Nippon Telegraph and Telephone Corporation

Mitsubishi Denki Kabushiki Kaisha

Ntt Electronics Corporation

Sony Corporation

Sumitomo Dainippon Pharma Co., Ltd.

Hiroshi Yamazaki

Takashi Goh

Yutaka Miyamoto

Takashi Saida

Ken Tsuzuki

Munehiko Nagatani

Shinji Mino

Takashi Yamada

Yoshiyuki Doi

Yoshiji Minagawa

Masanori Nakamura

Yoshiaki Ito

Hideyuki Nosaka

Hiroshi Shirakawa

Shigeo Tanaka

Makoto Sato

Toshio Watanabe

Hiroshi Takahashi

Takayuki Mizuno

Yoshio Osakabe

Kenya Suzuki

Akira Katsuyama

Atsushi Mori

Takayuki Kobayashi

Shin Kamei

Motohaya Ishii

Hiroto Kawakami

Kiyofumi Kikuchi

Takeo Saikatsu

Yasuo Kusagaya

Tsutomu Kitoh

Fukutaro Hamaoka

Noriko Kotabe

Akihide Sano

Hiroshi Terui

Takanori Nakamura

Yoshinori Anzai

Kouichi Sugiyama

Fumihiro Ebisawa

Tomoyo Shibazaki

Toshiro Kajiwara

Yuichi Kikuchi

Atsushi Murasawa

Takao Fukumitsu

Goroku Kobayashi

Hiroshi Harada

Shiro Kato

Yoko Kan

Yoshimi Hirokawa

An optical transmitter includes an I-component optical modulation unit, a Q-component optical modulation unit, and a 2×2 optical coupler. The I-component optical modulation unit generates modulated light based on an I-component data signal. The Q-component optical modulation unit generates modulated light based on a Q-component data signal. The 2×2 optical coupler receives the modulated light generated by the I-component optical modulation unit from a first input port, receives the modulated light generated by the Q-component optical modulation unit from a second input port, generates two optical QAM signals having a phase conjugate relationship from the modulated light which has been input from the first input port and the modulated light which has been input from the second input port, outputs one of said two optical QAM signals from a first output port, and outputs the other one of said two optical QAM signals from a second output port.

Optical transmitter

A signal generating device includes a digital signal processing unit, M sub DACs of which an analog bandwidth is f, M being an integer equal to or greater than 2, a broadband analog signal generating unit configured to generate a broadband analog signal that includes a component of a frequency of (M-1)for more by using M analog signals output from the M sub DACs. The digital signal processing unit includes components for generating M original divided signals that correspond to signals obtained by dividing a desired output signal into M portions on a frequency axis and down-converting the portions to the baseband, components for generating M folded divided signals by folding back the M original divided signals on the frequency axis, and a 2M&#xd7;M filter that takes the original divided signals and the folded divided signals as inputs and outputs M composite signals to be transmitted to the M sub DACs. The 2M&#xd7;M filter can set a response function independently for each of 2Mcombinations of input and output.

Signal generation device

An optical transmission system includes an optical transmitter and an optical receiver. The optical transmitter includes a low speed signal generation unit configured to generate, based on an input signal of a transmission data sequence and a signal obtained by cyclically shifting a spectrum of the input signal, a plurality of low speed signals, a high speed signal generation unit configured to digital-to-analog convert and synthesize the plurality of low speed signals to generate a high speed signal, and an optical modulation unit configured to transmit an optical signal obtained by modulation of the high speed signal to a transmission path. The optical receiver includes a reception unit configured to receive the optical signal from the transmission path and output the high speed signal obtained from the optical signal that is received, an optical-receiver-side high speed signal compensation unit configured to compensate, based on the high speed signal output by the reception unit and a signal obtained by cyclically shifting a spectrum of the high speed signal, for the high speed signal, and a reception data decoding unit configured to decode the high speed signal compensated by the optical-receiver-side high speed signal compensation unit to restore binary information included in the optical signal transmitted by the optical transmitter.

