Wavelength-swept fiber laser based on dispersion tuning for the 1700nm band

We present an active mode-locked dispersion-tuned swept laser (DTSL) operating in the 1700 nm band. The laser employs a ring cavity with 60 m of high-germanosilicate bismuth-doped fiber (BDF), serving simultaneously as the gain medium and dispersive element. Active mode-locking is achieved via an intra-cavity electro-optic modulator, enabling wavelength tuning without mechanical components. A broad tuning range of 51 nm (1674–1725 nm) is achieved, with an average output power of 40 mW. The pulse width decreases from 6.5 ns to 85 ps with increasing modulation frequency, following Δt ∝ fm-0.5 which confirms successful active mode locking. This work fills a notable gap in the realization of DTSLs in the 1700 nm band and demonstrates their viability for high-speed, robust wavelength-swept operation in this spectral region.