Fast Acquisition Tunable High-Resolution Photon-Counting OTDR

A 15 dB dynamic range and 4.6 cm spatial resolution tunable photon-counting optical time-domain reflectometer (PC-OTDR) is presented along with a Field Programmable Gate Array (FPGA)-based detection management system that allows several regions of the fiber to be interrogated by the same optical pulse, increasing the data acquisition rate when compared to previous solutions. The optical pulse generation is implemented by a tunable figure-8 passive mode-locked laser providing pulses with the desired bandwidth and center wavelength for WDM applications in the C-band. The acquisition rate is limited by the afterpulse effect and dead time of the employed gated avalanche single-photon detectors. The devised acquisition system not only allows for centimeter-resolution monitoring of fiber links as long as 12 km in under 20 minutes but is also readily adapted to any other photon-counting strategy for increased acquisition rate. The system provides a 20-fold decrease in acquisition times when compared with state-of-the-art solutions, allowing affordable times in centimeter-resolution long-distance fiber measurements.