MILLIMETER-RESOLUTION OPTICAL TIME-DOMAIN REFLECTOMETRY USING A 4-WAVE-MIXING SAMPLING GATE

We report an optical time-domain reflectometer that employs an ultrafa st optical switch based on nondegenerate four-wave mixing in a semicon ductor laser amplifier. Two-point spatial resolution on the order of 1 mm over 2 m is demonstrated; Fresnel reflections with optical return losses greater than 53 dB are detected. Submillimeter-resolution optic al time-domain reflectometery over a 100-m range should be possible wi th modifications to the pulse sources.