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The nonlinearity of a piezo-electrical transducer (PZT) driven fiber Fabry–Perot filter (FFP) is investigated and calibrated using a group of fiber Bragg gratings (FBGs). The peak positions of four series FBGs are used as wavelength references and detected by particle swarm optimization (PSO) algorithm with high accuracy and less computation time. Polynomial fit is employed to model the wavelength–voltage relationship of FFP. The absolute error in wavelength detection using the calibrated FFP is demonstrated by experiments to be as low as 25 pm. The wavelength resolution of FFP has also been studied by scanning the absorption spectrum of acetylene. The proposed approach of online calibrating the wavelength–voltage relationship of FFP has great potentials in applications where FFP is used as wavelength demodulator.

A practical mixed-gas sensing system utilizing a fiber Fabry–Perot (FFP) filter and Fiber Bragg Gratings (FBG) was developed. By modulating the transmission wavelength of FFP within the width of one absorption line of the target gas, the system can detect different kinds of gaseous species selectively. A FBG with center wavelength being aligned to the absorption peak of the target gas was employed as wavelength reference to make the transmission wavelength of FFP modulate stably in a required region. The properties of the proposed system were demonstrated experimentally by simultaneous detection of acetylene (C 2 H 2 ) and carbon monoxide (CO). Approximate linear relationships between the system responses and the input gas concentrations were demonstrated by experiments. The minimum detectable C 2 H 2 and CO concentration of ∼15 ppm and ∼300 ppm were also achieved by experiments respectively.

A tunable optical filter (TOF) based acetylene sensing system is proposed in this paper. By modulating the wavelength of TOF within the width of one absorption line of acetylene, both the sensitivity and selective sensing properties of the system for sensing acetylene have been much improved. Approximate linear calibration curves in sensing acetylene is obtained by experiments. The minimum detectable acetylene concentration of 5ppm is also achieved by experiments. The proposed system has great potential in developing mixed-gas sensing system.