EFFECTS OF TRAP LEVELS IN SINGLE-PHOTON OPTICAL TIME-DOMAIN REFLECTOMETRY - EVALUATION AND CORRECTION

Single photon detectors used in optical time-domain reflectometry (OTDR) suffer from carrier trapping phenomena. The effect has been known for a long time, but it was never analyzed. In this paper we show that 1) trapping effects can result in a severe OTDR trace distortion; 2) accurate measurements of trap releases open the way to the correction of the OTDR data. A simple procedure for off-line correction of the experimental traces is presented. Its applicability range is analyzed by using a Monte Carlo program which simulates the actual OTDR experiments. A dramatic improvement of signal-to-noise ratio in single photon OTDR is expected by exploiting the technique. Requirements for the electronics to be used for these measurements are also discussed.