US 4,789,241 AGranted

Optical fiber sensing systems having acoustical optical deflection and; modulation devices

AssigneeMcDonnell Douglas Corporation

InventorsRonald J. Michal, Eric Udd, Richard F. Cahill

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Abstract

There is provided by this invention an optical sensing system utilizing a Sagnac interferometer having a frequency shifter within the Sagnac counterpropagating loop that is generally comprised of a plurality of acoustic transducers mounted on acousto-optical material to frequency shift and beamsplit a light beam simultaneously within the material while at the same time having the capability of switching between an upshifted or downshifted frequency in either a Bragg or Raman-Nath mode of operation without realigning the optical beams. The acousto-optical material has a special configuration to eliminate back reflections of the acoustic waves that can interact with the light beam. In addition, special alignment of the transducers with dampening configurations also serves to prevent back reflections of the acoustic wave from interacting with the light beam.

Claims10

Dependent claims

A fiber optic sensor, comprising:

(a) a light source means for producing a first beam of light;
(b) a beam splitting means for receiving the first beam of light having a polarizing means connected to one output for polarizing a portion of the first light beam;
(c) an acousto-optic frequency shifting means connected to the polarizing means for frequency shifting and splitting the polarized portion of the first beam of light into second and third beams of light and recombining the second and third beams into a fourth beam of light;
(d) a dual array of acoustic transducers connected to opposite sides of the acousto-optic frequency shifting means each transducer driven with a successive time delay means for directing the acoustic wave such that the direction of the acoustic wave is controllable for acousto-optic interaction between the light beam and the acoustic wave;
(e) a polarity means connected to the dual array of acoustic transducers for changing the polarity of the frequency shift between the second and third beams;
(f) counterpropagating means for directing the second and third beams of light received from the frequency shifting means along a light path in counterpropagating directions;
and
(g) a detection means for detecting the phase modulated frequency contained in the fourth light beam recombined at the frequency shifting means including electrical circuitry means for measuring environmental effects on the counterpropagating light beams by detecting the nonreciprocal phase shift of the counterpropagating beams.

5 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/017,691Filed 24 Feb 1987
Granted: 6 Dec 1988
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

G02F 1/332
Acousto-optical deflection devices: comprising a plurality of transducers on the same crystal surface, e.g. multi-channel Bragg cell
G01C 19/726
With counter-rotating light beams in a passive ring, e.g. fibre laser gyrometers: phase nulling gyrometers, i.e. compensating the Sagnac phase…
G01D 5/266
Characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light: by interferometric means
G02F
Optical devices or arrangements for the control of light by modification of