<title>Interferometric fiber optic accelerometer</title>

Abstract

ABSTRACT A push-pull fiber optic accelerometer using a Michelson interferometer to detect the surface strains produced on a pair of coaxial flexing disks is described. The sensitivity below the disk's fundamentalresonance of 2.45 kHz is 50 radians/g. The fractional phase change per unit force A4/AF is 5.9 x 106 W1 . A noteworthy feature of this sensor is that the 5 meter sensing coils comprising the legs of the interferometer are totally internal to the sensor structure and thus are not exposed to platform or fluid underinvestigation. 1. INTRODUCTION The advantages of fiber optics that have been demonstrated in communication systems (i.e. high data rates, light weight cabling, electromagnetic interference immunity, long repeaterless and low power transmission) have yet to be realized in practical fiber optic sensing systems. This is due largely to the factthat optical fiber alone is not particularly sensitive or selective to the fields under investigation such as acceleration, pressure, temperature, electric, and/or magnetic fields. Thus in order to exploit theadvantages of fiber optic communications in sensing systems, first a practical mechanical to opticaltransduction mechanism must be designed to improve both the sensitivity and selectivity. Second asuitable optical detection mechanism must be chosen (e.g. to detect a change in intensity, phase, orpolarization). And third, a demodulation scheme is needed to convert the optical signals into voltage