Abstract

Optical time domain reflectometry (OTDR) is a valuable diagnostic tool for fiber-optic systems. Single-photon counting is a detection and measurement technique well suited to this purpose: results have been reported^1–3 showing that it makes possible achieving high sensitivity and a wide dynamic range. The object of the present work is to show that it also offers high spatial resolution in the localization of faults, opening the way to the accurate local characterization of fiber systems and components (connectors etc.). High resolution is achievable since suitable single-photon detectors with high time resolution are available, namely, avalanche photodiodes with a structure suitable to operate in the triggered-avalanche mode with bias voltage higher than the breakdown level. In fact, for silicon devices of this kind, called single-photon avalanche diodes (SPADs), we experimentally verified⁴ that a resolution better than 70-ps FWHM can be obtained.

© 1986 Optical Society of America