Investigation of internal fine structure testing and defect analysis methods for fiber optic couplers

This paper presents a method for testing the internal fine structure and conducting defect analysis of fiber couplers. By applying a broad range of thermal stimuli to the fiber coupler, the invisible internal fine structures within the device are transformed into thermal strain distributions experienced by the optical fiber. The Optical Frequency Domain Reflectometry (OFDR) is then employed with millimeter-level ultra-high resolution to observe the strain along the fiber, thereby inverting the internal structure of the fiber coupler, this process enables further defect analysis and quality evaluation of the device.