Wavelength-Switchable Erbium-Doped Fiber Ring Laser Using Inline Fiber Bragg Grating Filter

Here, we propose a wavelength-switchable erbium-doped fiber (EDF) ring laser by harnessing the unique switching feature of an inline fiber Bragg grating (FBG) filter based on a polarization-diversified loop. The inline filter consists of a four-port polarization beam splitter, three quarter-wave plates (QWPs), and two FBGs with different Bragg wavelengths. By adjusting the orientation angles of the three QWPs, this inline filter can select one of the two different resonances of the two FBGs. The proposed laser is composed of EDF pumped by a 980 nm laser diode, a wavelength-division multiplexing coupler, an optical isolator, a 3 dB optical coupler, and the inline FBG filter. At a special combination of the orientation angles of the three QWPs, one of the two reflection spectra of two FBGs could be chosen and thus the lasing wavelength of the proposed laser, which corresponds to the Bragg wavelength of the selected FBG, could be switched by adjusting the QWP angles. The fabricated ring laser accomplished stable and uniform lasing at each Bragg wavelength or switching operation between two wavelengths at proper QWP angle sets.