212-km ultra-long-distance hybrid Φ-OTDR/BOTDR based on remotely pumped optical amplification

In this paper, we propose and demonstrate a 212 km ultra-long-distance hybrid distributed optical fiber sensing (DOFS) system capable of simultaneously measuring vibration and strain/temperature along the sensing fiber. This is achieved by integrating phase-sensitive optical time-domain reflectometry (Φ-OTDR) and Brillouin optical time-domain reflectometry (BOTDR) into a single interrogator. The extended sensing range is realized through the use of wavelength division multiplexing, time division multiplexing, co-pumped distributed Raman amplification, and remotely pumped optical amplification technologies. The system achieves a 20 m spatial resolution for vibration sensing and a 50 m resolution for strain/temperature sensing, with strain/temperature measurement accuracy reaching 4.3 MHz. Notably, the single-end operation and simplified system architecture make this solution highly suited for industrial on-site applications. To our knowledge, this is the longest measurement range reported for hybrid DOFS systems without the aid of active repeaters or bi-directional distributed amplification techniques.