Nippon Telegraph and Telephone Corporation

Nippon Telegraph & Telephone Co.

Nippon Telegraph and Telephone Communications

Kazuto Noguchi

Akira Okada

Takashi Sakamoto

Morito Matsuoka

Yoshihisa Sakai

Kazutoshi Kato

Hiromasa Tanobe

Osamu Moriwaki

Osamu Mitomi

Sen-ichi Suzuki

Yasuhiro Suzuki

Toshio Suzuki

Kenji Kawano

Yasuo Shibata

Rieko Sato

Tsutomu Kitou

Yasumasa Suzaki

Mitsuaki Yanagihashi

Hiromichi Jumonji

Toshinori Nozawa

Masahiro Ueno

Hiroshi Miyazawa

Tadayuki Imai

Seiji Toyoda

Shogo Yagi

Kazunori Naganuma

Yuichi Okabe

Jun Miyazu

Shigeo Ishibashi

Sen-Ichi Suzuki

A wavelength swept light source includes a sawtooth waveform as a main waveform and an exponential component of the sawtooth waveform to the controlled voltage of the electro-optic deflector. The controlled voltage is controlled so that, as an oscillation wavelength to be swept is swept towards a longer wavelength side, a change rate of the oscillation wavelength is increased.

Wavelength swept light source

An optical communication system is constructed which enables highly reliable and flexible connection to communication nodes connected to a path establishment circuit, by utilizing wavelength-routing characteristics of a path establishment circuit such as an arrayed waveguide grating. The optical communication system has multiple communication nodes having a signal output port and signal input port pair, and a path establishment circuit having multiple optical input ports and multiple optical output ports which are set so that optical signals input from the respective optical input ports are output to predetermined optical output ports corresponding to the wavelengths of the optical signals.

Optical communication system

An optical communication network system and a wavelength-routing device and a communication node therefor are provided which can easily increase the optical paths between communication nodes, which are capable of expanding transmission capacity, and which excel in flexibility and expandability. An optical signal within a wavelength band (&#x3bb;B&#xb1;&#x394;&#x3bb;) which has been transmitted from a predetermined communication node (-through-) is subjected to wavelength-band demultiplexing of the wavelength bands by wavelength-band demultiplexers (-through-) of a wavelength-routing device (), and is then subjected to wavelength-routing by arrayed-waveguide gratings (through) according to the wavelength bands, and furthermore is multiplexed with optical signals of other wavelength bands by wavelength-band multiplexers (-through-), and after having been outputted, is transmitted to a communication node. In this manner, by varying the wavelength band (&#x3bb;B&#xb1;&#x394;&#x3bb;) of the wavelength of the optical signal which is transmitted from the communication node, it becomes possible to establish a single optical path between the communication nodes for each wavelength band.

Optical communication network system, wavelength routing apparatus, communication node, optical path managing method for use in optical cross connect apparatus, and apparatus for that method

A fiber optic communication system includes a device of switching and setting wavelength of optical signals used in communication by network-node equipments, which sets the mapping of the wavelength of the optical signal used in communication by the network node equipments, and the input/output ports of an array waveguide grating (AWG), so as to construct a predetermined logical network topology by a plurality of network node equipments which are connected via optical fibers to the array waveguide grating that outputs optical signals inputted to optical input ports, to predetermined optical output ports in accordance with the wavelength thereof. As well as enabling a simple construction, it is easy to realize flexible network design, construction, and operation, and different network groups can also be easily connected to each other. Moreover, a fiber optic communication system having robust security and which can be stably operated even at the time of failure is realized at low cost.

Optical communication network system

An optical communication equipment comprises shared optical sourcesto be shared by communication nodes, the wavelengths of optical signalsare converted into desired wavelengths &#x3bb;a&#x2013;&#x3bb;d according to the addressed information of the corresponding optical label signalsby using the shared optical sourcesand routed to the addressed communication nodes without being converted into electrical signals by using the wavelength routing function of the cyclic-wavelength arrayed-waveguide grating (AWG). The load of each communication node can be reduced by incorporating the multi-wavelength optical sources, which can be shared among individual communication nodes, into the router. Further, each communication node is provided with an optical gate or the like for returning the optical signal to the communication node from which the optical signal has been transmitted through the routerin order to adjust the transmission time lag between the optical signal and the corresponding optical label signal by the controllers

