Ultra-long-distance FBG sensor system based on spectrum-limited Fourier domain modelocking fibre laser with Raman pumps.

A novel ultra-long-distance (up to 76 km) fibre Bragg grating (FBG) sensor system based on a spectrum-limited Fourier domain modelocking fibre laser is proposed. Raman pumps are employed to form a Raman amplifier to compensate the transmission loss of the long fibre and ensure ultra-long-distance sensing. Strain sensing based on such an ultra-long-distance FBG sensor system is demonstrated with a signal-to-noise ratio over 22 dB and a sensitivity of 1.03 pm/µℇ in the wavelength domain or 18.3 ns/µℇ in the time domain. [ABSTRACT FROM AUTHOR]