Delay Compensated FBG Demodulation System Based on Fourier Domain Mode-Locked Lasers

Fourier domain mode-locked lasers are excellent wavelength-swept sources for high-speed fiber Bragg grating (FBG) demodulation. When the lasers are applied for remote FBG sensing, the transmission delay could make the sensing signal deviating significantly from its real position due to the short sweep period of the lasers, which can cause large wavelength demodulation error. An autocalibration method for compensating the delay is proposed by inserting a Fabry-Perot etalon with a wavelength marker into the reference optical path. Besides, the wavelength sweeping nonlinearity can be real-time monitored via the multiple combs of the Fabry-Perot etalon and absolute wavelength of FBG can be derived using interpolation algorithm. Experimental results show that this demodulation method is efficient and accurate.