Fabry-perot pressure sensing system with ratioed quadrature pulse detection
US5929990A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 19, 1997 |
| Grant date | Jul 27, 1999 |
| Priority date | — |
| Expiry date | Mar 19, 2017 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01J3/26
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A pressure sensing system employs a plurality of pulsed, single-wavelength optical signal sources, each emitting a distinct wavelength, whereby a multiplexed incident beam is generated. The incident beam is split into a first portion directed to first photodetector means that generate a reference signal for each wavelength, and a second portion that interrogates one or more Fabry-Perot pressure sensors. The interrogation beam portion is phase-modulated by gap width variations in the sensor(s), and is transmitted to second photodetector means that generate a measured intensity signal for each wavelength. For each wavelength, the ratio of the measured intensity signal to the reference intensity signal is taken, and yields two terms, one of which is an interference term that is proportional to the cosine of the Fabry-Perot phase shift angle .phi., which is a function of the gap width. By choosing wavelengths that are in quadrature relationship for a nominal Fabry-Perot gap width, the algebraic differences can be taken among the ratios to yield two expressions proportional, respectively, to the cosine and sine of the phase shift angle .phi.. An arctangent calculation is used to obtain …
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