Fiber optic sensors
US4924870A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 13, 1989 |
| Grant date | May 15, 1990 |
| Priority date | — |
| Expiry date | Jan 13, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01L9/0077
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Serveral improvements in fiber optic sensing systems are disclosed. One improvement incorporates a dielectric filter applied directly to the sensing end of an optical fiber detector which has the characteristic that it reflects back a reference light beam of one wavelength while passing a sensing signal of a different wavelength which is modulated in some predetermined fashion beyond the filter. Both light signals are reflected back through the fiber and are, accordingly, attenuated in the identical or nearly identical fashion in response to various noise sources. The ratio of the intensity of the two signals is proportional to the sensed parameter and renders the system essentially self-compensating. The dielectric filter is preferably directly coated onto the exit end of the fiber through vapor deposition techniques. Time division multiplexing is used to sequentially fire plural light sources and a single photodetector is used for measuring the intensity of the reflected back signals of the various wavelengths. Another improvement encompasses the detection unit in which the input and reflected signals are separated using an off-axis parabolic mirror which provides excellent separ…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.