High-Resolution FBG-Based Inclination Sensor Using Eigen Decomposition of Reflection Spectrum

A Temperature Independent Inclinometer Based on a Tapered Fiber Bragg Grating in a Fiber Ring Laser

“…V is the normalized frequency. The bending loss per unit length of step index tFBG can be expressed as follows [12]:…”

“…The bending loss per unit length of step index tFBG can be expressed as follows [ 12 ]: where α , R and Δ are the core radius, bending radius, and core-cladding refractive index difference, respectively. K 1 is a modified Hankel function.…”

“…Besides, in other applications, for example, virtual reality technology, gesture recognition [ 7 ], intelligent machinery [ 8 ] and environment monitoring [ 9 ] a kind of inclinometer which is cost-effective, extremely accurate, and simple in structure is needed. Over the past few years, fiber-optic inclinometers have been widely investigated because of their inherent advantages, including long-term stability and reusability [ 10 , 11 , 12 , 13 ]. Therefore, they perform well under small inclination change conditions.…”

“…Therefore, they perform well under small inclination change conditions. Typically, optical fiber inclinometers consist of a fiber Bragg grating (FBG) [ 12 ], tilted fiber grating (TFG) [ 14 ] and long period fiber grating (LPFG) [ 15 ], etc. Besides, dislocation optical fibers [ 16 ] and multi-core optical fibers [ 17 ] are also used to manufacture inclinometers.…”

“…Nevertheless, the output spectrum is chaotic. Kumar [ 12 ] reported an inclinometer base on a pendulum-based structure attached to its cantilever arm with an ultra-high resolution of 0.0008°. However, since, its complex structure the detection range is limited to 0–3°.…”