Spectral Compression of a Dispersion-Managed Mode-Locked Tm:Fiber Laser at $1.9~\mu \text{m}$

We demonstrate self-phase modulation (SPM)-based spectral compression of the pulse from an all-fiber dispersion-managed Thulium (Tm)-doped fiber laser at 1.9 μm. The laser consists of ultrahigh numerical aperture fiber for the dispersion management to avoid soliton mode-locking and is mode-locked by nonlinear amplified loop mirror. Spectrum of the pulse is compressed from 7 to 3 nm by SPM in an anomalous dispersion core-pumped Tm-doped fiber, together with a passive fiber. Numerical simulations agree well with the experimental results. Limitation of high-efficiency spectral compression due to soliton evolution in the anomalous dispersion fibers is also discussed.