Decoding the spectra of low-finesse extrinsic optical fiber Fabry-Perot interferometers

Abstract

A theoretical model is developed to address the fringe visibility and additional phase in the interference spectra of low-finesse extrinsic optical fiber excited Fabry-Pérot interferometers. The model described in the paper applies to both single-mode and multimode fiber excitations; according to the theory, the fringe visibility and additional phase term are primarily determined by the working wavelength and angular power density distribution outputting from the excitation fiber, rather than based on spatial and temporal degree of coherence. Under certain approximations, the output interference intensity and the spatial power density distribution projected onto the fiber axis form a Fourier-transform pair, which potentially provides a tool for spatial density distribution analysis of fiber output. With excellent agreement with experiments, the theory presented in this paper leads to design guidelines for Fabry-Pérot interferometric sensors and insightful physical understanding of such devices. Interferometric Optical Fiber Sensor Using Kirchhoff's Diffraction Formalism," Opt. Fiber Technol. 1(4), 380-384 (1995). 14. F. Pérennès, P. C. Beard, and T. N. Mills, "Analysis of a low-finesse Fabry-Perot sensing interferometer illuminated by a multimode optical fiber," Appl. Opt. 38(34), 7026-7034 (1999 Optical Society of America. Cheng Ma, Bo Dong, Jianmin Gong, and Anbo Wang, "Decoding the spectra of low-finesse extrinsic optical fiber Fabry-Perot interferometers," Opt. Express 19, 23727-23742 (2011 ©2011 Optical Society of America

High-resolution fiber optic temperature sensors using nonlinear spectral curve fitting technique

“…Second, as shown in Ref. 17, the change of the phase becomes so small at large cavity lengths; it can be neglected in our cases. Third, because this phase originates from the increased OPD than the absolute cavity difference due to beam divergence, this phase change can be described by introducing an effective cavity length L eff .…”

“…Both spectra exhibit a much higher interference visibility than those previously reported. 10,17 The envelope of spectra represents the spectrum of SLD (bottom curve of 2(a)), which is obtained using LabVIEW's low-pass filtering of the interference fringes. By normalizing the interference fringes with the spectrum of SLD, sinusoidal interference fringes with near-uniform amplitude are obtained (insets of Fig.…”

“…(1) due to the coupling between incident and reflected light. 17,18 Such a phase has not been taken into consideration in wavelength tracking methods because it is difficult to measure. This phase is important for the basic understanding of interference fringes, but the effect of such a phase on this curve fitting method and the accuracy of the temperature is negligible based on the following reasons: First, the temperature from the sensor will be calibrated according to the curve in Fig.…”

Resolution Improvement in Fabry-Perot Displacement Sensor Based on Fringe Counting Method

“…Number of fringes decrease steadily starting from 75 µm to 75.04 µm length of FPI cavity. Beyond 75.04 µm, the number of fringes starts to increase again due to incoherent superposition [17]. This pattern shows that the developed FPDS based on the improved FCM technique is able to detect the displacement up to 40 nm.…”

Signal processing of white-light interferometric low-finesse fiber-optic Fabry–Perot sensors

“…Intuitively, the greater the distortion is, the larger the phase term; as the distortion is OPD-dependent, so is the induced phase. For EFPIs, detailed analysis can be found in [25,33,34], and the case for IFPIs was studied in [35]. In general, for an EFPI, the phase term caused by wave front distortion is small and changes moderately with OPD; for an IFPI, due to multimode excitation, this term could be large and change more rapidly.…”