Fig. 1. Schematic of light with different wavelengths reflected in CFBG

Fig. 2. Simulation result of reflective spectrum for CFBG

Fig. 3. Schematics of cascaded CFBG stretcher and series CFBG stretcher. (a) Cascaded CFBG stretcher; (b) series CFBG stretcher

Fig. 4. Simulated reflective spectra of three stage series CFBG stretcher

Fig. 5. Schematic diagram of inscription of optical path

Fig. 6. Reflective spectra of CFBGs before and after optimization of optical path and reflective spectra of CFBGs in cascaded CFBG stretcher. (a) Reflective spectra of CFBGs before and after optimization of optical path; (b) reflective spectra of CFBGs in cascaded CFBG stretcher

Fig. 7. Reflection spectra and broadband pulse structure of series CFBG stretcher before and after structure optimization (insets are schematic diagrams of CFBG arrangement in series CFBG stretcher). (a) Reflective spectra and (b) stretched pulses before structural optimization of series CFBG stretcher; (c) stretched pulses and (d) reflective spectra after structural optimization of series CFBG stretcher

Fig. 8. Spectra and pulse of fiber source, and pulse after cascaded CFBG stretcher. (a) Output spectra and (b) pulse of fiber source; (c) pulse after cascaded CFBG stretcher (inset: pulse sequence)

Fig. 9. Spectra of fiber laser and spectra and pulses after connection with series CFBG stretcher. (a) Spectrum of source and spectra after direct connection and reverse connection with series CFBG stretcher; (b) pulses after connection with two series extenders (inset is pulse train); pulses of reverse connection with series CFBG stretcher (c) before and (d) after exposure optimization