Heterodyning Optical Fiber Hydrophone System.
Technical information series,
GENERAL ELECTRIC CO SYRACUSE N Y ELECTRONICS LAB
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Optical fiber data transmission lines combined with acoustic sensors that directly modulate the light in the fibers offer the possibility of dramatic reductions in the size, weight, and cost of low frequency sonar sensor arrays. A practical problem in such systems is distinguishing the desired modulation imposed at the sensor location from undesired extraneous modulations accumulated along the entire fiber lead length. A system is presented which solves this problem. It uses a pair of single-mode optical fibers connected to each sensor. The boundaries between the sensing element and the fiber leads are delineated by partially reflecting optical discontinuities. The sensing element can be any device capable of optically coupling the two fibers together with an optical transit time delay that is affected by acoustic vibrations. An acoustically driven gap between the planar end faces of the two lead fibers, and a coiled optical fiber are examples of two suitable sensors that have been experimentally demonstrated in this system. Optical heterodyning techniques are used to obtain a phase modulated IF signal out of each fiber. The phase difference between these two channels represents the acoustic signal at the sensor, independently of lead length effects. Experimental data is presented along with a detailed analysis of the system. Author
- Theoretical Mathematics
- Acoustic Detection and Detectors
- Fiber Optics and Integrated Optics