Distance Scale Calibration of Optical Time Domain Reflectometer Using Active Intensity Modulation

In this paper calibration of optical time domain reflectometer (OTDR) distance scale using active intensity modulation (AIM) is discussed. A setup is proposed to calibrate an OTDR over a distance range of 100 km based on AIM method. A commonly used method based on a recirculating loop (RL) is used to calibrate the same OTDR. The RL artefact is independently measured at the English National Physical Laboratory and therefore helps to validate the result obtained by the AIM setup. The parameters contributing the calibration uncertainty are investigated. Using our AIM setup, OTDRs can be calibrated over distances up to 100 km with uncertainty as low as ±4.4 cm for location offset and ±8.2 × 10−7 for distance scale deviation.