Patents by Inventor Tsutomu Kitoh
Tsutomu Kitoh has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).
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Patent number: 9306670Abstract: The present invention relates to an optical coupling/splitting device that realizes the splitting of a down-signal and the coupling of up-signals by the same optical device, and reduces coupling losses of the up-signal. An optical coupling/splitting device in the present invention comprises an optical coupling/splitting means for coupling a plurality of up-signals in a multi-mode for output and splitting a down-signal in a single mode for output, and a two-way optical propagation means for propagating the up-signal that is output from the optical coupling/splitting means in a multi-mode for output and propagate the down-signal in a single mode to be output to the optical coupling/splitting means.Type: GrantFiled: September 27, 2012Date of Patent: April 5, 2016Assignee: Nippon Telegraph and Telephone CorporationInventors: Masamichi Fujiwara, Kenichi Suzuki, Naoto Yoshimoto, Manabu Oguma, Toshio Watanabe, Hiroshi Takahashi, Hiromasa Tanobe, Tsutomu Kitoh
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Patent number: 9116305Abstract: An arrayed waveguide grating provided with a first slab waveguide formed on a substrate; a second slab waveguide formed on the substrate; a first input/output waveguide connected to the first slab waveguide; a second input/output waveguide connected to the second slab waveguide; two or more channel waveguide groups connecting the first and second slab waveguides, each of the channel waveguide groups formed of an aggregate of a plurality of channel waveguides having path lengths sequentially becoming longer by a predetermined path length difference; and an optical filter arranged in at least one of the first and second slab waveguides.Type: GrantFiled: December 28, 2012Date of Patent: August 25, 2015Assignee: Nippon Telegraph and Telephone CorporationInventors: Hirotaka Nakamura, Shinya Tamaki, Shunji Kimura, Takayuki Mizuno, Hiroshi Takahashi, Mikitaka Itoh, Tsutomu Kitoh
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Publication number: 20140376861Abstract: An arrayed waveguide grating provided with a first slab waveguide formed on a substrate; a second slab waveguide formed on the substrate; a first input/output waveguide connected to the first slab waveguide; a second input/output waveguide connected to the second slab waveguide; two or more channel waveguide groups connecting the first and second slab waveguides, each of the channel waveguide groups formed of an aggregate of a plurality of channel waveguides having path lengths sequentially becoming longer by a predetermined path length difference; and an optical filter arranged in at least one of the first and second slab waveguides.Type: ApplicationFiled: December 28, 2012Publication date: December 25, 2014Inventors: Hirotaka Nakamura, Shinya Tamaki, Shunji Kimura, Takayuki Mizuno, Hiroshi Takahashi, Mikitaka Itoh, Tsutomu Kitoh
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Patent number: 8787710Abstract: 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 ?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.Type: GrantFiled: June 2, 2010Date of Patent: July 22, 2014Assignee: Nippon Telegraph and Telephone CorporationInventors: Takayuki Mizuno, Takashi Goh, Hiroshi Yamazaki, Shin Kamei, Tsutomu Kitoh
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Publication number: 20140186040Abstract: The present invention relates to an optical coupling/splitting device that realizes the splitting of a down-signal and the coupling of up-signals by the same optical device, and reduces coupling losses of the up-signal. An optical coupling/splitting device in the present invention comprises an optical coupling/splitting means for coupling a plurality of up-signals in a multi-mode for output and splitting a down-signal in a single mode for output, and a two-way optical propagation means for propagating the up-signal that is output from the optical coupling/splitting means in a multi-mode for output and propagate the down-signal in a single mode to be output to the optical coupling/splitting means.Type: ApplicationFiled: September 27, 2012Publication date: July 3, 2014Inventors: Masamichi Fujiwara, Kenichi Suzuki, Naoto Yoshimoto, Manabu Oguma, Toshio Watanabe, Hiroshi Takahashi, Hiromasa Tanobe, Tsutomu Kitoh
