Derived Sequences Decoding Approach for Long-Range Distributed Temperature Sensors

A novel derived sequences decoding approach is proposed to solve the transient effect in the process of amplifying Golay codes pulse sequences by Erbium-doped fiber amplifier (EDFA) in long-range Raman distributed temperature sensors (RDTS). The derived sequences that maintain good cross-correlation with the attenuated sequences are used to decode without distortion to the greatest extent. Without adding the hardware equipment of the RDTS system, the attenuation of Golay codes is compensated in the process of decoding. The sidelobes of the time-domain correlation results can be reduced to less than 1% of the peak height. In addition, the return-to-zero (RZ) Golay codes output by the distributed feedback (DFB) laser is transmitted to the fiber to improve the signal-to-noise ratio (SNR). Finally, the maximum temperature resolution of ±2.5 °C is achieved at a 45 km-long single-mode fiber (SMF) when the spatial resolution (SR) is 5 m.