Abstract

Optical fiber communication systems are currently being developed for the telemetry of instrumentation data in various applications, including the transmission through electrically noisy environments and in situations where the environmental requirements involve the use of flameproof techniques. Such telemetry systems employ instrumentation transducers to measure vibration levels, temperatures, pressures, and other parameters. A frequent disadvantage with such an approach is the need for power supplies at the transducer to convert its output into a suitable modulated optical signal. This paper draws attention to the fact that optical fibers are microphonic in the sense that when they carry coherent optical signals, the fiber can pick up acoustic energy from the air and, through a parametric interaction, cause phase modulation of the guided wave. The fiber itself can act as a transducer, e.g., as a strain gauge, and its sensitivity may be enhanced by coiling a long length of fiber over a suitable former. Alternatively, its sensitivity can be conveniently decreased by coating the fiber with an appropriate amount of absorbent material. For many applications it would obviously be more convenient to couple mechanically some form of resonant mechanical transducer to the fiber.

© 1976 Optical Society of America