Simultaneous Measurement of Curvature and Temperature Based on Mach–Zehnder Interferometer Comprising Core-Offset and Spherical-Shape Structures

Design and optimization of photonic crystal fiber based sensor for gas condensate and air pollution monitoring

“…Figure 10 shows the V eff parameter as a function of operating wavelength with optimized design parameters for Λ = 3.00 m;  c = 1.08 m; d = 2.85 m, d c = 0.774 m, and d c0 = 1.08 m. The V eff parameter can be expressed by (6). With approximate perfect electric and perfect magnetic conductor boundary condition, FEM is used at the outer enclosure to achieve the index of space-filling mode [39].…”

“…The PCF can be designed for many significant applications in intelligent systems, and it has attracted too much concentration of researchers. The requirement of PCF is exponentially escalated for flexibility and variation of geometrical structures like D-shape [1], pentafgonal [2], tapered [3] panda-shaped [4], colloidal [5], spherical shaped [6], rhombic-shaped core [7], and spiral [8] shaped architecture. High nonlinearity [9], large mode field area [10], highly birefringence [2], and zero-flattened dispersion [11] characteristics have gained by modifying the design of PCF.…”

In-Line Mach-Zehnder Interferometer With D-Shaped Fiber Grating for Temperature-Discriminated Directional Curvature Measurement

“…fiber grating-based [1][2][3][4][5][6][7][8][9], interferometer-based schemes [10][11][12][13][14][15][16][17][18], etc. For fiber grating-based structures, such as fiber Bragg gratings (FBGs) written in multi-core fiber (MCF) and eccentric-core fiber (ECF) [3,4], long-period fiber gratings (LPFGs) [5][6][7] and tilted FBGs [8,9], they can operate in a large curvature range, but exhibit a lower sensitivity.…”

“…For in-line interferometer-based curvature sensors, Mach-Zehnder interferometers (MZI) as a common and effective scheme usually involves two fiber mode-coupling joints, where the two joints act as a beam splitter and a beam combiner. For instance, the MZIs consisting of up-tapers, lateral-offsets, peanut-shape or spherical-shape structures [10][11][12][13] are proposed to sense the curvature variation, while they cannot distinguish the direction of the curvature due to the symmetrical structure. For achieving directional curvature sensitivity, an asymmetric index perturbation in the cross section of fiber by use of CO 2 laser is introduced in the MZI, such as asymmetrical LPFG [14] and two tilted LPFGs [15], but their curvature sensitivity still need to be improved.…”

“…In the meantime, the temperature cross-talk in the curvature measurement is another issue. In general, the strategy for avoiding the cross-talk is to simultaneously measure curvature and temperature by examining different interference peaks [10,16] which possess different curvature and temperature responses. Another effective approach is to use special fibers in the MZIs for different temperature and curvature sensing mechanism, such as single-hole twin ECF [17], two-core fibers (TCF) [18], however, the fabrication and cost of these special fibers and control of splicing loss with standard single-mode fiber (SMF) need to be took into account.…”