Achievement of an 85 km Distance Range of Strain (Temperature) Measurements Using Low-Coherence Rayleigh Reflectometry

The possibility of measuring strain (temperature) over distances up to 85 km in a single-ended optical fiber using the technique of low coherence Rayleigh reflectometry has been demonstrated. The indicated range is provided by employing Raman amplification of radiation in combination with amplification by short erbium doped fiber segments built into the fiber under test. The possibility of tuning a low coherence source in a wide range of wavelengths made it possible to measure strain in the range of 500 με, which is equivalent to 56°C in units of temperature. At a unit measurement time of 10 min and a spatial resolution of 2.6 m, the standard uncertainty of the strain measurements was 3.8 με and of the temperature ones was 0.42°C.