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公开(公告)号：US20240039233A1
公开(公告)日：2024-02-01
申请号：US18021889
申请日：2020-08-25
Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
Inventor： Hiroto KAWAKAMI , Shoichiro KUWAHARA , Yoshiaki KISAKA
CPC classification number: H01S3/094011 , H01S3/094076 , H01S3/06754 , H01S3/094053 , G02B27/283 , H01S3/302
Abstract: A pump light generation unit of an optical amplifier pumping device outputs pump light with a single wavelength or a plurality of wavelengths from a plurality of output ports. A pump light multiplexing unit polarization-multiplexes or wavelength-multiplexes the plurality of pieces of pump light which has been output from the pump light generation unit. A polarization scrambler collectively polarization-scrambles the polarization-multiplexed or wavelength-multiplexed pump light which has been output from the pump light multiplexing unit and outputs the polarization-scrambled pump light to an optical waveguide for pump light. The optical waveguide for pump light inputs the pump light which has been polarization-multiplexed or wavelength-multiplexed by the pump light multiplexing unit to the pump light superimposition unit. A pump light superimposition unit multiplexes the polarization-multiplexed or wavelength-multiplexed pump light and signal light. A pump light output port superimposes the pump light on the signal light by outputting the pump light from the pump light superimposition unit to the gain medium so that the pump light propagates in the same direction as the signal light.
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公开(公告)号：US20240004132A1
公开(公告)日：2024-01-04
申请号：US18039094
申请日：2020-12-01
Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
Inventor： Hiroto KAWAKAMI , Shoichiro KUWAHARA , Yoshiaki KISAKA
Abstract: A depolarizer for depolarizing input light having a plurality of linearly polarized waves whose optical frequency interval is f includes: an input optical waveguide configured to propagate the input light while maintaining linear polarization; a first polarization-maintaining coupler configured to bifurcate the linearly polarized waves output from the input optical waveguide to a first arm and a second arm while maintaining a polarization state; a second polarization-maintaining coupler configured to polarization-multiplex and output the linearly polarized waves propagated through the first arm and the second arm; and a polarization-maintaining variable optical delay line arranged on at least one of the first arm or the second arm, in which the variable optical delay line is adjusted such that a difference in delay time between the linearly polarized waves propagated through the first arm and the second arm becomes close to (n+0.5)/f where n is an arbitrary integer.
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公开(公告)号：US20180323878A1
公开(公告)日：2018-11-08
申请号：US15774897
申请日：2016-11-10
Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
Inventor： Hiroto KAWAKAMI , Shoichiro KUWAHARA , Akira HIRANO
IPC: H04B10/516
CPC classification number: H04B10/50575 , G02F1/0123 , G02F1/225 , H04B10/50577 , H04B10/516
Abstract: An optical transmitter includes: an optical modulator including an MZ interferometer, a drive signal input electrode, and a phase difference adjustment bias electrode; a drive amplifier; a phase difference adjustment bias voltage generator; a dithering unit that applies dithering of a predetermined frequency to an amplitude of a drive signal or to a half-wave voltage of the MZ interferometer; a controller unit that changes a phase difference adjustment bias voltage based on a modulation component of the frequency that is superimposed onto modulated light that is output from the optical modulator, to thereby bias the MZ interferometer to a null point; and a synchronous detection circuit that synchronously detects the modulation component of the frequency that is superimposed onto the modulated light. The controller unit changes the phase difference adjustment bias voltage such that a result of synchronous detection by the synchronous detection circuit becomes maximized or minimized. Whether the controller unit maximizes or minimizes the result of synchronous detection is determined by a difference between a phase of a referenced clock signal and a phase of the dithering, and does not depend on the amplitude of the drive signal.
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公开(公告)号：US20230004027A1
公开(公告)日：2023-01-05
申请号：US17781339
申请日：2019-12-11
Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
Inventor： Hiroto KAWAKAMI , Shoichiro KUWAHARA , Yoshiaki KISAKA
IPC: G02F1/01 , H04B10/556
Abstract: Provided is a first bias power source that generates a first data bias voltage to be applied to an optical modulation unit for the I component, a second bias power source that generates a second data bias voltage to be applied to an optical modulation unit for the Q component, and a third bias power source that generates a quadrature bias voltage to be applied to an optical phase shifter, a data bias voltage adjustment unit that applies a feedback control to each of the first bias power source and the second bias power source, and a quadrature bias voltage adjustment unit that determines whether or not the quadrature bias voltage is optimal on a basis of a second optical QAM signal generated by an IQ optical modulator, and applies a feedback control to the third bias power source, in which a first optical QAM signal and the second optical QAM signal are generated by the IQ optical modulator but the optical phase difference between an optical electric field EI and an optical electric field EQ differs by π.
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公开(公告)号：US20200133035A1
公开(公告)日：2020-04-30
申请号：US16629174
申请日：2018-07-12
Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
Inventor： Hiroto KAWAKAMI , Shoichiro KUWAHARA , Akira HIRANO
Abstract: A control unit of a bias control circuit performs a loop process that fixes a second bias voltage and iterates a process of recording a pair of a first candidate bias voltage and a second candidate bias voltage that are a first bias voltage when optical power of a multi-level QAM signal output by an optical modulator is controlled so that the optical power converges to a value in the vicinity of the maximum value or the minimum value before and after a third bias voltage is increased or decreased by a half-wave voltage while changing the second bias voltage within a predetermined range. The control unit calculates the difference between the first candidate bias voltage and the second candidate bias voltage for each of a plurality of recorded pairs and determines a value between first candidate bias voltage and the second candidate bias voltage of a pair selected on the basis of the calculated difference as the value of the first bias voltage.
