Fig. 1. Schematic of OCDR system

Fig. 2. OCDR performance verification. (a) Spectrum of SLD source; (b) reflection curves of two defect points in optical fiber measured by OCDR

Fig. 3. Femtosecond laser fiber micromachining experimental device monitored online by OCDR system

Fig. 4. Measured reflectivity by OCDR versus pulse energy

Fig. 5. Reflection curves and microscopic images of feature points in different pulse energy regions measured by OCDR

Fig. 6. Measured reflectivity by OCDR versus pulse frequency

Fig. 7. Pulse energy threshold versus pulse frequency

Fig. 8. Measured reflectivity by OCDR versus direct writing speed

Fig. 9. OCDR reflectivity changes when pulse frequency is 1 kHz, pulse energy is 0.44 μJ, direct writing speed is 300 μm/s, and number of scans is 7