FIBER OPTICAL ACOUSTIC SENSOR SYSTEM AND METHOD USING PUSH-PULL TWO WAVELENGTH FABRY PEROT SENSORS

摘要

Two optical wavelengths are used to interrogate a fiber optic Fabry-Perot sensor ( 1-4) having a moveable diaphragm (34) that changes the width of a gap (36) between two reflective surfaces (38, 40). By picking the right operating point for the gap (36), the power output for one wavelength increases as the gap width changes and the power for the other wavelength decreases. A ratio of the difference of the two powers over the sum of the two powers is formed to generate a detected signal independent of power and phase fluctuations in a fiber (22) between signal sources (46, 48) and sensor (1-4) and between sensor ( 1-4) and detector (73). This ratio, which is called the visibility, has a response proportional to the pressure of acoustic disturbances that move the diaphragm (34). The push-pull sensor ( 1-4) can be used with both TDM and CW fan-out array architectures (45, 47).