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Patent number: 8737779Abstract: An optical wavelength multi/demultiplexer having transmission characteristics with a higher rectangular degree than a conventional one includes an AWG and two-stage lattice circuit. An example of a two-stage lattice circuit according to the present invention includes an input waveguide, a third optical coupler, a third and fourth arm waveguides, a second optical coupler, a first and second arm waveguides, a first optical coupler, and output waveguides. The optical path length differences between the third and fourth arm waveguides and between the first and second arm waveguides are designed to be ?L. The path passing the third and first arm waveguides differs by 2·?L in optical length from that the fourth and second arm waveguides. The paths passing the third and second arm waveguides and passing the fourth and first arm waveguides differ by ?L from that passing the fourth and second arm waveguides.Type: GrantFiled: August 25, 2010Date of Patent: May 27, 2014Assignee: Nippon Telegraph and Telephone CorporationInventors: Tsutomu Kitoh, Shin Kamei, Toshikazu Hashimoto, Yohei Sakamaki, Hiroshi Takahashi, Manabu Oguma
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Patent number: 8554040Abstract: A planar lightwave circuit is provided which can be easily fabricated by an existing planar-lightwave-circuit fabrication process, which can lower the propagation loss of signal light and which can convert inputted signal light so as to derive desired signal light. A planar lightwave circuit having a core and a clad which are formed on a substrate, has input optical waveguide(s) (111) which inputs signal light, mode coupling part (112) for coupling a fundamental mode of the inputted signal light to a higher-order mode and/or a radiation mode, or mode re-coupling part (113) for re-coupling the higher-order mode and/or the radiation mode to the fundamental mode, and output optical waveguide(s) (114) which outputs signal light. The mode coupling part or the mode re-coupling part is an optical waveguide which has core width and/or height varied continuously.Type: GrantFiled: July 25, 2012Date of Patent: October 8, 2013Assignee: Nippon Telegraph and Telephone CorporationInventors: Takashi Saida, Yohei Sakamaki, Toshikazu Hashimoto, Tsutomu Kitoh, Hiroshi Takahashi, Masahiro Yanagisawa, Senichi Suzuki, Yasuhiro Hida, Motohaya Ishii, Munehisa Tamura
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Patent number: 8538222Abstract: A planar lightwave circuit is provided which can be easily fabricated by an existing planar-lightwave-circuit fabrication process, which can lower the propagation loss of signal light and which can convert inputted signal light so as to derive desired signal light. A planar lightwave circuit having a core and a clad which are formed on a substrate, has input optical waveguide(s) (111) which inputs signal light, mode coupling part (112) for coupling a fundamental mode of the inputted signal light to a higher-order mode and/or a radiation mode, or mode re-coupling part (113) for re-coupling the higher-order mode and/or the radiation mode to the fundamental mode, and output optical waveguide(s) (114) which outputs signal light. The mode coupling part or the mode re-coupling part is an optical waveguide which has core width and/or height varied continuously.Type: GrantFiled: July 25, 2012Date of Patent: September 17, 2013Assignee: Nippon Telegraph and Telephone CorporationInventors: Takashi Saida, Yohei Sakamaki, Toshikazu Hashimoto, Tsutomu Kitoh, Hiroshi Takahashi, Masahiro Yanagisawa, Senichi Suzuki, Yasuhiro Hida, Motohaya Ishii, Munehisa Tamura
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Patent number: 8483525Abstract: When a conventional synchronized AWG is employed to extend a transmission passband, an increase in loss near the optical center frequency can not be avoided. Because of passband width limit, a problem has existed in that the synchronized AWG could not be applied for a large, complicated communication system wherein a signal light passes a number of points. Therefore, an optical wavelength multiplexing/demultiplexing circuit of the present invention is a synchronized AWG, which includes an optical splitter arranged in an interference circuit that is connected on the side of one slab waveguide. The splitting ratio of the optical splitter varies, depending on the optical frequency, and the value becomes minimum near the optical center frequency of the synchronized AWG. The optical splitter is operated so that the splitting ratio is comparatively great at optical frequencies distant from the optical center frequency.Type: GrantFiled: January 8, 2010Date of Patent: July 9, 2013Assignee: Nippon Telegraph and Telephone CorporationInventors: Tsutomu Kitoh, Shin Kamei, Toshikazu Hashimoto, Yohei Sakamaki, Hiroshi Takahashi, Manabu Oguma
