Regenerated fiber Bragg gratings (RFBGs) have garnered widespread attention owing to their fascinating high-temperature resistance. The flexible modulating refractive index of fiber Bragg gratings (FBGs) is conducive to boost the versatility of RFBG fabrication. Nevertheless, the impact of different refractive index modulation (RIM) amplitudes on regeneration rate remains ambiguous. Given this, an optical low-coherence reflectometry (OLCR) is employed for real-time monitoring of RIM during the regeneration process. Experimental results illustrate the regeneration rate remains consistent at different RIM amplitudes. Furthermore, a functional relationship between regeneration ratio and regeneration time is proposed. To enhance the OLCR signal intensity, a promising optimized strategy is raised by introducing a phase shift at the edges of FBG. This work deepens our understanding of the FBG regeneration process and immensely improves the manufacturing flexibility of RFBG.