Apparatus and method for reducing phase errors in an interferometer
US5120130A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 27, 1989 |
| Grant date | Jun 9, 1992 |
| Priority date | — |
| Expiry date | Sep 27, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01C19/721
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A fiber optic rotation sensor comprises a fiber optic interferometer loop formed from a highly birefringent optical fiber, and a short coherence length source for introducing light into the interferometer loop to provide a pair of waves which counter-propogate therethrough. A detector is included to detect the phase difference between the waves after they have traversed the loop to provide an indication of the loop rotation rate, in accordance with the Sagnac effect. Phase errors are reduced by selecting the coherence length of the source and the birefringence of the fiber, so that the loop is comprised of plural fiber coherence lengths. The term "fiber coherence length" should be distinguished from source coherence length. Fiber coherence length is the length of fiber required for the optical path length difference between the two polarization modes of a single mode fiber to equal one coherence length of the light source. In addition, phase errors are reduced by providing a birefringent waveguide between the source and the loop such that light propagates from the source to the loop in an optical path having a path length difference which is at least equal to a coherence length of …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.