Fig. 1. Schematic diagram of the formation principle of absorption saturation-based dynamic grating. (a) Population grating recorded by two counter-propagation coherent waves in an Er-doped optical fiber; (b) three level energy system of rare-earth ion; (c) profile of the recording interference pattern I(z) with fringe spacing Λ and contrast m=0.6 and a corresponding normalized profile of the optical absorption α(z)/α0 in the recorded grating

Fig. 2. Schematic of the all-fiber TWM configuration for detection of mechanical vibrations

Fig. 3. Spectra of EDF in different input powers. (a) transmission mode spectrum; (b) reflection mode spectrum

Fig. 4. Trace of two-wave mixing signals under 50 Hz frequency and 0.75 μm amplitude. (a) Using single-mode fiber; (b) using Er-doped fiber

Fig. 5. Trace of TWM signals under different input powers

Fig. 6. TWM response signal phase-modulated by square wave with different frequencies generated by vibrating mirror. (a) 50 Hz; (b) 500 Hz; (c) 1 kHz; (d) 3 kHz; (e) 5 kHz; (f) 10 kHz

Fig. 7. Fourier spectra of the detected TWM signals under different frequencies. (a) 50 Hz; (b) 500 Hz; (c) 1 kHz; (d) 3 kHz; (e) 5 kHz; (f) 10 kHz

Fig. 8. TWM signals observed in EDF phase-modulated by square wave with different amplitudes. (a) 0.19 μm; (b) 0.37 μm; (c) 0.75 μm