Fig. 1. (a) Schematic diagram of the EYDF-based reflective FPI. The micrographs of (b) the FPI and (c) the end of the HCF used for encapsulation. (d) Measured reflected spectrum of the FPI. The dotted curve is the spectral envelope. (e) Spatial frequency spectrum of the FPI.

Fig. 2. (a) Diagram of the experimental setup. C1 and C2, optical coupler. (b) Photograph of the FPI under pump light excitation.

Fig. 3. (a) The evolution of the reflected spectra of the FPI as the pump power increases. (b) The spectral envelope at different pump powers. (c) The partial magnification of the measured reflected spectra. (d) The phase shift at different pump powers.

Fig. 4. Output signal waveforms at different modulation frequencies. (a) 1 Hz with a temporal response of 204 ms. (b) 100 Hz with a temporal response of 2.5 ms.

Fig. 5. Output signal waveforms at modulation frequencies of 5 Hz, 10 Hz, and 50 Hz.

Fig. 6. Measured reflected spectra of the FPI at different RIs. The inset is the partial magnification near the wavelength of 1537 nm.