FIBER-OPTIC SOUND PRESSURE GRADIENT DETECTOR Russian patent published in 1997 - IPC

FIELD: underwater acoustics, applicable in laboratory and natural conditions for measurement of parameters of sound waves in liquid. SUBSTANCE: single- beam fiber Zender-Mach interferometer, having two fiber coils positioned at a definite distance from each other, is supplemented with a multiple- beam double-ring interferometer, having three optically integrated fiber coils. Two coils of both interferometers are common ones. Decoupling of the interferometers is effected due to the use of different lengths of waves generated by two lasers. The single-beam interferometer has a harmonic outlet curve, and the multiple-beam interferometer has a peaked outlet curve in the interference bands. At homodyne transformation it allows the multiple- beam interferometer to be used for reception of weak acoustic signals, and the single-beam interferometer- for reception of stronger acoustic signals. The detector has an electronic circuit of automatic selection of operating mode, depending on the level of acoustic signal. EFFECT: enhanced accuracy. 2 cl, 3 dwg