In this paper, we demonstrate and experimentally verify a tunable, multi-wavelength switchable ring-cavity erbium-doped fiber laser (EDFL). The hollow-core anti-resonant fiber (HC-ARF) filters, which are based on polarization interference, are fabricated using a bent HC-ARF. These filters were incorporated into a ring-cavity EDFL, achieving a tunable laser output ranging from 1547 to 1561 nm with a tuning step of 3.5 nm, and all measured optical signal-to-noise ratios (OSNRs) exceeded 35 dB. Additionally, the laser system supports switching from single-wavelength to three-wavelength operation near the 1560 nm region.

In this paper, to reduce the damage or absorption caused by radiation to optical fibers, we study lightweight and flexible anti-radiation films based on optical precision deposition technology. At first, anti-radiation composite thin films based on Kapton, ITO, and Cu (or Al) are designed and homemade with different structures. Subsequently, polarization-maintaining (PM) Yb-doped fiber (Yb-fiber) samples protected by these different kinds of anti-radiation films are irradiated with a dose of ∼150 kGy. At last, we comparatively investigate (1) the radiation-induced attenuation (RIA) of these PM Yb-fiber samples and (2) the lasing performance (threshold and slope efficiency) and gain performance of a 1064 nm fiber laser and amplifier using these irradiated PM Yb-fibers as the gain medium, respectively. The results show that such a film can reduce the RIA of the irradiated Yb-fiber by up to 2.84 dB/m and increase the output power by up to 75.3% at most. In addition, we also study the optical recovery of the PM Yb-fibers after radiation.