Switchable dual-wavelength erbium-doped fiber ring laser with tunable wavelength spacing based on a compact fiber filter

• A dual-wavelength erbium-doped fiber ring laser is demonstrated.
• The mechanism of the wavelength selection relies on a compact fiber filter.
• The filter is composed of a fiber modal interferometer and a fiber Bragg grating.
• The wavelength spacing can be tuned from 9.29 nm to 11.11 nm continuously.
• The laser can operate in dual-wavelength or in wavelength switching modes.

In this paper, using a compact fiber filter (CFF), we demonstrate a dual-wavelength erbium-doped fiber ring laser with tunable wavelength spacing. The two oscillation wavelengths are specified by a fiber modal interferometer (MI) and a fiber Bragg grating (FBG) embedded in the MI, which consists of the CFF. Due to the deeply saturated spectral hole-burning (SHB) effect in the erbium-doped fiber, stable dual-wavelength operation is achieved at room temperature and the wavelength spacing can be tuned from 9.29 nm to 11.11 nm continuously when the strain applied to the CFF is changed. By adjustment of the attenuator in the cavity, the laser can operate in dual-wavelength or in wavelength switching modes.