{'fraction_non_alphanumeric': 0.05414847161572053, 'fraction_numerical': 0.04279475982532751, 'mean_word_length': 5.095744680851064, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Multi-wavelength mode-locked thulium-doped fiber laser based on a fiber-optic Fabry–Perot interferometer and a nonlinear optical loop mirror

An all-fiberized multi-wavelength mode-locked thulium-doped fiber laser (TDFL) based on fiber-optic Fabry–Perot interferometer (FPI) and nonlinear optical loop mirror (NOLM) has been presented. The fiber-optic FPI played the roles of wavelength selective filter and output mirror, which constructs by a single mode-hollow core-single mode fiber structure (SMF-HCF-SMF). A NOLM with wavelength-dependent cavity loss was employed to alleviate the mode competition in thulium-doped fiber and enabled the multi-wavelength mode-locking. With proper manipulation of the polarization controller and the pump power, besides the single-wavelength (~1948 nm) fundamental and high orders harmonic mode-locked operations, switchable dual-wavelength (1924.67/1949.16 nm and 1949.64/1972.68 nm) and stable three-wavelength (1924.80/1951.42/1972.14 nm) mode-locked operations are obtained. The multi-wavelength mode-locked TDFL exhibits a good stability with maximum peak power fluctuations of less than 0.5 dB in 2 h.