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Patent number: 8463097Abstract: A planar lightwave circuit is provided which can be easily fabricated by an existing planar-lightwave-circuit fabrication process, which can lower the propagation loss of signal light and which can convert inputted signal light so as to derive desired signal light. A planar lightwave circuit having a core and a clad which are formed on a substrate, has input optical waveguide(s) (111) which inputs signal light, mode coupling part (112) for coupling a fundamental mode of the inputted signal light to a higher-order mode and/or a radiation mode, or mode re-coupling part (113) for re-coupling the higher-order mode and/or the radiation mode to the fundamental mode, and output optical waveguide(s) (114) which outputs signal light. The mode coupling part or the mode re-coupling part is an optical waveguide which has core width and/or height varied continuously.Type: GrantFiled: July 12, 2010Date of Patent: June 11, 2013Assignee: Nippon Telegraph and Telephone CorporationInventors: Takashi Saida, Yohei Sakamaki, Toshikazu Hashimoto, Tsutomu Kitoh, Hiroshi Takahashi, Masahiro Yanagisawa, Senichi Suzuki, Yasuhiro Hida, Motohaya Ishii, Munehisa Tamura
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Patent number: 8369666Abstract: An optical wavelength multiplexing/de-multiplexing circuit having a low loss and a flat transmission spectrum is provided. The optical wavelength multiplexing/de-multiplexing circuit compensates a temperature dependence of a center transmission wavelength which remains in an athermal AWG, and has an excellent accuracy of the center transmission wavelength in a whole operating temperature range or has a comparatively wide operable temperature range. The temperature dependence of the transmission wavelength in the athermal MZI is modulated and set so as to cancel the temperature dependence of the center wavelength which remains in the athermal AWG. The present invention focuses particularly on an optical coupler in the MZI and modulates the temperature dependence of the transmission wavelength in the MZI by providing the optical coupler itself with a mechanism which changes a phase difference between two outputs by temperature.Type: GrantFiled: June 30, 2009Date of Patent: February 5, 2013Assignee: Nippon Telegraph and Telephone CorporationInventors: Shin Kamei, Tsutomu Kitoh, Masaki Kohtoku, Tomohiro Shibata, Takuya Tanaka, Yasuyuki Inoue, Mikitaka Itoh
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Publication number: 20120311516Abstract: A planar lightwave circuit is provided which can be easily fabricated by an existing planar-lightwave-circuit fabrication process, which can lower the propagation loss of signal light and which can convert inputted signal light so as to derive desired signal light. A planar lightwave circuit having a core and a clad which are formed on a substrate, has input optical waveguide(s) (111) which inputs signal light, mode coupling part (112) for coupling a fundamental mode of the inputted signal light to a higher-order mode and/or a radiation mode, or mode re-coupling part (113) for re-coupling the higher-order mode and/or the radiation mode to the fundamental mode, and output optical waveguide(s) (114) which outputs signal light. The mode coupling part or the mode re-coupling part is an optical waveguide which has core width and/or height varied continuously.Type: ApplicationFiled: July 25, 2012Publication date: December 6, 2012Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Takashi Saida, Yohei Sakamaki, Toshikazu Hashimoto, Tsutomu Kitoh, Hiroshi Takahashi, Masahiro Yanagisawa, Senichi Suzuki, Yasuhiro Hida, Motohaya Ishii, Munehisa Tamura
