Long Distance B-otda And ¦µ-otdr Sensor System Optical Signal Processing Method

Long-distance optical fiber sensor is due to its long sensing distance and with no need for the repeater,so it has important application prospect in the safety testing of the large bridges, oil pipelines, subway, gas pipeline and other important facility. The research of distributed sensing technology Based on Brillouin scattering starts late, but owing to its higher measurement precision and spatial resolution of temperature and strain measurements, so this technology in the current attracts widely attention and research.The BOTDA has some deficiencies. This paper puts forward a method based on bidirectional Raman amplification which solved the low resolution of the back-end measuring and try to outspread the sensing distance. The BOTDA system achieved the distance of 50km and the spatial resolution of 50m. The paper represented the principle of the BOTDA system and the key devices for system selection and testing.This paper also introduces the distributed sensing system based on phase time-domain reflectometer (Φ-OTDR),theΦ-OTDR system is sensitive to the strain and expected to used for pipeline crossing and monitoring. The system achieved the sensing distance of 34km and the spatial resolution of 20m.