Patents by Inventor Masatoshi Saruwatari

Masatoshi Saruwatari 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).

  • Patent number: 6204944
    Abstract: An all-optical time-division demultiplexing circuit is designed to output all the channels of time-division multiplexed signal pulses to different output ports simultaneously. A pulse stream of time-division multiplexed signal pulses and linearly chirped control pulses synchronized with the signal channels are input into an optical Kerr medium. The optical Kerr medium provides locally cross-phase modulation to the control pulse, depending on the presence or absence of the signal pulses of each signal channel. And the optical Kerr medium modulates the power of the component frequencies &ugr;1, &ugr;2, . . . , &ugr;N of the control pulses in accordance with each of the signal channel, by inducing the optical frequency shift to compensate the control pulse chirp on the optical frequency axis. The Kerr medium outputs a power modulated control light, which is separated in a wavelength-division demultiplexing circuit into component frequencies &ugr;1, &ugr;2, . . .
    Type: Grant
    Filed: July 15, 1998
    Date of Patent: March 20, 2001
    Assignee: Nippon Telegraph and Telephone Corporation
    Inventors: Kentaro Uchiyama, Satoki Kawanishi, Masatoshi Saruwatari
  • Patent number: 6023360
    Abstract: A multiple-channel all-optical TDM-WDM converter and multiple-channel all-optical TDM demultiplexer which is able to simultaneously and spatially separate optical signal pulse trains of each channel from a TDM optical signal pulse train is structured without using a multistage-structure constitution. A control optical source 10 generates a control optical pulse train containing N optical frequencies, which is synchronous with optical signal pulse trains of N channels which are to be divided from a TDM optical signal pulse train wherein optical signal pulse trains of N channels have been multiplexed in time series. An optical wavelength multiplexer 11 combines the time-division-multiplexed optical signal pulse train and the control optical pulse train.
    Type: Grant
    Filed: July 14, 1997
    Date of Patent: February 8, 2000
    Assignee: Nippon Telegraph and Telephone Corporation
    Inventors: Toshio Morioka, Hidehiko Takara, Masatoshi Saruwatari
  • Patent number: 5999548
    Abstract: The present invention relates to a white pulse source that produces spectrally shaped white pulses of a constant optical output power over a wide wavelength range. The white pulse source includes a pump pulse source for generating pump pulses with a center wavelength .lambda.0 and a waveguided nonlinear optical medium with a length L. The waveguided nonlinear optical medium is characterized by two properties: the first property is that chromatic dispersion D(.lambda.0,z) at the center wavelength of pump pulses in ps/nm/km is positive at an input end of said waveguided nonlinear optical medium, where z=0, and decreases towards an output end. The second property is that said chromatic dispersion D(.lambda., z) has a maximum value D(.lambda.p(z), z) at a peak wavelength .lambda.p(z) within a range of propagation distance given by L1.ltoreq.z.ltoreq.L where 0.ltoreq.L1<L, and that said chromatic dispersion D(.lambda., z) has two zero-dispersion wavelengths, .lambda.1(z) and .lambda.2(z), where D(.lambda.
    Type: Grant
    Filed: June 16, 1998
    Date of Patent: December 7, 1999
    Assignee: Nippon Telegraph and Telephone Corporation
    Inventors: Kunihiko Mori, Hidehiko Takara, Satoki Kawanishi, Masatoshi Saruwatari
  • Patent number: 5923683
    Abstract: A coherent white light source generates a uniform and continuous coherent white light spectra over 200 nm at a low pump power. The source is based on a pump light source which produces pump optical pulses at a wavelength .lambda..sub.0 and an optical waveguide to receive a pump optical pulse at .lambda..sub.0 to generate a white pulse having a wavelength spread of .DELTA..lambda.. The optical waveguide is characterized by having dispersion properties such that four-wave mixing light having a wavelength spread of .lambda..sub.0 .+-..DELTA..lambda./2 is produced, and the power gain of the four-wave mixing light is greater than 1. These properties of the waveguide are defined by: the path length of the waveguide device ln G.sub.0 /(2.vertline..gamma..vertline.P) in units of ?km!, an absolute value of the dispersion slope to be not more than 16(.vertline..gamma..vertline.E)(.DELTA..lambda..sup. ln G.sub.0) in units of ?ps/nm.sup.2 /km! and an absolute value of the dispersion at the wavelength .lambda..sub.
