Patents by Inventor Mitsushi Nitta

Mitsushi Nitta 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).

  • Optical transmission system including optical repeaters with selectively enabled gain equalizers contained therein and including an add/drop apparatus with a plurality of individually selectable filters
    Patent number: 6144474
    Abstract: An optical transmission system including a plurality of optical repeaters arranged along a transmission line. A respective gain equalizer is arranged along the transmission line after an integer number of optical repeaters. Further, each optical repeater can include an optical amplifier, a gain equalizer and a connection mechanism. The connection mechanism has a first state and a second state so that (a) when the connection mechanism is in the first state, the gain equalizer of the optical repeater performs an equalization process on the light signal, and (b) when the connection mechanism is in the second state, the gain equalizer of the optical repeater does not perform an equalization process on the light signal. An add/drop apparatus is also provided for adding/dropping an individual wavelength signal from a wavelength division multiplexed (WDM) signal travelling through the optical communication system. The add/drop apparatus includes a plurality of filters, and a selection mechanism.
    Type: Grant
    Filed: October 14, 1997
    Date of Patent: November 7, 2000
    Assignee: Fujitsu Limited
    Inventors: Mitsushi Nitta, Shinichirou Harasawa, Hiroshi Nakashima
  • Optical branching and insertion apparatus
    Patent number: 6002820
    Abstract: An object of the present invention is to provide an optical branching and insertion apparatus with which the damage location can be searched for in all sections when a damage location is searched for in an optical transmission system in which an optical branching and insertion apparatus has been installed.
    Type: Grant
    Filed: December 24, 1997
    Date of Patent: December 14, 1999
    Assignee: Fujitsu Limited
    Inventor: Mitsushi Nitta
  • Optical repeater having loop-back function used in transmission system
    Patent number: 5296957
    Abstract: An optical repeater having a loop-back function is provided in a transmission system including first and second transmission lines. The optical repeater includes a first optical amplifier connected to the first transmission line, a second optical amplifier connected to the second transmission line, a loop-back unit connected to both transmission lines, and a control unit. The control unit controls the loop-back unit to form a loop-back line when a loop-back instruction is detected. Therefore, optical signals are directly amplified without being converted into electrical signals, and a loop-back signal (return signal) and optical signals are not mixed in the optical repeater so that a loop-back operation can be correctly carried out in an optical repeater having a small size and low power consumption.
    Type: Grant
    Filed: September 13, 1991
    Date of Patent: March 22, 1994
    Assignee: Fujitsu Limited
    Inventors: Masaaki Takahashi, Takanori Maki, Kazuya Amaki, Katsumi Kikawa, Mitsushi Nitta