Optical transmitting system, optical transmitting apparatus, optical receiving apparatus and transfer function estimating method

In the conventional technique, only an output having a bandwidth identical to the bandwidth of individual DACs has been obtained even by using a plurality of DACs. Also, even when the output of a bandwidth broader than the individual DAC is obtained, there has been a problem associated with asymmetricity of a circuit configuration. In a signal generating device of the present invention, a plurality of normal DACs are combined to realize an analog output of a broader bandwidth beyond the output bandwidth of the individual DACs, and the problem of the asymmetricity of the circuit configuration is also resolved. A desired signal is separated into a low-frequency signal and a high-frequency signal in a frequency domain, and a series of operation of constant (r)-folding the amplitude of the high-frequency signal and shifting it on the frequency axis to superimpose it on the low-frequency signal are made in a digital domain. The output of each DAC is switched by an analog multiplexer.

Signal generating device

A waveguide type optical switch that can reduce the number of intersections in a matrix optical switch having the configuration of connecting unit optical switches and optical combining devices or optical branching devices to have a connecting function from 'multiple inputs to one output' to 'one input to multiple outputs'. To reduce the number of intersections in an entire matrix optical switch, an optical combining device of M inputs and one output is divided into (M&#x2212;1) pieces of unit optical combining elements each having two inputs and one output, which are arranged immediately after (N&#x2212;1) pieces of respective output ports excluding one piece of the output port closer to the input in the matrix optical switch out of N pieces of the output ports in the optical switch of one input and N outputs.

Waveguide type optical switch

An optical modulator comprises an input optical splitting unit for bifurcating input light; a final optical coupling unit for coupling optical signals in a polarization state orthogonal to each other; an intermediate optical coupling unit provided in an intermediate position between the input optical splitting unit and the final optical coupling unit; first and second optical paths for connecting the input optical splitting unit and the intermediate optical coupling unit, optical path lengths of the first and second optical paths are approximately equal; third and fourth optical paths for connecting the intermediate optical coupling unit and the final optical coupling unit, optical path lengths of third and fourth optical paths are approximately equal; and three binary phase modulation unit arranged one by one in each of the three optical paths of the first, second, third and fourth optical paths.

Optical modulator

An optical modulation circuit includes: a first Mach-Zehnder modulating portion including a first output port and a second output port, wherein the first Mach-Zehnder modulating portion is push-pull driven by a main signal; a second Mach-Zehnder modulating portion connected to the first output port of the first Mach-Zehnder modulating portion, wherein the second Mach-Zehnder modulating portion is push-pull driven by a correction signal; and an asymmetric light combining portion combining an optical signal outputted from an output port of the second Mach-Zehnder modulating portion with an optical signal outputted from the second output port of the first Mach-Zehnder modulating portion in a light intensity coupling ratio of r to 1&#x2212;r, wherein an optical path length from the first output port to the asymmetric light combining portion is substantially equal to an optical path length from the second output port to the asymmetric light combining portion.

Light modulation circuit

In a nest MZI modulator in which each arm includes a child MZI, the power consumption is reduced. The hybrid integrated-type nest MZI modulator of the embodiment 1a is configured so that, instead of placing a relative phase adjusting section in a parent MZI, a bias electrode Bias 90&#xb0; in which an electric field is applied in the same direction to the polarization direction in both of the upper and lower arms is placed in each child MZI (see FIG.B). The bias electrode Bias 90&#xb0; provided in each child MZI constitute the entirety of a relative phase adjusting section. The optical signals are subjected to a phase change after the output from the child MZI (see FIG.A), because such relative phase adjusting section can subject the optical signals of the upper and lower arms of the child MZI to a shift change in the same direction, respectively.

Advanced-format optical modulator with low power consumption and low-loss characteristics

An object of the present invention is to provide a temperature-independent optical frequency shifter for generating sub-carriers with a miniaturizable configuration, as well as to provide an all-optical OFDM modulator using the same that is compact, has low temperature dependence, and is even compatible with different frequency grids. Provided is an optical frequency shifter and an optical modulator using the same, the optical frequency shifter comprises one input optical port, a 1-input, 2-output optical coupler optically connected thereto, two Mach-Zehnder modulation units individually optically connected to the two outputs thereof, a 2-input, 2-output optical coupler optically connected to the individual outputs thereof, and two output optical ports optically connected to the outputs thereof, wherein the two Mach-Zehnder modulation units are driven by periodic waveforms at the same frequency whose phases differ from each other by (2p+1)&#x3c0;/2 (p: integer).

