Highly sensitive fiber Bragg grating sensor interrogation system based on a Fourier domain mode-locked optoelectronic oscillator

We propose a fiber Bragg grating sensor interrogation system based on a Fourier domain mode-locked optoelectronic oscillator (FDML-OEO). The FDML is achieved by synchronizing the period of the driving current of the laser with the round-trip time of the OEO loop. By employing a narrow band electrical filter with the central frequency located within the sweeping frequency of the FDML-OEO, pulsed microwave output can be obtained. The wavelength shift of the phase-shift fiber Bragg grating (PS-FBG) can be interrogated by measuring the pulse interval variation. The experimental results indicate that the pulse interval of the generated signal has a linear relationship with the axial strain applied to the PS-FBG and a sensitivity as high as 0.42 mu s/mu s is achieved.