INTEGRATED OPTIC SILICON ACCELEROMETER

A NOVEL FIBER-OPTIC ACCELEROMETER IS INTRODUCED WHICH IS BASED ON THE PRINCIPLE OF THE MEASUREMENT OF ROTATION INTERFEROMETRICALLY. INTERFEROMETRY IS VERY SENSITIVE TO ANGULAR CHANGES BUT THE ANGLE OF PROPAGATION IN A WAVEGUIDE IS SET BY THE GUIDANCE CONDITION. AS A RESULT, NO PHASE CHANGE OCCURS INSIDE THE WAVEGUIDE DUE TO ROTATION. A METHOD TO TRANSDUCE PHASE CHANGE FROM THE FLEXURE OF A CANTILEVER IN A WAVEGUIDE CONFIGURATION IS OUTLINED AND A DETAILED DISCUSSION OF ITS OPERATION IS PRESENTED. SPECIAL ATTENTION IS GIVEN TO REDUCE THE COUPLING LOSSES AMONG THE VARIOUS COMPONENTS. THIS CONFIGURATION IS EXPECTED TO YIELD THE MOST SENSITIVE FIBER-OPTIC ACCELEROMETER BY VIRTUE OF THE MEASUREMENT OF ROTATION. INTERFEROMETRIC FIBER-OPTIC SENSORS EMPLOY SINUSOIDAL PHASE MODULATION BY WRAPPING THE FIBER AROUND A PIEZOELECTRIC CYLINDER. THIS TECHNIQUE HAS LIMITATIONS AND IS NOT MINIATURIZABLE. HIGH FREQUENCY MODULATION WILL BE DONE ELECTRO-OPTICALLY IN A CHANNEL WAVEGUIDE MODULATOR, WHILE LOW FREQUENCY PHASE FEEDBACK WILL BE EFFECTED BY UNBALANCINGTHE INTERFEROMETER AND VARYING THE DRIVE CURRENT IN THE LASER DIODE. THIS TAKES ADVANTAGE OF THE DEPENDENCE OF THE WAVELENGTH ON THE FORWARD JUNCTION CURRENT. THE RESULT IS THAT MODULATION IS DONE IN A WAY WHICH IS COMPLETELY COMPATIBLE WITH THE MICROFABRICATION AND INTEGRATED-OPTICAL TECHNOLOGY. THERE ARE CLEAR COST BENEFITS TO THIS APPROACH.