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Patent Agency Ranking
公开(公告)号：US20250028217A1
公开(公告)日：2025-01-23
申请号：US18715580
申请日：2022-10-17
Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
Inventor： Hiroto KAWAKAMI , Yoshiaki KISAKA , Shoichiro KUWAHARA
Abstract: A control circuit controls at least one optical path difference among optical path differences of two optical paths included in a single MZI or each of a plurality of the MZIs included in an optical circuit. The control circuit includes a reference light generation unit, a reference light input unit, an optical power monitor unit, and a controller. The reference light generation unit generates reference light respectively having N types (N is a natural number) of wavelengths different from the wavelength λ of input light input to the optical circuit in parallel or in a time division manner. A reference light input unit inputs the reference light to the optical circuit. The optical power monitor unit monitors a light intensity of propagated input light which is input light that has propagated through the optical circuit, and a light intensity of propagated reference light which is reference light that has propagated through the optical circuit, or a light intensity of light obtained by multiplexing the propagated input light and the propagated reference light. The controller performs control to correct the optical path difference on the basis of the light intensity of the propagated input light and the light intensities of N types of propagated reference light, which are obtained using the monitoring result.
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公开(公告)号：US20220216923A1
公开(公告)日：2022-07-07
申请号：US17595161
申请日：2019-05-23
Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
Inventor： Asuka MATSUSHITA , Masanori NAKAMURA , Kengo HORIKOSHI , Shoichiro KUWAHARA , Yoshiaki KISAKA
IPC: H04B10/61
Abstract: An optical transmission system according to an embodiment includes: an optical transmission unit which modulates an optical signal into which a known signal is inserted and transmits the optical signal; and an optical reception unit which receives the optical signal from the optical transmission unit, wherein the optical reception unit includes: an optical receiver which performs coherent detection of a reception signal of the optical signal received from the optical transmission unit; a receiver transfer function estimation section which estimates a nonlinear response transfer function of the optical receiver based on the known signal included in the reception signal after the detection by the optical receiver; and a receiver compensation section which compensates nonlinear distortion of the reception signal after the detection based on the nonlinear response transfer function which the receiver transfer function estimation section estimates.
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公开(公告)号：US20250158345A1
公开(公告)日：2025-05-15
申请号：US18840031
申请日：2022-09-14
Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
Inventor： Hiroto KAWAKAMI , Takayuki KOBAYASHI , Yoshiaki KISAKA , Shoichiro KUWAHARA
Abstract: A pump light generation device including: a first multi-mode laser that outputs first pump light; a second multi-mode laser that outputs second pump light; a first pump current/temperature controller that controls a temperature and a pump current of the first multi-mode laser; a second pump current/temperature controller that controls a temperature and a pump current of the second multi-mode laser; a first polarization maintaining variable optical attenuator that adjusts a light intensity while keeping a polarization state in a linearly polarized wave and outputs the first pump light; a second polarization maintaining variable optical attenuator that adjusts a light intensity while keeping a polarization state in a linearly polarized wave and outputs the second pump light; and a polarization multiplexing circuit that polarization-multiplexes and output the pump light, in which the first pump current/temperature controller and the second pump current/temperature controller perform control such that the longitudinal modes in the first pump light and the second pump light do not overlap each other, and the first polarization maintaining variable optical attenuator and the second polarization maintaining variable optical attenuator perform control such that intensities are equal to each other.
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9.发明公开公开(公告)号：US20240258760A1
公开(公告)日：2024-08-01
申请号：US18627950
申请日：2024-04-05
Applicant: Nippon Telegraph and Telephone Corporation
Inventor： Hiroto KAWAKAMI , Shoichiro KUWAHARA , Yoshiaki KISAKA
IPC: H01S3/10 , H01S3/30 , H04B10/2525 , H04J14/02
CPC classification number: H01S3/1001 , H01S3/10015 , H01S3/302 , H04B10/2525 , H04J14/0221 , H04B2210/25
Abstract: An aspect of the present invention is a distributed optical amplifier which includes: a pump light generator which generates pump light for optically exciting an optical transmission line; and a multiplexer which multiplexes n kinds (n is a positive integer) of light to be amplified and the pump light output from the pump light generator, and outputs the multiplexed light to the optical transmission line. When a center wavelength of the n kinds of light to be amplified is denoted as λS1 to λSn and a zero-dispersion wavelength of the optical transmission line is denoted as λ0, intensity of the pump light generated by the pump light generator is suppressed at n kinds of wavelengths represented by 2×λ0−λS1 to 2×λ0−λSn in comparison to intensity of other wavelengths of the pump light generated by the pump light generator.
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公开(公告)号：US20220263645A1
公开(公告)日：2022-08-18
申请号：US17628041
申请日：2019-07-25
Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
Inventor： Hiroto KAWAKAMI , Shoichiro KUWAHARA , Yoshiaki KISAKA
IPC: H04L7/02
Abstract: A synchronization detection device includes: a correction unit configured to correct sampled data of a waveform on which a dither signal is superimposed, for each period of a reference signal in accordance with a period of the dither signal; a multiplication unit configured to multiply the corrected sampled data by a weight coefficient that is different for each level of the reference signal and associated with a timing of the reference signal; and an averaging unit configured to derive, as a detection result, an average of a result of the multiplication of the corrected sampled data by the weight coefficient.
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