The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 23, 1997
Filed:
Feb. 04, 1997
Tatsuya Kumagai, Hitachi, JP;
Hiroshi Kajioka, Ibaraki-ken, JP;
Osamu Kobayashi, Hitachi, JP;
Munehiro Akiyama, Hitachi, JP;
Shigeru Oho, Katsuta, JP;
Hisao Sonobe, Katsuta, JP;
Hitachi Cable, Ltd., Tokyo, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
A phase modulated light is propagated through an optical fiber sensing loop, from which a propagated light is obtained. The propagated light is converted to an electric signal, from which a fundamental wave component and even number harmonic wave components of a phase modulating signal for the phase modulated signal are detected. In accordance with the changes of the fundamental and even number harmonic wave components, fault is detected. On the other hand, the electric signal may be integrated to provide an integrated signal. In accordance with the comparison between the integrated signal and a fault reference voltage, the fault may be detected.