Crescent shaped Fabry-Perot fiber cavity for ultra-sensitive strain measurement

Abstract

Optical Fabry-Perot interferometer sensors based on inner air-cavity is featured with compact size, good robustness and high strain sensitivity, especially when an ultra-thin air-cavity is adopted. The typical shape of Fabry-Perot inner air-cavity with reflection mode of operation is elliptic, with minor axis along with and major axis perpendicular to the fiber length. The first reflection surface is diverging whereas the second one is converging. To increase the visibility of the output interference pattern, the length of major axis should be large for a given cavity length. However, the largest value of the major axis is limited by the optical fiber diameter. If the major axis length reaches the fiber diameter, the robustness of the Fabry-Perot cavity device would be decreased. Here we demonstrate an ultra-thin crescent shaped Fabry-Perot cavity for strain sensing with ultra-high sensitivity and low temperature cross-sensitivity. The crescent-shape cavity consists of two converging reflection surfaces, which provide the advantages of enhanced strain sensitivity when compared with elliptic or D-shaped FP cavity. The device is fabricated by fusion splicing an etched multimode fiber with a single mode fiber, and hence is simple in structure and economic in cost.

Measurement of Structural Loads Using a Novel MEMS Extrinsic Fabry–Perot Strain Sensor

“…The interference device comprises two mutually parallel planes of high reflectivity, the distance between the two planes being d. As illustrated in Figure 1, when the incident light beam of the external broadband light source is traveling along the fiber core of the optical fiber, multiple reflections are transmitted between the two surfaces of the cavity to form an interference fringe and return to the optical fiber. Based on the theory of FPI, the light intensity of the interference signal is given by [22,29]…”

“…When the interference order satisfies M = 2m + 1, m is an integer and the intensity fringe dip appears at the interference spectrum wavelength [14,22].…”

“…However, it has an ultra-thin sidewall that sacrifices the mechanical strength. Liu et al [22] proposed a new ultra-thin crescent-shaped FP cavity by multimode optical fiber with higher sensitivity than conventional elliptical or D-shaped sensors. However, all these methods involve various complicated steps, expensive photonic crystal fibers (PCFs) [23], or other special optical fibers.…”

Flexible corner cube retroreflector array for temperature and strain sensing

“…3 – 8 Flexible optical sensors due to the advantages of low cost, compactness, low noise/interference, high sensitivity and reliability have been utilized in temperature and strain quantification. 9 – 11 However, these optical devices cannot sense temperature and strain simultaneously. Hence, the development of simple, cost-effective, and robust optical sensing technologies is highly desirable for remote sensing applications.…”

Simultaneous measurement of transverse load and temperature using hybrid structured fiber-optic Fabry–Perot interferometer

“…In recent years, fiber-optic Fabry–Perot interferometer (FPI) has drawn great attention and been used for various physical quantities sensing, such as temperature 1–3 , strain 4–7 , pressure 8–10 , and transverse load 11 et al ., due to its advantages of low cost, high sensitivity, ultra-compactness and reliability. During the physical quantity sensing process, temperature fluctuation will introduce extra error.…”