High spatial resolution phase-sensitive optical time domain reflectometer with a frequency-swept pulse.

A high spatial resolution phase-sensitive optical time domain reflectometer (ϕ-OTDR) with an optical frequency-swept pulse (FSP) is proposed, and the experimental results are presented in the Letter. The FSP ϕ-OTDR uses optical pulses with linear frequency modulation with higher pulse energy for longer sensing fiber and uses matched filter in the receiver to compress the processed pulse width. Thus, the contradiction between spatial resolution and the working distance in ordinary ϕ-OTDR is relaxed. A spatial resolution of 30 cm, a sensing distance of 19.8 km, and a signal-to-noise ratio of 10 dB for vibration sensing were obtained experimentally. To our best of our knowledge, this is the first time that a sub-meter spatial resolution over such a long sensing range has been reported in ϕ-OTDR sensors.