Jiro MORITA, Takeaki YOSHIMURA and Takumi MINEMOTO

Division of System Science, The Graduate School of Science and Technology, Kobe University, Rokkodai, Nada-ku, Kobe, 657 Japan

(Accepted November 25, 1994)

The critical power of the input pulse in which spontaneous Raman scattering is not seriously disturbed by stimulated Raman scattering in a fiber optic temperature sensor has been investigated experimentally and theoretically. The critical power determines the critical distance, which is nearly equal to the distance where optical time-domain reflectometry (OTDR) signal of the stimulated Raman scattering becomes maximum. From this fact, a new method to determine the critical input power with the OTDR system has been proposed, which may be applicable to most distributed fiber optic temperature sensors. It has been determined that the critical power of the input pulse is 4 watts for an infinitely long silica fiber.

Key words : stimulated Raman scattering (SRS), distributed fiber optic temperature sensors, optical time-domain reflectometry (OTDR), critical input power, silica fibers