Long-range BOTDA sensing using optical pulse coding and single source bi-directional distributed Raman amplification

In this paper we present a Brillouin optical-time domain analysis (BOTDA) sensor combining optimized optical pulse coding with return-to-zero (RZ) modulation format and first-order bi-directional Raman amplification, using a single, shared, high relative-intensity-noise (RIN) pump source. We show that coding provides great benefits in sensing performance, even when employing noisy high-RIN Raman fiber-lasers degrading single-pulse BOTDA-schemes. Combining pulse coding with the use of a single high-power source for Raman amplification allows us to achieve distributed sensing over 120 km SMF, achieving 2.3 m spatial resolution with 52με/2.6°C strain/temperature resolutions.