Method and apparatus for optical fiber length determination
US5149961A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 24, 1991 |
| Grant date | Sep 22, 1992 |
| Priority date | — |
| Expiry date | Apr 24, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01M11/335
- WIPO fieldMeasurement
- WIPO sectorInstruments
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.