Optical frequency shifter and optical modulator using the same

An optical modulator that supports a plurality of modulation formats is provided. The optical modulator includes: a distribution part including an optical demultiplexing/variable-branching switchable circuit; an optical modulator array; and an aggregation part including a combining ratio variable combining circuit and/or an optical multiplexing/variable-combining switchable circuit. The distribution part forms any or a combination of a variable 1&#xd7;M demultiplexer/brancher, a combination of one or more fixed ILFs and an optical switch and a combination of a plurality of variable optical couplers and an optical switch; the optical modulator array includes a plurality of optical modulators; the aggregation part includes a structure of any or a combination of one or more variable optical couplers, a combination of a plurality of variable attenuators, an M&#xd7;1 variable coupler, a variable M&#xd7;1 demultiplexer/brancher and a combination of one or more fixed ILFs and an optical switch.

A interferometer type polarization beam combiner and splitter, which can combine or split polarized light over a wide band, is provided. The interferometer type polarization beam combiner and splitter includes: an optical splitter; an optical coupler; an optical path length difference imparting unit, which includes a plurality of optical waveguides arranged between the optical splitting unit and the optical coupling unit; one or two input/output ports connected to the optical splitter; and two input/output ports connected to the optical coupler. A half-integer of a wavelength of &#x3bb;c is set as a normalized phase difference, for the optical path length difference imparting unit, between two polarization states, and means for generating a difference in refractive index dispersion is provided between the optical waveguides of the optical path length difference imparting unit, so that the change rate of the transmittance with respect to wavelength is suppressed for the two polarization states.

Wideband interferometer type polarization light beam combiner and splitter

In an optical component configured to fix to a mount an optical device chip in which waveguide type optical devices having different thermal expansion coefficients are butt-jointed, deterioration in reliability due to thermal stress is suppressed. The optical component () comprises an optical device chip () including an LN waveguide (), a first PLC waveguide (), a second PLC waveguide (), and a fiber alignment member (), a mount (), and optical fibers (). Each of connection faces between the first PLC waveguide and the fiber alignment member is configured as an tilted structure, and each of connection faces between the LN waveguide, and the first and second PLC waveguides is configured as a right-angled structure. In the right-angled structure, the connection faces are connected by an adhesive having a lower Young's modulus than that of an adhesive used on the connection faces of the tilted structure.

Optical component

Disclosed is an optical modulator which substantially lowers loss and has little attenuation in the intensity of an optical signal after modulation. The optical modulator includes a 1&#xd7;2 RZ pulse carver wherein optical phase shifters used for modulation are arranged along two arm waveguides held between a 1&#xd7;2 coupler and a 2&#xd7;2 coupler, two interferometric modulators connected respectively to two output ports of the 2&#xd7;2 coupler, and a 2&#xd7;1 coupler for combining the outputs of the interferometric modulators.

Load control system is for disconnecting abnormal sub-bus from main-bus; The load control system has switching circuit (50+51) for connecting the sub-bus (1A, 1B . . . 1N) to the main-bus (2) or disconnecting sub-bus (1A, 1B, . . . 1N) from the main-bus (2) and bus watch device (30A, 30B . . . 30N) for detecting abnormal state of the sub-bus and for operating the switching circuit to disconnect the abnormal sub-bus from the main-bus (2).

Load control system and method for disconnecting sub-bus from main-bus

Load control system is for disconnecting abnormal sub-bus from main-bus; The load control system has switching circuit (50+51) for connecting the sub-bus (1A, 1B . . . 1N) to the main-bus (2) or disconnecting sub-bus (1A, 1B, . . . 1N) from the main-bus (2) and bus watch device (30A, 30B . . . 30N) for detecting abnormal state of the sub-bus and for operating the switching means to disconnect the abnormal sub-bus from the main-bus (2).

Growing community of inventors

Atsugi, Japan

Hiroshi Yamazaki