The Fiber Optic Smart Bolt is an intelligent structural component that utilizes Fiber Bragg Grating (FBG) technology to measure internal strain through spectral variations. It enables real-time monitoring of bolt preload, deformation, loosening, fatigue, and other key parameters. Passive operation. A fiber Bragg grating is a periodic or aperiodic perturbation of the effective refractive index in the core of an optical fiber (see Figure 1). Typically, the perturbation is approximately periodic over a certain length of e. a few millimeters or centimeters, and the period is of the order of. We specialize in custom fabrication of fiber optical gratings (FBG) across wavelengths from 400 nm to 2000 nm, tailored to precise customer specifications.