30-km spontaneous-Brillouin distributed temperature sensor employing Simplex-coding and low optical input power

In this work we have applied optical pulse-coding technique to spontaneous Brillouin-based distributed temperature sensor (BDTS) based on the Landau-Placzek ratio (LPR). We experimentally show that pulse-coding applied to optical time domain reflectometry (OTDR) based BDTS allows for a significant performance enhancement, avoiding the use of optical amplification. Actually, by using 127-bit Simplex coding, we achieved about 7 dB signal-to-noise ratio improvement at the receiver, allowing for temperature sensing over 30 km-distance with temperature/spatial resolution up to 5.0 K / 40 m using only 10 mW optical peak power at the fiber input.