IdealPhotonics' fiber optic retroreflector is an optical device based on the principle of retroreflection. It achieves ultra-low insertion loss (<0.5dB) and high retroreflection accuracy (deviation angle <0.1°) through a cornerstone prism or fiber grating structure, making it widely applicable in fiber optic sensing, laser ranging, and other systems requiring optical path self-alignment."Sub-angle graded retroreflection," through a high-precision cornerstone prism (deviation angle <0.05°) or Bragg grating (wavelength-selective reflection) design, achieves the return of incident light along its original path (insertion loss <0.3dB), providing a calibration-free optical path self-alignment solution for distributed fiber optic sensing and coherent detection systems.