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Publication number: 20120304143Abstract: A planar lightwave circuit is provided which can be easily fabricated by an existing planar-lightwave-circuit fabrication process, which can lower the propagation loss of signal light and which can convert inputted signal light so as to derive desired signal light. A planar lightwave circuit having a core and a clad which are formed on a substrate, has input optical waveguide(s) (111) which inputs signal light, mode coupling part (112) for coupling a fundamental mode of the inputted signal light to a higher-order mode and/or a radiation mode, or mode re-coupling part (113) for re-coupling the higher-order mode and/or the radiation mode to the fundamental mode, and output optical waveguide(s) (114) which outputs signal light. The mode coupling part or the mode re-coupling part is an optical waveguide which has core width and/or height varied continuously.Type: ApplicationFiled: July 25, 2012Publication date: November 29, 2012Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Takashi Saida, Yohei Sakamaki, Toshikazu Hashimoto, Tsutomu Kitoh, Hiroshi Takahashi, Masahiro Yanagisawa, Senichi Suzuki, Yasuhiro Hida, Motohaya Ishii, Munehisa Tamura
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Publication number: 20120170891Abstract: An optical wavelength multi/demultiplexer having transmission characteristics with a higher rectangular degree than a conventional one includes an AWG and two-stage lattice circuit. An example of a two-stage lattice circuit according to the present invention includes an input waveguide, a third optical coupler, a third and fourth arm waveguides, a second optical coupler, a first and second arm waveguides, a first optical coupler, and output waveguides. The optical path length differences between the third and fourth arm waveguides and between the first and second arm waveguides are designed to be ?L. The path passing the third and first arm waveguides differs by 2·?L in optical length from that the fourth and second arm waveguides. The paths passing the third and second arm waveguides and passing the fourth and first arm waveguides differ by ?L from that passing the fourth and second arm waveguides.Type: ApplicationFiled: August 25, 2010Publication date: July 5, 2012Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Tsutomu Kitoh, Shin Kamei, Toshikazu Hashimoto, Yohei Sakamaki, Hiroshi Takahashi, Manabu Oguma
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Publication number: 20120063716Abstract: 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 ?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.Type: ApplicationFiled: June 2, 2010Publication date: March 15, 2012Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Takayuki Mizuno, Takashi Goh, Hiroshi Yamazaki, Shin Kamei, Tsutomu Kitoh
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Publication number: 20110268447Abstract: When a conventional synchronized AWG is employed to extend a transmission passband, an increase in loss near the optical center frequency can not be avoided. Because of passband width limit, a problem has existed in that the synchronized AWG could not be applied for a large, complicated communication system wherein a signal light passes a number of points. Therefore, an optical wavelength multiplexing/demultiplexing circuit of the present invention is a synchronized AWG, which includes an optical splitter arranged in an interference circuit that is connected on the side of one slab waveguide. The splitting ratio of the optical splitter varies, depending on the optical frequency, and the value becomes minimum near the optical center frequency of the synchronized AWG. The optical splitter is operated so that the splitting ratio is comparatively great at optical frequencies distant from the optical center frequency.Type: ApplicationFiled: January 8, 2010Publication date: November 3, 2011Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Tsutomu Kitoh, Shin Kamei, Toshikazu Hashimoto, Yohei Sakamaki, Hiroshi Takahashi, Manabu Oguma
