Switchable and broadly wavelength-interval-tunable multi-wavelength EDFL based on dual-channel Sagnac loop

A switchable and broadly wavelength-interval-tunable multi-wavelength EDFL based on dual-channel Sagnac loop is presented and experimentally investigated. The fundamental operating mechanism relies on birefringence-induced polarization-state evolution and counter-propagating optical interference within the Sagnac configuration, enabling efficient generation of stable multi-wavelength lasing with adjustable channel spacing in the EDFL. Through polarization controller (PC) adjustments, the laser achieves output spectra containing up to 8 simultaneous wavelengths. For single-wavelength operation, it generates emissions tunable between 1553.64 nm and 1558.84 nm with a minimum optical signal-to-noise ratio (OSNR) of 52.091 dB. The system demonstrates significant wavelength-spacing tunability across multi-wavelength regimes: dual-wavelength outputs achieve 25.80 nm maximum spacing, triple-wavelength 26.40 nm, quadruple-wavelength 18.20 nm, quintuple-wavelength 22.12 nm, sextuple-wavelength 11.92 nm, and septuple-wavelength 10.52 nm. The full operational spectral coverage extends from 1518.72 nm to 1560.08 nm. Featuring broad spectral tunability and multi-channel reconfigurability, this EDFL design delivers an innovative dynamically reconfigurable optical source platform optimized for next-generation fiber-optic communications and advanced optical sensing applications.