Patents Assigned to EG&G, Ltd.
  • Patent number: 5149961
    Abstract: In a method and apparatus for measuring length of an optical fiber, a light source of a selected wavelength transmitted along the fiber is modulated by both a first and a second light modulation signal, which light modulation signals each differ in frequency from a first modulation frequency by a fixed amount. A time detector responds, alternately during a period, to the light signal as modulated by of each of the first and second light modulation signals by using each of the light signal modulation frequencies as a reference. Consequently, the output of the time detector has a phase responsive to the effective length of the fiber. A phase sensitive detector receives as a signal input an output of the time detector means. A second modulation frequency defines the period of alternation of response and provides a reference input to the phase sensitive detector.
    Type: Grant
    Filed: April 24, 1991
    Date of Patent: September 22, 1992
    Assignee: EG&G, Ltd.
    Inventors: Timothy G. Arnold, Arthur J. Barlow