Dynamic distributed measurement of temperature changes using phase-sensitive OTDR with chirped pulses

A new and simple distributed fiber sensor which allows for the dynamic (single-shot) and quantitative measurement of perturbations is presented. It is based on a phase-sensitive OTDR using direct detection and linearly chirped pulses. Perturbations result in longitudinal shifts of the fiber trace, which can be calculated using a local correlation. As a proof of concept, distributed temperature variations of up to 5 Kelvin with millikelvin temperature resolutions over several minutes are demonstrated. Since the technique does not require a frequency sweep, operation ranging from dynamic strain measurements at kHz rates to temperature monitoring over several hours is readily envisaged.