Wavelength-spacing-controllable multi-wavelength fiber laser based on a Lyot-Sagnac filter.

Abstract

A wavelength-spacing-controllable multi-wavelength polarization-maintaining erbium-doped fiber laser (MW-PM-EDFL) in a linear cavity configuration is presented based on a Lyot-Sagnac filter and a nonlinear optical loop mirror (NOLM). Using a Lyot-Sagnac filter as the wavelength selective filter makes the wavelength spacing controllable by adjusting the effective length of polarization-maintained fiber (PMF) segments. An NOLM inducing wavelength-dependent cavity loss can be used as an amplitude equalizer, which is employed to suppress the mode competition resulting from the homogeneous line broadening effect of the erbium-doped fiber in the cavity. Thus, a stable wavelength-spacing-controllable MW-PM-EDFL is realized. In this experiment, 20 stable lasing wavelengths are obtained with a pump power of 170mW at 980nm when the length of the PMF is 13m. When the length of the PMF is 8m, 10 stable lasing wavelengths are obtained at 185mW pump power. The power fluctuations and wavelength shifts are less than 2dB and 0.02nm in 1h at room temperature. The demonstrated multi-wavelength fiber laser has great potential for applications in optical communications and optical sensing systems.