Abstract
To solve the cavity interrogation problem of short cavity fiber Fabry–Perot sensors in white light spectral interrogation with amplified spontaneous emissions (ASEs) as the white light sources, a data processing method, using an improved elliptical fitting equation with only two undetermined coefficients, is proposed. Based on the method, the cavity length of a fiber Fabry–Perot sensor without a complete reflection spectrum period in the frequency domain can be interrogated with relatively high resolution. Extrinsic fiber Fabry–Perot air-gap sensors with cavity lengths less than 30 μm are used to experimentally verify the method, and are successfully interrogated with an accuracy better than 0.55%.
Highlights
Fiber Fabry–Perot (FP) cavities can be used as sensors for the measurement of various physical parameters, such as temperature [1], pressure [2], strain [3], acoustic waves [4], magnetic field [5], etc
A continuous-wave laser with single wavelength output is used, which has to be stabilized at the Q-point of the fiber FP cavity, and only relative cavity length changes in a limited range can be measured
We propose a data processing method for the white light spectral interrogation of short cavity fiber FP sensors using an improved elliptical fitting equation with only two undetermined coefficients
Summary
Fiber Fabry–Perot (FP) cavities can be used as sensors for the measurement of various physical parameters, such as temperature [1], pressure [2], strain [3], acoustic waves [4], magnetic field [5], etc. This was proposed for the absolute cavity length interrogation of fiber FP sensors, but with a relatively low length accuracy [17,18] Another important and direct white light interference interrogation method, called white light spectral interrogation [19,20,21,22], uses an optical spectrum analyzer to directly determine the reflection spectrum of the fiber FP sensor and resolve the cavity length from the reflection spectrum. We propose a data processing method for the white light spectral interrogation of short cavity fiber FP sensors using an improved elliptical fitting equation with only two undetermined coefficients. A theoretical model of the method for short cavity fiber FP sensors is described in detail and it is verified through real experiments
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