LAUSR

In this work, a compact and cost-efficient approach is proposed for the generation of dual- and triple-wavelength fiber lasers (D-TWFLs) operating in the C-band using an in-line thin-core fiber filter (TCFF). Two TCFFs of lengths 4 and 6 cm are fabricated by splicing thin-core fiber (TCF) between single-mode fibers (SMFs), enabling stable comb-like filtering based on modal interference. The free spectral range (FSR) of the filter is obtained around 1.5 and 1.0 nm for the 4 and 6 cm TCFFs, respectively. By adjusting the polarization controller (PC) within the laser cavity, dual- and triple-wavelength operation is achieved with an optical signal-to-noise ratio (OSNR) of up to 43 dB. The lasers exhibit optimal stability for a 1-hour observation period, with wavelength drifts of less than 0.02 nm and power fluctuations of less than 0.7 dB. Compared to conventional multi-component filter structures, the proposed TCFF design significantly reduces cavity complexity while maintaining high performance. To the best of the authors’ knowledge, this is the first demonstration of D-TWFL operation in an erbium-doped fiber laser (EDFL) using a TCF (Nufern UHNA3) as a compact in-line comb filter. This approach presents a robust solution for multi-wavelength laser sources with potential applications in fiber sensing, microwave photonics, and DWDM systems.