    Type: Grant
    Filed: February 23, 1996
    Date of Patent: July 13, 1999
    Assignee: Nippon Telegraph and Telephone Corporation
    Inventors: Toshio Morioka, Kunihiko Mori, Masatoshi Saruwatari
  • Patent number: 5724126
    Abstract: In the method of measuring a distribution of zero dispersion wavelengths in an optical fiber in a longitudinal direction, an optical pulse and a pump light are launched into the optical fiber. A gain generation portion of the optical fiber which indicates that the optical pulse power is amplified based on modulation instability induced by the pump light is detected from a back-scattered light waveform of the optical pulse indicative of an optical pulse power distribution in the longitudinal direction of the optical fiber. A zero dispersion wavelength of the gain generation portion of the optical fiber is determined from the pump light wavelength.
    Type: Grant
    Filed: May 5, 1995
    Date of Patent: March 3, 1998
    Assignee: Nippon Telegraph and Telephone Corporation
    Inventors: Shigendo Nishi, Katsumi Iwatsuki, Ken-ichi Suzuki, Masatoshi Saruwatari
  • Patent number: 5706113
    Abstract: It is an object of the present invention to provide an optical clock phase lock loop capable of a higher operational speed than the conventional technology by utilizing high-speed optical phenomena other than gain modulation. In an optical clock phase lock loop for conducting locking control by means of obtaining the correlation of an optical signal and optical clock, after combining an optical clock of a short pulse containing a harmonics component with an optical signal by means of an optical coupler 102, and providing the resultant light to traveling-wave semiconductor laser amplifier 103, the correlation signal of the optical signal and optical clock included in the output signal of this traveling-wave semiconductor laser amplifier 103 is detected by means of optical bandpass filter 104.
    Type: Grant
    Filed: June 5, 1996
    Date of Patent: January 6, 1998
    Assignee: Nippon Telegraph and Telephone Corporation
    Inventors: Satoki Kawanishi, Osamu Kamatani, Masatoshi Saruwatari
  • Patent number: 5646774
    Abstract: This invention is an improvement of a mode-locked laser stabilizing method and apparatus used with a mode-locked laser apparatus which comprises an optical cavity which consists of an optical modulator which modulates the loss or the phase of light at a fixed frequency, an optical delay line to electrically change the optical path length of the cavity, and an optical amplifier which amplifies a modulated optical pulses. In this method, at least one of the relaxation oscillation frequency components and the harmonic components in the output optical pulses of the mode-locked laser are extracted, and a process of controlling the optical delay line by using the extracted frequency component as an error signal for feedback control and to suppress the error signal below a fixed value.
    Type: Grant
    Filed: January 16, 1996
    Date of Patent: July 8, 1997
    Assignee: Nippon Telegraph and Telephone Corporation
    Inventors: Hidehiko Takara, Satoki Kawanishi, Masatoshi Saruwatari
  • Patent number: 5604618
    Abstract: The present invention provides an optical parametric circuit for separating four-wave-mixing wave(s) (FWM wave(s)) from signal wave(s) and/or pump waves without using a wavelength filtering device, and optical circuits using the same. The optical parametric circuit of the present invention is made by connecting two output ports of a 2.times.2 optical directional coupler to a nonlinear optical medium via dispersive optical media, each of which has a specific length and a specific propagation constant. By inputting signal waves having carrier angular frequencies .omega..sub.Sj (j=1, 2, . . . N) and pump waves having carrier angular frequencies .omega..sub.P1, .omega..sub.P2 into the first input port of the optical directional coupler, the FWM waves, generated in the nonlinear optical medium, having carrier angular frequencies .omega..sub.fj (=.omega..sub.P1 +.omega..sub.P2 -.omega..sub.S) are output from the second input port of the optical directional coupler.
