Dual-Wavelength DC Compensation Technique for the Demodulation of EFPI Fiber Sensors

A dual-wavelength DC compensation technique for the demodulation of extrinsic Fabry-Perot interferometric (EFPI) fiber sensors is developed. The technique can overcome two problems in the measurement: the cavity length of the EFPI and wavelengths of light sources must be matched, and the DC component of the interferometric fringe must be eliminated. The proposed demodulation technique is verified by demodulating EFPI sensors with different cavity lengths and different phase modulations. Experimental results show that the demodulation technique can interrogate an EFPI sensor with any cavity length and any phase modulation. Besides, the technique has properties of high frequency, large dynamic range, and high sensitivity.