Photon Probe Fault Locator for Single-Mode Optical Fiber Using an Acoustooptical Light Deflector

A new backscattering technique for diagnosing the attenuation characteristics, spatial imperfections with length (fault location), and splice loss in a single-mode optical fiber has been developed by-using a TeO2 acoustooptical light deflector operating at 120 MHz. Due to the small insertion loss and high extinction ratio of the deflector, the dynamic range of the backscattered signal has been increased by at least 10 dB, which corresponds to the extension of 5 km in measurable length for fiber loss of 1 dB/km, compared with the conventional backscattering technique in which the beam splitter and polarizer-analyzer combination are utilized. Another advantage of this technique is in that the saturation of the amplifier is avoided by arbitrarily cutting off a large power in the early stage of the Rayleigh scattering signal. A single-mode fiber of 19.2 km in length has been examined, and the distance for fault location up to 18.4 km was obtained.