Optical packet routing network system based on optical label switching technique

An optical communication equipment comprises shared optical sourcesto be shared by communication nodes, the wavelengths of optical signalsare converted into desired wavelengths &#x3bb;a&#x2013;&#x3bb;d according to the addressed information of the corresponding optical label signalsby using the shared optical sources, and routed to the addressed communication nodes without being converted into electrical signals by using the wavelength routing function of the cyclic-wavelength arrayed-waveguide grating (AWG). The load of each communication node can be reduced by incorporating the multi-wavelength optical sources, which can be shared among individual communication nodes, into the router. Further, each communication node is provided with an optical gate or the like for returning the optical signal to the communication node from which the optical signal has been transmitted through the routerin order to adjust the transmission time lag between the optical signal and the corresponding optical label signal by the controllers

A light-controlled light modulator can achieve high-speed, low-loss wavelength conversion. Continuous light with a wavelength &#x3bb;j is launched into an MMI coupler via a port, and is split into two parts by the MMI coupler, which are led to a loop-type interferometer. In the loop-type interferometer, the two parts travel separately around the loop as clockwise traveling light and counterclockwise traveling light, are combined by the MMI coupler again via a filter-equipped phase modulator, thereby being emitted to the port. In this state, signal light &#x3bb;i(s) with a wavelength &#x3bb;i is launched into the filter-equipped phase modulator via a port. Even when the wavelength &#x3bb;i of the signal light &#x3bb;i(s) is equal to the wavelength &#x3bb;j of the wavelength converted output light, the wavelength conversion can be achieved with preventing noise from being mixed into the output light emitted from a port.

Light-controlled light modulator

An optical communication equipment comprises shared optical sources to be shared by communication nodes , the wavelengths of optical signals are converted into desired wavelengths &lgr; according to the addressed information of the corresponding optical label signals by using the shared optical sources and routed to the addressed communication nodes without being converted into electrical signals by using the wavelength routing function of the cyclic-wavelength arrayed-waveguide grating (AWG) . The load of each communication node can be reduced by incorporating the multi-wavelength optical sources, which can be shared among individual communication nodes, into the router . Further, each communication node is provided with an optical gate or the like for returning the optical signal to the communication node from which the optical signal has been transmitted through the router in order to adjust the transmission time lag between the optical signal and the corresponding optical label signal by the controllers

A light-controlled light modulator can achieve high-speed, low-loss wavelength conversion. Continuous light with a wavelength &lgr;j is launched into an MMI coupler via a port, and is split into two parts by the MMI coupler, which are led to a loop-type interferometer. In the loop-type interferometer, the two parts travel separately around the loop as clockwise traveling light and counterclockwise traveling light, are combined by the MMI coupler again via a filter-equipped phase modulator, thereby being emitted to the port. In this state, signal light &lgr;i(s) with a wavelength &lgr;i is launched into the filter-equipped phase modulator via a port. Even when the wavelength &lgr;i of the signal light &lgr;i(s) is equal to the wavelength &lgr;j of the wavelength converted output light, the wavelength conversion can be achieved with preventing noise from being mixed into the output light emitted from a port.

An optical control device include a substrate having an electrooptic effect, the substrate having ridges with optical waveguides. A buffer layer is formed on the substrate surface, and electrodes are provided. The electrodes includes at least one ground electrode, and a central electrode that is formed on the buffer layer over a ridge. The width of the central electrode on the side where the central electrode contacts the buffer layer is larger than the width of the optical waveguide. Because of this construction, the optical control device can achieve constant characteristics and a broad bandwidth.

Optical control device

An electrically controlled optical device effective index includes a traveling wave electrode, a shield conductor and a thick buffer layer of a low dielectric constant. The thickness of an overlaid layer disposed between the traveling wave electrode and the shield conductor as well as the thickness of the buffer layer is so determined that an effective index of a microwave transmitted through the traveling wave electrode approaches an effective index of light transmitted through an optical waveguide, and that a microwave conductor loss is reduced, and that a characteristic impedance of said traveling wave electrode approaches a characteristic impedance of an associated external microwave circuit.

Electrically controlled optical device

An electrically controlled optical device includes a traveling wave electrode structure, a shield conductor and a thick buffer layer having a low dielectric constant. The thickness of an overlaid layer disposed between the traveling wave electrode structure and the shield conductor, as well as the thickness of the buffer layer, is determined so that the effective index of a microwave transmitted through the traveling wave electrode structure approaches the effective index of light transmitted through an optical waveguide, so that the microwave conductor loss is reduced, and so that the characteristic impedance of the traveling wave electrode structure approaches the characteristic impedance of an associated external microwave circuit.

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Atsugi, Japan

Kazuto Noguchi