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Publication number: 20110116802Abstract: An optical wavelength multiplexing/de-multiplexing circuit having a low loss and a flat transmission spectrum is provided. The optical wavelength multiplexing/de-multiplexing circuit compensates a temperature dependence of a center transmission wavelength which remains in an athermal AWG, and has an excellent accuracy of the center transmission wavelength in a whole operating temperature range or has a comparatively wide operable temperature range. The temperature dependence of the transmission wavelength in the athermal MZI is modulated and set so as to cancel the temperature dependence of the center wavelength which remains in the athermal AWG. The present invention focuses particularly on an optical coupler in the MZI and modulates the temperature dependence of the transmission wavelength in the MZI by providing the optical coupler itself with a mechanism which changes a phase difference between two outputs by temperature.Type: ApplicationFiled: June 30, 2009Publication date: May 19, 2011Applicant: Nippon Telegraph and Telephone CorporationInventors: Shin Kamei, Tsutomu Kitoh, Masaki Kohtoku, Tomohiro Shibata, Takuya Tanaka, Yasuyuki Inoue, Mikitaka Itoh
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Patent number: 7856163Abstract: A planar lightwave circuit is provided which can be easily fabricated by an existing planar-lightwave-circuit fabrication process, which can lower the propagation loss of signal light and which can convert inputted signal light so as to derive desired signal light. A planar lightwave circuit having a core and a clad which are formed on a substrate, has input optical waveguide(s) (111) which inputs signal light, mode coupling part (112) for coupling a fundamental mode of the inputted signal light to a higher-order mode and/or a radiation mode, or mode re-coupling part (113) for re-coupling the higher-order mode and/or the radiation mode to the fundamental mode, and output optical waveguide(s) (114) which outputs signal light. The mode coupling part or the mode re-coupling part is an optical waveguide which has core width and/or height varied continuously.Type: GrantFiled: August 1, 2005Date of Patent: December 21, 2010Assignee: Nippon Telegraph and Telephone CorporationInventors: Takashi Saida, Yohei Sakamaki, Toshikazu Hashimoto, Tsutomu Kitoh, Hiroshi Takahashi, Masahiro Yanagisawa, Senichi Suzuki, Yasuhiro Hida, Motohaya Ishii, Munehisa Tamura
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Publication number: 20100274541Abstract: A planar lightwave circuit is provided which can be easily fabricated by an existing planar-lightwave-circuit fabrication process, which can lower the propagation loss of signal light and which can convert inputted signal light so as to derive desired signal light. A planar lightwave circuit having a core and a clad which are formed on a substrate, has input optical waveguide(s) (111) which inputs signal light, mode coupling part (112) for coupling a fundamental mode of the inputted signal light to a higher-order mode and/or a radiation mode, or mode re-coupling part (113) for re-coupling the higher-order mode and/or the radiation mode to the fundamental mode, and output optical waveguide(s) (114) which outputs signal light. The mode coupling part or the mode re-coupling part is an optical waveguide which has core width and/or height varied continuously.Type: ApplicationFiled: July 12, 2010Publication date: October 28, 2010Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Takashi Saida, Yohei Sakamaki, Toshikazu Hashimoto, Tsutomu Kitoh, Hiroshi Takahashi, Masahiro Yanagisawa, Senichi Suzuki, Yasuhiro Hida, Motohaya Ishii, Munehisa Tamura
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Patent number: 7590312Abstract: The present invention discloses an interferometer optical switch that can carry out switching over a broad band and has a high extinction ratio and large fabrication tolerance. The interferometer optical switch employs a phase generating coupler, the phase difference of the output of which has wavelength dependence, as at least one of the optical multi/demultiplexing device included in the interferometer optical switch. A wavelength insensitive interferometer optical switch is implemented by making the sum 2?{?1(?)+??L(?)+?2(?)} constant regardless of the wavelength, where ?1(?) is the phase produced by the first optical multi/demultiplexing device, 2???L(?) is the phase difference of the optical delay line with an optical path length difference of ?L, and 2??2(?) is the phase produced by the second optical multi/demultiplexing device.Type: GrantFiled: July 2, 2004Date of Patent: September 15, 2009Assignee: Nippon Telegraph and Telephone CorporationInventors: Takayuki Mizuno, Hiroshi Takahashi, Tsutomu Kitoh, Manabu Oguma, Shunichi Souma