus (), a multilevel encoding part () receives a predetermined first initial value (key information) and information data and generates a multilevel signal that varies in level substantially in a random number manner. A dummy signal superimposing part () superimposes a dummy signal on the multilevel signal. A modulating part () converts the multilevel signal to a modulated signal of a predetermined modulation form and transmits the modulated signal. The data receiving apparatus () demodulates the modulated signal to output the multilevel signal, and receives a predetermined second initial value (key information) and the multilevel signal to reproduce the information data.

Data communication system

An optical packet exchanger is provided which prevents a transmittable capacity of an information signal from decreasing, and which facilitates the extracting an address signal even if a modulation speed for the information signal becomes high. An optical modulation section () outputs an optical packet obtained by subjecting output light from a light source () to an intensity modulation using an information signal and a phase modulation using an address signal corresponding to a transmission destination for the information signal. An optical splitter section () splits the optical packet into two optical packets. An address reading section () reads the address signal from the phase of one of the optical packets output from the optical splitter section (). Based on the address signal output from the address reading section (), a path switching section () determines an output port for the other optical packet output from the optical splitter section ().

Optical packet exchanger

An optical brancher branches an input optical signal into two. An optical detector converts one optical signal branched by the optical brancher into an electrical signal. A first controller generates a control electrical signal having a waveform obtained by inverting the envelope of the electrical signal. Based on the control electrical signal, an optical signal generator produces a dummy optical signal having a waveform &#x3bb;d and an amplitude &#x3b1;/2. The other signal branched by the optical brancher is delayed by a delay unit for a predetermined time, and then multiplexed by an optical multiplexer with the dummy optical signal from the optical signal generator. An optical amplifier amplifies amultiplexed optical signal. An optical filter separates an optical signal of a wavelength &#x3bb;1 from the amplified optical signal. Thus, optical signal amplification can be carried out without optical surges.

Optical amplifying device

An optical transmission system is provided with a broadband optical transmitter including a broadband light source and a broadband optical modulator, an optical filter, an optical modulator, a transmission path, a wavelength router, and an optical receiver. The broadband optical transmitter outputs a broadband optical signal to the optical filter. The optical filter uses a branch wavelength bandwidth of the wavelength router as a basis for transmittance therethrough, and outputs only an applicable optical signal to the optical amplifier. The wavelength router simultaneously distributes the optical signal coming via the transmission path to each corresponding output port. In optical receivers, the optical signals penetrated through the wavelength router are converted into electrical signals.

Optical transmission system and optical transmitter used therein

This invention discloses an optical burst transmission system in which an optical generator generates Type 1 lightwaves having different wavelengths corresponding to transmission lines and having undergone intensity modulation with obtained data; a broad spectrum optical generator generates, by incorporating Type 2 lightwaves, a Type 3 lightwave using a fewer light emitting devices than the number of the Type 1 lightwaves, each Type 2 lightwaves having a corresponding wavelength apart from Type 1 lightwave's wavelength with an FSR interval and having undergone the intensity modulation with clock signals; an optical multiplexer multiplexes the Type 1 and Type 3 lightwaves to output the combination to each transmission line; and an optical routing unit extracts, from the combination, pairs of one Type 1 lightwave and one Type 2 lightwave having the corresponding wavelength, and guides pairs to each transmission line corresponding to the Type 1 lightwave's wavelength in each pair.

Low-cost optical burst transmission system, apparatus, and method

A data unitoutputs an information signal to be transmitted in the form of optical packets, as well as wavelength information representing a wavelength of each optical packet. A first modulating signal processing unitreceives an information signal, and inserts an electric signal ('dummy signal') in any no-data period during which the information signal is absent, and outputs the resultant signal as a modulating signal. The dummy signal has the same amplitude as that of the information signal. A wavelength information processing unitoutputs a wavelength controlling current corresponding to the wavelength information, and in any no-data period, outputs a wavelength controlling current corresponding to a wavelength which is different from the wavelengths represented by the wavelength information. A wavelength-tunable light sourceoutputs light of a wavelength corresponding to the wavelength controlling current. An optical modulation unitmodulates the light outputted from the wavelength-tunable light sourcewith the modulating signal, and outputs the modulated signal as optical packets. As a result, an optical surge is prevented from occurring at the time of amplifying intermittently generated optical packets.

Optical transmitter

An optical brancher branches an input optical signal into two. An optical detector converts one optical signal branched by the optical brancher into an electrical signal. A first controller generates a control electrical signal having a waveform obtained by inverting the envelope of the electrical signal. Based on the control electrical signal, an optical signal generator produces a dummy optical signal having a waveform &lgr;d and an amplitude &agr;/2. The other signal branched by the optical brancher is delayed by a delay unit for a predetermined time, and then multiplexed by an optical multiplexer with the dummy optical signal from the optical signal generator. An optical amplifier amplifies amultiplexed optical signal. An optical filter separates an optical signal of a wavelength &lgr;1 from the amplified optical signal. Thus, optical signal amplification can be carried out without optical surges.

An optical brancher branches an input optical signal into two. An optical detector converts one optical signal branched by t e optical brancher into an electrical signal. A first controller generates a control electrical signal having a waveform obtained by inverting the envelope of the electrical signal. Based on the control electrical signal, an optical signal generator produces a dummy optical signal having a waveform &lgr;d and an amplitude &agr;/2. The other signal branched by the optical brancher is delayed by a delay unit for a predetermined time, and then multiplexed by an optical multiplexer with the dummy optical signal from the optical signal generator . An optical amplifier amplifies a multiplexed optical signal. An optical filter separates an optical signal of a wavelength &lgr;1 from the amplified optical signal. Thus optical signal amplification can be carried out without optical surges.

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Kyoto, Japan

Toru Shiozaki