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:
Sep. 22, 1992
Filed:
Apr. 24, 1991
Timothy G Arnold, Windsor, GB;
Arthur J Barlow, Alton, GB;
EG&G, Ltd., Wokingham, GB;
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. The phase sensitive detector measures the ac component of time detector output in phase with the second modulation frequency to provide an indication of fiber length.