Demodulation of micro fiber-optic Fabry–Perot interferometer using subcarrier and dual-wavelength method

Subcarrier technology and dual-wavelength demodulation method are combined for tracking the cavity length variation of a micro fiber-optic Fabry–Perot (F–P). Compared with conventional dual-wavelength demodulation method, two operation wavelengths for demodulation are modulated with two different carrier frequencies, respectively, and then injected into optical link connected with the F–P cavity. Light power reflected for the two wavelengths is obtained by interrogating the powers of Fast Fourier Transform (FFT) spectrum at their carrier frequencies. Because the light at the two wavelengths experiences the same optical and electrical routes, measurement deviation resulting from the drift of optical and electrical links can be entirely eliminated.