    Type: Grant
    Filed: October 10, 1995
    Date of Patent: February 18, 1997
    Assignee: Nippon Telegraph and Telephone Corporation
    Inventors: Kunihiko Mori, Toshio Morioka, Masatoshi Saruwatari
  • Patent number: 5590143
    Abstract: A multiple-frequency-modulation mode-locked laser device which generates high-speed optical pulse trains and can be used as a high-speed optical pulse source in the fields of optical communications and optical measurement is presented, wherein the repetition frequency F.sub.rep and the pulse width .DELTA.t are able to be controlled independently with only the laser itself.A drive signal generation means is provided which generates a frequency-mixed drive signal mixed from at least two different frequencies f.sub.1 (=N.sub.1 f.sub.r), f.sub.2 (=N.sub.2 f.sub.r), . . . , which are integral multiples of the frequency spacing f.sub.r (=c/R) of the longitudinal modes of either a ring cavity or a Fabry-Perot cavity. This frequency-mixed drive signal is supplied to an optical modulation means of the cavity.
    Type: Grant
    Filed: March 2, 1995
    Date of Patent: December 31, 1996
    Assignee: Nippon Telegraph and Telephone Corporation
    Inventors: Hidehiko Takara, Satoki Kawanishi, Masatoshi Saruwatari
  • Patent number: 5574588
    Abstract: It is an object of the present invention to provide an optical clock phase lock loop capable of a higher operational speed than the conventional technology by utilizing high-speed optical phenomena other than gain modulation. In an optical clock phase lock loop for conducting locking control by obtaining the correlation of an optical signal and optical clock, after combining an optical clock of a short pulse containing a harmonics component with an optical signal by using an optical coupler 102, and providing the resultant light to traveling-wave semiconductor laser amplifier 103, the correlation signal of the optical signal and optical clock included in the output signal of this traveling-wave semiconductor laser amplifier 103 is detected by an optical bandpass filter 104.
    Type: Grant
    Filed: February 16, 1995
    Date of Patent: November 12, 1996
    Assignee: Nippon Telegraph and Telephone Corporation
    Inventors: Satoki Kawanishi, Osamu Kamatani, Masatoshi Saruwatari
  • Patent number: 5357359
    Abstract: An all-optical polarization independent optical time division multiplexer and demultiplexer which are stable as well as very fast, while being independent of the polarization state of the input optical signal pulses.
    Type: Grant
    Filed: August 11, 1993
    Date of Patent: October 18, 1994
    Assignee: Nippon Telegraph and Telephone Corporation
    Inventors: Kentaro Uchiyama, Toshio Morioka, Masatoshi Saruwatari
  • Patent number: 5267256
    Abstract: A wavelength division multiplex type mode-lock laser device which simultaneously generates high-speed optical pulse trains for more than one wavelength. This device simultaneously generates high-speed optical pulse trains at two or more wavelengths. A ring resonator type mode-lock laser device or a Fabry-Perot type mode-lock laser device is modified so that it has an optical path difference providing structure which provides different refractive indices for the polarization directions which are at right angles at one another. This enables configuring a resonator corresponding to the optical path lengths formed according to the refractive indices and hetero-wave length optical path equalizing means to provide different refractive indices for different wavelengths.
    Type: Grant
    Filed: September 14, 1992
    Date of Patent: November 30, 1993
    Assignee: Nippon Telegraph and Telephone Corporation
    Inventors: Masatoshi Saruwatari, Satoki Kawanishi, Hidehiko Takara, John Schlager
  • Patent number: 5083874
    Abstract: At least one optical repeater is connected in series to an optical signal transmission fiber of an optical fiber cable interconnecting transmitting and receiving terminals, and the optical repeater has an optical amplifier which is excited by pump light to amplify signal light. The pump light is supplied from the outside of the optical repeater, and the pump light supplied is input into the optical amplifier via at least one of its input end and output end. The optical repeater may include an optical divider for dividing the pump light supplied thereto into two, which are input into the optical amplifier via its input end and output end, respectively.
    Type: Grant
    Filed: April 10, 1990
    Date of Patent: January 28, 1992
    Assignee: Nippon Telegraph and Telephone Corporation
    Inventors: Kazuo Aida, Shigendo Nishi, Masatoshi Saruwatari, Kiyoshi Nakagawa