LAUSR

ABSTRACT In order to realize a wavelength-tuneable fibre-laser output, a ring-cavity erbium-doped fibre laser based on an all-fibre Mach–Zehnder interferometer (MZI) is proposed and experimentally tested. The MZI consists of a single-mode fibre, two segments of coreless fibre, and a seven-core fibre. For the proposed fibre laser, the length of the gain medium is 4 m and the lasing threshold is 75 mW. By adjusting the loss of the laser cavity, switchable single-wavelength laser emission is realized across the range of 1527.6–1549.9 nm and the wavelength interval is less than 2.4 nm; the peak power difference of each lasing wavelength is less than 7.9 dB. Tuneable dual- and three-wavelength laser outputs were obtained by adjusting the polarization controller. The 3-dB linewidth was less than 0.57 nm. The single- and dual-wavelength laser output power fluctuations were less than 1.4 and 1.7 dB, respectively, when monitored over a period of 30 min.